1964
Designer
Francois Sergent
Builder
CNSO (Constructions Nautiques du Sud-Ouest)
Associations
?
# Built
1972
Hull
Monohull
Keel
Twin
Rudder
?
Construction
FG

Dimensions

Length Overall
21 3 / 6.5 m
Waterline Length
18 0 / 5.5 m
Beam
6 6 / 2 m
Draft
2 5 / 0.8 m
Displacement
1,650 lb / 750 kg
Ballast
440 lb / 200 kg
• 1 / 1

Rig and Sails

Type
Sloop
Reported Sail Area
161′² / 15 m²
Total Sail Area
?
Sail Area
?
P
?
E
?
Air Draft
?
Sail Area
?
I
?
J
?
Forestay Length
?

Make
?
Model
?
HP
?
Fuel Type
?
Fuel Capacity
?

Accomodations

Water Capacity
?
Holding Tank Capacity
?
?
Cabins
?

Hull Speed
7.8 kn
Classic: 5.69 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

7.8 knots
Classic formula: 5.69 knots
Sail Area/Displacement
18.4
16-20: good performance

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.
18.43
<16: under powered
16-20: good performance
>20: high performance
Ballast/Displacement
26.7
<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

26.67
<40: less stiff, less powerful
>40: stiffer, more powerful
Displacement/Length
125.6
100-200: light

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
125.63
<100: ultralight
100-200: light
200-300: moderate
300-400: heavy
>400: very heavy
Comfort Ratio
10.9
<20: lightweight racing 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
10.89
<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
2.2
>2.0: better suited for coastal cruising

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
2.22
<2: better suited for ocean passages
>2: better suited for coastal cruising

Notes

“There have been 5, somewhat distinct versions, built from from 1964 to 1969. Variations concerned rig, keel, rudder, windows and interior construction. (No indication that hull was changed. There was even a different type with name “Girelle” with the same hull.)
Rig has changed from fractional to masthead sloop at the latest 1966. The photo shown here is of the early version and the drawing shows the later masthead version.
Probably with this change of rig draft and ballast of fin keel version has changed too: from 0.75 to 1.0 m and from 200 to 300 kg respectively.
The fin keel version was called “JOG” (Junior Offshore Group) (the latest since 1965; with a different rig and sail area.

In 1969, CNSO put the “Sport” version on the market: taller mast, more sail area, draft and ballast: ca. +0.6m, ca. +3m², +0.13m and +30kg respectively.

General summary of different versions is as follows:
- Twin keel (“standard-luxe”) early version
- Twin keel (“standard-luxe”) later version
- Fin keel (“JOG”) early version
- Fin keel (“JOG”) later version
- Fin keel version “Sport”
French web sites say that production ended 1972. This is in line with my investigations in the archive of the leading German yachting magazine “Yacht”. Advertising for SD stopped in 1971.
French sites say also that 300 SUPER DORADES’s were built. I’ve 2 indications that it was rather more than 600, first my own memory of numbers beyond 600 in the sails and the claim in an advertisement.”

Many thanks to ‘Super Dorade’ for sharing expertise on this and other subjects.

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