UK-Cherub Forum
Cherub Chat => Tech Chat => Topic started by: Banshee Ambulance on April 03, 2012, 07:50:07 PM
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I have just been reading up on some Farr 3.7 build blogs. The thought that I was having was... can you laser cut pre laminated foam/carbon sheets? Anyone got any ideas?
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Think water jet cutting might be more useful for this!
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Laser cutting generates a lot of heat and i think you'll end up with a proper messy/burned/melted edge. You could easily use CNC router or as cookie suggested, water jet cutting.
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An issue with doing foam panels might be that you usually want the edge to be angled, not at 90 degrees to the material. I wouldn't be surprised if the technology is there to cope with that, but it sure ups the complexity of the required data file. Most foam boats in our sort of size don't have anything like the number of pieces you have in these very sophisticated wood construction boats, so its less of an issue for boats. Building jigs on the other hand... But then you'd probably make those from ply or fibreboard anyway wouldn't you. Must admit those cutting plans for the Farr do look awesome, but I have a used Farr boat to do the next time I feel like getting embedded in wood shavings and there are no cutting lists for that one...
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I've cut 10mm MDF with the cutter at my college, and it got through it pretty easily, just made lots and lots of smoke. ::)
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An issue with doing foam panels might be that you usually want the edge to be angled, not at 90 degrees to the material. I wouldn't be surprised if the technology is there to cope with that, but it sure ups the complexity of the required data file. Most foam boats in our sort of size don't have anything like the number of pieces you have in these very sophisticated wood construction boats, so its less of an issue for boats. Building jigs on the other hand... But then you'd probably make those from ply or fibreboard anyway wouldn't you. Must admit those cutting plans for the Farr do look awesome, but I have a used Farr boat to do the next time I feel like getting embedded in wood shavings and there are no cutting lists for that one...
Use angled router bits around the edge
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I agree that the laser cut parts looked great. If we were going to build lots of cherubs and wanted to create a kit of parts an automated cutting process might create an advantage however for 2 or 3 boats you are likely to spend less money and time by creating some accurate ply or mdf templates from the first set and cut more from that. Then sanding the chamfered edges by hand afterwards does not take to long. With practice this would become a quick and accurate method.
I found that the cardboard E5 templates gave a good start to the shape but it took a while to turn this into an accurate shape by sanding, fitting and then sandiing some more ...
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Is this thread about what I think it is?
We could get together and pre-laminate lots of foam/carbon sheets, cut these sheets to a template then stitch and glue (or pin and glue) an E5?...lots of E5s
E6 curves are very lovely but in the end don't chines go just as fast in the end usually?
...especially if the E6 becomes the Olympic boat and generates interest in the class - this would be a low cost option for people starting out.
...back to the original Cherub vision but in carbon.
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Sorry, this is a bit of a (hobbit having a) 'This stuff comes in pints!' moment...
Are pre-laminated carbon/foam sheets available commercially?
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Are pre-laminated carbon/foam sheets available commercially?
I don't think you'd want to do a shell like that, but if you were putting an interior in a shell built by one of the pro guys (or a new interior in an old shell) then I reckon its worth considering. There should be a substantial saving because you are taking all the time consuming fiddly bits out of the build. I've had Bloodaxe make carbon panels for me in the past. I thought the price was reasonable. I didn't do anything sophisticated when I used them though, just made cardboard templates and cut the sheet when I was satisfied with the shape. Here's one I prepared earlier...
(http://www.devboats.co.uk/halo/images/stumpconversion/gallery/d-progress.jpg)
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One of the good things about foam carbon panels is that they are quite stiff, so not so good as ply for stitch and glue.
A prelaminated sheet is V useful for bulkhead.
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So...let the expertes do the fiddly bits then a double floor, a semi-sunken foredeck, the transome (such as it is) and use carbon tubing for the mast support, racks, rudder gantry...
hmmm...
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So...let the expertes do the fiddly bits
yep, although I'd say its the other way round - let the experts do the bit that's a nightmare if it all goes horribly wrong, and do all the fiddly time consuming and thus expensive bits yourself where in general its not a disaster if you stuff up and have to slice it out and do it again. For the same reason I'd probably buy pre-made tubes and glue them together rather than make them myself, although there's a lot of experience in tube manufacture available to the beginner through sticky weekends.
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I can thoroughly recommend this build technique. I used a FiberFusion in Falmouth to make a kit for a big foiler.
They have a 400 ton press for making carbon foam panels and a water jet cutter. The quality and precision of the parts is fantastic.
You send them a cad file and get a flat pack boat back in the post.
It then took a weekend to assemble the hull with no tooling except a very simple MDF jig that they also water jet cut.
There is no need to bevel the panel edges. The volume of bog required to fill it is trivial.
Next time I would try and make a roller to slightly crush the foam - Trap hook style - so that there is a small recess for the tape.
I would also add castelations to the panel edges so that they lock together rather than just fitting together.
The boat flew but was never fast. Compared with a Moth it felt like I was trying to fly the Queen Mary.
It also became clear that my initial presumption that you had to be <10 stone to sail a Moth was wrong.
I am trying to find the time to come up with a cad file for a simple canoe to build like this.
Clive
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All the carbon ribs for Invictus were made by Fibrefusion down at Falmouth, and I would concur with Clive that they are incredibly accurate and well made. The water jet cutting provides incredibly crisp parts and from memory they are not expensive.
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Does anybody else build in carbon like this?
Clive...that is seriously impressive. How much did the cut carbon kit cost?
The Cherub shape is only a little more complex than the foiler - a bow/snout section to fit the bottom and side panels into?
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You probably already know but...canoe/kayak plans. I like the Chesapeake 17LT
http://www.clcboats.com/
http://www.clcboats.com/shop/boats/kayak-kits/chesapeake-17-lt-sea-kayak-kit.html
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I think that the complete cut carbon kit was ~£1300 inc shipping.
It seamed reasonable value for the time it saved esp considering it was a 1 off.
There are a lot more water jet cutters around now the rates may have gone down.
Fibrefusion have the press as well so offer the whole service, and more experience of cutting foam carbon panels.
Thanks for the link.
Clive
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That's actually a pretty good price
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That looks like an interesting technique, the panels are bent more than I expected what was the thickness of foam used?
It gives me ideas, I am not sure I would build a Cherub like that though.
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I'm intrigued as to what Kevin Ellway would come up with as a CAD for an E6 kit and how much the kits would cost...bought in lots of 5 for instance
Double chine, single chine?
Some clever geazer come up with the (moulded) bow/snout section
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everything about the outer shell is curvy though, which could be problematic
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I used 8mm foam. I was happy bending it to 0.2% extension.
On a simple curve that gives a radius of 2m.
The same limit applies for compound curves.
Clive
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so a moulded bow section would be needed, but otherwise.... i think an E5 would be more suited to this than an E6 definately, the chines would make it easier
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That was my initial thought too John but I haven't seen an E5 close up.
I would like to see the 'cheap and easy to build by amateurs' ethos reclaimed.
There might be a natural progression for newcomers to the class:
* Buy an old-ish '97 Rules boat
* Sail for a season
* Build an E5/Banshee(?)/other hull (in pin and glue carbon), swap the rig over and still sail '97 Rules but be more competitive
* Sell the old '97 Rules boat, buy new '97 rig and make a bid for the '97 Rules trophy or buy '05 rig and move into twin-wiring
...or:
* Build new boat in carbon with '97 rig
* Sail for a while
* Add '05 sails and '97 rig becomes 'storm' suit
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Trouble is that you add a fair bit of work and weight on the shell with all the stitching together and so on.
I was wondering about getting a pro to build the shell below the chines and gluing on flat panels above the chines, but couldn't convince myself it would save an awful lot of time in the pro's shop, and thus much money. The other thing would be to do the bottom is say 4 or 5 planks each side and then flat topsides, but then you start thinking that really you should put a single skin over all the planks, and its not long before you might as well be building the shell on pre cut foam that has no skin at all - or maybe only on the inside.
Bare shell and flat pack interior ought to be a possibility though. heck, it ought to save time for pro built boats too. If I understand his thinking I could see this be something Roland might want to look into if the Arup skiff gets the nod - how many bare shells and flat pack interior sets could fit into a 20ft container for completion by a local boatbuilder? Shells, deck mouldings, flat pack interior frames, flat pack building frame, collection of carbon tubes... I'd hazard a guess that you'd get a year's production for a local builder or a viable fleet for a small nation in a single container.
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anyway nigel, they arent THAT hard to build for an idiot/teenager/noob to build anyway, mine hasnt fallen apart yet
(http://a5.sphotos.ak.fbcdn.net/hphotos-ak-snc6/72996_1580747606249_1462451748_31523639_5657414_n.jpg)
the chines on e5 ^^
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John, it's the cost of the pre-moulded shell rather than the difficulty...my thinking is that pre-laminated carbon sheets on an industrial scale (now starting to happen?) cuts costs.
Carbon/foam sheets are the new plywood
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PS How is Nomad doing? That's an old pic, yes?
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its caled anatidae[hobia, nomad was too plain for a cherub
(http://a6.sphotos.ak.fbcdn.net/hphotos-ak-prn1/552839_3593625246932_1462451748_33279865_525942720_n.jpg)
this is it on wed with me and digby
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Fantastic...you must be very proud
Quack!
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Trouble is that you add a fair bit of work and weight on the shell with all the stitching together and so on.
Stitch with carbon thread like they use to strengthen sails, epoxy inside...then cut off from the outside like they do on Mirror Dinghy.
I think it could be done down to weight but I'm no expert...the 12 foot lugsail dinghy we have has a single line of epoxy on the inside and no tape holding it together (9mm epoxy ply) that I can see. It was pinned (screwed) during construction, then the screws removed prior to finishing off. I think strength is achieved by overlapping the ply.
Our 16 footer is similar (I think) but using thinner ply. I don't see why carbon would be much different
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then think of the rig tension used on the osprey and compare it to a cherubs.... and also ospreys don't tend to jump (and subsequently land) off waves hugely often
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I'm no expert but rig tension is in the tubes
Falling off a wave?...Osprey weighs half a tonne and pirouettes quite nicely in a Solent chop
I think it could be done but:
a. Could it be built light?
b. How much would it cost?
The attraction of a kit for DIY duffers like me is major and even I could make a Mirror Dinghy.
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The thing is that building the shell on the mould is not the most expensive or difficult part of a boat. The tricky parts are getting all the ancillary bits on, and getting the strength in the right place, which you would still need to do with a flat pack.
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Whatever you buy as a kit will obviously need putting together in some way, surely less parts the better, as there are less things to get wrong.
If you want to try it, design a simple cherub shape and try and build it using balsa sheet, (you could probably get a Cad program to export all the right shapes for you then laser-cut them?) .
I've just designed and built a strip-planked balsa model by hand, I can assure you, I would have appreciated a mould! :D If the planks were pre-cut they would still be a pig, as they need to be super thin to bend round the shape, which has chines, I only just managed it. The thought of trying to build a cherub hull from panels like that is not a punishment I would wish on anyone.. ::)
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Yes...it would only work really well (in giving DIY duffers like me a not-too-daunting project) if someone took upon themselves to make a kit with all the bits and instructions...not that likely.
The bow is where the tricky bending is...there's probably a way around this
I think the saving could be £1500 on a boat. I did a 'beer mat' calculation and I think such a boat done entirely DIY would be £6000+ incl sails and all gear ('sticky weekend mast?).
Add £1500 to that and you have the cost of assembling pre-moulded hull and deck and completing yourself = £8k approx
You could sell a kit for £6000+ ex-sails
Might be a business model in this for someone? Not very like maybe but an Arup Skiff kit for £6k??? This might have takers.
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We chose to get the hull and deck shell for E-numbers made professionally and do everything else ourselves. This still involved a lot of work because we had to make, cut and sand and then fit all the other components.
This approach is acheivable by someone with limited initial experience.
It would have been a lot quicker if all the other components had been made and cut to shape.
One way around the hull and deck shell building is to make it with someone who has done the same before using the mould. if you were determined and with 2 people these two components could be made over 3-4 days. Over another similar period of time you could make the bulkhead panels, tubes and gantry depending on how that specific boat went together.
The ARUP Skiff concept focusses on reducing the number of components and including reinforcements into the main mouldings.
To put together a method of asisted building as above someone would have to create the templates for the all the other components. obviously this is of greatest benifit if several boats were going to be built. A scheme is more possible now that the rules have stabilised and the designs and boat layouts are becoming more similar.
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I have just been reading up on some Farr 3.7 build blogs. The thought that I was having was... can you laser cut pre laminated foam/carbon sheets? Anyone got any ideas?
Just in case you were thinking of building a Farr 3.7 with the same techniques as the ply boats that are currently being built, but out of foam / carbon. To avoid the up keep associated with wood boats and make a very light boat. My recommendation would be to build the hull in ply from laser cut ply and the decks (edit: and floor) in foam carbon. This removes most of the wood upkeep issues. Is cheap and reduces the weight of the boat. And as the decks are hand fitted there is no need to get water jet cut carbon foam. It also removes the issue of altering the files to accommodate the increased skin thickness needed for a foam hull.