Alcona 31 is a 31′ 3″ / 9.5 m monohull sailboat designed by Edward S. Brewer starting in 1979.
- Designer
- Edward S. Brewer
- Builders
- ?
- Associations
- ?
- # Built
- ?
- Hull
- Monohull
- Keel
- Long
- Rudder
- ?
- Construction
- FG
Dimensions
- Length Overall
- 31′ 3″ / 9.5 m
- Waterline Length
- 22′ 8″ / 6.9 m
- Beam
- 9′ 3″ / 2.8 m
- Draft
- 4′ 7″ / 1.4 m
- Displacement
- 10,350 lb / 4,695 kg
- Ballast
- 4,350 lb / 1,973 kg
Rig and Sails
- Type
- Sloop
- Reported Sail Area
- 455′² / 42.3 m²
- Total Sail Area
- ?
Mainsail
- Sail Area
- ?
- P
- ?
- E
- ?
- Air Draft
- ?
Foresail
- Sail Area
- ?
- I
- ?
- J
- ?
- Forestay Length
- ?
Auxilary Power
- Make
- ?
- Model
- ?
- HP
- ?
- Fuel Type
- ?
- Fuel Capacity
- ?
Accomodations
- Water Capacity
- ?
- Holding Tank Capacity
- ?
- Headroom
- ?
- Cabins
- ?
Calculations
- Hull Speed
-
6.1 kn
Classic: 6.38 kn
Hull Speed
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.
Formula
Classic hull speed formula:
Hull Speed = 1.34 x √LWL
A 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
- Sail Area/Displacement
-
15.3
<16: under powered
Sail Area / Displacement Ratio
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.
Formula
SA/D = SA ÷ (D ÷ 64)2/3
- SA: Sail area in square feet, derived by adding the mainsail area to 100% of the foretriangle area (the lateral area above the deck between the mast and the forestay).
- D: Displacement in pounds.
- Ballast/Displacement
-
42.0
>40: stiffer, more powerful
Ballast / Displacement Ratio
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.
Formula
Ballast / Displacement * 100
- Displacement/Length
-
396.6
300-400: heavy
Displacement / Length Ratio
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.
Formula
D/L = (D ÷ 2240) ÷ (0.01 x LWL)³
- D: Displacement of the boat in pounds.
- LWL: Waterline length in feet
- Comfort Ratio
-
32.5
30-40: moderate bluewater cruising boat
Comfort Ratio
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.
Formula
Comfort ratio = D ÷ (.65 x (.7 LWL + .3 LOA) x Beam1.33)
- D: Displacement of the boat in pounds
- LWL: Waterline length in feet
- LOA: Length overall in feet
- Beam: Width of boat at the widest point in feet
- Capsize Screening
-
1.7
<2.0: better suited for ocean passages
Capsize Screening Formula
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.
Formula
CSV = Beam ÷ ³√(D / 64)
- Beam: Width of boat at the widest point in feet
- D: Displacement of the boat in pounds
Notes
With a few modifications, such as a reverse transom, this is an unauthorized, unlicensed copy of the Brewer designed DOUGLAS 31.
Near sisteships: DOUGLAS 31, DOUGLAS 32, HULLMASTER 31.
HISTORY OF DOUGLAS 31:
DOUGLAS MARINE CRAFT - Douglas Badgley commissioned Ted Brewer to design the original Douglas 31s. His company, Douglas Marine Craft, built them in Port Stanley, Ontario, starting in 1967. Around 1970-1971 Douglas Yachts went out of business, and the molds were reportedly seized by creditors.
NORTH AMERICAN FIBREGLAS MOULDINGS - Jeffrey White of North American Fibreglas Mouldings Ltd. in London, Ontario acquired at least one set of Douglas 31 hull and deck molds, and modified them with a reverse transom designed by Ted Brewer to create the Douglas 32.
COMMAND YACHTS - In 1974, North American Fibreglas went into receivership and emerged as Command Yachts with the same crew and president, and a new model - The D-32 MKII. Station Omega, outfitted with a cabin heater, A/C & refrigeration, was boat of the show in the under 40 ft. class at the Annapolis Boat Show. Command Yachts was purchased by De Leuw Cather Canada who dissolved the boat building division around 1976.
BRUCE PENINSULA YACHTS - Apparently, the D-32 molds were then acquired by Bruce Peninsula Yachts, who produced Douglas 32 MK IIs in Port Elgin, Ontario, featuring a different cabin configuration.
HULLMASTER BOATS, LTD. - Hullmaster Boats, LTD acquired one or more of the original Douglas 31 molds about the same time as North American Fibreglas Mouldings, and concurrently built Hullmaster 31s in Picton, Ontario. The last Hullmaster 31 was built in 1979.
THE FIRST “KIT” BOATS- When Hullmaster went out of business, Doug Smith acquired the Douglas 31 molds and produced what has been referred to as “kit boats” - empty hulls that owners finished.
J&C FIBERCRAFT - It has been said that Doug Smith sold his business to Jed & Carol Benoit of J&C Fibercraft. It appears that J&C D-31s are direct descendants of Hullmaster. Either way, custom yachts of a high quality as well as kit boats from the D-31 molds were built by this company in Barrie, Ontario.
HINTERHOLTER - It is believed that the last six D-31 hulls were built and delivered as kit boats by Hinterholter Yachts out of Ontario around 1982.
