MST Hull & Fiberglass Repair Flashcards

Delamination of a fiberglass hull is best detected using which method?

Answer: Sounding with a plastic mallet

Tapping the hull with a plastic or rubber mallet produces a dull thud over delaminated areas, compared to a sharp ring over solid laminate.

Which type of resin provides superior adhesion and moisture resistance for structural hull repairs compared to polyester?

Answer: Epoxy resin

Epoxy resin bonds more strongly, absorbs far less water, and provides better chemical resistance than polyester for structural repairs.

What grit sandpaper is typically used for the final prep of gel coat before applying a color-matched gel coat patch?

Answer: 220–320 grit wet/dry

220–320 grit wet/dry sandpaper creates a surface profile that allows the new gel coat to bond while minimizing visible scratches.

Why is polyvinyl alcohol (PVA) film sometimes applied over a gel coat repair?

Answer: To exclude air and allow the surface to cure fully

Polyester gel coat requires exclusion of oxygen to cure tack-free, and PVA film seals the surface from air.

A spider crack pattern in gel coat typically indicates what underlying condition?

Answer: Impact damage or flexing stress in the laminate

Spider cracks (crazing) usually originate from an impact or chronic flexing that stresses the rigid gel coat beyond its limit.

What is the purpose of using a release wax on the repair mold when performing a gel coat blister repair?

Answer: To prevent the patch material from bonding to the mold surface

Release wax (or mold release agent) creates a barrier between the gel coat and the mold so the cured patch can be removed cleanly.