Flight, May 1923
THE SWANSON MODEL 3 SPORT 'PLANE
THE little sporting biplane shown in the accompanying illustrations was designed and constructed by S. Swanson of Vermillion, South Dakota, U.S.A., and was given its first test flights last September. The
test pilot on this occasion was Lieut. Vert Roggers, and on the first attempt he took the machine off after a short run over rough ground, thick with undergrowth, made one circuit of the field and then made a perfect landing. He took off again immediately, and climbing to a height of 1,000 ft. circled over Vermillion for about 15 mins., making another excellent landing at the conclusion. He reported that the machine was well balanced and light on the controls, answering promptly to the various manoeuvres.
Upper and lower planes are of "one-piece" construction, the spars being of routed I-section spruce, spliced in the centre to form a continuous beam with a dihedral angle of 4°. The webs of the ribs are of bass-wood, with the usual lightening holes, and the cap strips of spruce. The upper plane has a cut-away at the centre over the cockpit, and is fastened to the centre N-struts by four bolts. The lower plane is secured to the underside of the fuselage by three bolts. Ailerons are fitted to the lower plane only, and the aileron control wires run within the lower wing. Upper and lower planes are separated by a single I-strut each side. These struts are of built-up spruce laminations. The landing and flying wires are 5/32 in. cable, the flying wires being double.
The fixed horizontal stabiliser is built into the fuselage, and has an unsymmetrical streamline section, the top camber being two-thirds and the bottom camber one-third. The rear spar, to which the elevators are hinged, is a continuous beam forming part of the fuselage stern post. The elevators are of the divided type with a negative rake of 20°. The vertical fin is also built into the fuselage, and projects through on the lower side, forming a small lower fin, to which is attached the rubber-sprung ash tail skid. The hinged edges of the elevators and rudder are rounded, and fit into a groove in the edges of the fixed surfaces so that no gap is left between the surfaces, thus ensuring a smooth and even flow of air. There is no .external bracing on the tail plane whatever, and the control horns are built into their respective surfaces.
The fuselage is of the girder type, built-up of spruce, with ash longerons forward of the cockpit. The fuselage tapers to a horizontal knife-edge at the rear, and is given a good streamline by means of bass-wood stringers. The cockpit is exceptionally roomy for so small a machine. A 3-hr, petrol tank is mounted forward of the cockpit, just over the c.g. The engine is separated from the fuselage by an aluminium partition, and the cowling is of 20 ga. aluminium. The engine is an air-cooled 2-cyl. opposed Lawrence of 28 h.p. (1,500 r.p.m.), and the tractor screw has a diameter and pitch of 5 ft. 6 ins. The carburettor is mounted outside the fuselage, thus minimising the risk of fire.
The undercarriage is of the V-type, with a split axle, hinged 9 ins. on each side of the centre, and sprung by the usual rubber shock-absorbers. The struts are of streamline ash, and the wheels are 24 ins. by 2 ins. Standard stick and foot rudder-bar control is fitted, the movements of the surfaces being geared down.
The principal characterisitics of this machine are :-
Span 18 ft. 9 ins.
Chord 2 ft. 10 ins.
Gap 3 ft. 4 ins.
Stagger 1 ft. 2 ins.
Overall length 15 ft.
Wing curve U.S.A. 15.
Angle of incidence (top) 3 1/2°
Angle of incidence (bottom) 2°
Decalage 1 1/2°
Area of main planes 100 sq. ft.
Area of ailerons 12 sq. ft.
Area of stabilizer 7 sq. ft.
Area of elevators 5 sq. ft.
Area of fin 3 sq. ft.
Area of rudder 3 sq. ft.
Weight empty 370 lbs.
Weight with full load 570 lbs.
Weight per h.p. 20 lbs.
Weight per sq. ft. 5-7 lbs.
Speed range 40-90 m.p.h.