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.
Classic hull speed formula:
Hull Speed = 1.34 x √LWLA 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
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.
SA/D = SA ÷ (D ÷ 64)2/3
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.
Ballast / Displacement * 100
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.
D/L = (D ÷ 2240) ÷ (0.01 x LWL)³
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.
Comfort ratio = D ÷ (.65 x (.7 LWL + .3 LOA) x Beam1.33)
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.
CSV = Beam ÷ ³√(D / 64)
This from ‘Super Dorade’:
“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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