UK-Cherub Forum
Cherub Chat => Tech Chat => Topic started by: doug1720 on August 06, 2009, 05:55:57 AM
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Have been working on the plug for a couple of weeks....hope to get it finished this weekend.
Interested that the next AC may be in Ras Al Khaimah - this is one of the Emirates in UAE and about an hour and a half drive from where I live in Dubai.....looks like it will be great to watch.
It is quiet here as so hot and Ramadan coming up and so will get even quieter! This will help me get on with it!
I will update with photos on the build as I make progress.
Thanks.
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That is excellent you are getting started on your build, I look forward to seeing pictures of the progress.
I guess you will have the opposite problem to building in the North Scotland where it is sometimes difficult to get the garrage hot enough to cure the epoxy properly.
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Agreed ...unfortunately the summers are hot! Around 45 most days. Lows of 32 or so!
Like this until middle of September. Lots of AC everywhere so liveable.
I will post pics shortly.
Thanks.
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Been working over the weekend and starting to look like a boat. :)
Picture attached. Hope you all enjoyed the nationals.
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Looking good so far. Must be one of the cleanest boat-building workshops I've seen!
I must confess I didn't realise there was a Paterson 8 design yet. Is this a complete new Andy P. design, or an evolution of the P7? Is it optimised for use with T-foils like the Ellway 5?
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I think it will look more like an Elway 5 than a Paterson 7. I do not know about design optimised for T-Foils but certainly will give them a go. My son sails a foiling moth bladerider here and so I can get a closeup on the foils and management mechanisms for both daggerboard and rudder.
Wind conditions are 99% sea breeze, around 12-14knts. So looking to optimise for those conditions.
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Great photo. Really exciting there is a build in Dubai. Does sound like pretty much perfect cherub sailing venue. Shapewise there is a bit of a convergence - looks fast and pointy!
Nationals were superb - utterly excellent. I will be buzzing with it for months. I'll write in the proper thread though.
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Good to hear the Nationals went well.....I will put on more photos as the build progresses.
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Good to see some progress Doug !
P8 is a new design - based on the P7, with the widest part of the hull/chines moved aft, ie it has a longer and pointier bow.
Similar rocker, flat sections, low chines and vertical topsides to the P7.
With a little influence from the e5 - eg the more wedgy shape and the E5 type of stem/snout.
A liitle pic of an early version, before bending the sides in at the stem. ( also it was 13 feet long oops!)
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Any news on the build?
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We met Doug at Lymington. Lovely guy, plug still in progress.
Doug, when you are read this can I send my appologies as my phone ran out of batteries - thus loosing your phone number!
R
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Hi,
I must admit to getting slowly off the mark! I hoped to have a quiet time over Ramadan but ended up travelling all around the Middle East and back to UK.
It is a bit tricky getting all the supplies in the UAE, but have done that in the last couple of weeks. Vacuum Pump arrived (I bought a 99 quid version from Ebay).
Have started by making the bulkheads, wanted to practice before doing the hull - done!
I am putting some extra work into filling and fairing the mould; I hope this will reduce the filling and fairing of the hull!
I am planning for the next few weeks to get the hull done although recognising this is the easy bit ;D
Off travelling to North America for the week and then Istanbul but should have some time in the UAE to make progress.
I have also moved house...I now have a great garage to work from.
A couple of photos attached. (I have included one from a recent visit to Baghdad!)
The sailing conditions are really improving here - cooling down- and I have been out volunteering for the local club. My son has been out in his foiling moth in shorts and t-shirt!
As I get into the build I will be asking more details questions and so looking forward to your kind support!
Doug
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Good job! I can see the family resemblance of the P8 to the previous Patersons.
(Excellent use of palm trees and dappled shade, by the way. It is 8am here and grey and cold outside. 6 more months of this - nice!)
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Jealous? Not at all! ::)
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good stuff.
I could put a few more photos up of our build but it might be easier to stick them on a CD and post by snail mail.
Would be happy to share my thoughts with you.
Once you have a hull and bulkheads take a moment to think about the rig, mast position and spreader angles. These will help you fit the main bulkheads in the correct place and angle them correctly.
For us it was then make mast stump. While you are at it you may as well make all the tubes.
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I'm in Holland at the moment, but will post as much of the spars/racks/stump cookbook we used on the Exultant page tonight and then confirm the measurements over the weekend.
Careful though - too early to tell what will break yet!
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Thanks, some pics would be good. My address is Doug Hassell, PO Box 500516, Dubai, UAE.
I am interested in some details on the racks.....sizes, best mandrel diameter and layup.
Thanks,
Doug
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Thanks. Info would be good.
Doug
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Doug
PVC tubing intended for DIY use but can be used for mandrels can be found in such stores as B&Q.
from memory these come in the following Outside diameters.
12mm not bad for goose neck attachemnt in boom
19mm? good for small diameter struts perhaps for a gantry but small diameter tubes are difficult to make well
25mm good for tiller extensions, gantry struts, supports to a high mast stump.
32mm good for tillers
40mm good for tillers (but we use 32mm) beams connecting racks to hull
53mm good for rack tubes or beams connecting racks to hull.
The tension stays beneath the forward beams on the elways are made flat because Andy P and I used rectangular section beams laminated round a high density foam core. It is easier to join a flat stay to a flat surface of the beam. It may be easier to join a round section to a tubular cross beam.
I made the mould for the stay from a flat bit of wood and glued a wedge to the end at an angle of 30 degrees. sanded it filled any gaps and cover it with parcel tape.
Once I had used it I gave it to roland. I would agree that some layers of weave would provide some impact resistance.
I don't know what lay up Roland used for the racks.
I can provide you with the layups that I used for other parts on the understanding that I can't gaurantee they are correct. I have put full rig tension on the boat without a squeek from her but not sailed her in anger. I expect all is ok but the lay ups would be unqualified.
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Exultant's layups are here:
http://www.sailingsource.com/cherub/test/doku.php/tech/3206build
Diameters and tapers to follow on that page at the weekend.
Sails,
Doug is also keen to try to get hold of an older set of sails for his early voyages? This is definitely the place to share this...
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Hi,
Thanks for the information. I am taking next week off and so plan to make some progress.
In terms of sails I am planning to order a new set of sails but would like to have a spare set....I definately do not want to put the new sails up and go sailing for the first time and something goes and I have a big hole in the mainsail!
So I am very flexible on the state of the sails, just training sails.
Any thoughts? I will put pics on the site.
Thanks, Doug
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Been working on the mould....final filling and sanding and brown tape and release agent.
Then put the inner skin on this morning.
Pleased that all went OK although took me longer than I thought. Vacuum went OK although took some time to find all the leaks!
Also working on the daggerboard and will be sanding this tomorrow....can be seen in the background on the pics.
Used a 50:50 mix of very slow and fast harners...took about 4 hours to go off in 30 to 34oC. Seemed to be OK.
A couple of friends helping me next week and so hope to really make some progress. I will keep you updated.
Thanks,
Doug
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This looks great Doug! It's coming on nicely!
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Looking good, is that a cunning use of peelply at the bulkhead positions, with an extra strip of reinforcement?
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Looks like its going to be quick. Any thoughts on the rig? Keep us posted with pictures.
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Hi, I must admit that after spending so long on the mould and just getting the materials here I am really pleased to really get going.
Yes on advice from Andy I use peel ply on the mould where the bulkheads will be and put some unidirectional down under the 90 degree cloth. (I am also planning to put unidirectional around the edges of the bulkheads when they are fitted.)
In terms of the rig I need some advice. Mast is 2m from the end of the snout....1.7m from the stem. I believe the current thinking is max jib and smaller main and so thinking of jib around 5.5sqm and main the remaining 10sqm.
I want to go for a stiff rig - wind here is sea breeze only 99% of the time and rarely gets above 16knots and also is the tropical breeze without the power of wind in the UK - so little reason to power off? So thinking of two spreader. Any advice would be good.
I am going to make my own rig and plan to use layups on the wiki.
I am on the hunt for mandrels at the moment - no B&Q here and so more difficult!
I need to design the mast and decide on forestay length, spreader positions and length - all help accepted!
I need to get some wider unidirectional that will be suitable for the rig build - any ideas on sourcing. Also keen to get some carbon sock for the final layer?
Today I am working on the foam...I will post more pics.
Thanks,
Doug
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I need to get some wider unidirectional that will be suitable for the rig build - any ideas on sourcing. Also keen to get some carbon sock for the final layer?
We used 300mm wide uni cloth for mast 2 - on a rooughly 50mm mandrel it went round just over twice (as the cloth spreads out when you tighten it in). Not sure if would want to go more than 3 revolutions form a single bit of cloth - I'd get scarred.
I'll dig out the rest of my mandrel dimensions this weekend and post on the wiki - I think I can also try to dig up some pictures of the mandrel jig. BTW the mandrel we used for the mast was a "high pressure" plastic pipe - builders' merchant territory rather than B&Q.
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I want to go for a stiff rig - wind here is sea breeze only 99% of the time and rarely gets above 16knots and also is the tropical breeze without the power of wind in the UK - so little reason to power off? So thinking of two spreader. Any advice would be good.
Are you thinking enough about gust reponse? Its a key thing for keeping the boat manageable, and these days I tend to think of it as being more important than raw power.
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Jim, you used to crew! You should know that 'gust response' is just made up rubbish and the crews arms are what really count ;D
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Hi, agree that the rig needs to have some give in the tapered top section and not a tree trunk....I suppose I am explaining that because of the conditions here I will be in fully powered up mode a lot of the time and therefore eering to the tree trunk :) I think in the UK I would be looking at more of a balance between power up and depower.
Is 2 spreader the way to go?
Is there any information available on forestay, shroud lengths and positing of spreaders?
Foam on the hull!
Thanks,
Doug
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Thinking about ordering some sails. I was wondering about which manufacturers are working with the class and therefore know what works. I see a lot of boats with Hyde's - is there a contact there that I can talk to?
(I am still in the market for a set of second hand sails as training and backup!)
Doug
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I can provide you with the layups that I used for other parts on the understanding that I can't gaurantee they are correct. I have put full rig tension on the boat without a squeek from her but not sailed her in anger. I expect all is ok but the lay ups would be unqualified.
Phil,
I would be very intersted in the lay ups as getting serious on all the tubes now! email is dgh200 at gmail.com
Doug
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I have another question on the crew deck. I am going for 29er style all concave. So all control lines, pole, etc on top.
I am presuming I need to plan the placement of fittings and I am using low density foam (divinycell H80) that will not stand upto any fittings being screwed in? I am ok to put high density foam where required.....is there any information or pictures that would enable me to locate where I should strengthen the foam?
Unfortunately I do not have the opportunity to see another boat, otherwise this would be a lot easier!
Thanks,
Doug
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Hi Doug,
Have you had a look at Rigging Design (http://www.sailingsource.com/cherub/test/doku.php/tech/rigging) on the wiki?
A twin spreader rig is required with a masthead kite, or you will be needing a telegraph pole to keep it in the boat.
Thinking about a stiffer rig, this realy depends on your weight, the point where you start to depower will always be where the rig generates more power than you can hold down. You want to depower once you are flat wiring, it does not matter too much weather that happens every day or just occasionally, it should still be at the same wind strength.
For the fittings hard points, you do not have to use HD foam, you can use fronting plates where you bond a carbon nut plate to the deck where you want the fittings. or you can bond short carbon rods to the deck and tie the fittings to them, I will search out some pictures.
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I suppose I am explaining that because of the conditions here I will be in fully powered up mode a lot of the time and therefore eering to the tree trunk :) I think in the UK I would be looking at more of a balance between power up and depower.
Maybe but... you are going to be sailing a boat that is far more heel sensitive than anything you have been in before: flat is nearly everything. And I get the impression that winds in hotter parts of the world are likely to be particularly gusty due to heated air rising. There's also the business of learning to sail it. So spring in the rig gives you much more chance to keep the boat on its feet and driving...
The first time I learned about this was when I rerigged Halo from a tin mast to a plastic one. The original rig on Halo, was pretty much the telegraph pole to end all telegraph poles.... I was very much working on the theory that maxpower was needed for fat forward hand, so it had a solid section (too stiff - Superspars announced the M7 about 6 weeks after I'd ordered an M3) and high hounds to enable a high hoist for the kite.
(http://www.devboats.co.uk/halo1992.jpg)
The kite hoist is just above the top batten, and the jib about the second batten...
When I got a C-tech carbon rig the jib hoist stayed in the same place, but the mast was around 410mm longer so around 20% more topmast...
(http://www.devboats.co.uk/halo2003.jpg)
The difference in how much more manageable the boat was was phenomenal...
I've been learning a lot more about this playing with the rig on my Canoe... Whilst I like to think I wasn't a bad Cherub forward hand I'll cheerfully admit I'm a pretty crap helm, so I do need all the help from the boat I can get, and I sail pretty much exclusively inland, and base, at 400 acres, is not a huge pond. My boat has got an ex Shiny Beast 5515 Superspar, which is 25% thinner wall thickness than the usual thickness for ICs, so is basically flexible. Add to that I am now somewhat fatter than I was in Cherub days, so am towards the top of the Canoe weight range.
The boat has no kite, so I have a single spreader rig and thus rather less scope for using rig setup to tune power. I set the boat up originally with loads of gust reponse for learning - such that it was actually quite difficult to get sufficiently powered up to require hiking off the end of the plank. So loads of aft rake on the spreaders - as the gust hits the increased load on the shroud tends to push the mast forwards, take depth out of the middle of the sail and dump the leech.
After about a year I felt I could deal with less gust response, so ran the spreaders neutral. Grief! What a cow the boat turned into! Instead of accelerating in the gusts she just staggered, heeled and stopped... I must own up to being completely gobsmacked by the change in boat handling... Needless to say this was very slow as well as not much fun, even if I could get the weight out further and had more power, and spreaders settings reverted quite a lump of the way back and the boat was fun tosail again. Since then I've been playing with options - adding more cabon to various bits of the stick - to get more power in without compromising the handling too much, I could go on, but you get the picture...
Now because you need to be running a two spreader rig with caps to support the kite you have a great deal more control of the rig than with a simple rig like the Canoe, and its pretty easy to dial power in and out, chiefly with the caps and checks (D2s). Its probably also easier and safer to add stiffness to a mast by gluing more carbon on than it is to take it away.
If it turns out too floppy you just bang a ton more caps and checks on and get some more luff round put in when it comes to get the sail recut to sit the mast better (I don't believe its likely that you'll get the luff round right first time with a home built mast so always figure that's coming). You can always bang more carbon on later. If its too stiff, on the other hand, the whle business of working the boat up and learning to sail her will be horrible and the boat will be slow. I am quite convinced these days that far more races are lost with too stiff a rig than too flexible a rig, especially in unsteady winds, which according to everything I've read you are going to experience...
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Can't really help with the rig im afraid. However, a great guide to fitting bits onto sandwich structures can be found on the Carbonology 18ft Skiff build blog. This is the method I would use as you can think about where fittings will go after you have the boat in one piece.
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do you man the bit about ply and a stanley knife?
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Ply and Stanley knife - yes! Seems like a jolly good idea to me. If it works on an 18' it will probably work on a cherub.
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Chopping foam out and replacing it with HD foam or ply used be quite common in Cherubs: In about 1997 the N12's starting experimenting with gluing the fittings on. I remember being sceptical, but it is pretty much universal in modern Cherubs.
You bolt the fitting to a circle or oval of carbon plate. You then chop off the bolts flush with the end of the nut, put the whole assembly down on the boat, draw round it, and then rough up the deck before bogging the whole thing down. If you wrap up the fitting in tape or cling film it makes a good handle to hold it down while you clean up the fillet.
All of Atum's and Antidote's fittings went on with fronting plates. These are like backing plates...only on the front! None has failed so far and both boats had their socks sailed off them. In fact the first of Antidote's jib turrets did come off. I cockily glued it straight down (a 50mm by 50mm square) rather than making it a circle. It now has a 100mm circle so Lucy will have to pull pretty bloody hard on it to pull that one off.
It takes one epoxy hit so is quicker and easier than the old method.
For the fancy minded you can taper the edges of the plate to reduce the stress-riser. I do this if it is a high load one.
If the deck is flat such that the bolts are holding the plate away from the deck you can make a couple of holes in the top skin of deck to allow them to recess in there. Be sure to put bog down the holes though as it is the bog which grips the nut to allow you to replace the fitting when it knackers. I have done this a lot - esp the floor block for the kite.
A variation is putting the bolts under the plate sticking up. Andy and Jill Peters did this on their boat.
Variables:
Thickness of the plate - about 10 layers of 200g plain weave or equivalent. You should not be able to bend it by hand.
Size of the plate - about 10mm from the nearest approach of the fitting, unless the fitting is raised like a jub turret or under specific peeling load like the block which sends the kite halyard up the mast. This block was a fronting plate on to Atum's Stump, but on Antidote it is a large fronting plate on the deck.
Shape of the plate - circle is easiest to make using a holesaw. Avoid corners because they aid peeling.
Bog: epoxy+colloidal silica+glass bubbles. Make it up so it is like butter icing. Paint a little neat epoxy on the two surfaces to help a good bond form. Pile the bog on the fitting in a shallow cone so any bubbles get pushed to the edge. When you put it on the boat press down hard. I usually lean a heavy thing on it to keep it still while I clean up the fillet with a tongue depressor or coffee stirrer.
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=2688#th_feb_20061]http://www.sailingsource.com/cherub/test/doku.php/boats/2688?s[]=2688#th_feb_20061
(http://www.sailingsource.com/cherub/test/doku.php/boats/2688?s[)
Middle pic shows how we did it on Atum.
I did Antidotes while reviding for my (MSc) finals so did not take too many pics.
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Chopping foam out and replacing it with HD foam or ply used be quite common in Cherubs: In about 1997 the N12's starting experimenting with gluing the fittings on. I remember being sceptical, but it is pretty much universal in modern Cherubs.
1997? Several fittings, notably the kite halyard hoist/drop turning blocks, were installed like that on Halo in 1989 and I don't remember thinking it was especially innovative so I imagine I must have got the idea from someone else, presumably Amber Dragon, Johnny F or possibly Norwegian Blue, I don't recall. It was a ply plate glued on with glass all round the tapered edges: carbon was less prevalent then, but the same principle. And just to prove it, out of the bits box:-
(http://www.devboats.co.uk/surfacefitting.jpg)
Goodness knows why I left the bolts so long. The nuts were on the underside so they could be locked in by bog and give me half a chance of being able to replace the fitting if damaged. I never tested the theory!
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For the fittings hard points, you do not have to use HD foam, you can use fronting plates where you bond a carbon nut plate to the deck where you want the fittings. or you can bond short carbon rods to the deck and tie the fittings to them, I will search out some pictures.
Thanks. Have you got a source where I can buy these from?
Doug
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So spring in the rig gives you much more chance to keep the boat on its feet and driving...
Thanks for the advice and a key point as I think this could end up being more about swimming than sailng. ;D So a floppier rig and adjustment through rig tension. I will think about layup and post what I think I should do.
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Middle pic shows how we did it on Atum.
Thanks for all the information....another thing to make!
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Thanks for all the information....another thing to make!
As the project progresses you'll find the sad truth of home boat building - that it takes just as long to make up a fiddly little bracket as it does to lay up the entire outer skin of the boat - and there are a lot more fiddly brackets! Its why the mass production boats take so many compromises on layout to make them affordable to build, but also why our boats can be so much nicer to sail...
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Middle pic shows how we did it on Atum.
Thanks for all the information....another thing to make!
There are some more instructions and pictures on the tech (http://www.sailingsource.com/cherub/doku.php/tech/howto) pages, of the site.
I tend to make the plates up from offcuts as I go along out of wet carbon and any excess resin from when I do bigger jobs.
Just need some peelply, plastic sheet clamps and couple of blocks of wood.
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presumably Amber Dragon
The first time I sailed Amber I removed both the hoist and ruturn block in a replica of Jim's photos. Although this was in 2009, so the inset blocks of wood had lasted a good few years. On THe Flying Tirfle, Born Slippy and Exultant we used the fronting plate method and I have not to date managed to remove any fittgings (despite mutlipe attempts).
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Doug ,
I used fronting plates on E-numbers.
It does allow you to make the boat and think about fittings latter on.
This is very much down my street because i like to be able to see the thing i am attaching fitting too and all the bits that may get in the way of it.
I now have all the plates on that I think I need.
I have added some supports of 50mm high for the T-foil cleats which will sit between helm and crew position. Again these were put on once I had the kick bars in position allowing me to mount the cleat at the correct height.
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Thinking about ordering some sails. I was wondering about which manufacturers are working with the class and therefore know what works. I see a lot of boats with Hyde's - is there a contact there that I can talk to?
(I am still in the market for a set of second hand sails as training and backup!)
Doug
Unless you are going to take an exact GT60 set of Cherub sails Hyde have told me they aren't making any more Cherub sails.
If you look at the Second hand list you'll see I have some Hyde sails for sale, I might be tempted to sell one of the mains as well.
I guess you are closer to NZ than most of us so I'd talk to Ken Fyfe.
Although I am talking to Dick Batt at the moment about sails, but he is South Korea for 10 days so I can't give you any more info on that till nearer December.
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Daryl, He's back on the 15th. My boat is at his workshop waiting for him.
He sounds keen as mustard whenever I speak to him and his website has some encouraging promises*, but the proof of the pudding is in the eating!
*quotes to come later
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I have quotes.
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I have been working for last couple of days on getting the foam on and now have started the fairing and filling process. To give me abreak from the hull I am making the daggerboard....almost done.
Pic attached.
Doug
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That is rocking along. Did you vac the foam on or is that plastic saving "dog hair"?
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Doug,
i have a CD of pictures and layups ready to post to you. i regrett that some bits aren't well documented so feel free to ask more questions and i'll do my best.
I don't know how long things take but expect you should have it in a few days.
The hull looks good.
Andy P. did a great job on our shells such that we didn't have to use a lot of filler. The main issue was fairing in the overlaps between cloths so the fewer overlaps you have with the final layer the better.
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Looks to be coming along realy well.
When you are fairing the foam, before the cloth goes on dents are OK (can be filled later) bumps are not (you end up sanding of the carbon)
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That is rocking along. Did you vac the foam on or is that plastic saving "dog hair"?
Just got the dog....she is a great help. Used vacuum pump.... seemed to work OK.
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Looks to be coming along realy well.
When you are fairing the foam, before the cloth goes on dents are OK (can be filled later) bumps are not (you end up sanding of the carbon)
Thanks for the advice. Fairing the foam now and hope to move to outer shell tomorrow!
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Doug,
i have a CD of pictures and layups ready to post to you. i regrett that some bits aren't well documented so feel free to ask more questions and i'll do my best.
Andy P. did a great job on our shells such that we didn't have to use a lot of filler. The main issue was fairing in the overlaps between cloths so the fewer overlaps you have with the final layer the better.
Thanks for sending the CD. I am getting the uni for the mast, etc brought out to me on Monday and so can start on the racks in the next few weeks, etc for practice before the mast.
In terms of the outer shell I am really going to take my time so that filling etc afterwards will be at a minimum. Anyway that is the plan!
Doug
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I thought the other day that where you are expecting to overlap cloths on the outer layer of the hull shell you could just sand a little more foam away. This way you only have to build up localy near the overlap if you happen to have sanded off too much. If the overlaps stand slightly proud you end up ffilling everywhere else to fair in these high points.
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I thought the other day that where you are expecting to overlap cloths on the outer layer of the hull shell you could just sand a little more foam away. This way you only have to build up localy near the overlap if you happen to have sanded off too much. If the overlaps stand slightly proud you end up ffilling everywhere else to fair in these high points.
I have thought that also, the big problem I can see is aligning the cloth with the dent, things seem to stretch when wet out.
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Solution: Wet out the cloth on the buttered foam, trim the overlapping cloth to fit the desired overlap before overlapping it.
Caution: clean the scisors with thinners to avoid using lots of pairs.
We've probably gone through about 5 pairs of scisors during our build. Since they all came from a pound shop it's not a great outlay.
being a bit nerdy and thinking this through I would keep one pair of scisors for cutting peal ply which is a pain with anything but sharp scisors. Then avoid where possible getting the other scisors covered in resin. Difficult to achieve but a laudable target.
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During our build we had a Hierarchy of scissors (often corrupted by visitors, btu we were glad of the company). By the end I became rather an***y retentive about the misuse of the scissors reserved for the peel ply. Sounds like a League of Gentleman sketch:
"Black for paper, chrome for string, the blue one from this hook do swing.
We keep them clean, don’t be mistaken, for kitchen jobs like trimming bacon."
Back to the thread:
I'd worry about the carbon wanting to move under the bag, it seemed to strech out a little when under pressure in the initial hits. After a few scratched chin's we decided that we would do the bottom and sides in 2 hits. Hit 1 sides to chine intersection (not round the chine), hit 2 entire bottom panel (over the chine). Yes we did pre-sand the foam for the overlap, but I think this was overkill as you will want some filler on it to sand back to anyway.
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Wet out in place would help the movement issue, I have mostly been wetting out on a table lately so get a lot of stretching.
I got a pair of Teflon coated scissors a few years ago, I chip the cured epoxy from them every so often and then recoat in release wax. They are starting to get a bit blunt now, but have done quite a bit of work.
I also use release wax on plastic spreaders, and occasionally on pots so I can clean up eisly.
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I thought the other day that where you are expecting to overlap cloths on the outer layer of the hull shell you could just sand a little more foam away. This way you only have to build up localy near the overlap if you happen to have sanded off too much. If the overlaps stand slightly proud you end up ffilling everywhere else to fair in these high points.
Thanks for the advice. I spent a lot more time preparing and checking the cloth fits, etc before having a go at the outer shell. Was a lot harder to get it correct but got there in the end. i ended up with more like shrinkage and so next time would have larger overlaps when curtting the cloth. Vacuum went on really well and have left it to take a trip to Iraq.
I am off on the Dubai Muscat and then to Canada on Business and so a few weeks off.
I intend to take a lot of time over the hull fairing and multi task with lots of the other jobs so I do not get totally fed up.
I have a couple of pics that I will put on once I am back in Dubai.
Doug
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I am now considering the crew deck and am still undecided on the eventual design. I am thinking about the 49er style that fills the entire inside of the hull versus having a little of the hull side exposed with the crew deck below gunwhale height. One of my thoughts to not having the 49er style is that I would have to put more fittings like the racks through the deck. Maybe simpler to have all that fitting above the crew deck?
Any thoughts on this would be appreciated.
Thanks,
Doug
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I changed 2686 from having a sunken crew deck to one where it was flush with the inner gunnals, and the modified version was much easier to sail.
I did not have any of the wing support bars puncture the deck with the modified layout, however I was not hanging the rig loads on them so they did not need to be as strong.
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I changed 2686 from having a sunken crew deck to one where it was flush with the inner gunnals, and the modified version was much easier to sail.
I did not have any of the wing support bars puncture the deck with the modified layout, however I was not hanging the rig loads on them so they did not need to be as strong.
Thanks for the information. I suppose I would feel happier about seperating racks from the rig. I need to design what comes up through the crew deck...have you got any pictures of what that looks like on your boat?
Doug
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Photos attached show how our structure on EJ was done. The rear rack support was bonded down onto the deck (not shown brilliantly).
These come with a warning - we haven't sailed this enough to know if it will break...
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Would anything stop you having the rack support tubes in the place where the tie bars are and keep the whole thing below the deck?
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The concept behind this one was that the tension strut passes through the hull skin, this is lower to the water and has little drag if it gets wet (which it does). The compression member is higher and presents lots of drag when it is in the water (but by then so is the rig!).
Yes It would be possible to replace the struts by a bending member - like a beam stuck through/on the deck. We chose not to do this and copied Aunti Dot as I like things that are in tension/compresion or put basically - triangular ::)
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There are quite a few pictures showing how it went together originally and after the rebuild on;
http://www.sailingsource.com/cherub/test/doku.php/boats/2686 (http://www.sailingsource.com/cherub/test/doku.php/boats/2686)
The hull is a bit wider than the E5 which made it eisier to put the shroud points on the hull.
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The concept behind this one was that the tension strut passes through the hull skin, this is lower to the water and has little drag if it gets wet (which it does). The compression member is higher and presents lots of drag when it is in the water (but by then so is the rig!).
Yes It would be possible to replace the struts by a bending member - like a beam stuck through/on the deck. We chose not to do this and copied Aunti Dot as I like things that are in tension/compresion or put basically - triangular ::)
I cant work out how to do this on the new boat. I know I want a fore deck as I want quite a lot of freeboard and a low false floor but cant work out how to fit all the structural bits in and have space for a retracting pole and chut.
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Guys, Thanks very much for all the input. I am off sailing on the Dubai Muscat tomorrow and so up to my eyes in getting the boat ready, etc.
If the breeze is good I can get back early next week to Dubai I will do some research on all the information and come to some conclusions. The work will have to wait until I return from Canada on the 19 December!
Thanks,
Doug
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RS405 ,
The older designs such as the DOG had a false floor that went all the way to the bow and then a foredeck over the top. The modern boats have just got rid of the fore deck. Makes rigging some of the systems much easier and saves weight and time in the build.
The E5 has the same freeboard as the DOG at the bow.
It's quite straight forward to bring the compression beams to the mast stump as on the E5 and the connection to the gunnel is quite easy to allow for when trimming the deeck to size. I reffer you to the CD of photos. The tension stay needs to be integrated before the deck goes on but again is not difficult to do if you use the dry fitted beams to support the outboard ends.
With the narrow hulls i would have thought that you would struggle to provide enough support to the mast by only attaching the shrouds at the gunnels. We have a shroud base of 1.5m. Other boats have shown that you can go narrower and wider.
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The older designs such as the DOG had a false floor that went all the way to the bow and then a foredeck over the top. The modern boats have just got rid of the fore deck. Makes rigging some of the systems much easier and saves weight and time in the build.
Its worth nothing that IMHO you cannot do without the foredeck on a predominantly glass boat - even top quality biaxial glass as we used in the early 80s. The structure will bend significantly under rig loads: you need the extra support for the topsides. I can't comment on carbon boats, but a very interesting experiment would be to measure the distance between gunwhales at say three points between the mast and forestay both with the rig tension off and with it on. Repeatable differences mean that the boat is bending under load which is unlikely to be a good thing. Another useful exercise for those prepared to take the trouble is to make the same measurements before and after sailing without taking the rig tension off, and also to measure the rig tension before and after sailing. All this will tell you what is happening to the structure under load.
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JimC, I'm not sure I agree with you on this one. I would say that the no foredeck option would give you a stiffer boat regardless of material, if the crew deck is joined at the gunnels. This effectively turns the whole boat into a box girder. The lower you put the false floor you are lowering the stiffness of the boat by some function of x^3 where x=the distance between load beaing pannels.
With the older boats like the dogs this was corrected by adding side tanks (effectively another box down each side) and a foredeck. Banshee Ambulance will be an interesting one as it has no foredeck and a low flase floor.
I like the idea of measuring deflection under rig load. I think Frank B did this with some of his 18 footers. I will have a look in the book and find out what the delfections were.
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Off topic, but whilst I remember:
I need to publish a book. That way after a few years people will forget I speak nonsense and believe what I wrote - "coz it's in a book" ;)
Back on Topic:
I can see where youare comming from Jim, I wonder if the advent of the additional frame that forms the rack supports changes this slightly. These provide a very stiff compression path accross the boat at the mast? In this model the corner between deck/hull now becomes the compression path, with foredeck/crewdeck stabilising rather than actually taking the load. the shear path back to the stump is still a bit sketchy though, but that is why I'd still add a carbon front triangle (of bulkheads).
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I believe the initial idea was to put a foredeck on a carbon boat.
RS405 you are quite right that a higher floor will increase the depth of the hull girder and restore stiffness. Some of the 91 rules boats had quite low floors and needed the fore deck.
If you made an Elway 5 or banshee out of glass the glass boat would be less stiff than a carbon boat. I suppose where we are going is is that stiff enough. if not, the glass boat could be strengthened by adding a couple of layers of carbon along the hull at the gunnels and where the bulkheads sit. This strengthens up the main load paths without adding lots of weight. This effectively adds a stiffer composite space frame within a composite monocoque design.
if one were to try and save cost on the build of a hull, glass shells reinforced with carbon in this way and fitted with carbon bulkheads might provide a stiff and low weight boat.
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I would build in glass with carbon bulkheads. I think that will be more than stiff enough. Especially as the rig loads will go through the racks which would be carbon.
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Stu and I are building in glass with carbon bulkheads. I recon it will be fine. ;)
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For my tuppence I can see what Jim is saying and yes there is a pit that you could get into, but I think the current crop of boats differ as their space frames avoid this (i.e. none of the recent boats are actually monocoque). When you have the schematic for your structure I'm sure Jim'll* be happy to give it a once over, as will all your friends on here (none of us want to see folding boat).
*Please do not take offence, I've been wanting to type that for years ;D
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Hi,
I have got back from 3 weeks travel and thanks for all the posts and ideas.
I have managed to get the hull off the mould this morning ;D. Not perfect but I am pleased with the result :o Pic attached.
I know a long way to go, but a milestone!
I am going to read up all the info on the thread and put down some thoughts.
Thanks again.
Doug
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looks awesome doug
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Planning to weigh hull in the next couple of days. Any ideas how much she should weigh at this stage?
Thanks,
Doug
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JimC, I'm not sure I agree with you on this one. I would say that the no foredeck option would give you a stiffer boat regardless of material, if the crew deck is joined at the gunnels.
That's a concave foredeck though isn't it [grin]. That's obviously going to work far better than a low tank and unsupported gunwhales. Probably still worth taking numbers.
Actually it might be an interesting exercise for a windless day at a Champs - find out how much the boats move under rig tension and see if it correlates to various options in internal construction.
Congrats on finishing stage 1 Doug: the next stage of internal framing and decking is probaly the easy bit, but its then followed by the really time cosuming stage of doing all the fiddly stuff!
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Yes JimC, just a bit of terminology really. I think we can agree at bigger box, stiffer section.
Doug: Well done on getting this far and in such good time. Some of us sit about day dreaming and dont get on with it! Have you thought about what sort of deck you are going for? By looking at the amount of freeboard it looks like you might be going for the E5 style deck.
My boat will be a bit like this but I'm doing things a bit differrently.
Photo credit: NZ 12ft CA
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Hey man... that's one wicked sled! Congrats!
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Yes JimC, just a bit of terminology really. I think we can agree at bigger box, stiffer section.
Well done on getting this far. Have you thought about what sort of deck you are going for? My boat will be a bit like this but I'm doing things a bit differrently.
Photo credit: NZ 12ft CA
love the Belay device trap hooks on the NZ boat :o. I doubt that they last long in salt water though.
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Hi,
In terms of deck I am also wondering about volume of air in the hull. I think with a full gunwhale to gunwhale crew deck there will be too much bouyancy...boat will turn turtle quickly and the daggerboard will be very high out of the water.
Has any work been done or thoughts on this observation?
Because of this I am considering a crew deck that will be short of the gunwhales and so needing to step down into the boat when tacking, etc. From what I can see in terms of photos this is more like Banshee Ambulance.
Stiffen up the gunwhales with a few layers of carbon.
Thoughts appreciated as I want to get on and shape the bulkheads and some of this will depend on decisions made ::)
Doug
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Yes - the high floor thing is a worry. Atums was kept low (80mm at the back) for this reason.
We were a bit braver for Antidote. 170mm, which seems ok.
The Banshees (don't know about B Ambulance) have a thicker floor which may be a bit too much*, and the E6 (I think) has a flatter floor with more vertical sides to allow for the low floor and the high topsides. This is like Aqua and Ronin.
An unsupported gunwhale does need quite a lot of extra stuff on it to be strong enough, so a dished cockpit with steep edges may be something to consider. That way the deck will still support the gunwhale, you'll still have the low floor for ergonomics and statics, and topsides which are high enough.
* On the basis of one set of capsizes in Riot Van with Graham, I felt that the board was not too high out of the water, and I have no memory of the boat inverting more or less than other designs. What was apparent was the low static stability with one crewmember in the boat and the other in the water. I felt v high and unstable: on a bike but stopped! The other issue is getting aboard between the tubes and the hull. This was possible in Aqua, impossible in Atum (due to a late drafting error by me) and was part of the design brief for Antidote. 310mm is fine for us, but you have to watch your hook as you go through the gap. I don't think this is an issue for you, looking at those topsides.
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In Primal I changed from an unsupported gunwhale step down into the cockpit to having the cockpit deck flush with the inner gunwahle, it made the boat much easier to sail, I had a greater range of positions that I could stand and balance in the boat and it reduced the number of steps needed to tack.
It is also a smaller number of steps to build if the gunwales are level and should be stronger and lighter.
The hull is probably only 1m wide at it's widest point how far from the water can the centerboard be?
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Doug,
I have some good photos of my boat in build that might help you, you can download them http://www.langhambull.com/riotvan.zip (http://www.langhambull.com/riotvan.zip) - in a hurry right now but will try to tell you more about which bits are right/wrong soon !
Graham
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I have a low floor. 80mm @ transom / 200mm @ case / 260mm @ stem. With the low floor you'll need an extra bulkhead. Something that I designed my boat to have and Mike left out resulting in having to take the floor out and put back in the bulkhead. Due to floor flex and topside / gunwale flex. I also have a half deck / mast gate with a little extra bounancy coming from my gunwale height main bulkheads. They curved down in an arch to meet the floor from the gunwales. The cockpit side of the mast gate / half deck bulkhead should also be curved to reduce any point loading where the loads meet at the mast gate. This wasn't built with a curve as I had intended and as a consequence a remedial curved space frame has had to be put in under the half deck. The intention was a compromise to create a boat which floated low after a capsize, was stable after righting and gave the helm a good sitting in position downwind and allowed for a lower boom. ( my boat is also designed to be hiked with wide wings so this low floor should also make coming in from sitting easier ). And took the rig loads from my narrow shroud base. It's not exactly how I wanted it, but I should have built it myself if I wanted that, shouldn't I ? :D
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Hi, recovering from a night out at the yacht club on the beach! I hope everyone had a good time?
I have decided to go for a hybrid solution, so not full gunwhale to gunwhale but also neither a low false floor. I will see how it goes.
I weighed the hull and around 20kg.
Thanks,
Doug
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Hi, recovering from a night out at the yacht club on the beach! I hope everyone had a good time?
I have decided to go for a hybrid solution, so not full gunwhale to gunwhale but also neither a low false floor. I will see how it goes.
I weighed the hull and around 20kg.
Thanks,
Doug
Can you elaborate on this any further? Or give a diagram? I would be interested to see what you are planning.
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Hi Doug,
You can see in the purple picture the slightly recessed deck that I had, the problems with this were that I could not stand with both feet on the inner gunwhale and balance, so that meant that my in boat standing position was closer to the centerline, this gave problems with roll tacks and prestart manoeuvring. so after the deck was damaged on the rocks I decided to rebuild it a bit flatter and I was surprised how much easier the boat was to tack after the modification. I used one less step in each tack and was more balanced during the whole manuver. Ergonomically I found the flater cockpit much better.
Original setup
(http://www.sailingsource.com/cherub/test/lib/exe/fetch.php/boats/2686-20050611c.jpg?cache=)
during modification.
(http://www.sailingsource.com/cherub/test/lib/exe/fetch.php/boats/2686-20070315a.jpg?cache=)
When modifying I cut off a strip of hull the length of the cockpit that had been reinforced by adding an extra strip of foam and then a few layers of carbon over the top to take the punishment of being stood on and the two strips weighed in at 800g although they had absorbed some water where the foam had disbonded due to sailing abuse.
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To be fair Phil... you are not the normal sized Cherub crew i.e massive! ;D. So the situation you describe may not be suffered by everyone. Just something for Doug to consider when weighing up the pros and cons.
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To be fair Phil... you are not the normal sized Cherub crew i.e massive! ;D. So the situation you describe may not be suffered by everyone. Just something for Doug to consider when weighing up the pros and cons.
I am 6ft 3 and move about the boat like a small elephant so perhaps not so relevant to anyone else's sailing technique, however I have sailed the same boat with two different cockpit layouts and was surprised how big a difference it made, my comments were based on my sailing experience which is all I can use.
If I were building another boat i know what I would do.
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Doug try to imagine how you go across the boat during a tack. Where you might put your feet and what angle of heel the boat may be at. Also consider the distance between foot steps. This will depend on weather you have a short or long stride.
We put kick bars either out board of the spinnaker sock because without them we thought Sarah may struggle to get across the boat if we got a tack a little wrong.
It's a balance of structures; ergonomics; weight and static stability.
Our hull weighed 23kgs with the deck on and aft beams.
The spine and bulkheads weighed 2kgs.
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What's happening?
Or perhaps the shell weight of 20kg vs 13kg of my e5's have discouraged progress?
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Humm! i didn't want to say that 20KG sounds a bit heavy for just the hull shell.
Andy,
I suspect the shells that you made for us were lighter than 13 and 8kg respectively. As I mentioned above when bonded together with bulheads (1.9kg) and the aft beams (1.5kg) and centreboard case (probably another 0.7Kg ) it still came to 23Kg. That's not mentioning the bog fillets to bond the bulkheads in and deck on and connecting laminations for some parts. You did a great job as i expected.
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I think, as with any measurement it depends on how it is done! In theory of course, this should not matter for the case of measuring weight, but a boat is not an easy thing to measure on the bathroom scales. 20kg might be the figure that is thought to be correct but in my view, each technique for measurement will have its own assumptions and innacuracies. That is unless you have a pair of Cherub sized scales! Perhaps sharing measurement techniques would gain more than 'yours is heavier than mine'! :)
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Good point,
My method was based on a set of bathroom digital scales.
the boat was sat on two battens of wood 1 at the bow and one at the stern.
In turn the scales were placed under each batten and that end of the boat was weighed.
The scales were zeroed after the batten was sat on the scales.
We had previously checked the scales by placing 1 Sarah on them.
A Sarah is a british unit of weight measurment. ;)
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I see you very wisely didn't mention what one Sarah is equal to. As it might have been one black eye ;D
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Hi,
I am back on the project. I have spent only a few days in Dubai this year and so impossible to get aything done....work commitments :'(
Just finished the dagger board and daggerboard case and will plan to put the crew deck in when I return from a break in the UK....just bought a house in Lymington...walking distance from the yacht club!
Thanks for all of the comments.
My son who is at University in UK is thinking of getting a Cherub! So perhaps I will be on the water quicker than I thought!
Doug
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Which uni?
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Oxford.
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Nice place, sadly the head shrinking probably rules him out for a few weeks ;-) If he or yourself are free (and in the UK) do shout...
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Will do.
Doug
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Ok, so back to the build!
(Spent most of the year so far travelling across and around the Middle East.)
I spent the weekend leveling off the decks and bulkheads. Took a long time. Fitted the daggerboard case and cut the foam for the crew deck.
I hope I can get the crewdeck on this coming weekend.
Doug
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There are a couple of areas where I have still not finished my thinking and any ideas welcome!
My current thinking on the mast stump is to have a tall stump and bring back the shround loads under compression back to the top of the stump through some struts (like moth).
Put gooseneck on the stump and have a strut to the bow.
In terms of mast strut layup thinking of 8 layers of 200g uni and helical and 0-90 weave. I am not sure of the mast to mast stump connection point. Should I make a socket on the mast stump for the bottom of the mast?
Any thoughts welcome.
Doug
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Something like this? As for layup check out the build of EJ pages.
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Ergonomically I much preferred a free standing stump: makes it far easier to get crew weight forward. On Halo I used the bottom of a Finn mast. But that was with a full height foredeck and bulkhead: the structural issues are completely different with the layouts you use now.
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Something like this? As for layup check out the build of EJ pages.
Yes this was my thinking. Thanks for the photograph. How about a strut that goes to the bow or is this not required.
Doug
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I have not seen a strut to the bow used. I presume that it would make for a difficult self taking jib arrangement. If you were to do it like the boat in the photo you would have some form of strut under the foredeck from stump to stem. If you were going for a foredeck less solution the floor would be higher and the spine would do the same job.
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Thanks for that.
In terms of the mast to mast stump join is there a preferred approach....thinking of using the same mandrel for both and with more carbon in the stump then it will be thicker.
I am also interested in the height from the deck of the gooseneck. Presumably needs to be as low as possible to reduce heeling moment from the mainsail. Thinking of a GNAV to provide more room to get under the boom. Any thoughts appreciated.
Looking to make the stump and then put the crew deck on this weekend coming.
Doug
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Gnavs have their fans but not everyone likes them. Have a read of the rigging article on the site as that may be of some help. For my boat I am working on just under a meter from the crew deck to the gooseneck which I think is what Atum Bom is. C-Tech sell the fittings for the bast base and stump join so it might be worth getting hold of those first so you know what diameter to use for the tubes. Alternatively you could make your own to measure after.
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If you are going for a tall stump with solid lowers, you need to make sure that the stump is angled back in the boat enough so that the rig compression puts the lowers into compression. putting a strut going forward will stop a self tacker from working, and will make it likely that the jib will catch if using std sheets.
I like gnav's and have had them on two different boats. I think the combination of a gnav and stump is not a good idea as the gnav is working on a short section of mast so bends will have a smaller radius.
I think that there is less need for the gnav in the modern boats as in sub trapizing the crew should be in front of the mast, and once trapizing the T-foil is working so you are further back in the boat.
Have a look at
http://www.sailingsource.com/cherub/test/doku.php/boats/2688
for a tall stump,
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Surely if you've got a push kicker there's no point in having the stump? The reason I had the stump at least was to take the kicker bend loads out of the mast.
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Thanks for the thoughts. ;D
I will do some more thinking.
I am travelling back to Dubai tomorrow and should be able to start work on Wednesday.
Doug
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progress pics?
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Will do. Since moving I have not been able to find my charger but I will use my Blackberry if still cannot be found.
Had to delay my flight back from Riyadh and so will be a later start tomorrow!
Doug
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I don't understand why you would need a compression strut going forwards to the stem. Surely the solid lowers will be just as happy working in tension and compression.
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Hi Doug,
A low boom has got to be better aerodynamically, but we felt ergonomics trumped that concern. After we had Aquamarina, with a book 1.1m from the deck, we started to really value a high boom.
Atum has 1m from the deck to the bottom of the gooseneck fitting, which is a bit above the bottom of the boom. Antidote is 0.95m.
Atum has tension struts as solid lowers, with a very visible backward kink at gooseneck level. We did not have the problems of the jib catching etc, but it is easy to understand how this could have occurred, esp if we has increased the rake any more.
A low gooseneck and heavily raked boom for ergonomics is something we considered, but felt it was too radical. It would allow for a low stump with substantial lowers though.
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I don't understand why you would need a compression strut going forwards to the stem. Surely the solid lowers will be just as happy working in tension and compression.
Thanks. Agreed. I had seen this solution on other types of boats though.
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Hi Doug,
A low boom has got to be better aerodynamically, but we felt ergonomics trumped that concern. After we had Aquamarina, with a book 1.1m from the deck, we started to really value a high boom.
Atum has 1m from the deck to the bottom of the gooseneck fitting, which is a bit above the bottom of the boom. Antidote is 0.95m.
Atum has tension struts as solid lowers, with a very visible backward kink at gooseneck level. We did not have the problems of the jib catching etc, but it is easy to understand how this could have occurred, esp if we has increased the rake any more.
A low gooseneck and heavily raked boom for ergonomics is something we considered, but felt it was too radical. It would allow for a low stump with substantial lowers though.
Thanks for the detail, very helpful and I know I am asking some basic questions...would be a lot easier if I could see some boats!
I think I am going for a long stump, in terms of rake what should I be looking for?
Doug
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I don't understand why you would need a compression strut going forwards to the stem. Surely the solid lowers will be just as happy working in tension and compression.
Thanks. Agreed. I had seen this solution on other types of boats though.
The reason that some boats put solid lowers and a fwd strut is to get a fully triangulated stump-strouds-forestay combo. As there is a lot of depth to the triangles the structure becomes very stiff so you can build the bits lighter.
Without a forward strut the stump needs to be angled back further than the mast so that the rig tension is pressing it down pulls the top of the stump back approx 80 degres from the horizontal. If you are going to have a standard kicker (and it is worth building the structure for one as a backup for when the gnav breaks) then the fwd load on the gooseneck from full kicker needs to be taken into account.
If you have no stump you have to build your hull-wing structure strong and stiff enough to take all the rig loads. If you build a stump with solid lowers that due to the geometry are sometimes in compression and sometimes in tension, then you still need to build enough strength/stiffess into you hull structure to take all the rig loads.
The question to ask yourself is: Will the stump structure take enough of the rig loads to let you make the shroud bulkhead and wings and bridge deck or foredeck lighter than they would be with no stump and is the difference more than the additional weight of the stump structure?
Other questions to ponder are;
What is the windage of solid lowers, compared to wire?
How much does 1m of mast weigh and how big a difference will this make to the all up sailng weight?
Do I ever want to double stack the boat or to ship it to a different country in a container? Will a stump cause issues with doing this?
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Some things I partially understand and some things I don't:
1. Why would a mast stump with solid lowers need to be any more raked than a mast with wire?
I'm imagining a free force diagram with rig tension loads coming down the mast and acting vertically and a forwards horizontal load on the gooseneck.
Diagram attached.
Where there is both tension and compression forces on one solid lower I don't know which one will be bigger and how this balances out.
Carbon is stronger in tension than in compression, right? So as long as they are strong enough to take the compression loads they will easily be strong enough to handle the tension.
No engineering from me, just logic. Are they mutually exclusive?
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Stu your diagram and logic look about right, logic and engineering are not mutually exclusive, you just need to be careful when you simplify things to keep the important things and get rid of the unimportant.(hopefully I am doing this but I could be wrong)
To simplify the analysis I think it is best think about the joints between sections of the stump as pinned joints i.e. they will flex also think about the hull being very flexible.
The simplest is a boat with no stump and a perfectly straight mast , when you put the rig tension on the sides of the boat will flex up and in slightly. As this happens the distance from the shroud points to the gooseneck will reduce. If you had solid lowers, then the gooseneck would be pushed forward.
With this setup the only additional stiffness that the stump provides for the boat comes from the joints between the lowers and the stump (very little) and the stump to hull and spine connection. If the stump is about 1m from the deck connection to the gooseneck, then it either needs to be a large diameter, or very heavy to give you enough stiffness to make a difference.
Now think about having the stump angled back a long way, the rig tension puts the solid lowers in compression, and they press down at the shroud points forcing the sides of the boat down and out, this balances the up and in from the shrouds, and the boat is stiffer. The kicker loads reduce the effectiveness of this which is why the stump needs to be angled back further than you might think, and calculating the best angle would be extremely complex.
If you are using the stump to make the boat stiffer, then for it to be a gain you need to get back the of the extra weight of the stump and lowers back by making other bits lighter.
To summarise
No Stump ==> Bulkheads need to resist all rig loads
Free standing stump ==> Bulkheads need to resist all rig loads minus stiffness gained from stump
Stump with solid lowers that go into tension ==> Bulkheads need to resist all rig loads minus stiffness gained from stump and tiny bit from joints.
Stump with solid lowers that are always in compression ==>Bulkheads need to resist all rig loads minus stiffness gained from stump and minus compression of lowers acting at shroud points and a tiny bit from the joints.
It is worth noting that when you use a stump you get stiffness from the stump to hull joint, however you lose stiffness from the mast below gooseneck to mast above gooseneck joint.
Carbon is stronger in tension than compression but the stump to lowers joint, and lowers to hull joint is complex, can you be sure to get the full benefit of carbon's strength if the fibres are not lined up properly through the joint. There have been a lot of broken gantries because joining small tubes together at acute angles is difficult to do.
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A low boom has got to be better aerodynamically,
I don't believe that any practical boom height closes the gap sufficiently that it has an end plate effect (need to be inches at best I reckon), so I think you cn ignore that particular factor.
Higher is more heeling moment, but also more wind because of wind sheer, goodness knows what the best tradeoff is.
Therefeore *I* (for what little my opinion is worth) think that main/jib interaction is the main argument for a lower boom, but there is more than one way to skin that cat. I find Bethwaite's arguments for the mast cuff thing on the 9ers sufficiently compelling that I had one made for the Canoe, included in the meaured area, but must confess that I very rarely get round to rigging it. Its a suprisingy difficult thing to get right and convenient to rig. I bet the Bethwaites went through a few prototypes, and whilst their solution is a good compromise for a one design I'm sure it could be done better. If I had sailmaking gear/skills its something I think/hope I would play with a lot to get right.
To my unskilled eyes a number of the 2005 rules rigs look like too much rag crammed onto too little spar: it wouldn't suprise me if the last few percents of sail area are of minimal benefit on some boats, but I lack expertise... Its also suprising how little difference sail area makes to boat speed if you look at relative handicaps of otherwse similar boats...
Another reason for over-raking the stump is the practical one of making it easier to get the kicker anchor pivot point in the right plane. Assuming a tension kicker it also means that the mast compression is opposing the kicker push: if both mast compression and kicker loads are pushing the top of the stump forward...
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Just a quick question. Does anyone use a stump and not have the goose-neck on the stump?
I think the jib/main interaction is more important than it is usual given in comparison to mast height, particularly in lower wind speeds and high aspect ratio sail plans. One Javelin has its boom around 250mm lower than any other and due to the rules the mast height is also lower by 250mm and it was particularly fast in lower wind speeds compared to other hulls of the same design.
Doug, have you meet Rob Fordyce who is up in Dubai?
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Just a quick question. Does anyone use a stump and not have the goose-neck on the stump?
The E5s use a stump of sorts with the gooseneck on the mast but it is pretty low (almost deck level) so more of a mast step. As a consiquence they still have wire lowers.
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The stumped boats I can think of:
Atum Bom
Mango Jam
Suicide Blonde
Halo Jones
Loco Perro
all have the gooseneck on the stump.
Dangerous Beans has a highish complete foredeck and has a low gooseneck only about 300mm above that.
What are you thinking?
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Nautilus Pompilus has a stump, and i think the gooseneck is on the mast just above where the stump ends, but i will check on saturday, this is on a 97 rig
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Am i right in saying that Loco has no lowers.
Phil A is correct in saying that solid lowers in compression reduces the loads on the bulkheads and hull structure however I am not sure that you can save much weight from the main bulkheads under the mast/shrouds. E-numbers bulkheads were all 8m foam with 1 layer of weave on one side and a layer of biax on the other.
There is a saving to the boat's all up weight because the solid lowers and stump of a stumped boat can be counted as a part of the hull weight where as the lower m of the mast and the wire lowers of a non stumped boat can't.
We didn't go for the stump because of the practical problems of getting two boats into a single garage.
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No lowers when it was built. It had higher's to the GNAV goose neck.
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Loco has no lowers, the gooseneck is on the stump at about 950mm off the floor. But she does have a high foredeck to support the stump, also D2's that join the mast just below lower spreaders. Loco also has a GNAV like a 29er instead of a kicker.
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Fuzzy has a stump. The king post exploded and the easiest way to get to max height (I was about 700mm under) was to drop in a stump and have solid lowers. The GN is on the stump but I might be putting a detachable GN on the mast for my smaller Fyfe main. From memory it's about 350mm shorter in the luff and boom is going set properly weired. It's going to be lovley to sail in breeze with that much room!
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Fuzzy has a stump. The king post exploded and the easiest way to get to max height (I was about 700mm under) was to drop in a stump and have solid lowers. The GN is on the stump but I might be putting a detachable GN on the mast for my smaller Fyfe main. From memory it's about 350mm shorter in the luff and boom is going set properly weired. It's going to be lovley to sail in breeze with that much room!
Thanks for the info and the picture. Can you tell me how high the GN is from the deck?
Doug
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Just a quick question. Does anyone use a stump and not have the goose-neck on the stump?
I think the jib/main interaction is more important than it is usual given in comparison to mast height, particularly in lower wind speeds and high aspect ratio sail plans. One Javelin has its boom around 250mm lower than any other and due to the rules the mast height is also lower by 250mm and it was particularly fast in lower wind speeds compared to other hulls of the same design.
Doug, have you meet Rob Fordyce who is up in Dubai?
Rob had borrowed my V pump for the moth worlds and brought it back last weekend. It was because of the discussions with Rob that got me thinking and going on the forum re stump. BTW his old boat just won the Javelin Nationals! Rob has offered to help me finish the build!
Doug
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It's going to be lovley to sail in breeze with that much room!
On Taking Liberties the boom was 1.2m above the deck as that only had a small main on a full height mast. As you say Ross, it was very comfortable to sail with!
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What are you thinking?
Just curious more than anything as the trade-off is a little different with the hull, false-floor height and foredeck (or lack of) proportions are different to what you might see locally. In 12s/Rs there is usually no false-floor or it is very low and the hulls are quite depth so the stump is freestanding with the goose-neck always on the stump. This allows you to quickly change a rig if the wind strength changes as well as taking the forward loads on the boom due to the vang out of the mast reducing the bending. Javelins only have a stump if they are deck stepping the mast to reduce the buckling length of the mast and to include the part of the mast that is replaced by the stump in the hull weight to reduce overall sailing weight. In this case the goose-neck is always on the mast.
Rob had borrowed my V pump for the moth worlds and brought it back last weekend. It was because of the discussions with Rob that got me thinking and going on the forum re stump. BTW his old boat just won the Javelin Nationals! Rob has offered to help me finish the build!
It was Rob's Javelin I was talking about with the shorter mast than usual. If you hadn't meet Rob I was going to suggest you track him down and have a talk with him :)
David
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Got the carbon on the bottom of the crew deck and had a trial fit.
Will look to get the mast mandrel this afternoon....helping sailability this morning!
Trying to add some pictures but cannot manage to do it...changed from last time? Any help on how to do this now qould be appreciated. I press the insert image button and it adds some HTML code but no dialogue box for browsing, etc.
Doug
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Doug, the insert image button is for linking to images that are currently on the web. If you want to upload an image to the site you have to click on the "Additional Options" link below and that gives you the dialog to browse for pictures on your PC.
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I thought that was the way to add them but this option to browse is not turning up as an option!
Doug
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Just been out and bought a mandrel for stump... and mast!
Doug
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Hi,
Had a go at building the mast stump today. Pump on all afternoon and evening, Will see how it looks in the morning.
Planning to go for a long stump that has the GN at the top. Solid lowers.
Will update with some photos when I can.
Thanks,
Doug
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Good to hear a stump is on the way. It really is good to see a build coming along. Please can you post photos when you can? I am keen to see as many builds as I can before mine gets underway as there is limited info on post '05 builds on the site. Whatever you post would be a big help to all of us.
On a side note, it has been a long time coming but my build is getting going. I now know a lot more and have saved a lot of money by being patient. Racks and spars have been pretty much free! Foils have been purchased from a nice I14 owner. Degree ends 4th June, shame it isnt the 4th July, would be appropriate really! After that it will be Thunderbirds are go! Sorry to take over your thread but I thought news of another build would be a good thing.
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Some pics. Had to use my Blackberry as still have not found my camera battery charger :-\
I have levelled off the bulkheads and topsides. I spent quite a lot of time fitting the foam for the crew deck and then have carboned the underneath on the garage floor......ready to be fitted once I have the stump glued in.
I am not in Dubai at the moment and hope to make some more progress this weekend.
Doug
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Good work!
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Mast stump finished ;D
Can now get the crew deck fitted.
Travelling again but should do it in the next couple of weeks.
Thanks for all the support.
Doug
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Thinking of the next few jobs!
I have started making the rudder. Andy P design but I am going to add a t-foil half way up, I14 style.
Planning the racks and the serious business of the bowsprit, boom and mast! Once the crew deck is on I will begin the filling and fairing of the hull.
Doug
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Good work!
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I made the tube for the snout that the bow sprit slides through on the inboard end of the bow sprit it'self. Just make sure it is not a tight fit. You need this short tube to finish off the bow and hence the hull.
For the racks I was advised to line up the rack tubes so that they point at the level of the top of the bow. if you turned the boat upside down it would sit on the length of the racks and the bow. This is meant to make the asthetics of the boat look right.
Failing this attempt to get the racks parralell. I think we were within 5mm of this in all aspects.
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Thanks for the advice. I am really looking forward to getting the racks completed and on the boat. We sail over the winter here and so the season starts in September and this is the target!
Thinking of sails and also fitting out!
Doug
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Depending on the space in your workshop it may be best to leave the longtitudinal rack tubes till the end of your build, it is much eisier to get in to work on the cockpit and bottom of the boat if they are out of the way, and the boat takes up much less space.
I will also echo Phil's comment about lining up the racks, they can look very different when on the water compared with on shore, and the slightest mismatch becomes obvious.
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Hmmmm
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Depending on the space in your workshop it may be best to leave the longtitudinal rack tubes till the end of your build, it is much eisier to get in to work on the cockpit and bottom of the boat if they are out of the way, and the boat takes up much less space.
I will also echo Phil's comment about lining up the racks, they can look very different when on the water compared with on shore, and the slightest mismatch becomes obvious.
Good idea and thanks. ;)
Travelling for a week and a bit, both Europe and then Saudi Arabia. I have been making progress on fitting the mast stum this morning and so should get that in once I have returned.
It is getting very hot here!
Doug
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Well remembered Phil I tried to leave fixing the actual rack tubes until all the other structure was complete so I could get round the boat. I still ended up fitting them too early and had to cope with the 450mm of available space around each side of the boat whilst doing the fairing.
Since I bought my rack tubes and they were really shiny I left the packaging on them except where they bonded to the beams. This protected the racks until we had finished painting. I would reccomend taping polythene around them if you make your own to save accidental spills of paint, resin and accidental damage from moving the boat around.
No offence meant Roland. EJ still looks great.
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Well remembered Phil I tried to leave fixing the actual rack tubes until all the other structure was complete so I could get round the boat. I still ended up fitting them too early and had to cope with the 450mm of available space around each side of the boat whilst doing the fairing.
Since I bought my rack tubes and they were really shiny I left the packaging on them except where they bonded to the beams. This protected the racks until we had finished painting. I would reccomend taping polythene around them if you make your own to save accidental spills of paint, resin and accidental damage from moving the boat around.
No offence meant Roland. EJ still looks great.
Will do. I have a couple of days before going off to Saudi and so hope to make more progress.
Had the last day of saiing yesterday and went out for the day on a yacht. 12knots. Glorious weather. ;D
Doug
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Mast stump now in place and so can fit the crew deck.
Doug
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Hi,
I have been travelling for many weeks now but just had a weekend in Dubai. Got the crew deck fitted. ;D
I am interested in getting hold of the bowsprit bearing. Any thoughts on where to go?
Thanks,
Doug
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A couple of pics of yesterday's action :o
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Hi,
I have been travelling for many weeks now but just had a weekend in Dubai. Got the crew deck fitted. ;D
I am interested in getting hold of the bowsprit bearing. Any thoughts on where to go?
Thanks,
Doug
A lot of people go for a tapered carbon tube matched to the bowsprit, in theory when the pole is fully out the point loads are lower. The taper on the pole needs to be very exaxt, if you have a slightly bumpy home made pole, it can jam.
If you want some low friction bearings then you can use bits of a nylon chopping board, just cut a strip off and warm in boiling water to bend it to fit. They can be held in place with fillets of epoxy.
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I have a set of pole bearings and inboard and out board pole end caps. CNC machined from acetal, used on Bdagers, Subtle and Antidote. If you need some dimensions send me a mail.
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Hi,
A few pics. Working on the racks and finishing off the rudder.
It is very hot!
Doug
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Hi,
I have now made the four rack supports. Layup was 4 * 300gpm then 0-90 300gpm biax then weave to finish.
I am wondering about the bonding to the gunwhales. I was thinking of using some unidirectional and tying them in place. Other thought is that I make a cup fitting using some fo the spare bulkhead material to rest them on. Perhaps a combination of both of these?
(I am off travelling for the next week of so....then will look to get these fitted and then start to fair off the hull. Still need to finish off the rudder!)
Thanks,
Doug
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On the E5 we bonded the High density foam rack supports on the gunnels and then laminated a couple of layers of uni and 1 layer of weave down the inside skin of the hull. On the outside we put 1 layer of weave. The beams them selves were also connected to the hull skin by long strips of uni that went over the rack beam and the supports. The clever bit was that this was down before the deck was put on. The beams were removed leaving the support and a hoop of carbon uni over the top. See photo attached.
deck was then put on and beams slotted into position.
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Phil,
Thanks. It is really good to see a picture. ;D I have the deck on but I think can copy your approach as the deck is short of the top of the gunwhale.
I was not thinking of raising the gunwhale with a support. I can lower the inboard end to get a minimal inclination on the outboard end of the rack. (I am proposing to have the racks point to the bow.) I was wondering about your thinking about the supports?
Thanks,
Doug
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Dont u need tje racks fairly high to
let the spinnaker chute under?????
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John,
Thanks. Presumably not that tall at that point? Perhaps the pole end will be larger?
Other than that I presume no reason to make the racks higher than they need to be?
Thanks,
Doug
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Apparently you would be surprised at the increase in friction, im sure phil kitk will elaborate, also durely you need the racks high enough to clear spray????
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It is difficult to know with a new hull shape...
Atum's racks were a bit high for ergonomics, and in the design process Antidotes ended up 150mm lower, but those were a bit low, so E numbers are probably 40-50mm higher than Antidote's. Too low = getting knocked off the wire by waves when beating in breeze, and the spray battering the racks when going downhill, especially when the boat is overtrimmed (ie bow high) in waves and you are getting airtime. 50mm can make a big difference to both of these problems.
However the major concern is probably ergonomics.
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Hi,
Thanks for the feedback. I think I will have a trial fit of the rack supports and take some pictures and measurements and post them on the forum. And then ask and see if it makes sense!
Back home tomorrow evening and able to work over the weekend and so should make good progress.
Doug
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Hi,
Had a good weekend working on the boat. Completed the rack supports and made both of the compression struts. ;D
I have decided to elevate the racks up by 40mm and so have retrospectively added supports onto the gunwhales. Not finished yet but have put basic structure in place. Picture shows the current status. I am travelling this week but should be back on Wednesday or Thursday.
Doug
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Hi,
Heading back to Dubai and so will have a few days to make progress.
I will get the rack supports on and make progress on the rudder and tiller.
I will also start fairing the hull.
In terms of painting, what is usually done and what is the painting process. I have not investigated but I presume I can hire a compressor, etc locally?
Because of the temperature I am planning an off white finish to everything, so racks, mast, etc.
Any advice appreciated.
I will post a picture with better lighting once I have the rack supports and compression struts in place!
Thanks, Doug
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A standard car paint is used on many boats in the uk (2 part). We went for spraying, but really try to sand back to almost black after the primer has it can add a suprising ammount of weight.
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I used normal 2 pack paint and applied it with a roller and then tipped of with a foam brush.
I got a pretty good finish, the underside could do with flatting back with wet and dry, but you need to do that with a spray job anyway.
I suspect the biggest problem you are going to have will be the pot life due to the temp, this may also make spraying difficult.
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yup!
just had some paint repairs done on one of our ships out there and the pot life of some paints were down to 30 minutes, max overcoating time was 2 hours.
Check humidity limits for the paint your using. Humidity is likely highest in early evening but you probably know this already.
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Hi, Thanks. I will investigate what I can buy and come back to check. In terms of preparation i should use the primer and then top coat and can use this on all parts of the boat?
Doug
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Hi,
I have fitted some rack supports. The height of the gunwhale is 390mm and I have raised that by a further 50mm. I was wondering if this looked OK?
Pictures attached. I have added one from the bow. I am also keen to make sure that there is the ability to trapze directly from the hull...maybe I need to keep the rack support flat to help that?
I am ready to finish the supports and then put some uni around the top of the gunwhales.
Thanks,
Doug
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I can't remember the exact height of racks at this point on E-numbers and would have to measure the boat.
It sounds similar though. E-numbers is at the sailing club at present but I will be bringing her home on Sunday to check her over before the nationals. I can take some measurements then.
The issue that Will was talking about with respect to the beams catching spray was mostly related to the aft beams. These on E-numbers do not catch spray and are some 50mm higher that on Antidote.
John made a point about reasonable space below the forward beam/wing for the spinnaker chute. We have 115mm between our deck and the under side of the beam at centre and 65mm and hull side. This has proved to be a little low especially when we have the pole coming through the same gap and everthing wants to be near the mast stump. Another 20mm clearance would help a lot.
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Thanks, having some measurements would be very helpful. I presume the reason the rear racks as the boat is sailed upwind bow up?
The transom measurements are 300mm to the top of the gunwhale and then I have an ear that raises the rack bottom support to 350mm. The rack supports are angled upwards and so the outboard end higher than this.
In terms of the front rack supports I plan to have 120mm at the mast stump and higher at the gunwhale. So I think enough.
Thanks,
Doug
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Doug,
it sounds about right. The rear racks on the E5 are sloped up a bit so are higher outboard than at the gunnel. The forward racks are sloped less because the gunnel like yours is higher than at the stern.
I can trapeeze off the gunnel and the racks quite comfortably in E-numbers. i will make some measurements on the weekend.
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Phil,
Thanks.
Doug
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I have been working on the rudder and have routed the dimensions onto the blank. I am travelling again for a few days and will be working on the boat again on Thursday.
Doug
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The dimensions you want from E-Numbers are:
height of underside of aft beams from hull on centreline: 350mm
height of underside of fwd beams from hull on centreline: 485mm
height of top of racks is about 580mm all round.
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The dimensions you want from E-Numbers are:
height of underside of aft beams from hull on centreline: 350mm
height of underside of fwd beams from hull on centreline: 485mm
height of top of racks is about 580mm all round.
Thanks, I am back tomorrow evening and will keep working over the weekend.
Doug
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The fwd beams are plenty high enough and do not catch spray. The tension strutts underneath occasionally catch spray when sailing in step chop. They are about 200mm below the beams where they meet the hull. The aft beams clear any spray by about 20-40mm.
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The fwd beams are plenty high enough and do not catch spray. The tension strutts underneath occasionally catch spray when sailing in step chop. They are about 200mm below the beams where they meet the hull. The aft beams clear any spray by about 20-40mm.
Thanks, I measured the boat and all OK. ;D
Doug
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Hi,
I know you are all getting ready for the Nationals and I hope you all have a good time. I am continuing to work on the boat and do some travelling!
I am now turning my attention to spars and planning the mast, boom and bowsprit build. I was wondering if there were some measurements and spreader heights, etc I could use to help me plan the layup? Looking to use EJ cookbook.
Thanks,
Doug
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Hi,
I hope you all had a good nationals. I have a pic of the boat at the moment. I have started filling and fairing the hull. Rudder and foil also on the go. :)
I am preparing for the mast, boom and bowsprit!
Thanks,
Doug
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Good stuff Doug!
It certainly looks like it is coming along.
From experience the triangular webs supporting the gunnels may get some abuse during the enevitable capsize or the ocasional slip and fall. I would ensure that you have at least 2 layers of material over the foam core to avoid dents in them.
Alternatively you could bond and laminate carbon plates on to the triangles to mount fittings.
Phil
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Good stuff Doug!
It certainly looks like it is coming along.
From experience the triangular webs supporting the gunnels may get some abuse during the enevitable capsize or the ocasional slip and fall. I would ensure that you have at least 2 layers of material over the foam core to avoid dents in them.
Alternatively you could bond and laminate carbon plates on to the triangles to mount fittings.
Phil
Thanks, I will add some more protection.
(These are actually the bulkheads coming through the crew deck.)
I have built the compression struts and need to fit them.
Plenty to do but getting there. My wife even said that it looked like a boat!
(I am looking for it to cool down...over 40 a lot of the time and September is also humid!)
Doug
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Hi,
Back in the saddle!
Just had a month in Saudi conducting trials of equipment and systems and with organising that and moving villas in Dubai I have not done much in the last 8 weeks. :'(
Have been fairing the hull today and planning the rack tubes.
Rudder coming along nicely.
Also just bought a Beneteau 44.7 and will have my hands full in the new year. ;D
Doug
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Sounds good! Any pics?
Eternally envious,
Ross
;D
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I am away in Saudi at the moment but will get back to work on thursday!
Started on the bowsprit.
Picture of the 44.7. She is coming across the med at the moment. Arrive Dubai in Jan. Need to get the Cherub finished!
Doug
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I was looking for some advice as now thinking about the hull painting.
Because of the severe temperatures here I was thinking of painting all of the boat including the spars. The colour to be off white. Will I get into trouble as the spars are moving and the paint will come off? I know that sun protection can be provided by using an additive to the resin but I am keen not to have the spars black.
Thanks,
Doug
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There are quite a few masts that have been painted, you should be OK. If you varnished your mast the varnish would have to flex just as much as a paint covering would.
Two pack paint is much tougher than one pack so I would probably go for that. Check the specs and product description to look for the more flexible ones.
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Will I get into trouble as the spars are moving and the paint will come off?
I've used some odd stuff in the past (even aerosol car paint) and movement has *never* been a problem. Friction/abrasion from ropes rubbing on the spar either in transit or in the boat park on the other hand can be. I'd use whatever brand of two pot polyurethane is handiest and consider it the least of my worries.
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Thanks for the advice. I plan to go for a 2 part car paint and so should be ok.
Doug
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Hi,
I had a good weekend working on the boat. I am still fairing, made and fitted the tube for the bowsprit in the bow and finished the racks.
I am away again and should be back in Dubai for one more day before coming back to the UK for Christmas. ;D
I have the sail number, 3211, and will pick up deck gear when i am in the UK.
I need help in getting hold of some of the more specialised pieces. An example is the mast track. I will create a list of what I need and ask for help. (I would really like to take all the parts back to Dubai when I go back in January.)
Thanks,
Doug
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Thats fantastic Doug, I am sure plenty of people will be able to help you source your kit (I'm not the best man for the job) - where will you be based while you are in the UK ?
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That will be great.
I will be in Lymington.
I will take some pics on Thursday.
Doug
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Born Slippy has a source for mast track and will be able to tell youthe exact type of Plexus to use to glue it on.
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Thanks Phil, yes there is a good supply route for mast accessories available for Cherrubists via BGM - I'd missed this one. Have PM'ed Doug.
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Hi, made the bowsprit and racks ready to go on. ....looking like a boat :)
I am travelling for a couple of days but will get back to Dubai and take some pics.
I am interesting in a set of used sails. Not too worried about how used. I plan to buy a set but want to understand about the rig and also want to make sure the mast doesn't break and put a bit hole in a new mainsail!
I am back in the UK over Christmas and if anyone has a main/ jib for sail...I think I have an RS800 spinnaker located.
Doug
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Fairing down the second half of the hull and finally got around to the rudder. Should be finishing it this morning.
temperature is really pleasant here now, 24 yesterday. I am not looking forward to the weather in the UK (if I manage to get back on Friday that it :-\).
Doug
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Hi, have continued with the fairing!
Working on the rudder and planning to make the foil.
Some pics. Not so good as on my phone....wife has taken the camera to the UK already!
One of the pics shows the bowsprit going off with the vacuum pump and then me with it. The other one shows the boat on its side so i can fair the hull.
Doug
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Wow, thats amazing .... shorts !!!
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26 degrees today ;D
Mind you the summers are harsh.....not much sailing....45 degrees+
Doug
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I thought it cooled off in the evenings and got windy?
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In the summer it cools down to 30+ in the evenings or overnight. Really only breeze here is a sea breeze and in the summer with the humidity it can just be a mill pond all day (literally some days it is like a sea fog).
There are some light breezes around 1-2 knts that either add or subtract from the normal sea breeze.
Sailing in the afternoon. From 1 to 4 pm the best time. Usually more than 8knts, never more than 14.
Maybe 3 or 4 times a year a Shamal comes that can be 30 or 40knts. Always from Iran straight onshore.
It is wierd being able to rely on the weather being the same every day. Something like 330 days of sunshine a year here.
Water temperature means that shorts and t shirt do for most of the time. I dive and wear a 3mm shorty in the winter. 60 feet down in shorts and t shirt!
Doug
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Picture of the boat from this morning on the way to the airport.
Daggerboard, rudder, rack tubes and bowsprit done ;D
Paint job, boom and mast the big jobs left :o
Hopefully pick up hardware and old sails in the UK.
Thanks for all the help and tips this year. Have a great Christmas everyone.
Doug
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I am thinking about the mast design. In terms of rigging I am thinking of starting with a C-Tech style.
I have been measuring the boat and these are my current thoughts:
Mast bottom to deck 300mm
Deck to gooseneck 920mm
Gooseneck to lowers 80mm
Lowers to 1 spreaders 2100mm
1 spreaders to 2 spreaders 1900mm
2 spreaders to mast head 1800mm
This gives a total mast height of 7100mm so the maximum allowed.
Luff length is 5880mm.
Any thoughts or comments welcome. If the above is OK I will think about the spreader deflection.
Making the mast sometime in January.
Doug
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Doug the mast height of 7.1 meters is measured from the bottom of the hull not just the length of mast. We had a new c-tech mast recently if you wish I could get the measurements from that in the next day or two.
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Doug the mast height of 7.1 meters is measured from the bottom of the hull not just the length of mast. We had a new c-tech mast recently if you wish I could get the measurements from that in the next day or two.
I will make some more measurements to make sure. It would great to have a comparison. Thanks a lot.
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Working on the boat the last couple of days. Continuing hull fairing :(
Making the rudder stock and tiller.
Once I have the deck faired I can put the racks on....looking forward to that day ;D
I will put some photos on in the next couple of days.
Doug
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I have been busy with the big boat arriving and getting her into race trim. Also changing jobs has not helped.
The boat is almost done. Racks and jib track on. I will organise a paint job for the week after next when I am back in Dubai.
I have decided to buy a mast and boom and so have started the last major job; the t- foil.
I am getting there and looking forward to going sailing!
Doug
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Hi,
I am starting on the fitting out and wondered where I could get some small diameter glass fibre tube that i can use to sheathe the pintle and for the rudder gantry hinge?
I am thinking of using 5mm stainless steel rod.
Thanks,
Doug
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I'd seriously recommend using 8mm stainless (someone will email the grade, but not a low one).
We've broken/bent a few on several boats T and without, the shear loading from drag on the t-foil makes this load much bigger. The gap between stock/support also needs to be as small as possible to reduce bending load in the pin.
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Use 8mm stainless pins for the rudder and the swivelling gantry.
Sea Sure 18-39 bushes for the rudder pin bearing, and the gantry ends. ( ie the moving parts )
Lock the pin to the rudder stock.
The boat end of the gantry can be moulded carbon + a 8mm bolt so it doesn't move.
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Thanks for that. I am planning the paint job this week. Making the carbon front plates today and putting fittings on.
Will take some pics once done!
Getting warm!
Took the big boat out racing last Friday. Good fun but very hot - 40oC :o
Doug
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I have always just greased the 8mm pin and wrapped some glass around it to make the bushing.
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Thanks for that. What thickness of the wall should I be looking for?
Doug
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Thanks for that. What thickness of the wall should I be looking for?
Doug
2-3mm any less than 2 and it will be hard to cut. I usually use a strip of glass tape and wrap around in a spiral pattern, this gives a range of thicnkesses at the ends.
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Boat end gantry pivots.
I cheated and used some carbon uni tube from a kite shop. 8mm id tube is a standard size. An peice of tube can be bogged in position on the supports on the transom and then overlayed with a mixture od weave and uni to knit into the boat structure. Once cured the tube was trimmed to length. I used off cuts of this tube on the gantry itself but aligned each pair of pivot tubes with a stainless bar. This ensures that the rudder pin will fit and the gantry will pivot around the same axis.
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Thanks for that. What thickness of the wall should I be looking for?
Doug
2-3mm any less than 2 and it will be hard to cut. I usually use a strip of glass tape and wrap around in a spiral pattern, this gives a range of thicnkesses at the ends.
Thanks for that I will try as an option. (Also getting bushes from Sea Sure.
Doug
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Boat end gantry pivots.
I cheated and used some carbon uni tube from a kite shop. 8mm id tube is a standard size. An peice of tube can be bogged in position on the supports on the transom and then overlayed with a mixture od weave and uni to knit into the boat structure. Once cured the tube was trimmed to length. I used off cuts of this tube on the gantry itself but aligned each pair of pivot tubes with a stainless bar. This ensures that the rudder pin will fit and the gantry will pivot around the same axis.
I am back in the UK for a couple of days....flying today....and will try to buy some.
Thanks, Doug
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On a similar theme, is there somewhere that I can order the 8mm bar from in the UK (I found somewhere I could get 5mm from in Dubai but have not been back to them on the 8mm)?
Thanks,
Doug
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http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6614699
This is a lower grade (303). This may be what we used, but I thought we used 316, which RS (Not THAT RS) seem to no longer have on their website.
There are A316 stainless rods, but only in imperial dias.
Will
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303 was the grade that broke lots. 316 is the grade we bought a job lot of and are now running out of (1 bent breakage due to failure of bottom plate on stock!).
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Looks like I should go for A316 then?
No made it to the UK and here until Saturday and so hope to get some delivered.
Doug
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I got some 316 at
http://www.metals4u.co.uk/detail.asp?cat_id=83&prd_id=1688
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I got some 316 at
http://www.metals4u.co.uk/detail.asp?cat_id=83&prd_id=1688
I had a look and bought some. Much better value than RS!
Thanks,
Doug
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Bushes and 8mm rod both delivered and so all ready to head back to Dubai.
I have a few days in Dubai next week and will get some photos on the web.
Doug
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Hi, a quick update...
starting to glue fittings on...should finish tomorrow.....boat should be painted on Wednesday ;D
Doug
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All fittings on.
Boat getting painted and looks a lot different :)
Going for white to reflect the sun.
Will take pictures tomorrow.
Working on the trolley.
Doug
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Some pics of the undercoat.
I am very pleased to be at this point! ;D
Doug
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You should be pleased Doug, it looks fantastic, and to have built it without the benefit of local boats to look at for reference is an impressive achievement, i look forward to the dubai open !
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Looks great and will look even better with the top coat on.
Hopefully not too far away from it's first sail.
All the best!
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You should be pleased Doug, it looks fantastic, and to have built it without the benefit of local boats to look at for reference is an impressive achievement, i look forward to the dubai open !
Thanks.....pics with the topcoat . I have deliberately made it all white to keep it cool......white moths only became available to sail in Dubai :o
The first sail will have to wait as i am away to india for a couple of weeks then Boston for maybe a month. I am taking the T-foil to India to finish there.
Mast, boom and sails will be on order next week. Everything else is done!
I also have a trolley and trailer....just been converting them today to fit a cherub.
Target July....24 months after starting to build the mould :-\
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Hi, final topcoat on and put boat on it's trolley. Took it outside and got some better pics.
Off to India tomorrow for a couple of weeks of work.
Looking forward to going sailing ;D
Thanks for all the help and support so far.
Doug
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Well done! What a beaut!
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amazingly vertical sides!
awesome looking, very mean
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well done. she looks great!
Now comes the fun bit learning to sail her.
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Whats the latest Doug ?
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Don't know how you're getting on so far Doug, but when I bought my first Cherub the guys at my club told me it would take 4 years to learn how to sail it properly. That was over 20 years ago and I'm still not quite there. But really that's the whole idea.
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Hi all,
Sorry to be away for so long. :'( Most of last year was a pain. I changed jobs and then was in the US for over 6 months. Just got back to Dubai last weekend and have been working on the boat again. Putting fititngs on. I am still travelling a lot and not in Dubai that much but with a push would like the get boat sailing in the next couple of months.
Put the hull in the water today at the yacht club and looks great.
Doug
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Here she is............
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It's barely scraping above freezing here and snow is everywhere...you're just making me jealous :O)
Looks absolutely brilliant though.
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Looking good Doug, the question is how we persuade you to bring it to Wales in the summer :)
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Hi,
Got back from the US last year only to find I am now spending all of my time in India!
Had last weekend working on the boat.....rudder and foil finished, rudder gantry and rudder stock also finished. Jib track on. Most of the cleats on. ;D. Measured boat so I can order mast and boom.
Too hot in Dubai and so plan to sail in September.
I have some pics of the current fit out and will look to post them. Thanks for all the support and really looking forward to going sailing. 8)