Sport sailboat, material and hull shape.

Post by **jacquesmm** » Tue Nov 09, 2004 4:29 pm

Next dilemma: it’s not worth designing or building unless we use the right material and hull shape.
We can use two materials: our plywood composite or foam sandwich.
The plywood composite will be like all our other boats: easy to build and inexpensive. It forces us to design a hard chine boat. That will increase wet area and drag. The difference is small for a cruising boat but significant for a speed boat.
The alternative is foam sandwich. I can design a hull with mostly flat panels but rounded chine, a little bit in the style of the D. Dix or Roberts radius chine but with foam strips. It may be faster to build than the plywood version in part because with foam there are not fillets but it will cost more.
I would specify vacuum bag or infusion for all the flat panels and leave the hull vacuum bag as an option. I think I can design that hull lighter and stiffer than the plywood one.
In each case we will use carbon fiber for keel fin, rudder and spars.
I would really prefer to design for foam sandwich but what do you think?

Jonnas · Post by **Jonnas** » Tue Nov 09, 2004 5:21 pm

Personaly, I see this boat as a step further, both in sailing and building. It won't be the first boat I'll build neither the first I'll sail. So, a combined challenge would be my goal. Have a sailboat that will provide added performance but not extremely demanding on sailing, and build it with both best material and technique available for amateur (home) building. Thus my vote goes to foam sandwich.

Yoda · Post by **Yoda** » Tue Nov 09, 2004 7:01 pm

I did a lot of sailing when I lived in SoCal. And the thought of a different building method sounds interesting. Never liked a hardchine boat. So I pick the foam sandwich.

anonymous · Post by **anonymous** » Tue Nov 09, 2004 7:33 pm

Ahhh! Help, can't vote...

Once again democracy at work. Unless Jaque can convince me that the foam sandwich is easier (not necessarily quicker) and there is a foam-core-for-dummies book somewhere, I would have to say plywood would be my preference. The cost, "new" technique (or should I say different/non-main-stream), vacuum bagging set-up, etc weighed off against the potential performance gaines (through weight savings, stiffness, hull design, etc) still have not convinced me to sway away from plywood. If I want a true performance hull, I would likely reach into my pocket and buy one - ready made for sailing...

Plywood please.

anonymous · Post by **anonymous** » Tue Nov 09, 2004 9:37 pm

Vote for hard chine here due to the simpler building process.

chrisobee · Post by **chrisobee** » Tue Nov 09, 2004 9:50 pm

I have voted for the round bilge and the foam sandwich. However I do so with some trepidation. My financial resources are not great and you could easilly price me out of the boat. what general price to build are you talking here, and what magnitude of performance gain would the foam option give?

LarryA · Post by **LarryA** » Wed Nov 10, 2004 1:21 am

I vote for both

Steal a page from the Radius Chine designs, use ply for the flat/slightly rounded panels that make the sides and the bottom, round off the "chines" by using foam (or strip ply or something a la radius chine). Not sure this is really doable but it seems like a nice middle ground.

Perhaps an all carbon version over foam would be nice - vacuum bagged etc - we are talking speed here afterall.

kiwi · Post by **kiwi** » Wed Nov 10, 2004 3:44 am

jacquesmm wrote:Next dilemma: it’s not worth designing or building unless we use the right material and hull shape.
We can use two materials: our plywood composite or foam sandwich.
The plywood composite will be like all our other boats: easy to build and inexpensive. It forces us to design a hard chine boat. That will increase wet area and drag. The difference is small for a cruising boat but significant for a speed boat.

Hard chine with how many chines is my first question? The performance hit is most noticed in light conditions with this type of boat. There is so much sail area and power in these things that as soon as the wind picks up a bit I think that the difference will be less noticed even when racing. Having crawled under a few boats in La Rochelle recently the hulls of some of these craft _ARE_ hard chined!!!

Easy to build, inexpensive and fast are the keywords.

If was to build foam core then it would be carbon fiber - out go "easy" and "inexpensive". Vacuum bagging is not "easy". It isn't out of reach for an enlightened amateur, but it isn't my idea of having fun either. Before finding Bateau.com my heart was set on building a Farrier trimaran. Unfortunately Ian dropped the 22' he was planning and the other boats were beyond my budget (I have done a bit of research on what is needed). I have watched the rebuilding of a Paris-Dakar car in carbon fibre where some bits were vacuum bagged. Making flat foam cored panels for deck and cabin is not the same as building a round hull.

I say by all means design a foam core boat but you are then addressing a whole new market segment (probably a good business plan BTW). France would not be in the heart of that market segment because if I want a sports boat I have an embarassing choice. If I want a cheap fast boat I wait a season then buy a used boat from some semi-pro that has raced the death out of it.

If I were to build one myself then economy and ease of building come to the fore. A multi chined stitch and glue ply composite would best suit my needs. On the marketing side of things maybe it would be a good idea to separate the plans into two different lines of product?

Hope that helps

Tony

esparver · Post by **esparver** » Wed Nov 10, 2004 6:06 am

I'm with Kiwi (Tony)!

One thing that distinguishes you for other designers is the focus in the ease of building, that is, for the completely amateur. There are several plans/kit for 5.5-6.5 fast boats but, to the best of my knowledge, only one “cheap, easy and performant” boat this size: mike waller’s TS540 (http://www.wallerdesign.com/ts540.htm).

So, to summarize: keep it simple and cheap, but fast… don’t make just another one, make a reference boat for Stitch&glue construction.

A 6m (20 feet) cabined multichine fast boat made of plywood/epoxi/FG resin would be very appealing to me. If I ever want to build a radical/expensive/difficult-to-build boat it would be a Mini-Transat...

Just my 2 cents…

kiwi · Post by **kiwi** » Wed Nov 10, 2004 6:48 am

Yoda wrote: I once was interested in a Trimaran. Then Piver died at sea in his own design. He talked about how safe they were all the time. How they were so light they would would just skip away from a breaking wave. Sorry, just reminiscing.

Piver "designed" floating appartment blocks that just happened to have three points of contact with the water... I was tallking about real trimarans. I put Ian Farrier designed boats on a par with bateau.com designed boats - plan quality, engineering knowledge, sailing experience of designer...

Oh, did I say he is from New Zealand too

Tony

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