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 Hudson Force 50 is a full keeled pilothouse cutter ketch, from the drawing board of William Garden, a US and Canadian trained naval architect. Introduced in 1973, they were built in Taiwan at the rate of twelve to fifteen per year until 1984 when the boatyard burned down.
They are nearly identical to the Formosa 51, the molds for the Force 50 come from the same plug that formed the Formosa 51. It is said William Garden did kind of a “private label” deal with Formosa, and some believe the Force 50 is has more of a seaworthy classic flavor with subtle improvements. The Force 50 is known to have less room below decks primarily due to her lower freeboard.
This is a go anywhere sailboat with a touch of the traditional complete with a long bowsprit and on some boats, wooden spars. Teak abounds above and below decks.
As testament to the boats seaworthiness, owner Tom Allen recalls a single handed passage between Los Angeles to Monterey, “I lost my main sail rounding Point Lobos in 55 to 60 knots of winds. I was popping out of 25 foot seas with half the boat coming out of the swell and then slamming onto the bottom of the wave. It sounded like someone taking a sledgehammer and hitting the front half of the boat. When I arrived in Monterey I kissed the ground realizing that this is a very sturdy 30 year old boat that I would definitely trust my life in.”
Three staterooms, master is aft with head, two double guest cabins forward with shared head and step in shower. Pilothouse with inside helm station, and lower saloon with desk. L-shaped settee to starboard going forward to starboard is a double guest cabin and to port is the head and shower. Forward is an upper and lower to starboard, workbench and cupboards to port.
The condition of these boats vary widely, some have been well cared for while others have been neglected to “desperately needing a refit” status. Prices for these boats can seem cheap but be aware fixes on boats of this size can be considerable, three to five times more than an equivalent 30 foot boat is a good rule of thumb.
Have your surveyor check the boat thoroughly in the usual places, the hull on haulout, the numerous through-hull fittings, bulkheads, chainplates and rigging, engine, drivetrain, electrical systems, and particularly the metal fuel tanks. Water intrusion in the deck and pilothouse area is sometimes a problem. Also check over the base of the mast and booms on boats with wooden spars.
» Owner’s online forum can be found at www.force50.org
Thanks goes to Tom Allen for co-writing, providing research and owner feedback to this article.
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