The theoretical maximum speed that a displacement hull can move efficiently through the water is determined by it's waterline length and displacement. It may be unable to reach this speed if the boat is underpowered or heavily loaded, though it may exceed this speed given enough power. Read more.
Classic hull speed formula:
Hull Speed = 1.34 x √LWLA more accurate formula devised by Dave Gerr in The Propeller Handbook replaces the Speed/Length ratio constant of 1.34 with a calculation based on the Displacement/Length ratio.
Max Speed/Length ratio = 8.26 ÷ Displacement/Length ratio.311
Hull Speed = Max Speed/Length ratio x √LWL
A measure of the power of the sails relative to the weight of the boat. The higher the number, the higher the performance, but the harder the boat will be to handle. This ratio is a "non-dimensional" value that facilitates comparisons between boats of different types and sizes. Read more.
SA/D = SA ÷ (D ÷ 64)2/3
A measure of the stability of a boat's hull that suggests how well a monohull will stand up to its sails. The ballast displacement ratio indicates how much of the weight of a boat is placed for maximum stability against capsizing and is an indicator of stiffness and resistance to capsize.
Ballast / Displacement * 100
A measure of the weight of the boat relative to it's length at the waterline. The higher a boat’s D/L ratio, the more easily it will carry a load and the more comfortable its motion will be. The lower a boat's ratio is, the less power it takes to drive the boat to its nominal hull speed or beyond. Read more.
D/L = (D ÷ 2240) ÷ (0.01 x LWL)³
This ratio assess how quickly and abruptly a boat’s hull reacts to waves in a significant seaway, these being the elements of a boat’s motion most likely to cause seasickness. Read more.
Comfort ratio = D ÷ (.65 x (.7 LWL + .3 LOA) x Beam1.33)
This formula attempts to indicate whether a given boat might be too wide and light to readily right itself after being overturned in extreme conditions. Read more.
CSV = Beam ÷ ³√(D / 64)
The modernized and bigger sister of the famous Crealock 37, the Pacific Seacraft 40 employs the same design principles that made the 37 such a classic bluewater cruiser – seaworthiness, sea-comfort, and real world performance. Many will recall designer “Gentleman” Bill Crealock’s point that a comfortable boat translates to less crew fatigue which translates to swift passages and therefore safe passages.
The Pacific Seacraft 40 retains much the same look and configuration as the Crealock 37 introduced a whole two decades earlier. The canoe stern hull has large overhangs and there’s a low freeboard by modern standards. Below the waterline sits a moderately long cruising fin keel with a skeg-hung rudder far aft, and like all boats from Pacific Seacraft, a cutter rig is used.
Below decks is a sensible bluewater layout which will serve well both under anchor as well as at sea with considerations such as the U-shaped galley, and a seagoing double quarter berth. There’s plenty of well thought out stowage particularly suited to extended voyaging. Engine access is also good.
Hull construction is solid and traditional. The fiberglass is hand-laid with osomsis-resisting vinylester resin with balsa coring above the waterline (and away from any through hull fittings like chainplates). The coring provides greatly increased hull rigidity. The decks are also balsa-cored. The hull to deck flanges are bedded in pulyurethane and through-bolted and capped with a teak rubrail. Internal bulkheads are both bolted and bonded to the hull and deck.
Undersail, though not considered a speed demon, the Pacific Seacraft 40 can log consistent 140 mile days and do so with very good sea-comfort. The boat is well balanced and directional stability is good making her particularly easy to helm.
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