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 Pretorien 35 is a French built cruiser-racer from the drawing board of the UK firm Holman & Pye that made its introduction in 1979 and has since been quietly attaining cult status. The trademarks of this classic include huge stowage, capacious accommodations, and seaworthiness all wrapped up with a build quality that rivals that of some of the finest production boats in the world. All in all, the Pretorien 35 today is an excellent example of a go-anywhere cruiser offering excellent value for money.
Built by Chantier Henri Wauquiez in Mouvaux, France, a total of 212 boats were produced between 1970-1986. Many were exported to the United States, so exampled can be found on both sides of the Atlantic.
The boat feels distinctly British, but perhaps this is not so surprising given that Wauquiez, admired English boats and in particular the designs of Kim Holman. He had purchased his first boat in 1964, the English-built and Holman-designed Elizabethan 29, loving her sheerline and her tracking on open water. This lead to his first foray into the boating business by fitting out Elizabethans for the French market.
It was a time when the IOR rule was making a large impact on cruising designs – a high aspect ratio rig, large foresails, small mainsails, and a hull with pinched ends and a wide beam carried aft. The entry is raked while a reverse transom helps deliver a long waterline length of 30’ 4”. The fin keel draws a healthy 6 feet while her large skeg-hung rudder is mounted well aft providing great steering control. Of note is a ballast to displacement ratio of 46%, this is a stiff and powerful boat.
This era of Wauquiez boats were sometimes called French Swans, they are great looking boats with a low slung wedge deck that flows beautifully into her lines. The Pretorien 35’s popularity was no doubt aided by Hal Roth who circumnavigated in Whisper with his wife Margaret well documented in his book How to Sail Around the World.
The quality of construction of the Pretorien 35 is among the highest found on any production boat and is undoubtedly for ocean sailing. The solid fiberglass hull features six full-length stringers which longitudinally still the boat, they encapsulate the bulkheads which themselves are tabbed into the hull with 18 oz cloth, used for better resin saturation. The overall fiberglass work is very tidy but note that she was built in the days before vinylester resins were used, so osmotic blistering is commonly found below the waterline. This is just cosmetic so unless you’re planning to keep one for a long time, it’s not usually worth repairing.
The deck is balsa cored, with solid fiberglass in regions where through deck fittings were mounted. The deck joint, on an inward flange, is both through-bolted and glassed over. The external ballast keel is mounted on a deep keel stub with 3/4″ stainless-steel bolts.
Helped by her beamy sections, the Pretorien’s interior feels very spacious and compares well to those found in more modern boats. The layout is no nonsense, with a roomy v-berth forward, followed by a head and hanging locker section. The saloon is large with two settees either side of the dinette. Further aft is a spacious galley to starboard with double sinks close to the boat’s centerline, but some will find their depth a tad shallow when the yacht is well healed. Opposite the galley on port is a nav station. There’s a small separate stateroom to the aft on port side which features a smallish double berth. A great deal of storage is found throughout the boat and the joiner work is excellent. Ventilation on the other hand has been found lacking and some owners have installed extra ports and cabin fans.
She’s well balanced and easy to steer. In wind speeds of less than eight knots she’s definitely sluggish. She starts to shine in moderate breezes and when the wind really picks up, her capability to hold onto sail when other boats reef, helps her sail like a much larger yacht. Owners report the boat possesses enough tracking stability to fly spinnakers in high winds without any tendancy to broach which was common for boats of IOR design. Beating to windward you can count on sailing relatively narrow angles of 40 degrees or better.
Hal Roth documents the Pretorien 35’s ability to log 150+ mile days offshore – that’s a very fair number for any cruising sailboat. Through the years she has garnered a reputation for being stable, dry and seakindly. These are all very desirable qualities for offshore passagemaking.
Teak decks that were optional on Pretoriens were too thin and many are worn after a few rounds of refinishing, exposing fasteners and flaking caulk. Typically redecking is a large and expensive job, so either look for ones without teak or ones that have had this job completed.
Most Pretoriens have saildrives fitted, in these models closely inspect the drive, particularly the through-hull seal and signs of corrosion in the aluminum.
Pretoriens were built in the days of polyester resin, so keep an eye out for osmotic blistering below the waterline, particularly in earlier models. Note these are only cosmetic but will have impact on the price.
On some boats the headstay fitting installed ex-factory was supported under the deck with only washers instead of a backing plate. Check and remedy as necessary.
The original 23 hp engine found on some boats may be a bit small; the optional 28 hp engine is preferable.
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