Енциклопедія яхт
Thru-hull (hull fitting)
Thru-hull fittings on yachts: what they are, how they relate to seacocks, and what FairHelm checks on used boats in Northern Europe.
Що це
A thru-hull is a fitting that penetrates the hull so seawater, sinks, toilets, or instruments can pass the laminate. It is not the valve alone: the flange, sealant, backing, seacock, and hose form one system.
Anchor
On Baltic and North Sea boats FairHelm usually meets bronze or composite thru-hulls below the waterline tied to seacocks. Plastic fittings above the waterline appear on vents and drains. Material choice and age matter more than brand names in listing photos.
FairHelm judgment
FairHelm judgment: treat every below-waterline thru-hull as a survey item. Seize, corrosion at the flange, mismatched metals, and cracked hose tails beat cosmetic bilge photos. Do not accept "recently replaced" without yard notes or photos of the closed valve.
Limits
This page does not invent failure rates or claim one alloy always lasts N years. Condition depends on electrolysis, antifouling schedule, and winterisation. Ask a named surveyor for the boat in front of you.
Часті запитання
Q: Is a thru-hull the same as a seacock?
A: No. The thru-hull is the hull fitting. The seacock is the valve. Both must work.
Q: Should every thru-hull have a seacock?
A: Below the waterline, FairHelm expects a working valve. Above-waterline drains may differ. Confirm on the specific boat.
Q: Can I ignore plastic thru-hulls if they look clean?
A: No. Check for UV damage, cold cracks, and hose clamps. Clean looks do not prove integrity.