boat design for cylinder construction

[rapscallion]

I am researching a trimarans with the idea of building one. I came across the "cylinder construction" method and was intrigued. I'm am such a newbie at this so please forgive me if this question is completely obsurd..

I was wondering what the viability would be to construct a trimaran center hull using a single half mold... and "stacking" two half molds on top of each other to create a wider beam higher up the hull.

I know that is a terrible description. I saw some pictures here of a hull cut in half and a canoe like section inserted at the bottom of the separated hull. It looked like a clever idea to me.

so I was thinking, maybe just make two half molds form the same "cylinder" and simply stack them to make one complete half of the hull (complete half....scheesh)

The idea is it get a slightly more complex hull shape as easialy as possible... if futzing with it to get it to work would be more difficult than just making a proper half mold in the first place than maybe it wasn't such a good idea.

thanks in advance for your input...

[messabout]

Rapscallion;
You use the term "cylinder". Does that mean a round cylinder ? If so, I presume that you have been looking at those ubiquitous pontoon boats. The round cylinder or segment thereof is not a particularly efficient shape for a boat. The shape is efficient on pontoons only to the extent that they are easy and cheap to construct that way. Hydrodynamicly they leave something to be desired.

If this is not the pontoon variety of cylinder, You may be thinking of a system of boat building called "constant camber" That system uses a series of molded shapes that does indeed produce a good boat. But those shapes are not really cylindrical. I think that method is a product of a famous multihull guy named Jim Brown. You could Google around and find some information about that subject.

You used the word; mold. Are we to assume that you will build with fiberglass thus requiring a mold ? Are you convinced that it must be of fiberglass ? Post some more detailed information about what you want to build. Size, where the boat will be used, budget, daysailer or cruiser, power or sail (sail I assume), your experience as a builder of things not necessarily boaty, etc.

[Raggi_Thor]

I think he means a combination of cold molding each half of the hull as a cylinder surface, with a very simple jig or mold, and then torture it into one hull, like Kurt Hughes,
http://www.multihulldesigns.com/pdf/cm33.pdf

It's not the same as constant camber, but is based on some of the same philosophy.

One common misconception with all kinds of "simplified boat building" is that the hull in general and the skin specifically represents a major part of the total work or cost :-)

[tri - star]

There was a consortium put together, that came up with this procedure.

I seem to remember the main person, with the money, was a visionary
guy - named Weld (?).
Who commissioned a tri, designed by Newick - called Gulf Steamer (?)
Newick was involved in the " constant camber " project as well.

It's possible that Jim Brown was the third person.
They tried to set up a yard - where Mr Marcos and wife lived.
To, alturisticaly, make low cost fishing boats.

The story goes; that soon after they got there. - It became apparent that
the under-the-table costs, would soon excede, even Mr. Weld's deep pockets.
So they left.....

Some times it's no fun at all - in the world of Multi-Hulls !

By the way: The key elements of this procedure is: Epoxy and Wood.
Deviations from these core componants will prove to be problematic.
Also, they came up with some very clever geometry, that already does,
what I think you are looking to do,

Cheers all !

[rapscallion]

Thanks for the response. I was wondering if anyone had an example of a boat with the geometry figured out... I looked around and couldn't find it

[fhrussell]

Jim Brown is credited as the inventor of the "Constant Camber" building method. You could contact John Marples as well...his designs are mostly CC built and probably has more experience than anyone with this method. He has had tremendous success with his designs and the wood quality doesn't necessarily have to be very high. Personally, I would always opt for decent ply; being such a low portion of the overall build....why scrimp there?

As for Cylinder Mold building, Kurt Hughes probably designed and built more boats with this method, although he seems to be downplaying this method these days. I think he sited the 'loosy-goosy' nature of the process,. It's hard to land true points and one needs to do a lot of eye-balling to get things just right. It does seem to be a quick and easy solution, though, and probably even easier for people with experience in CM building.

[tri - star]

Dick Newick might not agree totaly with you fhrussell.
Especialy, the last time I talked with him....

[fhrussell]

Jim Brown does own the patent though....:

http://www.searunner.com/agreement.html

And he may not be in agreement with you or Dick. The only in-depth conversations I had about the process have been with Jim and Marples. ...it never did come up with Dick, ..last time we spoke, at least.;-)

I know Newick has been around since the very early days and is certainly one of the very few great designers, builders, and gurus of the multihull scene and he has certainly designed boats using the CC method, but Brown and Marples have made a career based on this process, and I have used it myself on one project with their guidance.

Anyway.....

[rapscallion]

I wish I could talk to those guys.... sounds like you two know what you are talking about... could you reccomend some of the better tri home build designs? or any designs for that matter? (17 to 32 feet LOA)