On Jun 24, 10:41 pm, bill wrote:
I'm doing some repairs on my sailboat, an old Oday day sailer, and
when I removed the seat from one side I found a large tube of
styrofoam created with some large version of something like 'great
stuff' and a bunch of small sheets of white styrofoam. Is this
floatation required, beneficial? What type of products are available
to create custom styrofoam under the seat?

Thanks

I wouldn't worry too much about floatation on that particular boat.
For custom floatation you could go to a Big Box hardware store like
Home Depot and buy a few sheets of blue insulation board. It is very
inexpensive, easy to work with and form, and impervious to water. Or
visit a custom surf board shop and pick up a block of foam.