Cheoy Lee Offshore 40

1964 — 1976
Designer
Philip Rhodes
Builder
Cheoy Lee Shipyard
Association
Cheoy Lee Association Web Site
# Built
156
Hull
Monohull
Keel
Long
Rudder
?
Construction
FG

Dimensions

Length Overall
39 9 / 12.1 m
Waterline Length
27 11 / 8.5 m
Beam
10 9 / 3.3 m
Draft
6 0 / 1.8 m
Displacement
20,720 lb / 9,398 kg
Ballast
7,900 lb / 3,583 kg (Iron)

Rig and Sails

Type
Sloop
Reported Sail Area
742′² / 68.9 m²
Total Sail Area
743′² / 69.1 m²
Sail Area
371′² / 34.5 m²
P
41 2 / 12.6 m
E
18 0 / 5.5 m
Air Draft
?
Sail Area
372′² / 34.6 m²
I
47 0 / 14.3 m
J
15 9 / 4.8 m
Forestay Length
49 7 / 15.1 m

Make
?
Model
?
HP
?
Fuel Type
?
Fuel Capacity
30 gal / 114 l

Accomodations

Water Capacity
100 gal / 379 l
Holding Tank Capacity
?
?
Cabins
?

Hull Speed
6.7 kn
Classic: 7.09 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

6.67 knots
Classic formula: 7.09 knots
Sail Area/Displacement
15.7
<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.
15.74
<16: under powered
16-20: good performance
>20: high performance
Ballast/Displacement
38.1
<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

38.13
<40: less stiff, less powerful
>40: stiffer, more powerful
Displacement/Length
422.0
>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
422.01
<100: ultralight
100-200: light
200-300: moderate
300-400: heavy
>400: very heavy
Comfort Ratio
42.6
40-50: heavy bluewater 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
42.6
<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
1.6
<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
1.57
<2: better suited for ocean passages
>2: better suited for coastal cruising

Notes

Also known as the EMPIRE 40 and a variant of the RHODES RELIANT 41, all from the same builder. The OFFSHORE/EMPIRE 40 was created in an effort to reduce costs of contruction and design royalties of the RHODES RELIANT. Although from the same basic tooling, the OFFSHORE 40 has iron instead of lead ballast, and differences in other construction details. Sold as a sloop or yawl.
In the mid 1970’s, Cheoy Lee Yard built another OFFSHORE 40 (variously designated as the OFFSHORE 4O MKII and then OFFSHORE 41), which was a different boat entirely and thought to be designed by Raymond Richards). See OFFSHORE 41.
(Variants of both the Rhodes and Richards design were at one time offered at one time or another under the names OFFSHORE 40 and OFFSHORE 41.)
Also offered with a yawl rig.
Photo from original Cheoy Lee literature.

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