Sailing Yacht

Overview

A sailing yacht drives to windward by turning wind into forward force across two surfaces working together: the sails above the water and the keel below it. The sails act as vertical foils that develop lift when air flows across them at an angle, and the keel develops an opposing sideways lift in the water that stops the boat sliding to leeward. The difference between those two forces, resolved along the hull, is thrust. The ballast carried low in the keel resists the heeling moment the rig produces, so the boat stands up to its sail rather than capsizing.

The hull described here is a 12 m masthead sloop, a single mast with one mainsail and one headsail, sized for coastal cruising and club racing. Its main groups are the Hull & Deck Structure and deck structure, the Fin Keel & Ballast and Spade Rudder, the Rig & Standing Rigging and Sails & Furling, the Deck Gear & Running Rigging that trims them, Wheel Steering, an auxiliary Auxiliary Diesel & Saildrive for harbours and calms, plus the Electrical System, Navigation Electronics, Tank System and Accommodation systems that make it liveable.

Hull and appendages

The hull is a foam-cored GRP moulding laid up in a female tool, stiffened internally by a bonded structural grid, transverse bulkheads and longitudinal stringers that spread rig and keel loads into the skin. The deck is a separate balsa-cored moulding joined to the hull at a bonded and bolted flange. Where the shrouds land, stainless chainplates tie their tension directly into the grid rather than into the relatively soft skin.

Two appendages do the hydrodynamic work. The Fin Keel & Ballast is a cast fin with a lead bulb at its root, bolted to a reinforced sump through eight keel bolts; the fin gives lift and lateral resistance while the bulb lowers the centre of gravity for stability. The Spade Rudder is a balanced spade: a foam-filled GRP blade moulded around a stainless stock that runs in two self-aligning composite bearings, with a tiller arm at its head for the steering link. Being balanced, part of the blade sits ahead of the stock so helm loads stay light.

Rig and sails

The Mast is a tapered, anodised aluminium extrusion stepped on the keel and passing through the deck. It is held up by wire standing rigging: cap, intermediate and lower shrouds each side, a forestay forward and a backstay aft, all tensioned through bronze rigging screws. Two pairs of spreaders push the cap shrouds outboard to give the wire a useful staying angle. The masthead fitting carries the halyard sheaves and the stay tangs.

The working wardrobe is a Mainsail set behind the mast on the boom, and a Genoa set on the forestay. The mainsail luff runs up the mast track on sail slides, and battens support the roach that extends its area beyond a straight leech. The genoa rolls away on a Headsail Furler, a drum-and-foil unit that winds the sail around the forestay so the crew can reduce headsail area without leaving the cockpit. A boom vang holds the boom down to keep the mainsail leech tight when sailing off the wind.

Deck hardware

Running rigging carries the loads from the sails to the crew. Halyards hoist the sails, sheets control their trim angle, and both are handled through Deck Gear & Running Rigging: geared self-tailing winches give the crew the mechanical advantage to sheet a loaded sail, rope clutches hold each line so a winch can be freed for the next job, and turning blocks route lines aft to the cockpit. The mainsheet runs to a traveller car on a track so its lead angle can be set across the boat. Forward, an electric windlass with a chain gypsy raises the anchor.

Propulsion

For harbours, locks and windless days the boat carries a Auxiliary Diesel & Saildrive: a three-cylinder freshwater-cooled marine diesel of about 29 kW. Engine heat is dumped into raw seawater through a heat exchanger fed by an impeller pump, and the exhaust is water-injected to cool and quiet it. Drive reaches the water through a Saildrive Leg, a right-angle leg passing through a rubber diaphragm in the hull bottom, which is simpler to install and align than a conventional shaft. A folding propeller swings its blades shut under sail to cut drag. Flexible mounts isolate engine vibration from the structure.

Systems and electronics

House power comes from battery banks split into a starting battery and a deeper house bank. They are charged by an engine-driven alternator under way, by deck-mounted solar panels at anchor, and by a shore-power charger in the marina, with breakers and busbars in the distribution panel feeding each circuit. The Navigation Electronics suite is built around a chartplotter that shows charts and instrument data; a masthead wind sensor reports apparent wind, a through-hull transducer reads depth and boat speed, and the Autopilot steers a set course by driving a ram on the rudder quadrant. A VHF/DSC radio with a masthead antenna handles distress and traffic calls.

Accommodation

Below decks the Accommodation fits six berths, a galley and a head into the hull. The galley sits beside the companionway with a gimballed gas stove that swings to stay level under heel, a 12 V compressor refrigerator and a sink on a foot pump. The head holds a manual marine toilet plumbed through seacocks to the Holding Tank. Bonded plywood joinery forms the lockers, bunks and cabin sole, and a folding saloon table sits on the centreline.