I would guess it all depends on YOUR defilation of 'foam'.

When this question comes up there are usually references to ' . . .pouring
foam . . .'. I would absolutely NOT use any of the 2-part 'Pour-in-Place'
foams. Your are really in it, as regards solutions to 'What if . . .?'
problems.

What I think of in this situation is the foam 'Swim Noodles' or big blocks
of Styrofoam. Cut to roughly 'rod shape' about the ID of the mast. Just
shove them into place with a long piece of 1x1 or lengths of 1in PVC.

The reasoning behind ANY foam or flotation material is to fill AIR SPACE. It
is the AIR that gives the actual buoyancy. That's why they designate the
'Marine' foam as '2 pound', '3 pound', etc. That means that for each cubic
foot, the foam weighs 2 pounds, etc. Therefore, when calculating buoyancy .
.. . a cubic foot of water {there is a slight difference between Salt and
Fresh}weighs about 62 pounds MINUS the weight of the foam EQUALS the ability
to support 60 pounds per cubic foot of that particular material.

Regards & Good Luck,
Ron Magen
Backyard Boatshop

"Robert or Karen Swarts" wrote in message
...
Assuming one makes provision to access and mechanical or electrical
components within the mast, are there any compelling reasons NOT to foam
fill the mast?

Bob Swarts