Hull, keel and appendages

The watertight envelope of the vessel — shell, structure, coatings and identification.

The hull, keel and hull appendages form the watertight envelope of the vessel. Every other system on board is mounted to, penetrates, or is protected by this envelope. Its integrity is non-negotiable — a compromised hull is not a maintenance issue, it is a survival issue.

Overview — what this group covers

Hull, keel and appendages is the group of primary structural components that define the vessel below and at the waterline. YachtPrep tracks three core areas within this group — the hull shell and its integral structural appendages, the applied paint systems that protect it, and the builders plate that identifies it.

These components are not interchangeable with fit-out items. They cannot be replaced on a whim, they cannot be deferred indefinitely, and they cannot be inspected from the cockpit. Each demands a documented specification, a scheduled inspection cadence and a recorded service history — the foundation of every insurance survey, pre-purchase survey and flag state inspection.

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Structure — hull, keel and appendages

The hull is the single load-bearing structure that carries the vessel and everything on it. On a sailing yacht, the keel is integral to hull loads; on a motor yacht, the shaft bracket, rudder skeg and bow thruster tunnel are all hull appendages that transfer concentrated loads into the shell.

• Hull shell — the primary laminate, plating or planking. Thickness, lay-up schedule and core material (if cored) are the specifications that determine design strength. Osmosis, blistering, delamination and impact damage are the failure modes that reduce it.

• Keel — the ballasted structural member on a sailing yacht. Keel bolts, keel stub, and the hull/keel joint are the highest-stress interface on the vessel. Grounding events, even minor, must be logged against this record.

• Appendages — rudder, skeg, shaft bracket (P-bracket), bow thruster tunnel, stern thruster tunnel, trim tabs. Each is a structural discontinuity and therefore a potential crack initiation site. Each requires its own inspection schedule at haulout.

Every through-hull penetration — sea water intakes, exhaust outlets, log and depth transducers, bonding studs — is a hole cut into this structure. Those penetrations are tracked separately under through-hull fittings, but their integrity depends on the surrounding hull laminate being sound.

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Protection — paint and coating systems

Paint is not cosmetic on a yacht. It is the active barrier between a structural material and a corrosive, abrasive, biologically aggressive environment. A failed coating system is a failed hull in slow motion.

Three coating systems apply to the hull:

• Antifouling — the below-waterline system. Biocidal, eroding, hard or self-polishing; selected for the vessel's operating profile and regional legislation. Performance degrades from the day it is applied — an annual or bi-annual reapplication cadence is typical, and each application must be logged.

• Primer and barrier coats — the foundation beneath both antifouling and topside finishes. On a GRP hull, an epoxy barrier coat is the defence against osmotic blistering. On a metal hull, primer is the defence against corrosion. Barrier coat service life is measured in years, not months — but once breached, the hull is exposed directly to seawater.

• Topside finish — the above-waterline coating. Polyurethane or two-pack finishes give UV resistance and gloss retention; gelcoat restoration is the alternative on older GRP hulls. Cosmetic appearance is a side effect of the real function — protecting the substrate from UV and salt.

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Identification — the builders plate

The builders plate is the vessel's permanent identification — builder, yard number, year of build, CE / ISO category, design displacement and design waterline. It is the reference every surveyor, insurer and chandler will ask for when parts need to be matched to the original specification.

The plate itself is a small component but it is the primary link between the physical vessel and its design documentation. Photograph it. Record every field. Keep it with the vessel's compliance record for the life of the yacht.

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Maintenance and lifecycle tracking

Hull, keel and appendages are inspected on a haulout cycle, not an underway cycle. That makes documentation between haulouts the only reliable source of history — written records, photographs, coating product data sheets, paint dates, anode condition logs and any grounding or impact notes.

Record	Why it matters
Hull construction and material	GRP single-skin, cored laminate, aluminium, steel, timber — determines every inspection and repair method.
Keel configuration	Bolted fin, encapsulated, lifting, twin — dictates the inspection of keel bolts or hull/keel joint.
Antifoul product and application date	Schedule renewal, verify compatibility, track biocide legislation changes.
Barrier / epoxy coat history	Service life of the osmosis barrier; due date for reapplication.
Haulout inspection notes	Blisters, cracks, impact damage, rudder bearing play, cutless bearing wear — the record that feeds pre-purchase survey.
Grounding / impact events	Even minor contact must be logged — latent damage to keel joint or rudder stock may not be visible without ultrasonic test.
Builders plate record	Permanent vessel identification — required for every insurance and flag state correspondence.

A documented hull history is the single most valuable record on any yacht. It is the item that makes the difference between a successful pre-purchase survey and a failed one; between a clean insurance renewal and a loaded premium; between a routine haulout and an unplanned repair. YachtPrep is designed so this record is built day by day, not reconstructed under pressure.

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Components

See below for the components available in YachtPrep to manage your hull, keel and appendages.