wrote in message
ups.com...
Leaving the frames out would be good - otherwise I'd have to put a
layer of wood on the inside too (for comfort reasons - it is a hot
tub).

Don't know if anyone has mention this before, but as I understand epoxies
are highly sensitive to temperature. This was googled out on "epoxy
temperature" search:
http://www.epoxyproducts.com/novolac.html

Brian Whatcott wrote:

This is a speculative idea, rather than the fruit of long experience.
Yes I am thinking of ply ribs in two directions at right angles,
Whose faces are all vertical, so that in plan view, they would look
a noughts n crosses game of lines say 1/4 in thick, and in side view
they would be 2 inches deep and wide (at the sides.)
An internal and external skin would then provide a strong stiff light
structure. The crucial detail is making the inside skin fair and
smooth. This is left as an exercise for.... :-)

Brian Whatcott

Interesting idea. For the inner/outer skins, did you have in mind
multiple layer of wood like the boat Meindert Sprang pointed out, or
fiberglass, or both?

I wonder also if it would be wise to put a coat of epoxy on the inner
ribs, to prevent rot (just in case steam managed to work through the
outer skin somehow). Perhaps regular wood sealer could even be used
instead of epoxy, since its adhesive properties aren't needed, only a
moisture barrier.

I anticipate the tub being about 104 degrees F. So notwithstanding any
problems with my heat source, I should be below the 140-160 degree
maximum (for wet conditions) of regular epoxy. Although my heat source
is wood-fired, I have a thermostat of sorts worked out. I can probably
control the temperature to within a few degrees.

On 23 Oct 2005 14:26:33 -0700, wrote:

Brian Whatcott wrote:

This is a speculative idea, rather than the fruit of long experience.
Yes I am thinking of ply ribs in two directions at right angles,
Whose faces are all vertical, so that in plan view, they would look
a noughts n crosses game of lines say 1/4 in thick, and in side view
they would be 2 inches deep and wide (at the sides.)
An internal and external skin would then provide a strong stiff light
structure. The crucial detail is making the inside skin fair and
smooth. This is left as an exercise for.... :-)

Brian Whatcott

Interesting idea. For the inner/outer skins, did you have in mind
multiple layer of wood like the boat Meindert Sprang pointed out, or
fiberglass, or both?

I wonder also if it would be wise to put a coat of epoxy on the inner
ribs, to prevent rot (just in case steam managed to work through the
outer skin somehow). Perhaps regular wood sealer could even be used
instead of epoxy, since its adhesive properties aren't needed, only a
moisture barrier.

I thought, fix thin laths to the inner rib contours. The laths need
not be gapless. Then a layer of glass on top.

Brian W