Many members and potential competitors have asked that we publish the MASF rating rule.
They have commented that it is too secret and not well understood. We the rating committee
agree. So here's a beginning explanation.
Measurement rules by there nature are not perfect. The fewer measurements that are used, the more likely that a clever designer can exploit the formula. The performance systems also have had there critics. Many feel that the system of appeals of ratings have flaws and that it comes down to who can complain the loudest about their rating. Some of these systems end up rating both the boat and the skipper. Neither is perfect. We prefer in our club currently to use a measurement based system as it has shown in the past to closely bunch corrected times in many of the races that have used it.
The original formula was inherited from our sister organization on the west coast FOMA. It should be noted that this formula is targeted to a very small segment of cruising multihulls. It is not intended to rate boats at the extreme end of its definition. It can not adequately come up with a number for small or high performance beach cats or for very large (60+) tris. The formula that produces the rating takes several major dimensions into account. Weight, length and sail area are the major inputs. We use what's known as a time on time allowance handicap system. This system accounts for speed difference in races by the amount of time that a yacht spends racing instead of the actual distance sailed. This number is used to calculate the correct time by the simple formula
Elapsed time * rating = Corrected time
So how is the secret elusive rating derived. Quit simply we input the measured data from each boat into a computer program (actually a Lotus Approach database) and it spits out a number. We do a sanity check to make sure that the data is correct , and let it stand on its own merit. Only in very rare cases does the ratings committee adjust the rating if they feel that there is a problem.
The Basic top level formula for the MASF rule is:
waterline * sail area / weight
In a nutshell this equation is the push of the boat divided by the pull.
However each component then uses a modifying factor to balance their relative importance. As a result the above formula becomes: (please note that ^ means exponent, for example ^.5 means square root).
waterline^.5 * sail area^.33 / weight^.3
An additional scaling factor of .24 which effects all boats the same is used to keep corrected times to roughly the same scale as the elapsed times.
There is also a coefficient used to modify the whole formula which is an assigned number which is either 1, .994 or .98 .
 | Weighed boats and measured sails will receive a rating coefficient of 1.0. |
| Un-weighed boats that have sails measured will receive a rating with a coefficient of .994. This should be understood as a clear disincentive to boats sailing under MASF without weighing! |
| Un-weighed and unmeasured sails will receive a rating with a coefficient of .98. Unless a boat is sailed extremely well, she will not correct at the top of the fleet. |
This is the basic formula however there are further calculations for adding up sail area for inclusion into the formula. In brief each sail is weighted differently. The order of these sails in order of most heavily weighted to least is: mainsail, jib/genoa, screacher/reacher, spinnaker.