82 FOREST AND STREAM. [J4n. is, i<jo 2 . 
CHEROKEE — SAIL PLAN. 
The Rating Rules. 
Editor Forest and Stream: 
I have been reading with much interest the letter you 
published on the above subject in your copy of the 21st 
ultimo, signed by Mr. Phillips, who commences by what 
is now becoming the fashionable introduction to such let- 
ters, viz., the assertion' that plain yachtsmen care not to 
wrestle with such subjects, but leave rating rules to naval 
architects and mathematicians, yet continues in a well- 
argued letter to show that at all events one plain yachts- 
man ; s very well up in the subject. With your permission 
I will examine his discussion. 
Firstly, he asks how is the factor, displacement, to be 
found. A weighing machine up to ten tons can be pur- 
chased for a small sum. It is handy, and can be hooked 
to the jib of any crane, or if there be no crane, to the 
cross of an impromptu derrick. Slings round the small 
yacht complete the requisite stores. Two or three men 
could eas : ly weigh a small yacht in half an hour. There 
is absolutely no difficulty in weighing a small yacht. It 
is quite as simple a job as weighing a lead keel, which is 
insisted upon in the one-design classes, as, for instance, 
when building the 20-tonners in the Clyde O. D. class. 
In the larger classes, if any objection be raised to a 
builder's certificate of such displacement obtained from 
the yacht's drawings in the usual way by means of the 
planimeter and Simpson's rule, then we must do with an 
approximation, which is quite correct enough for rating 
rule purposes, and which cannot certainly be objected to in 
the United States, where a similar approximation has 
been permitted for twenty years or so in the finding of 
sail area for rating rule purposes. At the present time the 
English rating rule requires the official measurer . to take 
measurements on the yacht's external cross section at a 
point 0.6 of the L.W.L. from the front end of it. such that 
any one can, from the published measurements subse- 
quently plot with very fair accuracy the said cross sec- 
tion. G B and D are quite sufficient for this purpose, and 
from the cross secticn thus plotted M the area of im- 
mersed section can at once be found by a planimeter. 
Having found M and knowing L, the approximate dis- 
placement in English tons (of 2.2-tolbs.) is found by the 
formula M X L -f- 60. Thus a 30-footer (L.W.L.) hav- 
ing a section M = 16 sq. ft. w*ould be about eight tons 
displacement. 
The argument that asking for displacement encroaches 
too much on the secrecy of design, does not therefore 
seem to be reasonable, because jk the present time the 
English rule requires that yachts shall be so measured that 
practically the said displacement can at once be found 
from the published measurements, by any expert. Again. 
Mr. Phillips thinks that the displacement could not be 
kept stationary for all races. Quite so. There would 
be no need. I would simply find the yacht's smallest dis- 
placement and give her a premium on that. Any increase, 
unless permanent, would give her no rating advantage, 
and therefore qua rating need not be considered. If the 
increase were permanent, her master would, of course, 
take good care to have her rating corrected. On the 
other hand, any decrease in displacement by, say. the use 
of hollow vice solid spars', would, of course, require a 
corrected rating, which her competitors would insist upon, 
just as they would in the event of her taxable sail area 
being increased. 
Mr. Phillips, on these very insufficient and ea«y an- 
swered objections, considers that a displacement rule, 
however excellent in theory, would in practice be "simplv 
vile." 
He then proceeds to argue that the prime function of 
a rating rule is to measure the size of a yacht. If this 
were really so, surely the most effective rule would be 
that for registered tonnage, and every owner would 
naturally reduce freeboard, and all internal dimensions to 
the utmost in order to rate as low as possible. 
If is true that when racing first commenced the aim 
of the rule for time allowance was to measure size; but 
we have got a little beyond that primitive idea, and now 
our rating rule for racing is a measure of speed, which, is 
quite another affair: We no longer race with cart horses, 
but with thoroughbreds. 
No racing man is likely to disagree with Mr. Phillips' 
second proposition, that restrictions should not be em- 
bodied in a rating rule. That is my objection to "shape 
rules," like the present Y. R. A. (British) and German 
rules. 
Mr. Phillips' third proposition that restrictions suit- 
able to one class or size are unsuitable to another, is com- 
mon sense, but is outside the argument if his second 
proposition be accepted, as above, viz., that restrictions 
and rating rules should have nothing in common, and 
Mr. Phillips' fourth proposition can be regarded like No. 3. 
The statement then made that a strictly scientific for- 
mula has been deduced by naval architects, that other 
things being equal and length variable, the possibilities 
of speed vary as the square root of the length, is certainly 
not accurate if scientific. The late Mr. Froude proved 
that resistance 4*»e to water friction Varfes wfth the area 
and nature of the wetted surface, and with a power of 
the speed less than the square, that it is independent of 
displacement and that it can be readily tabulated. 
The residuary resistance, however, due to wave or 
eddy making cannot be so dealt with, and at present can 
be found only by trial either of a ship at sea or of a model 
in a tank. Evidently, therefore, the total resistance, and 
therefore the speed, cannot be accurately described as 
varying with a particular power of length, and it is also 
Impossible to have other things equal when length varies. 
For instance, if beam remained constant, the ratio of L to 
B would not remain the same, L varying; and contrari- 
wise, if the ratio remained unaltered, B would have to 
vary with L. 
But it is not even a fact that increase of L per se neces- 
sarily reduces wave making resistance. The general ten- 
dency is that way, but at and about certain speeds for 
each shape in an increase of length may produce an actual 
increase of resistance. 
The "strictly scientific formula" is, however, sufficiently 
accurate for rule purposes, and for the production of a 
time scale, and it is far wiser to race by such a scale than 
by one which is altered tyrannically by a governing body 
for the purpose of taxing excessively and therefore of dis- 
couraging all yachts exceeding a given rating, which has 
been done by the British Y. R. A. in their time scale above 
80 rating. 
Mr. Phillips' remarks on the time scale are excellent, 
but he should bear in mind that rating length is not hull 
length, but has nearly 50 per cent, of it indicating a co- 
efficient of power, and consequently the application of the 
"formula" which is strictly scientific only as regards hull 
length, is purely arbitrary. His definition that on a given 
lengthy sail is a coefficient of power is very neat, and his 
deduction as also that the Seawanhaka rule is conse- 
quently a good measurement rule; but when he adds 
shortly afterward that this measurement is one of size, I 
for one cannot agree with him. believing it as I do to be 
a measurement of speed and not of size — racing size, 
perhaps, which practically is speed. The Seawanhaka 
rule's cnly defect, in my opinion, is the omission to tax 
the third principal speed producer— small displacement. 
The introduction of this additional tax is the thing I 
have been advocating for years. 
As. for racing under restricted rules, or in one-design 
classes, they give excellent sport, but thev impede evolu- 
tion, ^nd Mr. Phillips' opposition to restrictions being 
practically introduced by a complicated, rating rule, is 
most cordially echoed, by Thaiassa.. 
