MTC MTC Hull & Structural Systems 2 — Questions and Answers
Question 1: What is the purpose of 'osmotic barrier coating' applied to a fiberglass hull below the waterline?
- To add weight for stability
- To prevent water penetration that causes blistering (Correct answer)
- To improve antifouling paint adhesion only
- To reduce hydrodynamic resistance
Correct answer: To prevent water penetration that causes blistering
Osmotic barrier coatings (typically epoxy-based) seal the fiberglass laminate against water absorption, preventing the hydrolysis that leads to hull blistering.
Question 2: A marine technician notices soft spots in a fiberglass deck. What is the MOST likely cause?
- Insufficient paint thickness
- Water-saturated core material (balsa or foam) (Correct answer)
- Improper antifouling paint application
- Overloading the vessel
Correct answer: Water-saturated core material (balsa or foam)
Soft spots in cored fiberglass decks are almost always caused by water intrusion into the core material, which weakens it structurally and must be replaced.
Question 3: What is the recommended procedure for sealing a deck hardware fitting to prevent water intrusion?
- Apply marine-grade sealant (polysulfide or polyurethane) under the fitting base (Correct answer)
- Use standard household caulk
- Leave a gap for drainage
- Tighten the fasteners very firmly without sealant
Correct answer: Apply marine-grade sealant (polysulfide or polyurethane) under the fitting base
Marine-grade sealants such as polysulfide or polyurethane create a flexible, waterproof bond between hardware and the deck surface, preventing water from entering the deck core.
Question 4: Which of the following best describes 'freeboard' on a marine vessel?
- The height of the mast above deck
- The vertical distance from the waterline to the top of the hull at the side (Correct answer)
- The horizontal width of the hull at its widest point
- The length of the keel
Correct answer: The vertical distance from the waterline to the top of the hull at the side
Freeboard is the distance from the waterline to the upper deck edge, and greater freeboard generally means more reserve buoyancy and better seakeeping in rough conditions.
Question 5: When inspecting a vessel for compliance with US Coast Guard standards, what does 'maximum persons capacity' refer to?
- The number of lifejackets required
- The maximum number of people the vessel can safely carry based on weight and stability limits (Correct answer)
- The number of seats installed on the vessel
- The crew size required by law
Correct answer: The maximum number of people the vessel can safely carry based on weight and stability limits
Maximum persons capacity is calculated based on the vessel's length and beam, representing the safe limit of occupants to maintain adequate stability and freeboard.
Question 6: What is the function of limber holes in a boat's structural frames?
- To allow electrical wiring to pass through frames
- To allow bilge water to flow freely to the lowest point for pumping (Correct answer)
- To reduce hull weight
- To ventilate the bilge area
Correct answer: To allow bilge water to flow freely to the lowest point for pumping
Limber holes are cutouts at the bottom of frames and floors that allow water to flow freely to the bilge sump where it can be pumped out.
MTC MTC Hull & Structural Systems 2
What is the purpose of 'osmotic barrier coating' applied to a fiberglass hull below the waterline?