,-great posts by all ,-

On speed theory and comparing performance of catamaran design --
Is there a generally accepted formula in design that compares all small cat design based on L B W and S A
Length Beam Weight and Sail Area

Numerous partial comparisons are made ,-weight to sail area ratios ,-stability and righting moment with sail area . etc.

this is listed on the Texel site
There are 20 elements of speed, according to Olin Stephens (1972).


length
sailarea
displacement
prism. coeff.
asp. ratio rig
ratio main/jib . .
beam
wetted surface
center of effort
draught
ballast
combined 1 - 12
fulness ends
weight distribution
freeboard
windage rig
motor
material
course stabil.
steering stabil

6.

There are 7 elements of speed which have nothing to do with the design.

helmsman
crew
organization
condition of sails
condition of bottom
tactics / strategy
luck
7.

Follow the "KISS" principle, "keep it simple stupid", for formulas. There are 4 formulas available to approximate the performance. Bruce nrs (1967), IOMR (1968), KSP since 1976, Texel Rating since 1984 Edmund Bruce, pioneer of Amateur Yacht Research Society, died 1973.
IOMR = International Offshore Multihull Rule (California, 1968).
KSP = Kelsall Shuttleworth Performance. (MOCRA formula, around 1978).
TR = Texel Rating by Nico Boon, 1984, slightly modified in 1993.

8.

IOMR, KSP and TR use length, sailarea and weight (displ.) only..

RL = rated length, RSA = rated sailarea, RW = rated weight. (kg.).

General form of these formulas : 100 / (c * RL p * RSA q / RW r).

Bruce (metr.) =2.5209 * RL 0 * RSA 0.5 / RW (1/3 ).
Bruce (imp. ) = 1 * RL 0 * RSA 0.5 / RW (1/3 ).
MOCRA (metr.) = 100 / (2 * RL 0.5 * RSA 0.5 / RW 0.5 ) .
MOCRA (imp. ) = 100 /(0.5 * RL 0.5 * RSA 0.5 / RW 0.5 ).
TR (metr.) = 100 / (0.99 * RL 0.3 * RSA 0.4/ RW 0.3)
TR (imp. ) = 100 / (0.3397* RL 0.3 * RSA 0.4 / RW 0.3).
IOMR (metr.) = 100 / (1 *RL 0.311 * RSA 0.42 / RW 0.318).
IOMR (imp. ) = 100 / (0.3275 * RL 0.311 * RSA 0.42 / RW 0.318).

IOMR here, is a "translation" into a powerformula of the IOMR formulas.

9.

Above Beaufort 5 or 6, stability of a design is the limiting factor for speed. A rating has to be calculated then by using the smaller sailarea making heeling moment = righting moment. No other formula required..
In very light winds use TR (metr.) with c = 0.89 and RSA ^ 0.5..
(rev.7/96).

end Texel -info

A different approach to rating catamaran design in concept is to have a base equation that does not attempt to handicap design ,--but only compare it to scale of design variation of
L B SA and W .
This would provide information on the most effecient design type in each size for racing , results varying with race conditions and teams abilities as always.
For handicap racing an efficiency factor could be added to this base equation .
This may be based on improved yardstick system numbers ,Again as a percentage of this base rating applied to handicap racing only.
The base rating would provide a beginning number for new design . Be readily available to calculate modification of sail or spin sizes .Could be applied accurately to distance racing w spin non spin classes.

Ideas -concepts added -
thanks