P.Bowers Curtiss Aircraft 1907-1947 (Putnam)
Miscellaneous Aeroplanes, 1910-14
In addition to the principal pusher and flying-boat designs, Curtiss produced others within this period. While not all were designed by Curtiss, their construction provided additional experience.
Pfitzner Monoplane. Late in 1909, Alexander L. Pfitzner, who occasionally helped Curtiss with powerplant problems, undertook the building of a monoplane of his own design in the Curtiss shops at his own expense, although Curtiss employees built some of the parts. While it owed much to the layout of the contemporary Curtiss biplane, it had one unique feature. Mindful of the Wrights, Pfitzner achieved lateral control by means of telescoping wingtips, extending one tip to increase the lift on that side.
Pfitzner's monoplane was barely successful, flying on 21 December, 1909, but it did earn him the distinction of flying the first American monoplane.
Flight, February 26, 1910
A NOVEL MONOPLANE.
ALTHOUGH most of the machines which have been experimented with in America have been of the biplane type, there is one monoplane with which a certain measure of success has been attained. This is the invention of Mr. A. L. Pfitzner, who has been for some time associated with Mr. Glenn Curtiss, and from the two photographs, which we reproduce from the Scientific American, it will be seen that the design is in some ways reminiscent of the Curtiss biplane. The novel feature of the machine lies in the means for maintaining lateral stability. At each end of the main plane there is a sliding tip, which normally lies 15 inches beyond the main plane. These tips are interconnected, and controlled by the steering-wheel, so that when one is slid out to its full extent of 30 inches the other is completely withdrawn, any movement of one being accompanied by a corresponding adjustment of the other.
The main plane itself measures 31 ft. by 6 ft., giving an area of 186 sq. ft., while the sliding wing tips are 2 1/2 ft. by 5 ft. Fourteen feet in front of the main plane is the elevator, a single plane 6 ft. by 3 ft., while above it is the triangular rudder 2 ft. high by 3 ft. in length, and both these are connected-up to the single steering wheel. At the rear, 10 ft. from the main plane, is the horizontal tail 6 ft. by 2 ft.
It will be seen that a single propeller is fitted, driven by a 25-h.p. 4-cyl. Curtiss motor. With 6 gals, of petrol in the tanks, 1 gal. of oil, and 1 1/2 gals. of water the machine weighs 430 lbs. The propeller is 6 ft. in diameter, and is said to give 235 lbs. thrust at 1,200 r.p.m.
A large number of short flights have been made, and the machine rises from the ground very quickly, the average distance run to get up being about 100 ft., when the machine was tried over snow.
Flight, March 12, 1910
THE PFITZNER MONOPLANE.
IN our issue of Feb. 26th we published a couple of photographs, together with a few particulars of a monoplane which embodied many unique features, and which had been constructed in the Curtiss factory at Hammondsport, New York, by Mr. A. L. Pfitzner. We are now able to give scale drawings of this machine, and in view of its unique design, and the fact that it has already flown, although only very short distances, we think these further particulars will be welcomed.
Each of the wings of the main plane is made in three sections, each 5 ft. long, which are attached and connected by steel sockets and steel cable, the latter forming a symmetrical double king truss with the beams, the king posts being at the junction of the detachable sections. The two wings are set at a dihedral angle of 5 deg. The surface is single, with the framework exposed on the under side, and consists of vulcanized Japanese silk material which is stretched over the ribs by lacing at the junction of each of the seven sections. The curvature of the surface is of the high-speed type, with the centre of pressure 18 in. from the leading edge. The ribs have a camber of 3 3/4 in. in a 6 ft. length, the highest part of the surface being 1 1/2 in. above the leading edge, while the angle of incidence is 8 deg.
The unique feature of the monoplane is the system of equalisers at the tips of the main planes. The main surface, as will be seen from the plan, stops short 30 ins. from the end of each wing, and in this space slides a panel 30 ins. wide by 50 ins. deep, of the same curvature as the main surface. These two balancing tips are inter-connected to the hand wheel, and normally they project 15 ins. at each end.
The system of control, which is shown clearly in our diagram, is a combined one in which all the necessary movements are connected to the one wheel and column. The elevating plane, which is in front of the machine, is operated by giving the steering column a movement to or from the body of the operator; while steering to right and left, by means of the vertical rudder placed above the elevator, is effected by twisting the steering column wheel; and lateral stability is maintained by turning the wheel. This being connected by cables to the balancing tips causes one of them to project further out and the opposite one to be withdrawn a corresponding amount. By the side of the controlling column is a lever connected to the throttle of the motor, while a switch button on the steering-wheel enables the Bosch high-tension magneto-ignition to be switched off for the purpose of stopping the motor. The motor is a 25-h.p. 4-cyl. Curtiss, and drives a 6 ft. spruce propeller of 4 1/2 ft. pitch, giving 235 lbs. thrust at 1,200 r.p.m. It is said to weigh only 6 3/4 lbs.
A noticeable departure from usual monoplane design is the placing of the propeller and engine behind the operator. The design of the chassis, too, is also unusual. It will be noticed that four wheels are employed, and the machine so balanced as to enable it to start in any direction. The chassis is built up of four vertical posts, each forked at the bottom, and holding a 20 in. diameter wheel fitted with a pneumatic tyre. These four posts are spaced by seamless steel tubing, while at the bottom there is a wooden skid which takes the strain after the first shock has been absorbed by the wheels.