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 Rasmus 35 is often dubbed as the first production sailboat to come from Hallberg-Rassy, a name that’s become one of the most respected and prestigious in the world of cruising yachts. With a design from Sweden’s Olle Enderlein that was well ahead of its time in the late 1960s, the boat has enjoyed a large following with an incredible production run of 760 hulls spanning 12 years.
With its full keel and center-cockpit layout the boat was designed for long distance cruising from the outset. Rig options came in both ketch and sloop configurations, and of particular note is her well protected cockpit which featured a fixed windscreen which was a trendsetting innovation in its day.
Through the years the Rasmus 35 has proven herself with numerous and regular circumnavigations under her name and continues to be a practical choice for extended voyaging, able to swallow large amounts of gear and accommodate a decent crew count without being cramped. Also a trademark for Hallberg-Rassy is a generously sized engine which makes cruising life a little easier.
The Rasmus, being the German name for “God of Winds”, could be said to be a Swedish and German creation. Originally drawn in 1966 by leading Swedish yacht designer, Olle Enderlein, the boat was built by German expatriate, Christophe Rassy, in 1967 when he founded his boatbuilding business in Kungsviken on the old premises of the Hallberg boatyard who had moved on to larger facilities. The first two boats were built entirely of mahogany, taking a full year to build before production moved onto fiberglass molds by hull #3.
The boat was considered quite large at the time as well as being innovative with its fixed windscreen and powerful engine. With the Rasmus 35 being well received, by 1972 Rassy expanded his operations by buying the Hallberg boatyard from Harry Hallberg who was at that point looking to retire. Since the Hallberg brand was already well-known in Sweden, with four designs in production, Rassy adopted it in forming the new Halberg-Rassy name.
Production of the Rasmus 35 continued through to 1978 with a total count of 760 hulls. In the United Kingdom versions of the boat were called the NAB 35 and although the hull moldings were from Sweden they were fitted out by British builder Reg Freeman Yachts. These boats featured a more substantial wheelhouse shelter.
Probably the yacht’s most defining trait is its ample stowage and accommodations spanning three separate cabins in a centre cockpit layout – not bad for a 35 footer. The mahogany interior would have you want to check twice to be sure that the boat is fiberglass from belowdecks.
Each cabin features two berths accommodating a total crew of six in relatively spacious comfort, something rare to find in a 35 footer. In the forepeak are twin v-berths, further aft is a separate head with a locker area opposite. The main saloon features a large seven foot dinette which can be lowered to form a double berth. Opposite this area is a well equipped galley.
The separate aft cabin, which always provides a well appreciated luxury of privacy during extended passage-making, must be accessed externally from the center cockpit. It holds two berths which can be set up as a queen bed or two singles.
The cockpit not only being well protected due its center location, has a fixed windscreen, and additionally the cockpit could be optioned with a fixed ceiling instead of the standard folding dodger for further protection.
Apart from the original two Rasmus 35s built entirely from mahogany, the hulls were of solid laminate fiberglass with molded in longitudinal stringers and molded fiberglass tankage. The deck and cabin house is of fiberglass cored with one inch thick polyvinyl foam which has merits for lightness, stiffness not to mention acoustic and thermal insulation. Mating the two in the area of the hull to deck joint are many layers of overlapping fiberglass laminate on the internal corner of the hull and deck. On the exterior of this area the two moldings form a bulwark which is sealed with plastic filler and topped by a teak cap rail.
Iron is used as ballast, the 5,500 pound casting is encapsulated in fiberglass, and the rudder stock and fittings have been cast in bronze. All workmanship in the hull, deck, rudder, and chainplates were of high quality, enough to meet Lloyd’s standards.
Early Hallberg-Rassy models prior to German Frers’ designs from 1989 onwards were known to be solid, sea-kindly but a bit slow, and the Rasmus 35 is no different. Due to her narrow beam she rolls a little more than most and she suffers from excessive leeway drift when sailing to windward due to her short 4′ 3″ keel – particularly beyond 15 degrees of heel. Owners report that better progress can be made by sailing faster and flatter to the wind, throwing in tacks through 110 degrees than to go too close-winded. Of course Hallberg-Rassy’s tradition of having powerful engines fitted is always helpful for extended windward passages and reassuring in a storm. In this case the Volvo-Penta MD21 diesel is rated at 75hp but we also note in real world circumstances where the output must be sustained the MD21 can only manage 42hp.
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