Keith,
All polyurethane foam is open cell and will, over time, absorb liquid.
additionally, it sticks to anything tenaciously. It is ideal as an
insulator. It is a fire hazard because it gives off toxic fumes. It is very
popular with steel hull owners because of its ability to prevent inside
condensation, which is the death to steel vessels. It should never be
applied where it will see water. If used, it should be painted with a
special waterbased fire retardant paint. This paint will protect the foam
from absorbing splashed water and water vapor. If floatation protection is
the reason for use, don't. Use hyperlon fabric chemically welded into custom
airbags. You will not regret the slightly higher initial cost. Just remember
to use padding on hard spots to prevent abrasion.
Steve

"keith" wrote in message
...
Just a quick question. Is polyurethane buoyancy/flotation foam in
aerosols the same as the polyurethane foam sold at builders merchants
for sealing voids and cracks etc?

The reason that I ask is that my local chandlery has aerosol foam that
looks about the same if you read the ingredients etc on the tin, but
the builders is cheaper.

Keith