Firstly the ratings for a typical windward-leeward bouy race :





Secondly the CUSTOM ratings for a specific one-way distance race on a given day (Steeplechase, Tybee 500, etc)




If you don't spot the changes right away then look at the following boats

F18 (stays at rating 100 by design, it is used a pivot point)
Hobie16 (has to sail seriously faster, when compared to pivot F18, due to having a reaching leg and hardly having any spi leg for the F18 to stretch its legs)
A-cat (has to sail alot faster, relative to the pivot F18, because their is so much upwind work for it to excel in)

These are 3 extremes, All boats are affect proportionally. The reason that the F18, F20, Tornado, M20 and SC20 don't change rating is because these are simply impacted by negative factors as much as the positive factors. For example the M20 gains on the upwind but looses alot but not having much spi sailing as well. These two apparent compensate eachother largely and its rating only drops on point in the heavy air.

Think really hard before you reply to these numbers, some numbers may sound weird at first but really, they all make sense when you analyse what is REALLY going on.

Of course the CUSTOM ratings converge back to their standard values when the distance race course input approaches that of a typical bouy race as we all expect would happen.

I will admit to the Shark rating being a little bit harsh but then again that boat is so outdated in its design. It has the same general dimensions as the H20 but still can't seem to speed up till within 12 % of the H20 speed under USPN. And it only just reaches 86 % of it potential speed as predicted in its handicap. That is what old technology does to performance of a catamaran ! This problem point has been identified and we are discussing how to adress it.

Have fun, comparing boats and numbers.

Wouter