Re: [VAL] Stuff on the bottom of the bathtub

["chyde" <brownhyde@xxxxxxxxxxxxxx>]

Chris & Ed,
Acrylic hot tubs are thermoformed out of large sheets of acrylic, then
reinforced with fiberglass applied to the back surface. Urethane foam blocks
and spray on Urethane foam are often used to insulate and to create a flat
surface on the bottom of the tub. Urethane foam is compatible with polyester
resins and epoxy resins (styrofoam is not) commonly used in fiberglass
construction so you are able to glass right over the shaped foam without
worrying that the foam will degrade. I don't believe that urethane foam
blocks are available at the retail level but you can buy it in a sprayable
form. Look in the insulation dept of any home renovation store for the
sprayable "gap sealer" for homes. You will be able to spray this stuff onto
surfaces and it will expand considerably. Once it has hardened you can shape
it with common hand tools like saws and rasps. Covered with fiberglass, it
turns into a structural element.
As far as repairing the surface gelcoat on the tub, you are better off
repairing it as you would repair an auto body or a boat then paint it with
modern two part auto paint. Old gelcoat parts typically show small hairline
cracks. These cracks are not structural. Just grind or sand out the crack
right down to the glass then build it up again with body filler. I have been
using PPG Concept two part auto paint on my restorations. You can get
virtually any color mixed at an auto body supply shop. They can also add
"flatting" agents if required. You can also purchase mixed colors that were
mistakes (at a reduced price) then play with the color mixing yourself.
Hope this helps out,
Colin
(Building monocoque composite accessible vehicles in my other life.)