The chief distinguishing feature of the Gallaudet seaplane is the employment a four-blade propeller acting as a pusher in connection with a fuselage design similar in most respects to the tractor type.
Top Speed: 92 m.p.h.
Engine: two Duesenberg inlines
Wingspan: 47 feet
Weight: 4,600 pounds
Specifications from “Practical Aviation,” by Charles Hayward, 1919
The manner in which the propeller is mounted and driven is also unusual. For structural reasons, both the camber and the angle incidence of a propeller blade, by which it develops useful thrust, vanish as the blade tapers toward the hub. Consequently, there is a considerable proportion of each propeller blade which does not contribute to the thrust but which does help power the machine as a whole. In the Gallaudet design, this addition to the drift has been eliminated by housing the structural parts ui the four-blade propeller in a drum, the periphery of which coincides with the section of the body at that point so that only the effective portions of the propeller blades revolve in the air stream. This s said to give an increase in propeller efficiency of nearly 10 per cent. A further advantage results from this location of the propeller in that the centers of thrust and resistance become coincident.
Planes
Both wings are of the same size, the span being 48 feet with a chord of 7 feet and a gap of 7 feet 7 inches. There is no dihedral angle but the planes are marked by a pronounced sweep back and stagger, the former amounting to 8 degrees 30 minutes, while the latter brings the upper plane 1 foot 9 inches forward of the lower. The angle of incidence is 7 degrees, while the ends of the planes are raked at an angle of 22 degrees. The main planes are built in six sections, the central sections, above and below the fuselage, having an area of approximately 25 square feet, while each of the four outer sections has an area of about 140 square feet. Ailerons are employed on both upper and lower planes and have a total effective surface of 56 square feet. The center panel struts are spaced 2 feet 4 1/4 inches apart and the center interplane struts are placed 8 feet 8 inches from them; the distance from the center to the outer interplane struts is practically the same, leaving an overhang of 5 feet 2 inches from the center line of the outer strut, to the outer tip of the aileron. The fore and aft spacing of the interplane struts is 4 feet 4 inches. The total lifting area is 658 square feet, and the machine complete weighs 3600 pounds and is capable of carrying a useful load of 1000 pounds.
Tail Unit
The horizontal stabilizer has a total area of slightly over 30 square feet divided into two equal section- either side of the fuselage.
It measures 10 feet 4 inches along the rear beam and has a depth of 6 feet, the surface itself being a positive angle equivalent to a difference in height of 3 inches between the leading and trailing edges. Owing to the large amount of side surface presented by the fuselage, which tapers but slightly in a vertical plane to the rear end, no vertical stabilizing is employed. The elevators have a span of 12 feet and are 2 feet x inches wide, giving a total area of 23 square feet. Each elevator is attached to the rear beam of the horizontal stabilizer by means of four hinges. A balanced type of rudder with its surface equally disposed above and below the fuselage is employed. It measures 5 feet in height and has a maximum width of 3 feet 6 inches, giving it a total area of 12 1/2 square feet.
Fuselage
The over-all length is 29 feet 6 inches with a maximum width and depth between the central wing panels of 3 feet 6 inches. The observer and the pilot are seated in separate cockpits in the nose of the fuselage and, from this point back to the mir end of the motor housing, the sides of the body are flat, rounding off at top and bottom. From the tip of the nose to the leading edge of the propeller is Hi feet. Aft of the propeller, the body tapers to a vertical chisel edge which forms the rudder post.
Power Plant
Immediately back of the pilot are installed two Duesenberg motors of the four-cylinder vertical water-cooled type, the radiators being placed along the sides of the body and flush with it, as will be noted in the general view. These motors measure 45 by 7 inches and at their normal rate of 2100 r.p.m. develop 150 h.p. They are so arranged that either one or both may be used to drive the four-blade propeller through spur reduction gearing. The weight of each motor unit, including its reduction gear, is 509 pounds. The four-blade propeller is 9 feet 6 inches in diameter and is of special hubless construction designed to eliminate the drift caused by the inactive parts of the propeller blades of the usual type. Instead of four blades and their supports centering in a hull, this propeller consists of the useful sections only of four blades attached to ¡i metal ring, the latter being driven through an internal gear and spur gearing from the motors. This power plant gives the machine a maximum speed of 92 m.p.h. and a landing speed of 45 m.p.h. With a total flying weight of 4600 pounds, the cruising radius is 1000 miles. The machine was designed to comply with specifications calling for a maximum speed of 88 m.p.h., but by careful streamlining of every surface the speed was increased to the figure given.
Floats
The Gallaudet machine shows clearly the difference between the type known as flying boats and as seaplanes.
This is a seaplane in that it is simply an aeroplane in which a supporting plane and floats have replaced the usual landing gear whereas, in a flying boat, the fuselage and the landing gear are one. It must not be inferred from this, however, that a seaplane is simply any aeroplane to which floats are attached. The mail float is 25 feet long with a maximum beam of 3 feet 6 inches and maximum depth at the step of 2 feet 6 inches, the step being located Hi fret 6 inches from the forward nul of the float, which projects 1 foot in advance of the nose of the fuselage and 8 feet forward of the upper plane. It is attached to the fuselage by a pair of struts at the forward end and a single strut at the rear, while two pairs of short struts hold it to the lower plane. This float has a V type bottom, turtle-back deck, and two air vents running from the back of the step to the deck of the float. It is equipped with a rudder for use when in the water. The center line of buoyancy is located at a point 1 foot 3 inches forward of the step, while the center line of lift of the machine occurs 1 inch back of the buoyancy line. The wire bracing of both the planes and the floats has been omitted in these drawings for the sake of clearness. The wing tips are 1 foot 3 inches wide and have a flat bottom. The main float, as well as the wing-tip floats, is made of mahogany.