Re: Boat design question
I'm afraid I need to re-agree with the guy agreeing with me
The wood is ok for support structure generally... although it's a bit chunkier than I'd choose for the same job.. plywood would be stronger, lighter, and less bulky.
But the thing is, your boat is designed to flex a bit... the foam is very rigid, but not completely, and the fiberglass isn't completely rigid.... because it's designed to flex, it avoids failures from forces that would destroy other boats. It bends rather than breaking.
The wood, on the other hand, won't bend, or at least won't bend as much. What'll happen is that your hull and the foam will bend around it, then the wood's stiffness will take over and keep it from going farther... which sounds good, except that the wood won't be transferring that force to the hull evenly. It'll be concentrating it into the spots where those vertical bits touch the keel (normally we'd consider those to be "hard spots" which are to be avoided). The keel on most boats won't flex, but yours might, at least relatively speaking.
Bottom line... you DO NOT NEED any support structure for the hull itself. If you want to support the deck, pour the foam then cover the top of it with a layer of wood or a thick layer of glass, for puncture prevention. Or make your deck thicker, or glass a skeleton of thicker ribs on the deck bottom before you install it.
If you try to build the classic stringers/ribs setup into this boat, you're just going to make it very heavy and less durable. It's a classic design for a reason, and although it seems intuitively you'll make it stronger and better by adding things, you
really won't.
If you must have more strength, put in denser foam.. it's only slightly heavier, and if you go to 8 or 16 lb foam your hull will essentially be solid plastic, tougher than anything but a steel plate hull.
If you haven't done it already, go read on the net why Boston Whalers are considered to be strong and unsinkable... not to mention how expensive and sought after they still are.
There's even an ad picture of one cut in half at the midpoint, across the gunwales... two people on the helm, the outboard sinking down and the front out of the water... and still floating.
Erik
