SAMS Hull Inspection and Materials 2 — Questions and Answers
Question 1: When inspecting a fiberglass hull, what does a 'thud' sound during sounding indicate compared to a sharp 'click'?
- Sound laminate with good resin saturation
- Delamination or void within the laminate (Correct answer)
- Properly cured gel coat surface
- Adequate core density
Correct answer: Delamination or void within the laminate
A dull thud when sounding a fiberglass hull indicates delamination or a void where layers have separated.
Question 2: Which coring material is most resistant to moisture absorption in a sandwich-construction fiberglass hull?
- End-grain balsa
- Plywood
- Cross-linked PVC foam (Correct answer)
- Divinycell H-grade
Correct answer: Cross-linked PVC foam
Cross-linked PVC foam has a closed-cell structure that resists moisture absorption better than balsa or plywood core materials.
Question 3: A surveyor observes blistering on a fiberglass hull below the waterline. What is the primary chemical process causing osmotic blisters?
- Oxidation of the styrene resin
- Hydrolysis of ester linkages in polyester resin (Correct answer)
- Galvanic corrosion of embedded hardware
- UV degradation of the gel coat
Correct answer: Hydrolysis of ester linkages in polyester resin
Osmotic blistering results from hydrolysis, where water permeates the gel coat and reacts with ester linkages in polyester resin, forming acidic byproducts.
Question 4: What ASTM standard governs the testing and classification of marine-grade plywood used in hull construction?
- ASTM D1761
- BS 1088 (Correct answer)
- ASTM D3043
- APA PS 1-09
Correct answer: BS 1088
BS 1088 is the British Standard that defines marine-grade plywood with face veneer quality and waterproof bonding requirements widely used in boatbuilding.
Question 5: During a steel hull inspection, what technique is used to measure remaining plate thickness without removing interior linings?
- Caliper measurement at cut sections
- Magnetic particle testing
- Ultrasonic thickness gauging (Correct answer)
- Eddy current testing
Correct answer: Ultrasonic thickness gauging
Ultrasonic thickness gauging allows non-destructive measurement of steel plate thickness from one side without removing interior linings.
Question 6: Which type of aluminum alloy is most commonly specified for recreational boat hull construction due to its corrosion resistance in saltwater?
- 2024-T3
- 5086 or 5052 series (Correct answer)
- 7075-T6
- 6061-T6
Correct answer: 5086 or 5052 series
5000-series aluminum alloys (5086, 5052) contain magnesium and offer superior corrosion resistance in marine saltwater environments.
Question 7: When inspecting a wood hull, which structural member connects the keel to the stem and sternpost, forming the backbone of the vessel?
- Keelson
- Garboard strake
- Deadwood (Correct answer)
- Hog
Correct answer: Deadwood
The deadwood is the solid timber section connecting the keel to the sternpost (and sometimes stem), forming part of the hull's backbone structure.
SAMS Hull Inspection and Materials 2
When inspecting a fiberglass hull, what does a 'thud' sound during sounding indicate compared to a sharp 'click'?