From AVIATION, September 28, 1925
THE first of the three Curtiss racers under construction at the Garden City plant of the Curtiss company, was put through its preliminary trials during the week of Sept 19 and was considered in every way to be a great achievement in racing airplane design. Several flights in the earlier part of the week when Lieut. Alford J. Williams, U.S.M., who is to pilot the Navy entryin the Pulitzer Race, nd Lieut. James H. Doolittle, A.S., flew the plane for short trials, served to indicate the through airworthiness of the racer. It was not until this was defintely demonstrated that attempts to determine the speed qualities was made. On Sept. 18 Lieutenant Doolittle, for the first time, opened the throttle wide and flew the actual course of the Pulitzer Race from Mitchel Field, where these tests were carried out. W. L. Gilmore, chief engineer for the Curtiss Company, timed the trials and reported an average speed of 254 m.p.h. for two circuits of the course, thus exceeding by approximately 11 m.p.h. the last Pulitzer speed figure set up when the Navy Curtiss racer won this race at St. Louis in 1923, the speed then being 243.6 m.p.h.
On the same day Lieutenant Williams flew the new racer and made a speed course trial, flying over a distance of one kilometer. Electrical timing gave the exact passing of the wires at the end of the course. The airplane climbed to a height of two or three hundered feet and dived for the starting line, flattening out approximately 100 ft. above the ground and proceeding level over the kilometer course. There was a favorable trailing wind of about 10 m.p.h., which would increase the actual speed made by the plane. The one kilometer distance, however was covered in an elapsed time of but 7.4 sec., which indicates a ground speed of over 300 m.p.h. This flight, although recorded by the officials of the Curtiss company, was not officially observed and cannot therefore, be recognized as a world speed record. Trials for the purpose of bringing back to America the speed record of the world will be made at a later date.
The new Curtiss Racers, though differing very slightly in general design from the 1923 type, flown also in last years Pulitzer race, possess, however, a number of detailed modifications tending toward the attainment of an even greater speed.
Its total weight, ready for the race, will be only about 2,150 lb. Built on the monocoque principle, the body or fuselage of the craft consists of four longitudinal members of wood, supported by diaphragms or bulkheads at regular intervals and covered with thin layers of wood veneer. These layers, in order to ive the greatest strength possible, are cut in narrow strips, approximately two inches wide, securely glued and tacked to the longitudinal members at an angle of approximately 45 deg. to the center line of the fuselage. Suceeding layers of this veneer are placed at an angle of 90 deg. to each other. The extreame strength of such construction as regards twisting and bending is obvious. The wings and tail surfaces are built up of wood, ribs and spars also covered with thin strips of plywood. These strips are of two ply spruce about 3/32 in. thick.
The general appearance of the airplane is that of a very cleanly designed conventional one-strut biplane. The overall span or width of the airplane is 22 ft. The total wing area not including that of the axle fairing, is approximatly 144 sq.ft. When the airplane is fully loaded, every square foot of the wing surface supports 1.9 lb. of load in flight.
Preliminary ground tests which have been conduted have proved the structure to be extremely strong, the successful loading in many cases having been carried well beyond the high required factor of safety.
The engine is the most noteworthy feature of this new racing airplane, it being a very definite advance upon the D-12 type with which the previous racer was fitted. Through similar in size and appearance to the D-12, the new engine is designated the type V-1400, is no less than 30 lb. lighter, while developing over 100 hp. more than the earlier engine. Its rated power is stated at 619 hp. at a propeller speed of 2500 r.p.m. Thus, the new engine represents an increase in power of 20 per cent over that eveloped by the D-12, which gave 500 hp. Ligheter weight, greater power, and consequently increased efficiency, therefore, mark the advanced features of the V-1400.
In the plane itself every attention has been paid to the streamlining of all parts, just as in past years, and all turnbuckles and bracing fittings are built into the fuselage or wings and it is claimed that a saving of approximately 50 per cent in head resistance of these parts is thereby obtained. Extreme care has been given to the metal fittings throughout, ample strength being assured in all cases, and bronze of a tensile strength of 105,000 lb., has been utilized, this being approximately twice that of normal bronze.
The streamlining has been carried out in a similar manner to past practice in the Curtiss racing designs, and the landing gear and wheels are alost identical with that of the last racer, there being an airfoil shaped axle between the wheels which are themselves streamlined across the hubs with aluminum discs. The wing radiators are slightly modified, mainly in the matter of size, being a little longer than in former Curtiss racers. They are constructed of brass sheeting .004 and .005 in. thick, and this, it will be noted, is thinner than the average sheet of paper. The wing radiators contain twelve gallons of water which circulates at the rate of seventy-five gallons per minute.
Finally, as usual in recent Curtiss airplanes, all three planes will be equipped with the Curtiss Reed duralumin propeller.
The main dimensions of the 1925 racers are:--
Span......................................21 ft. 9 in.
Chord, upper wing.........................4 ft. 8-1/4 in.
Chord, lower wing.........................3 ft. 3-3/4 in.
Overall length............................19 ft 9-3/4 in.
Weight fully equipped.....................2200 lb.
It is a very interesting feature that in this airplane, with its engine developing no less than 619 hp., the total power loading is but 3.75 lb. per hp., and this figure compares very favorably with the loads per horsepower of earlier types of engines alone. Thus, it will be recalled that the original Curtiss OX engine, which weighed 400 lb. and developed 9 hp.and was considered a very fine engine, was loaded to the extent of 4.5 lb. per hp. in itself, and the great improvements which have been made can be visualized by a comparison of this figure with the loading of the complete Curtiss racer of but 3.75 lb. per hp. including pilot and sufficient fuel for a two hour flight.