glassfiber over concrete

[tropicalbuilder]

Hi,
rebuilding a fiberglass boat with an internal keel of concrete glassed over..
I have to replace part of the glass over the concrete, but before I have to fill some imperfections and fair the keel top with new concrete... what kind of concrete is best?
how long before i can glass on top of it?

[gonzo]

Fair it with polyester putty. The humidity in cement will create a lot of problems with the fiberglass otherwise.

[tropicalbuilder]

ok .. sounds good