Question 1

Why should keel bolts on a fin-keeled sailing yacht be periodically inspected, particularly on an older vessel?

Accepted Answer

Keel bolts carry the full loading of the keel, which is both a major structural element and often the vessel's main source of stability — corrosion, stretching, or crevice corrosion (often hidden from simple visual inspection) can weaken them over years, and a keel bolt failure is a serious, sometimes catastrophic structural event A keel carries real, ongoing structural loading and is often central to a sailing yacht's stability — keel bolt failures, though rare, are serious enough that periodic inspection (often as part of a haul-out survey, since crevice corrosion can hide beneath washers or in the bolt itself) is standard practice on vessels of any real age, not an optional extra.

Question 2

What is osmosis in a GRP (fibreglass) hull, and what are the classic early signs to look for?

Accepted Answer

Water gradually permeating through the gelcoat into the underlying laminate, reacting with residual chemicals to form a mildly acidic solution that draws in more water and can create small blisters — small, weeping blisters in the gelcoat below the waterline, sometimes with a vinegar-like smell when pierced, are the classic early sign GRP osmosis is a slow, gradual moisture-ingress process rather than a sudden failure — the classic tell is small blisters in the gelcoat below the waterline, which when pierced can release a mildly acidic, sometimes vinegar-smelling fluid. Catching it early (regular hull inspection when lifted out) makes a real difference to how straightforward and affordable it is to address.

Question 3

Why does antifouling paint need reapplying periodically, and what determines roughly how often?

Accepted Answer

Antifouling works by slowly releasing biocides (or, for some types, gradually eroding) to deter marine growth — its effectiveness diminishes over a season or more as the active ingredient depletes, so it needs reapplying periodically, with the exact interval depending on the paint type, local water conditions, and how much the boat is used versus left static Antifouling isn't a permanent barrier — it works by actively deterring growth through a slowly-depleting biocide or a controlled erosion of the paint layer itself, so its protection genuinely runs out over time. How long varies with paint type and local conditions (warmer, nutrient-rich water tends to grow fouling faster), which is why "when did you last antifoul, and where" is a real, relevant maintenance question.