prototype boat and model questions

[jason vandeusen]

Hello all,

My brother and I are planning a new project, we want to build a new boat. This will be our second boat build. This has been years in the making after fishing rivers for steelhead and trout. The good thing is that we know exactly what we need in a boat after using so many others.

After much thought and discussion and not to mention research we have decided on another river pram. Our first boat was a 8' hankison drift pram that is nine years old and still going strong. I plan on restoring that boat this summer and adding a small outboard.

The new boat will be a hybrid, a combination drift pram and power boat. The boat will be 12' long and around 55" wide at the bottom. Our goal is around 125 -150lbs bare hull. This will be another stitch and glue boat which we have experience in. 2 person capacity and around 6hp. Should work great.

My main question is that we would like to assemble a working prototype to test the hulls motoring and rowing qualities and also get a feel for draft and balance issues. We were thinking about using Luan plywood for the prototype .We want to keep the costs down as our budget is limited to a few thousand dollars for the two bare hulls. I am against covering the Luan hull with fiberglass due to increased cost but my brother insists that it needs it for strength purposes. Who is right here and what are your thoughts on building an inexpensive prototype out of plywood.

Secondly if anyone could point me towards some information on building scale models from plans that would be appreciated. I want to try some cardboard models first.

Jason

[ancient kayaker]

This thread has a discussion on use of Luan ply: http://www.boatdesign.net/forums/boat-design/luan-reliability-9414.html

General concensus about luan seems to be that quality has slipped alarmingly in recent years and for a boat you want to keep it's not worth it. However, for a short-lived test platform, why not? I don't think the bother and expense of glassing the hull is worth it for a temporary boat, cheaper, quicker and better to use thicker ply which should also reduce the risk of catastrophic failure. Certainly, based on my own experience, the 1/8 "door skin" ply should be avoided like the plague.

I use card models a lot, with popsicle sticks, coffee stirrers and shishkebab sticks for frame members. Mostly I use them to test out new construction methods, or just to get a feel for any weak points in a hull. Model aircraft glue is fast setting, don't use the stuff meant for assembling plastic models.

[jason vandeusen]

Thanks

I will be going with generic 1/4" and 3/8" sheathing plywood. Its cheap and alot stronger than luan. Epoxy encapsulation without glassing. This will be cost effective and time saving. I have some left over epoxy so this will work.

Jason

[ancient kayaker]

Should be adequate for a lightly used prototype, but I might be inclined to use 3/8 all over it there is not much price difference. How do you plan to join the ply at the seams? You could get by with glass tape and epoxy: both sides with a fairing of epoxy filler on the inside so the tape will follow the curve. Or you can use lumber battens, say 2 x 2 for the proto.