Technically, you could use anything you'd normally use around the house, but
going with something 'waterproof' would be best so it doesn't absorb water.
Are you using epoxy? If so, most epoxy users will mix a thickener such as
phenolic microballoons and silica into some epoxy to thicken it up and use
that for filling holes. Not sure what polyester fiberglassers use. Maybe
it's possible to thicken polyester resin with wood flour or something, and
use that?

Brian D



"Donnie Gilliland" wrote in message
...
I'm building a small tunnel hull and am at the point where I need to fill
the screw and nail holes. Does anyone have a favorite putty they would
recommend ? I will be fiberglassing the outside of the hull and then
painting.

Thanks in advance.
Don