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 Spencer 35 is a semi-custom bluewater cruiser designed by John Brandlmayr. Many of them have made offshore passages, including the well known “Whisper” owned by noted author Hal Roth. There were 64 hulls produced in Canada by Spencer Boats Limited during a production run that lasted more than twenty years.
Spencer Boats began production of moulded fibreglass sailboats in 1958 with the Spencer 28. The yard was located on Canada’s west coast, in the town of Richmond, British Columbia. Eventually, the line of sailboats grew to include numerous models up to 53 feet in length. The most popular was the Spencer 35, introduced in 1962.
The popularity of the Spencer 35 was no doubt helped by several books written by Hal Roth. These books, classics of early cruising literature, described the adventures of Hal and Margaret Roth aboard their Spencer 35 Whisper, which was built for the Roths in 1966.
Most of the models in the Spencer line were designed by John Brandlmayr, a prolific designer of a wide variety of pleasure and commercial vessels and co-founder of the company. John died suddenly in 1974, and a few months later his partner Phil Hantke also passed away. John’s wife Pat, who had been involved in the business since day one, carried on the business for the next decade with the assistance of their son Grant (who went on to become a naval architect himself) and the company’s skilled employees.
Like many sailboat builders, Spencer Boats ceased business in the economic downturn of the early 1980s. The last Spencer 35 was built in 1983.
The Spencer 35 is an attractive traditional design. With an overall length of 35’ and a displacement of 12,000 pounds, it has a full keel with a cutaway forefoot and an attached rudder. It has a narrow beam of 9’6” and a waterline of 25’ that lengthens considerably when heeled. There are traditional wineglass sections and 4500 pounds of lead ballast encapsulated in the fiberglass hull. The standard rig was a sloop, with optional ketch and cutter rigs. Tiller steering was standard, although the occasional boat can be found with a wheel.
Yachts built by Spencer Boats enjoy a reputation of being very well constructed. Spencer Boats attached the bulkheads and deck to the hull while the hull was still in the mould, to ensure that the hull remained undistorted. The hull deck joint is heavily fiberglassed, forming a strong monocoque structure. The bulkheads are bonded to both the hull and deck, and the furniture is also bonded to the hull for additional support.
One advantage of the wineglass sections is that there is room in the bilge area for tankage, and this is where both the fuel tank and the main water tank are found. This keeps the considerable weight of the fuel and water supplies down low, and also frees up space above the cabin sole for storage. The tanks are moulded of fibreglass and then glassed into place.
There were significant changes to the design with the introduction of the Spencer 35 Mark II in 1974 (although some of the modifications may be found on some earlier boats as well). Prompted by the experiences of Hal Roth on Whisper, the cabin on the Mark II was extended 30” aft. This resulted in a smaller cockpit that was more suited to ocean cruising. It also resulted in considerably more room below. In addition, the Mark II has an improved rudder design and a higher aspect rig.
The Mark II also has an airex cored hull, rather than the solid fiberglass hull of the original design. Spencer Boats was a pioneer in the use of cored hulls, and by all accounts the hulls have held up very well. The coring starts several inches down from the sheerline and continues to the turn of the bilge, below which the hull is solid fiberglass. The deck is cored with end-grain balsa. The Mark II also has a substantial fibreglass toerail, instead of the teak toerail found on earlier boats.
There is no “standard” interior layout for the Spencer 35, because of its semi-custom nature. Rather than being built to standard specifications on a production line, each boat was built in accordance with the wishes of the commissioning owner. However, there is commonly a forward cabin with a v-berth followed by a decent sized head to starboard and a hanging locker to port. The narrow saloon generally has two settees with a centre-line table, although some boats have one U-shaped or L-shaped settee and an offset table.
The original design has a small galley aft to starboard, and a side-facing chart table to port. The Mark II model has a much more spacious galley (well known designer Ted Brewer described the galley layout as one of the best he had seen on a boat this size). In addition, the Mark II added a quarterberth and has a forward facing chart table.
The headroom in the main cabin is a 6’4″, with a few inches less in the head and forward cabin. The berths are all a generous length as well. The interior finishing varies, as some of the boats were sold as kits. However, the yard finished interiors are of a high standard with attractive teak joinery. The size, style, and location of portlights and other fittings and hardware may differ considerably from boat to boat, because of the semi-custom nature of the production.
The Spencer 35 is surprisingly nimble and responsive for such a traditional looking design. With its moderate displacement, narrow beam, and slack bilges, it is relatively tender initially. However, it stiffens right up at 25-30 degrees and has a very good capsize ratio of 1.68.
The Spencer 35 is generally very well-behaved on all points of sail, although it can roll a bit downwind in heavy following seas. Not surprisingly, it does not point quite as high as many more modern designs. However, it has decent performance upwind and doesn’t pound in a chop (although with its low freeboard and high angle of heel it can be a bit of a wet ride).
It has a very seakindly motion, with a high motion comfort ratio of 32. While It isn’t likely to be first across the line in many races around the buoys, it is a respectable long distance performer – the Spencer 35 “Haulback” placed first overall in the 2002 Singlehanded Transpac.
» Ted Brewer, Spencer 35: She’s capable of cruising anywhere in the world in comfort, Good Old Boat, Issue 38 – September/October 2004
» Ferenc Mate, Best Boats to Build or Buy (1982), Chapter 23 (focuses on the Spencer 1330, but also addresses the Spencer 35 and Spencer yachts generally)
» Hal Roth, Two on a Big Ocean (1972), After 50,000 Miles (1977), Two Against Cape Horn (1978), Always a Distant Anchorage (1988)
» Marianne Scott, Bluewater Spencer: A baby-blue Mark II Spencer 35 heads for the horizon, Good Old Boat, Issue 38 – September/October 2004
» Spencer Yacht Owner’s Association’s Facebook Group
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