T&T: Filling pockets behind stringers in older trawler

[Bob Austin]

A lot would depend on what the material in the area you want to fill is. If
the boat is fiberglass, and the stringers are absolutely encapsulated in
glass, then filling with any material will work.  20 to 30 gallons is a
considerable amount.  This is too much for the spray cans of foam.  The pour
in foam does expand about considerally: the 4 lb pourable urethane foam will
give 2 cubic feet   The 16 lb urethane foam will give 8 cubic feet    and 80
lb kit will give: 40 cubic feet (if you really need a lot).  Use a material
which will not absorb water.  Be sure that the area you are foaming is clean
and down to glass. Be sure that there is no rotten wood, or stringers with
limber holes cut in them, which were not glassed, where water would have
caused rot present.  I would agree with putting a layer or two of glass in
epoxy over the foam.

If the boat is wooden, then an entirely different process is used--and
concrete was used fairly frequently.

Bob Austin