Originally Posted by Kris Hathaway
Looking for clarity because I've seen many different interpretations of whether the F18, F16, F14, and A-Cats are formula or box rule classes. Further, I suspect that the usage of "Formula" for the "F" series classes contributes to the confusion. Of course, I am leaving out the Nacra F-17 which is actually a one-design (?) smile.

My understanding is that a true "formula" class is exemplified by the 12-Meter keelboat class where it is a function of length, beam, displacement, and sail area (simplified). All of the variables must result in 12 meters via the class' formula. Accordingly, 12-meter yachts typically range from 20 to 23 meters in length because of the formula. Length is dictated by the formula, not by a maximum length constraint.

Whereas, a true "box rule" class defines limits, maximums (ie: length) and minimums (ie: weight), and all boats must measure within the constraints or "box". However, box rule classes do not preclude the usage of formulas. Sail measurements for all of the aforementioned beachcats employ formulas to calculate sail area; however, the resultant sail area is still subject to maximum constraints within the "box" rule.

SO....is it correct to say that F18, F16, F14, and A-Cats are technically box rule classes, not formula classes?

I suspect that the usage of "formula" for the formula series beachcats comes from the conceptualization of the Formula 18 class via SCHRS formulas to compute performance parameters (per International Formula 18 history website page)? The label "formula" stuck and was adopted with by the similarly subsequent F14 & F16 "box ruled" classes. "Formula" certainly is more sexy than "Box Rule 18 or BR18" from a marketing standpoint.

Plausible explanation? Is there more to it? I did not wish to muddy the waters with development vs semi-development nor "open class" topics. Thanks in advance for any further insights.


Formula rules can limit building materials also .Box rules do not.
A and C class cats are box rules- You can use anything to build them.Sky is the limit.
The F-18s are formula because of material limitations( aluminum stick, No carbon, etc). I can't speak for F-16 because I never read their rules.

At least that's my take on it.

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