| American R = | LS | ÷ constant (say 72) | (XI.) |
| M |
L.S. being cubic, and the variable divisor M. being superficial, the quotient is linear, and a constant divisor can be chosen which will convert the result into American rating, which is expressed in 'corrected' feet.
The general tendencies of the Y.R.A. rule would be modified by the introduction of M. as proposed in XI., a large immersed M.S. being encouraged, without the necessity of employing a deep narrow body, as may be seen on the following table, where 'Bedouin' figures out very well owing to her large but not deep immersed M.S. The author claims with some confidence that this modified rule presents the best solution of the problem yet suggested. But there is really no problem requiring solution at present. So long as yachts like 'Britannia' and 'Satanita' are built for racing under the Y.R.A. existing rule of rating, grumblers will not command an audience. In the event, however, of yachts like 'Pilgrim' or 'Jubilee' winning in our waters a change of some sort will be required.
The measurement of M. can be easily done in a few minutes, with yacht afloat, as described on p. 87 of the 'Field,' January 21, 1893.
The Seawanhaka rule (III.) can be treated similarly, the divisor 2 being thereby avoided. It becomes
American R = L + √S - √72M (XII.)
The action of these rules may be seen from the table on p. 180; column headed XI. giving the rating under the modified Y.R.A. rule, and column headed XII. giving the rating under the modified Seawanhaka rule. Each result is in 'corrected length.'
The dimensions in above were obtained from the drawings in Dixon Kemp's 'Yacht Architecture,' 2nd ed., except 'Decima's' and 'Doreen's,' which were kindly given by their designers.
It will be found on trial that 72 M. is approximately equal to the mean value of S. and L2 in successful yachts.