# 1907 APBA Rating Rules

### Power Boat Ratings Under New Rule Codes

*Similarities and Differences Under the New and Old Bodies*

Changes Are Progressive

*Jamestown Committee Responsible for the Principle Innovations*

**Force Action On Old Legislators**

The determination of some of the advocates of the American Power Boat Association to obscure the question of rating in which they have been forced to accept practically intact the new features introduced through the Jamestown Exposition Committee seems persistent. At present there are being raised loud cries about the baneful influence being introduced into the sport by the prominence of manufacturing interests in contradistinction to the amateur element. One's sympathy is naturally with the amateur as against the professional in any controversy between the two, but such a sentiment does not weigh in cases where the amateur has flagrantly persisted in doing injustice to the complaints of those who happen not to be in authority, when the professional stands ready to take such action as will deal fairly with all. The American Power Boat Association before the introducing of this new element in power boats was determined that no changes should be made in its rules. After the introduction of the new force, the American Power Boat Association did effect changes in the rules and they were practically the changes suggested to the Jamestown Committee by motor experts. There is now little essential difference in the two rules, save in terms of measurement, and these differences will likely be sunk when the time comes to again revise the rules next year.

Taking the two formulas adopted for rating and comparing them it is found that the same factor enter into both, couched in different terms. The American Power Boat Association; 18 times cube root of HPxsquare root LWL divided by MS.

The Jamestown Committee takes; 11 times cube root of HP x square root of LWL divided by D.

The difference in the constants is of no consequence whatever, and both consider horse power and the load water line length as positive factors and displacement as negative. The Power Boat Association interprets its displacement in terms of the area of the midship section, which is absolutely correlative, while the Jamestown Committee takes its displacement measurement in cubing inches.

The Power Boat Association also allows as a substitute for its midship measurement requirement, which has caused many complaints, the application of the formula: WxC divided by L, which means the weight (plus 300 pounds allowance for crew) multiplied by a constant and divided by the water line length. The constant is .0284 for sea water, and .0291 for fresh water. The Jamestown rule simply takes the actual weight, or , when this is impossible to secure, the ascertainment of displacement in the usual manner in yachting.

When it comes to the rating of motors for their horse power there is the same analogous action in most instances, though the Jamestown Committee improves upon the Power Boat Association rule by adding the additional consideration of the stroke of the engine. The American Power Boat Association rules that the horse power of gasoline engines shall be computed by multiplying the piston area by the number of pistons receiving direct explosions and divide by a constant. Thus, AxN divided by C. The constant (C) for four- cycle engines is fixed for 2; for two-cycle engines of over six-inch stroke, the constant is 1.65, and for two-cycle engines of under six-inch stroke it is .65, but the addition is made to the formula that the stroke in feet is included. Thus, AxNxS divided by C.

The Jamestown Committee rules use the AxN formula for all engines of over six-inch stroke; that is, the total cylinder area divided by 2 for the large four-cycle engine, but employs the stroke in the smaller stroked engines of both types. In the formula, AxNxS divided by C, it uses the stroke in inches and divides by ten for the four-cycle variety, and the same formula divided by .85 in the two-cycle variety.

There are the same minor differences in meeting the condition introduced by
the *Chip's *extra compression cylinder last year. The Power Boat
Association declares that:

a.-- In four-cycle engines having a compression cylinder or any device forcing the mixture into the working cylinder, the horse-power shall be increased 10 per cent.

b -- In four-cycle engines having a compound of expansion cylinder or cylinders, 20 per cent of the piston area of such cylinder shall be added to the area (AxN) of the high pressure or working cylinders, and then divided by the regular constant.

c -- In two-cycle engines having a compression cylinder or cylinders, the horsepower shall be augmented by the ratio that such cylinder bears to the volume of the working cylinders, volume being determined by piston area multiplied by stroke.

d -- In two-cycle engines, where a rotary compressor is used, the constant shall be one half that of the four-cycle engines.

*(Transcribed from the New York Times, Jan. 20, 1907, sec. V, p. 16.)*

[Thanks to Greg Calkins for help in preparing this page — LF]