Inspecting a boat for problems within the fiberglass structure is very important.

Rotten wood is common and disbonded and delaminated layers are a big problem.

There are several things to consider and look for.

The video below demonstrates that sound is an important tool to help identify problems.

From Skipper Rudy

Fiberglass boats – testing your stringers for rot.
Also explaining the differences of; bond, dis-bond, de-lamination.