Rehd:

The problem with sealed air chambers as flotation is that they are sealed. Sounds redundant, but you have probably already gone throught the postings on venting other sealed cargo compartments -- and the problems you can get if you don't vent them.

A brief recap, though for those who are not as up to date. When those sealed compartments warm up the air inside expands and can exert a good deal of pressure of the materials and joints. When the air inside cools, it contracts, and the outside air exerts a great deal of pressure on the compartment. Any perfectly sealed area therefore is going to be expanding or contracting depending on temperature. If the change in temperature is great enough, something will give.

It only takes a very tiny hole to allow the pressure to equalize. I suspect the 'inspection' ports fit loosely enough that a small amount of air can be sucked into the box seat base, or expelled from it, so that pressure equalization can occur. They may also be there to allow drainage of any water that might leak in.

If the bases of the seats are basically square, you would probably be best off with foam panels, or even the cheaper bead board inulation. 4 x 8 beadboard in 1 inch thickness sells for anywhere from 99 cents to $6 a panel, sepending on sales and suppliers near me. After you have sealed the wood and finished the fillets on the seat, cut squares out of the panels, and place them in the seat cavity. Make the squares a tad over size and they will be a tight fit, so they don't flap around, and just push them in firmly. If you use peanuts you will have space between the peanuts where water can fill in. This reduces the flotation abilty of any given volume of space. since the seats completely surround the floatation foam you can use the cheapest material (and bead board is definitely cheap) without regard to any structural properties. Bead board is definitely lacking in significant structural properties, but if it is protected by being totally enclosed by plywood it should work beautifully as flotation. Include the inspection ports/hatches/covers or whatever.

The insulation boards, no matter whether they are foam or bead, will be cheaper and faster to use than the expanding foam. You can't overfill with them, and should the compartment ever develop a leak or need to be opened, they can be removed, dried out, and then returned to their place. Try doing that with a plug of expanded-in-place foam.

If you attach the seat tops with a hinge and a latch, so they can be opened, you can fit the under-seat compartment part way with foam for flotation, and use the remainder as a storage area for fishing tackle, bait, or whatever.

Best of luck with this project.

PGJ

: Hi Paul

: Hey, some good ideas there. The seats are totally enclosed with plywood,
: then, fiberglassed and then painted. They sold Steve the little video with
: the boat, and we're building it " As Pictured." Glen-L calls for
: the seats to be plywood boxes, and filled with foam. I'm sure it's
: overkill with this little boat, but, that's what the video shows. I'm not
: sure why the inspection plates are there unless they want to open it up
: and see the foam. I can't imagine it, but, this IS California. ??? Since
: this is basically a one-man craft ( because we are both good sized boys )
: I may include the foam Ice cooler up front. I checked around for the
: two-part foam and I couldn't believe the price. I found it here at
: Precision Plastics in Fresno and it was $54.48 for two 32 oz cans. Don't
: know how far that will go, but, it's pretty much half of what we have in
: the boat already. NOT!! I think the foam peanuts idea is a good one here.
: The sheet foam would work too, but, would probably cost more. Thanks for
: the ideas.

: Rehd