UK-Cherub Forum
Cherub Chat => Tech Chat => Topic started by: john_hamilton on April 21, 2010, 03:08:36 PM
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Well, i have just put a deposit down on a hull shell, rack tubes and deck from Andy P, so i guess its kind of then beginning of a new boat! fun times! me and digby will be following the kirks example of building, and have rack supports (old windsurf masts that will be beefed up a bit), foils (no t-foil made yet), a tiller and stock made all ready. just thought i would borrow a bit of forum space to document build aswell as to ask questions on how to do various things!
oh, a digby doesn't know we havefunding yet, hopefully it will be a good suprise!
yey!
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Well done! That is at least two new new boats on the go now.
Edit: I think Stu/Ross' boat may have been number 4 but I think that has stalled.
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We were No.5. I think Johns is No.6.
Quick count:
Antidote,
Usagi,
E-Numbers,
Exultant Jubilation,
Stu, myself and I,
and now John
<<Edit BS >>
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sorry i was just going from the forum, the last metion being the kirks boat as number 3, my misstake :0
edit: tthnaks whoever edited the name :)
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latest progrss, inner skin and side foam on the shell, being finished on wednesdayiash, then on with building the deck!
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Cool, Looks good John.
I bet you are quite excited at seeing your boat take shape.
Let us know when will be suitable to plan our get together. If you want we can do a lot of stuff before you get the shells if that fits your time better and plan a second session to fit stuff together.
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Action!
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ill let you know within the week phil, just trying to gety my head around revising in study leave at the moment, hard to keep willing.
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Understood.
Like all adults I will have to say concentrate on your revision and exams everything else can wait a little longer.
No pressure, just excited to see another boat taking shape and happy to help.
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John, I know the feeling. I 'm working for exams too. They are all over soon and then we can get on with building. I also have a stump sized bit of 600 mast for you. I will also have a load of carbon windsurf mast which you may be able to have some of for tillers and the like.
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sounds awesome rob,
just had my RE exam, basically 2 1/2 hours of writing bull.
only 22 exams to go
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7 exams left...... phil k i will try and ring you tonight, i am banned from working on the boat for the next two weeks untill exams are over, we will try and sort out>??? :S
PROGRESS
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Weapon!
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;D
im so exited haha
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I know how you feel, getting ours next friday!! ;D
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Wow that is impressively quick Simon. The female moulds just reduce the 'finishing' time of a boat so greatly. Have you decided on a colour scheme yet?!
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We think so ;)
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Ok John. I await your call. Good luck with the exams.
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ok, have just come back from a 350mile road trip to IOW to collect, awesome looking!!!
phil, are you available anytime in the week 12-18th July???#
also, has anyone got a spare 05 rules kite suitable for an E5, i.e. relatively high aspect ration/ flatish
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Good news - now a summer of sticky before hitting the wet stuff in time for the nationals.
Send a picture!
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Sorry John, That is a busy week for work. Also Thornbury regatta on the 17-18th.
Can we chat to go through the calander to see if there are some opportunities in the following week?
otherwise i may be able to do something in the second week of August 9th-13th after the ent nationals. sarah may also be able to help too.
The other way is to spend an evening making some of the bits and a day somewhere else sticking things together.
Where are you? if not so far from me it may be possible to do it this way. PM or call to discuss. ta.
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I am very envious, I am still waiting for something to get sticky with. Have you still got the white Hyde kite that came with Cheese? it is a new ex Daemon kite that was a bit flat for Cheese but should be good on an E5
ok, have just come back from a 350mile road trip to IOW to collect, awesome looking!!!
phil, are you available anytime in the week 12-18th July???#
also, has anyone got a spare 05 rules kite suitable for an E5, i.e. relatively high aspect ration/ flatish
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Where's the pics John? We are are also still waiting, role on sat 3rd July
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When you arrange a date, can we come and play boat building too please?
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ill have to ask my parents, but you probably can :)
ill keep u all updated, it all depends on how phil wants to do it of course
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It's up to you at the end of the day John and your parents (sponsors).
The more the merrier.
I'm offering my recent experience of E5 building to help you on the way and ensure you end up with a sound, light and competative boat.
We just need to fix a date and ensure that we have all the materials and consumables available.
Gantry mould and Pole mandrel required i think. Are these available Dave? If so can they find themselves a lift back to Bristol perhaps.
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Both are welcome to come via BGM and the Poole regatta?
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that would be good, but im not there :(
also, the boat has a name:
"anatidaephobia" - the fear that somewhere, somehow a duck is watching you!
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we laminated the bulkhead and spine panels on friday night over at the kirks, they have turned out very light and stiff, when cutting the spine panels today, me and digby wondered about the best way of connecting them together?
bog and a carbon layer?
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well me and my gran stuck the spine together today, we used the same carbon as the panels had, with a little reinforcement on the end bit of the join. to fill any gaps left by our dubious cutting yesterday, we used a mainly silica based bog to fill the gaps, then laminated each side. The process seems to have gone well, but we shall see how strong it is tommorrow. we are trying to help the curing along with some floodlights before we get a fan heater, pictures below
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Silica is mainly used as thikening agent. It should be combined with micro fibres/ balloons. Having said that, the backing plates on Antidote were all stuck down with just silica bog having run out of micro fibres/ balloons and none have come off yet (to my knowledge).
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Yes sorry, i assumed that everyone uses balloons anyway so didnt mention, oops
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An interesting thing that I learned about Colloidal Silica recently is that it can be used to make your resin tackier when it is wet, which is useful for odd shaped joints and if you have to laminate on an overhead surface.
What you need to do is measure out your resin, stir in a small amount of colloidal silica, and leave over night. When you want to laminate, just add the hardener and use as normal.
You can get the same effect by adding silica just before laminating, however to get the same effect you need to add more.
I tried it out on a repair recently, and it worked quite well.
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Very neat bulkheads John!
At present if you are doing laminating in the day time it probably dosen't need any additional heat. It may take a little longer to fully cure though.
I have mixed a bog of silica, resin and hardener and put a thin smear over any cured lamintae I wish to laminate new cloths on to. The tackiness ensures good contact and eradicates bubles and voids. It also helps you get all the edges of the new laminate down which avoids them pealing off in the future.
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You did well to keep Digby away from the Lwnmower - or is it currently doing 120 down the inside lane of the M1?
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he didnt quite manage to get his hands on that particular one, though he did go home with our other ride on lawnmower on a trailer to play with :)
soon to be seen driving along the motorway to scotland, exceeding the speed limit :D
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Looking good John. Have you decided to use those tube I gave you or will they just be mandrels? Hope the stump is long enough.
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the tube with the track on is hopefully going to be a stump, the spinnaker pole shaped one may be also used as a spinnaker pole, provided i can reinforce it enough
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If you're going to reinforce a tube, you might as well make a new one surley?
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it all depends........
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a very busy day today !!!!!
me and digby woke up at 9am, and cut out the remaining bulkheads, phil and sarah then arrived at 1030am, a mention must be given here to oscar the guinea pig who was an incredibly usefull aid to navigation to our often hard to find house, with Sarah's help of course!!!
the next 10 hours followed in a whirlwind of work...
by the end of day 1 we have:
1/ 75% fitted hull, deck and bulkheads (alot of sanding)
2/ made a mast stump from an old piece os Rs 800 mast (yet more sanding tho remove the track)
3/ laminated up some 2mm carbon plate for various uses (very strong)
4/ vac-bagged the tension struts (very clever mould - thanks phil)
5/ laminated both the forward and rear rack beams (some very good use of old drainpipe as mandrels)
6/ made a centre board casing
7/ phil jigsawed through the hull shell, accurately thankfully (sounded like it was going to break)
8/ learnt a huge deal
8/ destroyed at least 4 pairs of scissors
altogether, a very productive days work, pictures to follow :)
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John, Digby, Sarah and I have had a very productive 2 days. It is amazing how quickly things have come together. I will let John inform you all of the progress made today. i would just like to say the boys have worked really hard and learnt a lot of skills in laminating, fitting and most importantly measuring everything carefully. The tubes we made yesterday came out really well in fact as did everything.
Many thanks to John's mum for being such an excellent hoast and opening their house, garages and garden to us and feeding us very well.
All appreciated
I look forward to John's veiw of things and pictures.
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well today was brilliant, even if not quite as fun as yesterday, we have made excellent progress
we have got the bulkheads, spine, transom ears and rear beam supports fitted to the hull, just some filleting and carbon to do there....
all of out bits we made yesterday turned out brilliantly, with the rack beams exceptionally good :)
we learned a huge amount, thanks philand sarah a huge amount!!!!!
later this evening me and digby managed another hit after the kirks had left, it turns out that digby had managed to cut the mast stump perfectly and it was perfectely central, now bogged! We have also finalised the bog on the transom ears :) finally, we have sorted the centreboard casing and started the link between the spine and case :)
productive day!!!!!!
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edit: no pictures yet as my mums iphone is playing up!!!!!
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John,
I would work out the centreline on the deck before you add too many additional protusions. I suggest once you have marked the centreline on the deck, that you measure back from a datum mark at the bow to position the mast stump. Once you are happy with this measure back for the centreboard case sleave.
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Have done so phil!!!!! So far with case and stump etc added shell weighs 15.3kgs
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pictures are now up on 3209's boat page :)
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Looking good John any ideas on a colour scheme?
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this pretty much sums up how far i am
http://www.sailingsource.com/cherub/test/lib/exe/fetch.php/boats/3209-01072010_3jpg.jpg?cache=&w=900&h=675
regarding colour, i have'nt got the foggiest apart from its got to be individual
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Going for a box case. Is this because you haven't built the board yet or you want to play with different shapes?
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As i understand, both Daryll,
We used the same case concept and leant John the mould to save time and effort.
The box also allows for the unnexpected grounding damage without damage to the hull integrity and a complicated intrusive repair.
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Looks like they can't wait to start playing with it either, spotted on Digby's Facebook!
(http://sphotos.ak.fbcdn.net/hphotos-ak-ash2/hs347.ash2/62766_1194800805515_1693310633_364916_2951995_n.jpg)
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THE SUN! I remember that. Leeds is so very...gray.
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Any progress with the build?
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right, i have not been home for a month recently, so very little progress, and also no access to the forum :(
i have a question though: when im trying to fit my deck, i need to make holes for the rear rack beam supports, how best should i do this? i was going to use a dremel and cut upwards whilst the deck is on so i can get the holes in exactly the right place.
also, when finishing the fillets off with carbon, how much of an overlap is needed?
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Ok John,
You can use strips of carbon weave about 7cm wide. This should give about 25-30mm overlap either side of the fillet. Cut strips a little wider because they will fray when handled. I think we used about 10cm wide strips which were excesive in hindsight.
you should fit the rack supports first carbon them on to the hull. then place the deck over the mast stump and lower down on to the rack supports and jib track ends.
Then draw round the rack supports on the underside of the deck. Remove the deck and cut along the lines. The aft racks should sit above the deck level. I fited my aft racks first.
If you have a weekend or even a Friday/saturday I could come up and give you a hand.
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Ok John,
You can use strips of carbon weave about 7cm wide. This should give about 25-30mm overlap either side of the fillet. Cut strips a little wider because they will fray when handled. I think we used about 10cm wide strips which were excesive in hindsight.
10mm overlap to fibres is Ok if you are really neat.
Cut the strips on the bias ( ie at ±45° )
Then they don't fray at the edges
easier to stay bent around corners
twice as many fibres across the joints.
Plain weave is stiffer and better than twill which wobbles about and gets a mess / stretchy .
Also do it this way for gunwale joining etc.
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Andy's post makes good sense and I am grateful that he has shared this with us.
My experience with using +-45 degree strips was that I found this tricky. To avoid the strips getting narrower and longer you can wet them out on a strip of polythene and transfer the wetted out carbon to the joint on the polyethene. otherwise wet out in situe on the fillet. I find that this gives the carbon a choice of sticking to the brush/spreader or the boat.
If you can perfect this technique and handling thin strips of weave/twill weave you can save some weight and money.
Good luck!
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In regards to colour, how about this for inspiration!
http://www.google.com/m/search?site=images&gl=uk&client=ms-android-htc&source=mog&hl=en&aq=f&oq=&aqi=g4-k0d0t0&fkt=1309&fsdt=29265&q=white+with+red+stripe#i=47
Need to find.someone to.paint it, any ideas?
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Sorry meant this... http://www.moddedmustangs.com/wp-content/uploads/2007/05/white-red-stripe-gt500.jpg
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John's E5 is coming on. On the 20th we built a new pole and finished the internals of the hull on the 20th. With snow outside it was difficult to keep the garge warm enough for the resin. In the end we had to concentrate on warnming a smaller volume to achieve a good curing temperature by constructing a tent over the boat with polyethene sheeting.
the next day we got the pole off the mandrel using a tried and tested tug of war method with the pole/mandrel tied between too cars.. Attempt no. 1 had an unusual result that I manged to pull Nichola's car through the snow. Swapping over and letting nichola pull resulted in a successful extraction.
We then bonded the deck on.
All went well.
I'm sure that John's christmas will be filled with lots of sanding and fairing.
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Also we ordered deck hardware from Allen through Roland, which came the day after it was ordered, hence I have managed to get the gantry system done and dusted, just waiting for a spindle for twist grip, which will be made in college forge after term starts
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does anyone know a ballpark figure for shrouds, caps, d2s, etc....????
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Depends entirely on your mast and terminal choice.
If ordering an aussi mast I think it is generally suggested to get them to send the T's - then it is up to your local chandler for rates or call Welsh Harp (they and many others will make shrouds to the length of your choosing).
If you want basement prices then there is always the DIY method offered by BGM. The wire itself costs under £1 per m (I'm sure it is nearer 30p a m, but can't find the last receipt for stainless) and the terminations (eye and ferrel) are about 50p per end. We have no inclination to do T's though as that needs a bigger press (nasty holes in mast precious).
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have PM'd you roland.
now i have been fairly bored recently and have been looking through various skiff sailing books and have found that the optimum jib/main ratio is around 27/73, which equates to around 4.2m2/11.3m2 on a cherub. what has everyone else got?
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I was looking at the I14 website and interested that they go for a 'W' jib track to enable a jib overlap. I presume this would mean a larger jib than usual?
Doug
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now i have been fairly bored recently and have been looking through various skiff sailing books and have found that the optimum jib/main ratio is around 27/73, which equates to around 4.2m2/11.3m2 on a cherub.
Interesting, where did you read that? I think Kevin believe's in something a bit more weighted towards the jib because it gives a better drive/heel ratio. However, a bigger main gives a better drive/drag ratio. So the optimum depends on how heavy you are and how much wind you're sailing in.
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now i have been fairly bored recently and have been looking through various skiff sailing books and have found that the optimum jib/main ratio is around 27/73, which equates to around 4.2m2/11.3m2 on a cherub.
Interesting, where did you read that? I think Kevin believe's in something a bit more weighted towards the jib because it gives a better drive/heel ratio. However, a bigger main gives a better drive/drag ratio. So the optimum depends on how heavy you are and how much wind you're sailing in.
Kevin and Stu are on the right track - Theres not really any optimum ratio untill you start to factor in average wind stengths, crew weights etc... Ive no idea what the general trend is in the class but Ive got a feeling that would leave you on the far end with an unusualy small jib/large main.
Doug - the W jib track is very neat and does give you room for a slightly larger jib - but its not a huge difference. Phil has a W track on Pocket rocket and may be along to comment on exactly how much you can gain that way.
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Stu I was reading frank.bethwaites most recent book, those.numbers are based on a light-crewed 12 do I thought it may be similar x
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Ratio also depends on the total sail area -
With a small sail area ( ie 97 rules ) it was better to have a big main and small jib ( shiny beast was only 3m² jib, + so had a bigger mainsail than everyone else ) more like 25:75.
The 05 rules allowed much more sail, but putting all the extra area on the main was not a good idea, hence a lot of track moving, adding big jib roaches etc to try and get the jib bigger, and keep the main at a managable size. I believe that the newer boats (built rather than converted to the new rules ) have masts further aft, ~ 5.5m² jibs, and the rigs are slightly undersize ( by ~ 0.5m² ) so about 35:65
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the W jib track is very neat and does give you room for a slightly larger jib -
First W track I ever saw was on Tim Dean's Fizzy Shark, think that was long before any 14s... The trouble with paying too much attention to Bethwaite's recomended ratio is that its for a boat with unrestricted mast height. The very aggressive mast height limit in the 2005 rules means you have a lot of tradeoffs to make.
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I think quite a lot of thought was put in to a W track on Shiney Beast. IIRC the conclusion was that the track has a minimum radius that the car can get around and with the length of the track on Cherubs it ends up with a bit of a flat spot in the middle rather than a full on W.
Perhaps the next step is to find a traveller car system that can cope with smaller radius turns?
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I put a W track on Pocket Rocket, and it works OK, it gets the track about level with the mast, the trouble is that it is a very tight bend radius for the track so they often break them when they are bending them, and they end up slightly notchie.
I have thought about making a track out of a carbon tube moulded to the right shape, and then run a block along the track.
Not sure of the best mould material.
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E-Numbers Jib came in at about 4.7m^2. We weren't to fussed about reaching maximum area so didn't go for a huge roach on the jib. The overlap is enough for the top jib baten to get caught on the mast in light airs escpecially when sailing downwind when there is little pressure in the jib. As has been said above there are a lot of trade offs. Our main is only about 10m^2. We opted to go for an efficient shape instead of the max area. For our weight this has proved to be pleanty of power across the wind range. More area in the main requires longer battens and most of the area ends up higher up in the sail. Controling that area in a balance of mast tip stiffness, sail shape and cap shroud tension with the addition of cunnigham on the water. There are a number of examples where too much main sail roach or a poor match between mast and sail has led to too a rig that doens't work.
Our approach was to rig the boat with the correct rake and mast bend and ask the sail maker to make a set of sails to fit. if you give your sailmaker a clear direction on how you would like to trade off between power, efficiency, weight, ease of use height of boom, he will be able to give you a better set of sails.
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Allen quote 1.5m radius as OK for their larger track (it may be 1.15 as my handwriting is poor). You can go smaller with their 29er version. Although both o these have balls.
If bending about one axis only (i.e a W in one plane) then the track method we used would be simple, cheap and light.
Cut the track shape you want into a piece of 4x2 wood. Screw this to a sheet of ply. Cover with parcel tape. Vac a few layers of carbon over the top. Demold your z sectioned w and attach to boat. Bolt track hole by hole onto your chosen shape.
Allen tracks/car is about 55GBP + vat
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This is an area we decided not to be smart-arses about. It is really important that they work, so we went for a 49er track with rollers instead of balls. The radius is really big at 2.6m or something so the clew is a long way back.
I have seen poor experiences with lightweight tracks blowing up (2006 nationals, Loco Perro, among many others) and I have seen the balls fly out for reasons unknown when sailing with Gav at Neyland in Mango Jam.
We chose simplicity and reliability over lightness and fanciness and when the time came to choose for Antidote we did the same again.
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W tracks gain very little. I was going to try on Shiny but it would of gained around 3mm further aft. I opted for flat section with curve at both ends. You would gain more because I hope your mast will be further back but even so.
As for choice of material This is one part of the boat I think you get what you pay for.
Personally I think Will's 49er option is the way to go. Failing that go for the best car and track money can buy.
Though if your are brave and want to build your own I think it would be very difficult to underestimate the amount of punishment a track takes.
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Ofcourse the counter argument to all of that is W tracks do look good.
Probably why it took me so long to decide against one.
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the only reason locos track came off is i became a member of the moscow state circus and and went flying and kicked it off otherwise it held up well. having said that it came off in one piece and it was stuck on and we went sailing the next day. The jib had terminal damage though
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The Ronstan 19mm ball track ( like on 29ers ) is good, but you must get the undrilled track it you want to bend it. It only needs support at the ends and middle if it's prebent. The 49er track is a bit sturdier, fits Ok and works as Will said.
The 29er track is predrilled, but not bent, so this is only Ok if you bend it into place and use hundreds of bolts on a curved bit of structure.
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The 29er track is predrilled, but not bent, so this is only Ok if you bend it into place and use hundreds of bolts on a curved bit of structure.
Have tested this one to destruction and can confirm it is fairly correct.
On EJ we tried a bent 29er track with holes and it was disastrous. Now we have 9 bolts attaching the thin track to a carbon Z spar (spar weight about 150g + 8 bolts - rest of boat still carries a fair bit of lead).
Dave Ching has recently made a new track for shiny out of the 29er un-drillled. The old track lasted a fair amount of abuse and nationals wins (?) before exploding. Allen have very kindly made a new part number so we can order raw track before their guys drill it and cover it in black anodisation. With a longer lead time they will also do anodised undrilled (6-8 weeks)
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Class Anodising Tank?
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If you order it with enough time spare the gents at Allen will anodise it for almost nothing.
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hmm, where to have the boat painted???? ideas/suggestions?
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Not in the kitchen!
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I think that unless you know someone with the kit to spray it and can get a good deal on the paint then the best bet is to just paint it by hand.
If you apply the paint with a roller and then tip it off with a foam brush you can get a pretty good finish. Once done you can flat it back with wet and dry, then polish, which you would need to do to get a proper finish after spraying anyway.
I would recommend two pack paint the last stuff I used was Jotun they have a wide range of colours, and it is pretty tough.
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are there weight issues with painting it yourself?
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Spraying will be lighter than rolling by about 0.5kg for the top coat.
We used a high build primer which was compatible with the top coat. We used an acrylic car paint for the top coat but this only gives a good finish if sprayed.
If rolling and brushing we had good results on Slippery with Epithanes boat paint. Limited range of colours.
Personally I would spray again.
We found that after we faired the hull and then put the first coat of high build on it showed up all the defects. We wet sanded and applied 2 more coats of high build before we were happy.
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are there weight issues with painting it yourself?
If you are not careful you can get weight issues with either method. If the person spraying is not focussed on getting the thinnest coat then it is easy to add thickness quite quickly, particularly if they do a primer, then undercoat then colour then lackour .
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The other option for home spraying is to borrow a compressor, leads and spray head from a friend. Remember to promise them that you will clean the system thoroughly and buy a replacement gun if you stuff up (£75) and I think you'd find a ready offer from this post!
You'd still have to buy the paint at a lower discount than a commercial spray centre will get it, but most car suppliers will give you a very full shopping list of colours.
Spray training available on collection of the kit - or you could come over when we spray Born slippy in a few weeks!
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sorted hopefully :)
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might change the name to "nomad" for personal reasons!
just managed to destroy my first attempt at a centerboard with far too low density foam!!!
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I would reccomend that you use 200kg/m^3 foam for the centreboard.
It is easier to router and a little bit more stable when you get to the very thin bits.
No stringers required. 1 sheet should be plenty although you may need to be inventive with the sizeable off cuts to get the full length required.
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is using 1mm dyneema for the new trap wires brave or stupid? its got a avg breaking load of 154kg, but i would assume thats from a static load, and also that splices weaken it?
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Bearing in mind that you often run through a cherub and grab the wire as you jump out before hooking on, I hope you plan on wearing gloves. At least all your fingers will be findable after.
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davro said the dynamic loads may be a bit too much, so moving up to 2mm with a big trap handle
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1mm dyneema - I agree with Simon that it is more a sliced finger issue. I think the elastic rope on the hook will take care of dynamic loading...probably
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We had 1.5mm for a while (breaking load of 300kg). and have now changed to 2.5mm. The big enemy was chafe around the metal trapeeze adjuster. We had a similar problem near the top but solved that by using earth sheathing on the eye of the splice which attached the trap line to the mast. basically dynema against dynema is ok for chafe but against anything harder can be a problem. especially if you didn't really have much margin for chafe in the first place.