Small Tri's under 20', any mention of foils is banned..

I have been talking to Mike Waters who designed the W17.
The boat meets most things I have the room to build.
The only problem is I don't like plywood boats, I want the sexy curves.
Anyone have a suggestion?
I thought about buying the plans and modifying the shapes, but I am just too lazy. And I would be changing a boat that has been developed and turning it into an unknown.
I have plans for a Cross 18 and have considered the same thing.

 

There are designs out there which are rounded and curvy, but they need to be made in glass, carbon and foam cored, would you forsake speed in the plywood style of build to a more expensive in both cost and hours to build, but get that very modern looking shape ?

 

Wayne,

My primary choice would be strip planked and I would accept more time than plywood. I'm not sure I can't do it cheaper as long as I paint the boat.

I know there are other designs, are you talking about those offered as plans?

I may well have forgotten about them.

 

If you will consider stripped plank, would you consider strip planking in foam as per the A Class builds in America, it works out a much easier method, quicker than conventional planking with the benefits of light weight and cheaper cost ?

 

Foam planking

John Lindahl at http://lindahlcompositedesign.weebly.com/lr4-build.html has the best description.

 

I could look at it again.
When I did years ago the foam was significantly more expensive than cedar.
Thanks for the reference

But I do like wood.

 

What about multiple tortured ply sections? I'm looking at simulating hull construction using several full length tortured ply sections, each the length of the hull, and then joining them longitudinally such that the slope across the join is smooth. This (in theory, at least) allows a curvy shape without longitudinal chines, and allows a round bilge hull with topside flare, as per a small tri centre hull. I've not finished the simulation, but hope to get back to it soon. It is a promising way to make fair hulls using flat grp panels as well as ply, provided the grp can be adequately sheared (probably a single layer on foam core).

This means only a couple of longitudinal seams, rather than the dozens required for strip planking.

 

Plywood and sexy curves....

Just a thought - but the tornado hulls as outriggers are plywood and certainly look fantastic. Not sure if one could scale up the tortured ply into more width?

I also wanted a classic look - even though I have read that the performance difference from smooth to a few chines is extremely minimal. For me I went with stitch and glue for my main hull which Paul modified as strip planking (without wood being available here for this sort of thing) was exceptionally daunting. He is happy to modify plans it seem and design new boats from scratch. And hundreds of his boats have been build. I do regret not getting something with more chines, because it was super easy to assemble (though I had the planks routed - Paul supplied a .dfx file). But with lots of chines one can still have a stunning hull shape.

16' PORT SORELL ROWING SKIFF is a great example of a multi-chine that is plywood with great lines, and could possibly also be a main hull. Its on his website for Selway-Fisher.

I found Paul very helpful in terms of ply wood thickness to use, beam, height etc.

The shape you see on Dougs post with the cable ties showing took two hours with a drill and cable ties. So the basic shape comes together extremely fast. Of course adding the cloth is a bit more tricky. I have no doubt with the 'bulkhead breaks' for lack of a better word that more chines would have been just as easy.

In short - it might be worth thinking about stitch and glue from such an exprerienced designer like Paul. Natruallly one will need to add in framing for strength etc.

I am working on my next one to follow. Some time on Carson's hulls and adding loads of chines creates some lovely shapes.

http://www.selway-fisher.com/Rowskiffs.htm#SORE - maybe take a squizz.

 

I'd be interested to see your concept on the tortured ply.
Previously I had a plywood Tornado.
Everything I have read about the method says you will have to have a closed section to actually torture (3d shape) plywood.
So I can see having a bottom section and a top section with an internal divider, but that seems heavy.

Actually I looked at something similar at work and concluded that you really could not simulate the torturing without a lot of work on a FEM.

I don't see how you are going to get flair without a sub deck.

 

Anthony,

Have you looked at the Gougeon Brothers book on tortured ply?
You certainly can change the shape within limits.
You can even do a model to see what will be successful shapes.
Its a lot cheaper than just trying and more conclusive that wondering.

Also have you ever seen the old Searunner Tri building manual. Chines on those boats were rounded to a limited extent to make a smoother looking hull.

FYI, the Cross 18 and W17 are already stitch and glue available plans. Probably at least a dozen more examples also.

 

tortured ply and ladder chassis

I have indeed -I have been buying up yachting construction books until they outweighed the luggage allowance for my brother to bring them out from the UK. (Postage in SA is a bit dodge...).

Great book. Bit daunting though - so I am using my micro cat hulls for starters. I do think Tornado is a great example of what can be done with plywood though.

I don't want to hi-jack the thread with my own build, but I do have something in mind that might be of interest / cause palm head smacking / generate an idea / smirks etc:

What I haven't seen any trimarans do is use a ladder chassis and 'hang' the three hulls beneath it. Made of aluminimum it would be light and strong, with telescopic elements (trailoring), could carry side benches for seating (feat hang into the hull), and cross sections attach to the mast(s), carry lee boards.

This way the main hull could be quite light and simply build, and could save on a lot of over engineering inside without heavy re-enforcing for the mast, centre boards, seating etc.

This does have drawback of welding in aluminium.... I plan to outsource - but for those who want to do it all themselves this might lack in appeal. Thoughts?

 

Its been done, but not as high tech as you imagine.
It originally used an aluminum ladder as a crossarm for a canoe main hull.
Latest Version:
http://www.outsideconnection.com/gallant/bluetri/
The original:
http://www.outsideconnection.com/gallant/trimaran/

 

It is a lot of work with FEM, and it needs an explicit solver, or a lot of iterations. I've been looking at the tortured method as a means of making a mould, so supporting the edge is easier with external reinforcement, but not impossible internally with bulkheads and longitudinal stringer along the joint. The tornado uses internal bracing in the bow as well, and a similar structure (bunk base?) may work.

 

How about the Trika 540 from Dudley Dix's agent Klaus Metz?
http://www.dixdesign.com/Trika_540.htm

Looks like a pleasant afternoon out.

 

Don't mean to be a killjoy but why not buy a Weta 16 off the shelf?