Hey Mike,

You sure do generate a lot of ideas :-) I think we are closing in on the solution (though I don't know if anybody else is still tuned in).

> Unfortunately, if the foam does not retain your butt's or yak's shape
> after it is set, then the idea is pretty much useless. But I wonder, how
> would it spring back? If the plaster is cross linked maybe the worst you
> get is a little bit of a fuzzy surface?

I would guess that the compressed areas of foam might not have enough plaster left to hold the foam in shape.

> The idea of containing the mold is to make it light and thin - say 1/2 -
> 1" thick. So that you can move it around , cut it and shape it
> easier. Or add more plaster etc. here and there to fix it, say extra
> burlap on the back. The idea of the two cheap plastic sheets (say 6 mil)
> is that all the mess is contained. Just throw the plastic in the garbage
> can.

OK. Here we have something, I think the key to your approach is just what you said: "containing the mold". Using two plastic sheets would allow the plaster to squish out all over the place.

What we need is a bag that is strong enough that the plaster cannot escape while setting - forcing it to (just) float you (not too high - your cheeks should be touching the kayak for lowest CG), conform to your butt and the shape of the kayak at the same time.

Creases in the bag could cause some problems with voids in the pattern but they could be repaired after. The trick would be to use the right amount of plaster and adjust the volume of the bag to control the thickness of the pattern. Should be easy enough - throw in the plaster, squeeze out the air, duct tape the bag opening to a dowel and roll up the bag (like a toothpaste tube) until you get the thickness you need and sit in it.

It would be just a matter of letting the plaster come to full cure, making a fiberglass copy of the top & bottom and epoxying them together. Betcha you could make a pattern in an hour with this approach.

If you wanted to get real fancy you could make a negative mold from the pattern, cast a wax pattern in it, fiberglass the wax pattern using pigmented epoxy, drill a hole in the fiberglass shell, melt out the wax and fill the fiberglass shell with expanding foam, glue it to the bottom of the yak.

> I dunno, any reaction to any of this stuff Hank?

> -mike

Your other ideas sound "interesting". I am sure that it would be a lot of fun to try them out - take a video, could be worth some money ;-)

Hank