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)
Not to be mistaken for Pacific Seacraft’s earlier 1977 full-keeled Mariah 31, the Pacific Seacraft 31 introduced in 1987 shares its heritage with the celebrated Crealock 37 which earned a spot on the American Sailboat Hall of Fame for its seaworthiness and build quality. The diminutive 31 foot design encapsulates the same concepts of comfort and safety but in packs it into a much smaller package. It’s a pricey boat given her size, but you can expect Pacific Seacraft’s usual high build quality. Overall she’s proven to be a surprisingly roomy boat, easily handled and well suited to couples.
To describe the history of the Pacific Seacraft 31 we need to go back a few years to 1980 when Pacific Seacraft acquired the molds for a boat called the Crealock 37, the previous owner, Cruising Consultants, had built a few boats before going bankrupt. The Crealock 37 was designed by Bill Crealock, and over time it garnered such a reputation that it entered the Sailboat Hall of Fame. By the early 1980s Pacific Seacraft recognized the need for a smaller version and Crealock was approached to design the smaller sibling along the same concepts of the 37. This smaller boat was launched in 1984 as the Pacific Seacraft 34.
In 1987, an even smaller 31 foot version was introduced to fill out the range. This boat, also designed by Crealock, became the Pacific Seacraft 31 and it enjoyed an initial twelve year production span between 1987 and 1999 with 79 hulls produced. In 2002 production was restarted after Pacific Seacraft continued to get numerous customer request for a smaller boat. Total production stands at some number over 100 boats thus far.
The Pacific Seacraft 31 differs from the larger boats in the range in that it makes a departure from the traditional double ender styling in favor of a near vertical transom which opens up more space in the aft sections. The long cruising fin, bustle and skeg hung rudder is still there and above deck a cutter rig is retained, though there is an option for a simpler though less ocean-going sloop rig.
There is a shoal draft version which features a Scheel keel drawing 4′ over the standard 4′ 11″. The patented Scheel keel is said to reduced leeway and improve tracking over a standard shoal draft fin. Other variations include tiller steering found in earlier boats, later boats offered Edson rack-and-pinion steering.
On deck is a relatively large cabin truck with lots of portlights. The cabin top is flat featuring a large forward two-way hatch as well as twin dorade vents. Further back in the cockpit are seats that are 7 feet long with contoured backs; three lockers are below the seats, there’s also a vented gas locked on the starboard coming. The helmsman also has a contoured seat.
Down below the boat has a very open feel which is usually the domain of much larger vessels. The V-berth is 6′ 6″ in length with plenty of storage alongside the hull, as well as above and below the berths. A curtain separates the V-berth from the main saloon. In the saloon are twin settees either side of the table which seats six comfortably and attaches to the compression post. The table can be stowed away completely beneath the V-berth.
Further back on port is the galley with its two burner stove and twin sinks, unfortunately both are a decent distance from the boat’s centerline . Opposite on starboard is a standup nav-station. There’s also a seagoing double berth on the port quarter which can be access by climbing through behind the galley.
The engine is located in the usual location below the companionway stairs which forms an engine cover, there is very good access from all sides to the engine and the stuffing box is very easy to reach.
The hull is laid up by hand in solid fiberglass and water resisting vinylester resin is used on the outermost layer and isophthalic polyester resin in the layers below. This combo should provide excellent resistance to osmosis. Some articles document the hull being hand-laid with vinylester resin throughout with kevlar fiber reinforcing which provides excellent toughness; this may be true for later boats.
Lead is used for ballast. The fiberglass rudder has internal reinforcing from a steel plate and mounted to the fiberglass skeg which itself is reinforced with steel. The pivot is bronze.
The deck is made of marine plywood sandwiched between GRP on both sides with a non-skid pattern molded on the top. The hull-to-deck join is glued and is solidly through-bolted with 1/4 inch stainless bolts every four inches.
The interior is built from a single full-length molded pan bonded to the interior of the hull. It’s a method that’s consistent with many modern production boats, cheaper to build with advantages in increased hull stiffness, reducing creaks and groans but has the sacrifice of accessibility to all areas of the hull.
The boat with its long cruising fin and skeg-hung rudder tracks well. The best point of sail is beam or broad reach, however it’s not particularly close-winded with boat speed dropping off quickly with apparent wind angles of less than 40 degrees. Overall the boat is well balanced and is easily sailed short handed.
There are no reported weaknesses for this boat, in general Pacific Seacraft build very strong purpose-driven boats. Most problems that have been reported have resulted in owner neglect and to a lesser degree age. Prices have remained high reflecting buyer demand.
As of 2010 the asking price is in the range of:
1987-1999 $90k – $110k USD
2003-2007 $155k – $180k USD
» Pacific Seacraft 31 info at the official Pacific Seacraft website.
» Twenty Affordable Sailboats to Take You Anywhere by Gregg Nestor (Ch 16. p145-p152) ISBN:978-0939837724
» Blue Water Sailing Magazine, Jan 2005, review of the Pacific Seacraft 31 by Greg Jones.
» Latitudes and Attitudes Seafaring Magazine, Feb 2009.
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