Yacht rating Rules

A description and analysis, as of 1895

"With shame I confess that the problems and calculations, the combinations of straight and crooked lines, with large and small numerals and Latin and Greek letters, the mathematical contortions and algebraic hieroglyphics ... are meaningless to my uncultured eyes. They are fascinating; I admire their beauty, and can well understand that inventing rules for rating must be a most charming pursuit for intellectual yachtsmen ..."
                       Earl of Dunraven, KP, CMG ^[1]

Introduction

Early competitive yachting probably dates to October 1661 during the reign of King Charles II; the first Yacht Club – the Royal Cork Yacht Club – was founded in 1720 as the Cork Water Club; the Prince of Wales’s Cup, from Greenwich to the Nore and back, was sailed in 1749; the end of the Napoleonic era saw a significant increase in sailing for pleasure. It is well established that no owner accepts that his yacht is the slowest in the fleet, leading to the ineluctable fact that richer owners could afford newer, and often bigger yachts, from specialist designers and built by the most experienced craftsmen, thus winning the majority of races. Yachtsmen searched for means to narrow the gap and promote the sport of yacht racing. Handicaps, or "ratings" were born: the faster boats took a penalty, while the slower designs were advantaged, leading to the possibility of "correcting" race results on a time^[2] basis.

Many elements determine the speed of a sailing vessel. The amount of sail (and its aerodynamic efficiency) that can be carried for given winds produces the power. Resistance is more complex. The weight or true displacement of the vessel, the friction caused by underwater surfaces, and hull form or shape all contribute to drag. Increasing the length of a yacht was early understood as a "go fast" factor, but it was not until William Froude (1810-1879) and his son Robert Edmund Froude (1846-1924) developed (and confirmed through tank testing) the mathematics involved in hydrodynamics, particularly in the "wave-line" theory proposed by John Scott Russell in 1844. The last quarter of the nineteenth century saw solid development in both yacht design and the means to refine the rating, and thus the handicapping of yachts competing between themselves.

Various associations, yacht clubs and national "authorities" in England and the United States, eventually joined by France and other countries, used the expertise of recognized designers, naval architects and other well-known specialists to reach consensus on the rules, hopefully stable enough for a few years. The honourable intentions of these bodies were generally well respected, but mistakes were made, technology and hydronamics were progressing fast; and above all it was the same designers and architects who could find the loopholes, and beat or cheat the rules, when given a commission for a new yacht.

An attempt will be made to treat the subject as simply as possible, but the devil is alweays in the details. The following basic abbreviations will be used, variances being noted in the text :—

Measurement and rating

Until well into the nineteenth century the only measurements in regular use, were the "tonnage" dimensions. In 1694, the tonnage formula was:

Based on volume (not displacment), "tonnage" gave rudimentary possibilities of speed capability. If the subject of rating were treated historically, it would be necessary to begin with the old tonnage rules ; but here we examine the late 19th century and the more important of the rules of that period.

England and America had used rating rules for some years, and France determined to do the same in October 1892.

It was thought that the efficiency of a sailing yacht could be calculated very similarly to that of a steam yacht, the sails being the motor in one, the engines in the other. But we know that the efficiency of a steamer should vary directly as her indicated horse-power, and inversely as her displacement. The same idea should apply to sailing yachts. It is, in fact, almost impossible to rate a sailing yacht satisfactorily without taking into account both her sail-area and her displacement — or something very closely allied with the latter.

A length and sail-area rule proposed by Mr. Dixon Kemp^[3] in 1880 was adopted in 1883 for second-class racing, and in 1886 this alternative rule was adopted as the sole rule. It is :—

This important step was taken after a careful and exhaustive inquiry conducted by a special committee appointed by the Council, Y.R.A., and presided over by Sir William Forwood^[4]. The committee took the evidence of our most noted yacht architects, and finally reported in favour of Rule (I), and of the present classification (except 25 rating, which was afterwards added by the Council). The report met with general approval, the Y.R.A. put its seal upon it, and gave it a tenure of seven years subject, however, to General Rule 12, by which any change at any time can be made by the requisite majorities.

The tonnage time scale in use before 1886 was altered to agree with the new rating, which cannot be said to represent anything but what it really is — the product of a yacht’s taxable length and her sail-area.

The classification and the divisor did not alter the rule one iota. They are purely arbitrary, as was very clearly stated in an excellent letter by Mr. G. B. Thompson, published in the ‘Field’ of December 17, 1892. He said very truly that the 5-rating class is in reality the 30,000 class, and the 10-rating class is the 60,000 class. If the divisor 6,000 be altered alone, the result is precisely the same as altering the rating itself in like ratio, and in the same direction. Thus (R x divisor) and (L x S) must each equal 120,000 in the 20-R. class, and must each equal 240,000 in the 40-R. class, and so on. In short, the Y.R.A. rule may be regarded as :— In each class L x S = a constant, for boats at the top of the class.

By a subsequent decision in general meeting, Y.R.A., December 6, 1892, L would in future be measured between the outer edges of the official marks, which must be affixed by the owner and always show clearly above the waterline when a yacht lies in smooth water in racing trim.

L, therefore, was no longer L.W.L., but L.O.M. (Length by owner’s Official Marks), rather longer than L.W.L.

By Rule 3, Y.R.A., in calculating a yacht’s R, a fraction of or exceeding 0.01 counts as 1.0 in classes exceeding 10 R. ; but in classes exceeding 1.0 R. and not exceeding 10 R., a fraction less than 0.1 counts as 0.1; and in classes not exceeding 1.0 R. fractions from 0.01 to 0.99 inclusive count for their value.

Example: Dacia’s certificate, June 1892, recorded S = 887.6 and L = 33.83 and R = 5.00. But her S x L ÷ 6,000 = 5.005 and 0.005 was "a fraction smaller than 0.1" ; consequently, by the wording of Rule 3, her R. = 5.01, and she was over-rating ; but the secretary, Y.R.A., when questioned, stated that the "Y.R.A. only recognizes two places of decimals," and words to this effect were added to Rule 3 at the general meeting February 22, 1893.

The Time Allowance

The time scale for differences of R. under Rule I. was based on the conception that a racing yacht’s "capability for speed varies as the fifth root of the rating," the argument leading to this being that :-

speed varies as √L (1)
and that sail varies as L√B (2)
and by the rating rule, R varies as S x L
it therefore follows from (2) that R varies as L²√B
and, assuming that B varies as L (3)
it follows that R varies as L²√L or L^5/2
therefore . . . L varies as R^2/5
Hence, by (1), speed varies √R^2/5 or 5th root R. — Q.E.D.

The Y.R.A. time scale therefore rests not only on the two assumptions (1) - vaguely correct - and (2) - quite tenuous - mentioned in the rule book, but on the further assumption (3) - which we know to be incorrect.

However, the 5th root of R. gave a time scale which was found to act fairly well in practice, and this being so, the theory of the time curve became a matter of minor importance.

At first (1886 and 1887) the adoption of the unrestricted rule met with some opposition, especially in the small classes, where a few of the most experienced yachtsmen advocated restrictions in L.W.L. or L.O.A., and in mainsail area. But the majority determined, and rightly, to give the rule free scope ; and the results on the whole were found to be highly satisfactory, fine seaworthy vessels, driven by a small sail-area at great speed, having been produced in the large classes. The evolution in the small classes was more rapid, and in 1892 some rather undesirable types were prize-winners, and yachtsmen who wished to protect themselves against similar vessels in the large classes induced the Y.R.A. to appoint a special committee to consider whether the unrestricted and unaltered rule should be continued beyond the seven-years period, terminating in 1893. This committee, under the presidency of Sir George Lampson, obtained the opinions of our leading designers, as was done in 1886, and the designers themselves met in conference twice, and jointly addressed two letters to the Rule Committee in which they finally recommended the adoption of the Seawanhaka rule for rating racing yachts and a classification of corrected lengths suitable for the existing British racing fleet; also other details, the most important being a proposal to tax overhang above the W.L. and cut away keels below it.

The Rule Committee adopted the recommendation as to change of rating rule, but proposed a modification whereby the British rating and time scale could be retained.

When this report was brought before the Council it was overturned, some of the committee themselves voting against their own report. But the action of the Council has since been justified by the production of several splendid specimens of yacht architecture to race under the Y.R.A. rule of rating.

The elements of the fastest types which were developed in small yachts under the rule can be found in the tables given in the chapter on "Racing in the Solent Classes", Yachting, Longman Green's Badminton Library edition of 1895.

One of Britain's ablest designers had consistently advocated the introduction of a tax on beam into the formula. He did so in 1886, and again in 1892, when he proposed to tax draught also. Unfortunately the mathematics of the rule made it difficult, if not impossible, to do so, because the blow on L. is lessened when it is shared by other quantities. However, Mr. Watson’s modification of the rating rule, proposed in October 1892, was:

English R = (2L + 2B + D) x S ÷ {constant, say 17,000} . . . . (II.)

Doreen was of smaller rating, although both longer and more beamy than Decima. They were of the same rating for racing by the Y.R.A. rule. Mr. Watson’s formula therefore encouraged even greater length of hull than the Y.R.A. rule. No such difficulty is encountered by the introduction of such taxes into the Seawanhaka rule, where the plus sign replaces the multiplying sign used by the Y.R.A. This rule was adopted by the American Yacht Club of its name in 1882, the form being

American R = (L + √S) ÷ 2 . . . . . (III.)

The New York Yacht Club had raced for a number of years under a similar rule for time allowance.^[5]

American R = (2L + √S ) ÷ 3 . . . . . (IV.)

and just as the Y.R.A. rule can take the form

L x S = constant in any class,

so these rules can take the forms :-

L + √S = constant, in any class . . . . . III.
2L + √S = constant, in any class . . . . . IV.

It then becomes evident that any sacrifice of S. to obtain greater L. under Rule IV. is only half as effective as the same process under Rule III. Conversely, any sacrifice of L. to obtain more S. is twice as effective under Rule IV. as under Rule III.

Again, as comparisons between L. and S. had to be brought to some common measure, the Y.R.A. form . . . L. x S. = constant in any class, may be read L. x √S. x √S. = constant, and it then became clear that any sacrifice of S. to get L. is twice as effective as in Rule III., and four times as effective as in Rule IV. ; and conversely, that any sacrifice of L. to get more S. is half as effective as in Rule III., and one-fourth as effective as in Rule IV.

Dixon Kemp who authored the Y.R.A. rule has pointed out that it can be converted into the American form of ‘corrected length' as :—

American R = ³√L x S . . . . . (V.)

See his second edition of Yacht Architecture. The sail curve is precisely the same as that from the Y.R.A. rule.

An examination of this form of the Y.R.A. rule is interesting. By cubing V. and comparing it with I., it will be seen that six thousand times the English rating equals the cube of the American rating derived from formula V.

When English and American rules are examined diagrammatically, the sail-curves take three positions that differ considerably in their steepness — the Y.R.A rule giving a curve nearest to the horizontal which indicates R. = S. ÷ constant, proposed by Mr. Richardson in 1886 (or R. = √S ÷ constant if expressed in American measure ; or R. = S √S divided by a constant if expressed in English measure) ; and the New York Rule taking a position nearest to the vertical denoting R. = L. under which the Solent Length Classes used to sail.

The Seawanhaka rule gives an intermediate curve — perhaps the ‘happy medium’.

The curves have been plotted for yachts of 40-rating by the British rule, and the following table gives the actual numbers :—

Each L. and S. rule for rating racing yachts must have a turning-point, or best length, in each class for winning prizes in a given climate. It depends far more upon the average wind-pressure during the racing season than on any assumed connection between L. and √S. It will vary on different days, and for different seasons, and for different localities. The average wind-force is stronger on the Solent than on the Clyde, and stronger at Rothesay than at Sandy Hook. But type is another matter. Type is governed by the racing rule, and differences of climate have very little effect upon it. The best proportional length also varies in different classes, the water being rougher and the wind harder, comparatively speaking, on small than on large yachts, thus causing the former to develop L. and sacrifice S. to the utmost. Under the tonnage rules it is true that the small yachts carried the larger comparative sail-plan, but this was due to other causes, such as their greater comparative draught and ballast.

The best length under L. and S. rules also varies with the rating rule, those rules having sail-curves nearest to the line R. = S. developing the greatest length, and those having sail-curves nearest to the line R. = L. developing the greatest sail.

Still another factor governs the best length in any Class – lightness of construction ; and this depends on four other factors : cost, design, workmanship, and strength of materials.

We are therefore met by quite a crowd of considerations when endeavouring to determine best length ; but in comparing the rating rules we can eliminate many of them by making a few assumptions and a reasoned analysis.

First, assume that a new boat is built with the lightest possible hull consistent with strength, and of the best possible design for the 40-R. class 1894, and that her L. = 62 ft., therefore S = 3,871. (See preceding table.)

Second, assume that a longer boat and a shorter boat, equally well built and designed, are tried and are beaten, and that 62 ft. is then acknowledged to be best Length for 44-ratings in the prevailing climate.

Third, assume that the class is converted in 1895 into one rated at 61.5 American R., Queen Mab being thereby placed at the top of the class by the Seawanhaka rule without alteration. The 62-ft. yacht, however, must clip to 3,721, or 150 off her S. as a 40-rater.

But the shorter boat, say a Queen Mab of 59 ft L.W.L., which we assumed to fail when racing under the Y.R.A. rule, could now add 30 ft. and sail against the crack 62-footer with an advantage of no less than 180 sq. ft. of canvas.

Evidently, the best length under the British rule being 62, the best length under the American rule is something less ; how much less being only determined by trial, and depending on the numerous factors mentioned above. Moreover, an arbitrary limit of L.W.L. is thus shown to be less necessary under the American rule than under the Y.R.A's ; and with L. so greatly developed in Britsh racers at the time, it was seen to have already gone beyond the best length for the American rule, especially in the small classes. This was carefully pointed out by Col. John Townsend, R.E., of the Royal Victoria YC, (using his habitual pseudonym 'Thalassa') in two letters to ‘Land and Water,’ October 5 and 9, 1892. Mr. R. E. Froude also stated the case very clearly in the ‘Field,’ December 31, 1892 ; but it is very difficult to convince the defenders of the Y.R.A. rule that any other rule is superior.

Mr. Dixon Kemp, in his excellent work on ‘Yacht Architecture', says (p. 15, 2nd edition) in comparing rules I., III., IV. : ‘Of these rules, that of the Y.R.A. admits of the employment of the greatest length for any given rating’; and the length referred to was evidently best length in a given climate.

The Seawanhaka rule was therefore superior if excessive length be feared ; and being a plus formula, it lends itself readily to the adoption of any desired tax on other linear dimensions.

For instance, G.L. Watson’s (designer's) proposal (II.) might be put into the plus form, as :

American R = (2L + 2B + D + √S) ÷ 3.8 . . . . . (VI.)

This shows the value of a plus rule over a multiplying rule, and the value is not lost when a plus rule is converted into an English rating rule by cubing the former and dividing by a constant. Thus, the Y.R.A. Rule Committee proposed to convert the Seawanhaka rule into an English rating rule by cubing it and dividing by 6,000, the result being :

English R = (L + √S)³ ÷ constant, say 48,000 . . . . . (VII.)

The variable within brackets in VI. can be cubed and divided by a constant in a similar manner. But the cubic forms of the ‘plus’ rules are clumsy, and seem difficult to those who cannot compute by logarithms (remember, no computers in 1895.) No real advantage wass gained by adhering to the English rating and time scale and classification. In fact, the American time scale was simpler. If, therefore, a ‘plus form’ of rating need ever adopted, it would be much better to adopt ‘corrected length’ as the rating, together with the American time scale. The classification could, of course, have been chosen in such a manner that British racing yachts would have been at the top of the classes without any important alterations.

Another rule was proposed in a leading article of the 'Field’ on October 15, 1892 :

English R = L² x √S ÷ constant, say 6,000 . . . . . (VIII.)

It gives a sail-curve nearly parallel to the one produced by the New York rule, and may almost be regarded as that rule dressed in Y.R.A. uniform ; but the advantages of a plus rule are lost, whereas in the conversion of the Seawanhaka rule proposed by the Y.R.A. Committee 1892 they were retained.

Similarly, the Y.R.A. rule — varying as cube√L x S (see V.), or as cube√L. x √S. x √S. — may be considered as equivalent to the plus formula L.+ 2√S. ÷ constant, and the English and American rules may therefore be regarded to vary as follows :

Mr. Herreshoff had recently proposed a rule of rating based on L x √S, which is an area, but the cube root of tonnage is placed in the divisor ; and this being linear, it converts the rating into linear measure, an area divided by a line being a line. The result being linear, it was translatable into American rating and time allowance.

Mr. Herreshoff’s proposed rule was :—

A critique on this rule by the editor of the ‘Field,’ December 17, 1892, suggests that the cube root of 100 T. should be taken, as there are 100 cubic feet in a registered ton. This is unnecessary. So long as S. is superficial, and T. cubic, the √S. and the ³√T. will be linear ; and a constant can be selected which can convert the quotient resulting from the rule into corrected feet or inches, or metres, as required for the linear rating adopted.

Mr. Herreshoff’s rule when tested was not encouraging ; Doreen’s length so corrected being 2 1/2 per cent. smaller than Decima’s. The rule evidently did not encourage that compactness of hull dimensions which Mr. Watson considers desirable. It also appeared to put a premium on abnormal freeboard, so as to increase T. by means of a large body over the water-level.

This was pointed out by the editor of the ‘Field,’ December 24, 1892, and an improved rule suggested in which displacement was used as a divisor in place of tonnage. W. the total weight of a yacht in English tons dead weight is of course her displacement, and the rule proposed may be written :—

So far as L. and S. are concerned this rule produces a similar sail-curve to the Y.R.A. rule (see diagram); but the divisor would encourage a large powerful hull, and the rule would therefore produce a shorter type with more sail than then existed in English racers. The practical difficulty of discovering W., either by measurement or by some system of weighing the yacht complete, has to be considered in connection with this rule.

The most important point to be noted about these rules (IX. and X.) is the fact that Mr. Herreshoff and Mr. Dixon Kemp proposed them — showing that two of the leading experts consider it necessary to encourage greater displacement by means of the rating rules. The question, therefore, arose whether the desired result cannot be effected in a less objectionable manner; and it appeared to John Townsend that dividing the Y.R.A. rule by some area proportional to that of the immersed mid-section (M.S.) would have the desired effect, and would avoid the difficulties already mentioned. The actual area of M.S. cannot be found without encroaching on the finer points, or 'secrets' of a yacht’s design; but M. the area of immersed mid-section can be easily found, with yacht afloat, if measured internally^[6], and the Y.R.A. rule could take the form :—

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 have been 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 in the following table, where Bedouin figures out very well owing to her large but not deep immersed M.S. John Townsend claimed with some confidence that this modified rule presented the best solution of the problem yet suggested. But there was really no problem requiring solution at that time. So long as yachts like Britannia and Satanita were built for racing under the Y.R.A. existing rule of rating, grumblers would not command an audience. In the event, however, of yachts like Pilgrim or Jubilee winning in British waters a change of some sort would have been required.

The Seawanhaka rule (III.) can be treated similarly, the divisor 2 being thereby avoided. It becomes :-

The action of these rules may be seen from Table 2, giving the rating under the modified Y.R.A. rule (formula XI) and the rating under the modified Seawanhaka rule (formula XII). Each result is in ‘corrected length.’ The dimensions in the table 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 L.² in successful yachts.

The New French Rule

On November 5, 1892, it was announced in the ‘Field’ that the Union des Yachts Français had decided to adopt a hull- and sail-area rating, it being considered by the ‘active element in French yacht racing’ that ‘the type . . . produced by the French length and girth rule is inferior to the type produced by the British and American rules . . . British yachts having defeated those of France, although handicapped by the French rule of rating.’ The conclusion was scarcely a logical sequence from the premises. It should have been that French racing yachts were not the correct evolution of the French rule of rating. But there was now concern with the new French rule (proposed by M. Godinet) in which sail was an important factor. In its simplest form, it is :—

English R = (4L — G) G√S ÷ 520 . . . . . (XIII.)

G. being the greatest girth from top of deck planking port, around the keel to ditto starboard, plus extreme beam. Each of the three factors L. G. √S. being linear (metric measure) the result is given in cubic form, and was converted into English rating by the divisor selected, and the Y.R.A. time scale was been adopted by the Union des Yachts Français.

The editor of the ‘Field’ considered that ‘the rule is calculated to prophesy the evolution of any rule, more to produce a poor kind of vessel for match sailing or anything else ; but it is hazardous to prophesy the evolution of any rule, more especially one which taxes L., B., D., bilge, and S. No doubt the tax on D. is doubtful policy, and it seems very unnecessary when we consider the small depth of water in many French harbours, which is the most efficient check on D. it is possible to conceive for large yachts, and in the small classes D, gives grip and power to windward, and seaworthiness.'

A careful analysis of the rule confirms the conclusion arrived at by the editor of the ‘Field’. It certainly appears that the rule has a sail-curve nearly as steep as the New York rule, which has been abandoned because it encouraged such large sail-plans. For this reason, therefore, if for no other, the new French rule seems to be inferior to the Y.R.A. and the Seawanhaka rules. A good letter on the subject of girth, by a leading designer (Fife), was published in the ‘Yachtsman,’ September 8, 1892, and, as described on p. 87 of the ‘Field,’ January 21, 1893, the measurement of M. can be easily done in a few minutes, with yacht afloat.

On the whole, English yachtsmen probably felt very disinclined to adopt the new French rule for British yacht-racing.

Older Rules

Having looked into the more important national rules in which sail-area and some hull dimension or dimensions are combined in the formula for the rating, whether the result be cubic, linear, or otherwise, it is important to recall the simple sail-area rule proposed by Mr. Richardson in 1886, viz.

R = S ÷ 100 . . . . . (XIV.)A

The rating so obtained being neither cubic nor linear, but superficial, difficulties as regards time scale arose, and neither Mr. Richardson nor the Council appeared to notice that the Rule could easily be made linear by putting it in the form

American R = √S . . . . . . (XIV.)B

when American rating and time scale could have been adopted. Also that it might have been rendered

English R = S√S ÷ constant . . . . . . (XIV.)C

which is the cubic form, suitable for the Y.R.A. rating and time allowance.

The graphic result in the sail-diagram is the same in each case, viz. a horizontal line for any given class, the limit for each class being one of sail-area alone.

It was not adopted because the Council considered that the type evolved from it would be one of excessive length and small displacement; and our experience with the Y.R.A. rule, which approaches it more nearly than any other hull- and sail-area rule, has shown that this estimate was correct.

We will now examine a few of the rules which rate yachts entirely by hull-measurement. The simplest of the kind is the pure length rule, used for some years on the Solent for racing small yachts up to 30 ft. of L. [See Badminton Library, 2nd ed., 1905, p.222-294, "Small yacht racing on the Solent".]

American R = L . . . . . . (XV.)A

Some trouble was taken in 1884 to produce a special time scale for this formula. It was quite unnecessary, because the time scale for tonnage (see XVIII.) then in use could have been employed, (XV.)A being modified to

R = L³ ÷ constant . . . . . . (XV.)B

and by adjusting the constant this form of the length rule can be adapted to the time scale of any cubic rule. Thus, the divisor 5,000 adapts it to the Y.R.A. time scale for rating.

The type resulting from the length rule was, of course, a very fast and powerful boat for its L., carrying an enormous sail-spread — somewhat costly to build ad race.

Older tonnage rules

Our grandfathers raced their yachts under the old tonnage rule,

Tonnage R = L x B x H ÷ 96 . . . . . . . (XVI.)

H. being depth of hull to deck beam, and L. being measured in various ways at different times. After 1854 it was taken on deck from stem-head to stern-post, and certain deductions made for rake. Eventually the Thames Rule :-

(L—B) x B x 1/2B ÷ 94
      or B²(L — B) ÷ 188 . . . . . . . (XVII.)

was evolved and adopted by the Y.R.A. in 1876. And in 1878 it was decided to measure L. on the water-line. In 1880 the Y.R.A. altered the rule to :-

English T = B (L + B)² ÷ 1730 . . . . . (XVIII.)

The type evolved, as might have been anticipated, had a long, narrow, heavily ballasted, deep-bodied, wall-sided hull, possessing little beauty, small initial stability, and no great speed, considering the sail-area employed to drive it. There was little scope for improvement, and the energies of our best designers were directed to producing yachts which carried large sail-plans on narrow hulls, their L.W.L. often approaching and sometimes exceeding six beams. Nevertheless, this ‘1730 Rule,’ as it is often called, governed first-class racing in British waters from 1880 to 1886.

As was noted by the historians of the Royal Yacht Squadron in 1902: "The 1730 rule [in effect from 1881], which had fixed tonnage by certain multiplications of length and breadth, had resulted in the evolution of an unwholesome type of vessel which gained an artificial stability for its huge spread of canvas on minimum beam, by a portentious depth of keel and by the employment of huge masses of lead as outside ballast. These vessels of the type known as 'plank-on-edge' were useless for any purpose except the hunting of cups, were uncomfortable to live in, impossible as cruisers, and unsaleable except as mere heaps of scrap material when their racing career was at an end."

Another hull-measurement rule is the one used for some time in France, and often called the ‘Girth Rule.’ In its simplest form, it was :—

French T = G² (2 L — B) ÷ 176 . . . . . . (XIX.)

G., the girth, is taken as in Rule XIII. The rule taxes draught heavily, and does not appear to have given satisfaction, or it would not have been changed in October 1993 to No. XIII.

Many other hull-measurement rules might be mentioned; in fact, during the mid-1890s the yachting press was full of such proposals, with the proviso that those who made them must be aware of the general feeling among sportsmen in England, France, and America that sail-area should be taxed in the formula for rating. It was suggested that any lengthy discussion on rules which did not conform with this opinion was, therefore, a waste of time and energy, and the hull rules described here have been mentioned primarily on account of their historical interest.

The rules are numbered consecutively in the order in which they have been examined; the tonnage rules last, although some of them are the most ancient. But it may be convenient for the reader to have them grouped somewhat differently and this has been done in Tables 3 and 4 which also afford an opportunity to compare two yachts of similar hull-dimensions, but differing in regard to their length and sail-area, except that the product is equal. Doreen and Decima make an excellent pair for such a comparison, being each 10-rating by the Y.R.A. rule, and of nearly the same beam, draught, girth, and depth of hull, but differing in length and sail-area.

The tendencies of those rules which aimed at encouraging a larger body, like Mr. Herreshoff’s, or a larger immersed body, like X., XI., and XII., are shown in Table 4. Owners and designers were invited to work out some examples for themselves to test their action, as the New York committee had reported in 1895 being in favour of some such modification of existing rules.

Notes

Bibliography