Allied Seawind MK II Ketch

1975 — 1982
Designer
Thomas Gillmer
Builder
Allied Boat Company Inc.
Association
Allied Seawind II Home Page
# Built
130
Hull
Monohull
Keel
Long
Rudder
?
Construction
FG w/balsa deck & coach

Dimensions

Length Overall
31 7 / 9.6 m
Waterline Length
25 5 / 7.8 m
Beam
10 5 / 3.2 m
Draft
4 5 / 1.4 m
Displacement
14,900 lb / 6,759 kg
Ballast
5,800 lb / 2,631 kg (Lead)
Drawing of Allied Seawind MK II Ketch
  • 1 / 6
  • 2 / 6
  • 3 / 6
  • 4 / 6
  • 5 / 6
  • 6 / 6

Rig and Sails

Type
Ketch
Reported Sail Area
555′² / 51.6 m²
Total Sail Area
470′² / 43.6 m²
Mainsail
Sail Area
203′² / 18.9 m²
P
33 9 / 10.3 m
E
12 0 / 3.7 m
Air Draft
43 0 / 13.1 m
Foresail
Sail Area
267′² / 24.8 m²
I
38 9 / 11.8 m
J
13 8 / 4.2 m
Forestay Length
41 1 / 12.5 m
Mizzen
PY
18 6 / 5.6 m
EY
9 1 / 2.8 m

Auxilary Power

Make
Westerbeke
Model
?
HP
27
Fuel Type
Diesel
Fuel Capacity
40 gal / 151 l

Accomodations

Water Capacity
60 gal / 227 l
Holding Tank Capacity
?
Headroom
6 2 / 1.9 m
Cabins
?

Calculations

Hull Speed
6.5 kn
Classic: 6.77 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

6.46 knots
Classic formula: 6.77 knots
Sail Area/Displacement
14.7
<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.
14.66
<16: under powered
16-20: good performance
>20: high performance
Ballast/Displacement
38.9
<40: less stiff, less 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

38.93
<40: less stiff, less powerful
>40: stiffer, more powerful
Displacement/Length
401.6
>350: ultraheavy

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
401.56
<100: ultralight
100-200: light
200-300: moderate
300-400: heavy
>400: very heavy
Comfort Ratio
36.8
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
36.83
<20: lightweight racing boat
20-30: coastal cruiser
30-40: moderate bluewater cruising boat
40-50: heavy bluewater boat
>50: extremely heavy bluewater boat
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
1.7
<2: better suited for ocean passages
>2: better suited for coastal cruising

Notes

From (BlueWaterBoats.org)[http://bluewaterboats.org/allied-seawind-ii-32/]:

Following in the hallowed footsteps of the original Seawind, a salty 30 foot ketch designed by Tom Gillmer that happened to be the first fiberglass sailboat to circumnavigate the globe, the Seawind II is a larger, more comfortable redesign that’s a foot longer, a foot wider, and over 23% heavier. These boats were launched in 1975 by Allied Yachts and they had a reputation for being solidly built, though with a history of inconsistent and uninspiring internal finishing. The company went out of business four times, before finally shutting down for the fifth time in 1981, spelling the end of production for the Seawind II.

Allied Yachts was founded in 1962 on the Hudson River a hundred miles north of New York City in the small town of Catskill as a partnership between a fiberglass boat builder Lunn Laminates and a yacht brokerage of Northrop and Johnson and racing sailor Thor Ramsing. Their first boat, the Seawind, a popular 30’ 6” ketch had the company busy keeping up with demand.

These were still the exciting pioneering days of fibreglass sailboat construction when the material was still considered experimental and hulls were conservatively built extra thick. When New Yorker, Alan Eddy, setoff in 1963 to eventually circle the globe in Apogee, the accomplishment did much to not only put to rest skepticism over fibreglass construction, but also to establish Allied’s reputation for building seaworthy sailboats.

Despite the original Seawind proving itself as a competent bluewater sailboat, it had minimal accommodations that were, at best, cramped. So after over a decade of successful production of the Seawind, Allied approached Gillmer to evolve the design into a successor – the Seawind II. Though it was only 13 inches longer, its beam was 13% wider which resulted in a displacement 23% heavier. The result was a much more comfortable boat with significantly larger internal volume and improved accommodations.

Structurally the new boat was just as sturdy and had improvements over the original construction. The hull was hand-laid and substantially thick and well supported bulkheads that were fiberglassed into place. Furthermore the hull-deck joint, which was prone to leaking in the original Seawind was improved with no expense spared. The new joint was complex, labor intensive to construct but very strong. Both hull and deck had outward flanges at the sheer line. These flanges were coated with sealant and a teak batten placed between them. Hull, deck, and batten were then through-bolted vertically with stainless steel bolts. After the sealant cured over a number of days, the joint was ground flush on the interior of the hull and glassed over heavily. Meanwhile on the exterior a heavy aluminum extrusion was filled with bedding, capped over the flange, and horizontally screwed into the teak batten.

The deck and cabin were of fiberglass cored in balsa wood. All deck hardware was through-bolted and reinforced with fiberglass backing plates to distribute the load. The mast was deck-stepped and supported from below by a substantial oak compression frame that extends into the bilge. Ballast is an internal lead casting glassed into the keel.

There’s very little exterior wood on the Seawind II, even the dorado boxes are molded in, resulting in a low maintenance boat, but also gives her an austere look.

Unusual to see in a sailboat this small is a ketch rig which was offered as standard, there was an optional cutter rig which carried slightly less canvas but had similar performance. As to be expected, Seawind II sails well under heavy sea conditions, but perhaps surprisingly it’s quite competent in light weather as well. She has a very comfortable motion at sea, is well balanced with very little signs of weather helm.

Overall the Seawind II today is a practical and affordable choice as a go-anywhere cruiser. She’s strong without being overly heavy, well constructed and proven. Many examples on the used market have held up well, with later models generally having better finished interiors.

Links, References and Further Reading

» Seawind II owners association website
» Sailing Magazine, Feb 1999, Used Boat Notebook by John Kretschmer

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