In reply to "gunwhales and front seat", posted by Ryan on
You're correct about stiffness Ryan. Just like a steel I beam the more distance between the top and bottom chords the stiffer it will be. In this case, spacers or frames between inwales and outwales will be strong and stiffer than just clamped together. The biggest reason I do this is to minimize the little spaces to seal and varnish that are hard to get to. With the peices together with no spaces they are very simple and clean to epoxy seal, sand and paint, varnish. If you are concerned about stiffness you can make the pieces a little thicker, although I've found that 3/4"x 1 1/2" is pretty stiff an the gunnels actually don't take direct hits all that often. The biggest time I see them flex is putting the trailer strap on.
As to the front cooler, it's my opinion to make them as light as possible since all that wood adds up. Since the stress on the seats is mostly straight down you can use the plywood on edge and it's very strong when glassed in and built like an egg crate with a few other bulkheads dividers. 1/4" unless you plan on using it for a kicking board.