Need some design work

[cs]

This is for all you folks out there that play around with hull software (are you listing John?). I need somebody to draw a float for an outrigger on my canoe. The canoe is flat-bottomed and about 14' long. I want the float to be about 2'-3' long. All I want is somebody to draw something that can be used to develop the curves on a sheet of plywood.

Chad

[John Bell]

I'll do it, but first explain what you're trying to do.

How much bouyancy do you need? Why so short? The hull speed of the short ama will be much less than that of the rest of the boat. A longer one may actually make less drag.

JB

[cs]

I want to be able to get the complete ama out of one sheet of plywood. This is another one of my expirments. You remember my canoe? Well I'm thinking about over the winter of making it a sailing canoe.

Chad

[John Bell]

Are you thinking proa or trimaran?

[cs]

I'm thinking proa (if that means single out-rigger) I may go with one on the other side, but not at first.

Chad

[John Bell]

Since I have no idea what I'm doing, this is pretty easy!

I drew an ama, 80" long by 12 wide, vee bottomed. It's good for about 80 lbs maximum displacement at the point it submerges. It will just fit on a single sheet of plywood, but I'd suggest 3-4mm instead of 1/4" .

Is this what you had in mind?

http://jmbell.home.mindspring.com/images/ama.gif

[ 10-31-2002, 02:49 PM: Message edited by: John Bell ]

[Todd Bradshaw]

A proa is a somewhat different concept. When tacking a regular outrigger canoe, the outrigger will be to windward on one tack and to leeward on the other tack. A proa always has it's outrigger either to windward (Pacific Proa) or to leeward (Atlantic Proa). Rather than tacking by turning the bow through the eye of the wind to change direction (like normal sailboats and regular outriggers)the proa "shunts". The bow becomes the new stern, the stern becomes the new bow and the rig swivels around so that it's pointing the other direction. The boat then sea-saws it's way up or downwind, always keeping the outrigger on the same side with respect to the wind.

It would be easier to design a conversion to turn your canoe into either a simple outrigger or a trimaran with small amas than to make it into a proa. John's right though, you need the ama(s) to be longer. Otherwise it will probably just get stuffed into waves, cause a whole lot of drag, and maybe get torn off the boat when it trips over it. They don't have to be huge (some of the real native ones were kind of a fat stick) but you don't want them too short.

This is a trimaran configuration that one of my customers built for his Mad River "Monarch", which is a fairly skinny decked tripping canoe. Your ama should be somewhat similar in length, though it would be possible to reduce the volume somewhat. http://www.imagestation.com/picture/sraid28/p59565753615f802cdbc1de7a35ade329/fd6827ed.jpg

I've been doing a little sail design consulting with Gary Dierking in New Zealand who has an interesting site with some of the outriggers and proas that he builds. Among other things, he's got a couple sets of downloadable, free plans that might be of interest in designing your outrigger. Check out:
http://homepages.paradise.net.nz/garyd/index.html

Here is one of Gary's boats
http://www.imagestation.com/picture/sraid37/pd24adcbbf06ba70daf9a19982819578a/fd197b56.jpg

Unless you really want to overpower your canoe with sail area, the first thing to try would probably be just sailing it as a canoe using somewhere around 45 sq. ft. of sail. Adding an outrigger can add stability to the package, but it also can drastically change the way the boat responds and you may or may not like the change. If you do decide to build the outrigger, you may be able to scarph plywood and get one that's suitably long enough from one sheet. Making one that's too short to work properly, just to avoid buying enough plywood to build it would be false economy.

[ 10-31-2002, 03:10 PM: Message edited by: Todd Bradshaw ]

[Paul Scheuer]

What Todd said about starting without an outrigger. There are plenty of canoes sailing with a leeboard and usually a rudder (some don't). Try the Wooden Canoe Historical Association, WCHA.org.

[Bruce Taylor]

Try the Wooden Canoe Historical AssociationBetter yet, try Todd's book. It has all you need to know, and then some.

[cs]

Okay we will go with the longer amas and do it outrigger style. How long should they be?

Chad

[NormMessinger]

There was an article in WoodenBoat, not too many years ago, by the CLC Dude, with complete instructions for making the complete outrigger assembly.

--Norm

[John Bell]

Went to 10', narrowed them up at bit and prettied up the sheer. You can easily get two out of two sheets of ply. I'll dimension them if anyone's seriously interested.

10' Ama PDF (http://jmbell.home.mindspring.com/images/ama10.PDF)

http://jmbell.home.mindspring.com/images/ama10.gif

[cs]

Looks good John. Throw some dimensions on that and I'll download it and build that on one of them slow days this winter.

Thanks

Chad

[John Bell]

Chad, you've got mail...