MST MST Hull & Fiberglass Repair 2 — Questions and Answers
Question 1: Delamination of a fiberglass hull is best detected using which method?
- Sounding with a plastic mallet (Correct answer)
- Visual inspection only
- Pressure washing the surface
- Applying heat with a heat gun
Correct 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.
Question 2: Which type of resin provides superior adhesion and moisture resistance for structural hull repairs compared to polyester?
- Epoxy resin (Correct answer)
- Vinyl ester resin
- Standard orthophthalic polyester
- Acrylic resin
Correct answer: Epoxy resin
Epoxy resin bonds more strongly, absorbs far less water, and provides better chemical resistance than polyester for structural repairs.
Question 3: What grit sandpaper is typically used for the final prep of gel coat before applying a color-matched gel coat patch?
- 220–320 grit wet/dry (Correct answer)
- 36 grit dry
- 80 grit dry
- 600 grit wet only
Correct 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.
Question 4: Why is polyvinyl alcohol (PVA) film sometimes applied over a gel coat repair?
- To exclude air and allow the surface to cure fully (Correct answer)
- To add UV protection permanently
- To create a non-skid texture
- To prevent osmotic blistering
Correct 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.
Question 5: A spider crack pattern in gel coat typically indicates what underlying condition?
- Impact damage or flexing stress in the laminate (Correct answer)
- Excessive UV exposure only
- Improper color matching of gel coat
- Normal aging requiring no action
Correct 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.
Question 6: What is the purpose of using a release wax on the repair mold when performing a gel coat blister repair?
- To prevent the patch material from bonding to the mold surface (Correct answer)
- To increase the cure speed of the resin
- To add color pigment to the gel coat
- To improve UV resistance of the finished surface
Correct 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.
MST MST Hull & Fiberglass Repair 2
Delamination of a fiberglass hull is best detected using which method?