Dixie II
[1908]I suppose the most striking fact about Dixie's recent victory in the Harmsworth Cup Race is the fact that a boat with a single screw and 200 h.p. beat one with twin screws and 400 h.p.
This fact, together with the world's record of 31.05 knots or 35.75 statute miles per hour made as the mean for four runs over the New York Y.C.'s measured course in Hempstead Harbor, led THE RUDDER to ask the writer to tell its readers how it was done.
When Commodore Schroeder came to see me last Winter about a new boat to defend the Cup I was well aware that the Englishmen were building a boat of 400 h.p. but, judging by their previous boats, I believed that a boat with a trial speed of 35 miles would be fast enough to win, and with a margin. I also felt sure that this speed could be obtained with a single engine, if we could produce a boat of no greater displacement than the old Dixie, but with 200 h.p. or more instead of the 130 h.p. or less that had driven the old boat to victory the previous Winter.
The question then was, Could we get an engine of 200 h.p. to weigh not more than 2,000 lb?
After discussing the matter with several engine builders, the Crane & Whitman Company, of Bayonne, N.J., agreed to build me such an engine. Although they had never built such an engine I had sufficient confidence in my brother, Mr. H. M. Crane, the head of the company, to contract with them for such an engine and guarantee Mr. Schroeder 35 miles an hour in a boat conforming to the Harmsworth rules.
In predicting with any confidence this great speed I had to rely largely on data obtained from the earlier boats, Vingt-et-Un II, Challenger and Dixie. The calculations based on these boats showed that, unless something unforeseen occurred, we should require between 180 and 200 h.p. to obtain the guaranteed speed.
Fortunately, I could guard against the unforeseen by the help of the Government testing tank in Washington.
The elder Froude proved nearly thirty years ago that at "corresponding" speeds the resistance of a small model bore a definite proportion to the resistance of a full-sized ship.
For example,. the resistance of a 10-foot model ay 15 knots speed would be just be 1-64 the resistance of a 40-foot model at 30 knots speed, with some slight modification for the fact that the frictional resistance of the large boat, increased in slightly less proportion than this.
We tested in the tank two models each 10 feet long, one of Dixie I and one of Dixie II.
These model tests verified the calculations and showed us that, with a proper propeller, 207 b.h.p. was a conservative figure for 35 miles.
The principal change in Dixie II's model was in the use of a flat stern instead of the modified Normand type of the old Dixie.
The construction is very little changed from the old boat, being a simple ribband carvel with mahogany planking, elm framing and yellow pine stringers, keel, gunwhale, etc.
The fastening is almost entirely of brass screws. The hull was built by Woods, of City Island, N.Y., and is a beautiful piece of work, weighing complete, with engine foundation, struts and engine hood, 1,130 lb.
The engine is of the eight-cylinder V-type, the cylinders being 7 1/4 inches diameter and 7 1/4 inches stroke. The total weight, including reverse gear, was 2,100 lb, and the total horsepower developed 220 at 900 revolutions.
The light weight of the engine was obtained by compactness of design and the use of high-grade steel.
The base is of manganese bronze and there are five bearings with an unusual amount of bearing surface.
The valves are in the head of the cylinders and are operated by a single cam and rocker.
The engine was thoroughly tested in the shop, so that the first day it was put in the boat, Dixie ran from Bayonne to Oyster Bay without a skip and entered the trials next day at Huntington, where she won with ease. The propeller with which she raced is the first and only one designed for her, and is 26½ inches in diameter, 49 inches pitch, with a developed surface of 365 square inches.
Transcribe from The Rudder, Sep. 1908, p. 162.
[Thanks to Greg Calkins for help in preparing this page —LF]
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