Hull Inspection and Materials Flashcards

A surveyor observes longitudinal cracking along the topsides of a fiberglass vessel near the sheerline. What is the most likely cause?

Answer: Stress cracking from hull flex or impact loading at a stiff structural transition

Longitudinal cracking near the sheerline typically results from stress concentration at the transition between the flexible topsides and the stiffer deck structure.

What does the term 'hogging' describe in relation to hull deformation?

Answer: The hull's ends drooping below the midship section, creating a convex keel line

Hogging occurs when the bow and stern sections sag relative to the midship, causing the keel to bow upward amidships when viewed from the side.

When inspecting a hull with a wood-epoxy (WEST System) composite construction, which defect most compromises the integrity of the epoxy barrier coat?

Answer: Crazing or checking of the wood substrate allowing moisture intrusion

Wood checking or crazing creates cracks that penetrate the epoxy barrier, allowing moisture to reach the wood substrate and initiating rot in a WEST System hull.

A surveyor finds pitting corrosion on the interior of aluminum hull frames. What is the first investigative step to determine the cause?

Answer: Test the bilge water pH and check for contact with dissimilar metals or alkaline materials

Pitting in aluminum frames is often caused by galvanic action with dissimilar metals or by alkaline bilge water (from cement ballast or cleaners), so testing bilge water pH and checking for dissimilar metal contact is the diagnostic first step.

What is the function of the 'deadrise' measurement in hull form assessment during a marine survey?

Answer: It quantifies the angle of the hull bottom from horizontal, affecting wave-entry performance and stability

Deadrise is the angle of the hull bottom measured from horizontal; higher deadrise (V-bottom) improves rough-water performance while lower deadrise increases stability and load capacity.

Which non-destructive inspection method is most appropriate for detecting subsurface delamination in a fiberglass laminate over a large hull area?

Answer: Infrared thermography

Infrared thermography detects delamination by identifying temperature differentials caused by voids that retain or release heat differently from solid laminate.

When a surveyor notes 'starved laminate' in a fiberglass hull layup, what condition does this describe?

Answer: Laminate with insufficient resin saturation leaving dry fibers and voids

Starved laminate has insufficient resin to fully wet out the reinforcing fibers, resulting in voids, dry spots, and significantly reduced structural strength.