Yankee 30 MKIII (3/4 Ton)

1973 — 1990
Designer
Sparkman & Stephens
Builder
Yankee Yachts Inc.
Association
IOR 3/4 ton
# Built
?
Hull
Monohull
Keel
Fin
Rudder
Skeg
Construction
FG

Dimensions

Length Overall
30 0 / 9.2 m
Waterline Length
25 0 / 7.6 m
Beam
8 11 / 2.7 m
Draft
5 6 / 1.7 m
Displacement
10,000 lb / 4,536 kg
Ballast
4,850 lb / 2,200 kg (Lead)
Drawing of Yankee 30 MKIII (3/4 Ton)

Rig and Sails

Type
Sloop
Reported Sail Area
463′² / 43 m²
Total Sail Area
464′² / 43.1 m²
Mainsail
Sail Area
193′² / 17.9 m²
P
37 5 / 11.4 m
E
10 3 / 3.1 m
Air Draft
?
Foresail
Sail Area
271′² / 25.2 m²
I
42 5 / 13 m
J
12 9 / 3.9 m
Forestay Length
44 4 / 13.5 m

Auxilary Power

Make
Universal
Model
Atomic 4
HP
30
Fuel Type
Gas
Fuel Capacity
17 gal / 64 l

Accomodations

Water Capacity
30 gal / 114 l
Holding Tank Capacity
?
Headroom
?
Cabins
?

Calculations

Hull Speed
7.1 kn
Classic: 6.7 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

7.11 knots
Classic formula: 6.7 knots
Sail Area/Displacement
16.0
<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.
15.96
<16: under powered
16-20: good performance
>20: high performance
Ballast/Displacement
48.5
>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

48.5
<40: less stiff, less powerful
>40: stiffer, more powerful
Displacement/Length
285.7
275-350: 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
285.72
<100: ultralight
100-200: light
200-300: moderate
300-400: heavy
>400: very heavy
Comfort Ratio
31.1
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
31.06
<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
1.67
<2: better suited for ocean passages
>2: better suited for coastal cruising

Notes

In addition to the taller rig and increased ballast, this model featured a redesigned rudder which accounts for it’s greater listed water line length.(unmeasured by the IOR) Later still, the interior was changed which included, among other details, an extended port side settee with removable dinette.
After Yankee Yachts went out of business in 1975, a few boats were built by Heritage Boat Works and Vashon Island Boat Works, both of Oregon, USA. (Rig dimensions listed here are from the MK III published sailplan though they are not necessarily consistent even within this particular version.)

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