Flight, January 1922
THE BARNHART TWIN 15 "WAMPUS-KAT"
EVEN if the aviation industry is in a bad way out in the "States," as their reports have it to be, they have one advantage over our own state of affairs, and that is, there appear to be plenty of firms in
a position to turn out new and experimental machines of various types, both for Government and commercial purposes. Within the past few months we have seen particulars of or references to about a dozen different new American machines of more or less original design.
One of the latest of these is the Barnhart Twin 15, "Wampus-Kat," a medium-sized, moderate-powered twin-engined commercial biplane, a product of the C. R. Little Aircraft Works, of Pasadena, California. The design of the "Wampus-Kat" is the result of some months' study and planning on the part of G. E. Barnhart, with the financial assistance of C. R. Little, a retired business-man and aviation enthusiast. The main planes are of equal span and chord, without stagger or sweepback, and are of the folding type. The folding operation takes very little time, and is accomplished by releasing four lock pins and four master pins. Dummy or auxiliary struts are provided which properly space the upper and lower planes in relation to their fittings. There are also provided spacer bars, which tie the wings, when folded, to the fuselage at the rear outer struts.
During the tests the machine, with the wings folded, was towed over very rough ground at 30 m.p.h., and there was no shake to the wings, nor was any alignment or tightening of wires required, it was also towed through streets and traffic with the wings folded back, and after arriving at the flying field, the machine only required a matter of minutes to make ready for flight. The hinge on which the wings turn is a universal joint, so that there is little likelihood of it being overloaded due to any angularity of the wings or deflection of the spars. With the wings folded the engines are exceptionally accessible.
There are seven wing panels; a top centre section extending from port to starboard engine mountings; two lower centre sections running from fuselage to engine mountings; and the four upper and lower outer panels, which are of the same shape and size. The wing section employed is R.A.T. 6A. The struts form a three-bay system with lift wires double and landing wires single between the fuselage and engines all wires are duplicated. The main spars are of hollow box girder construction, with block external and internal strut points. These blocks are all properly tapered so as to allow the bending stress being brought in gradually to the strut points. The ribs have spruce webs with lightening holes and reinforcement for horizontal shear. The attachment to the spar is by U shear blocks, which relieve the cap strips of vertical shear load. Cap strips are of spruce with a groove for the ribs. All internal and external fittings are mild steel, of clean cut simple design for ease of production. The wings are internally braced with double steel wires and adjustable turnbuckles. All external strut fitting bolts straddle the spar, and are prevented from sliding by special blocks and bolts through the neutral axis of the spar, which gives the fittings a permanent tie. Where the wings join the fuselage, or each other, there are pin joints parallel to the neutral axis of the spars. The covering is grade A linen, sewn on to the ribs, and given six coats of dope and three coats of Cosmolac varnish. Ailerons are hinged to both upper and lower planes.
The fuselage is of rectangular section, and is well stream-lined. In its design an effort has been made to maintain consistent and uniform strength throughout, and special attention has been paid to the ease and quickness of effecting repairs. It is built up of four ash longerons, with spruce struts for transverse and vertical members, the whole structure being trussed with steel wire and adjustable turn buckles. The floor and dome of the pilot's and passengers' cabin is of mahogany three-ply wood with natural finish. Accommodation for four persons is provided for in the passengers' cabin, the seats being readily removable, which enables the number of passengers or goods to be carried to be arranged as desired. Ventilation doors are provided in the dome of the cabin in addition to a large emergency door. Two side windows are provided for each passenger, and in the floor ahead of the passengers is a large negative observation lens through which all the passengers may view the ground. Ample room is provided as the floor space is 6 ft. by 3 ft. 8 ins., and at the rear of the seats is a space for luggage. The pilot's cabin is in the nose, forward of the passengers. For vision the pilot has three side windows, and one in the floor, whilst, in addition, he can see above him through the opening in the dome. Entrance to the cabins is through the floor in the nose of the fuselage. All control wires and attachments are protected against the catching of clothing or jambing by passengers or goods. The outside of the entire fuselage except the cabin dome is fabric covered; the fabric is laced on to the longerons and struts on three sides of the fuselage, bottom and sides, the top being a detachable turtle deck. The fuselage is large enough for a man to work inside making any adjustment, and with the laced fabric and breaker strips he can open any portion that might require repairs.
Special "Dep." control is employed for elevators, ailerons and rudders, and the engine controls - duplex throttle spark retard, and switches - are within easy reach of the pilot. All instruments - one for each engine of the following: tachometer, oil pressure gauge and thermometer - are mounted in full view of the pilot.
The landing gear is of the four-wheel type, and is exceptionally strong. Two wheels are mounted below the fuselage, and one under each of the engines, the inner and outer wheels being connected by a tubular steel axle. The construction is of wood and steel. Each wheel is carried by a U of nine lamination ash, 2 1/8 by 2 ins., streamlined with a hollow spruce fairing. The entire strut assembly is wrapped with linen treated with dope and natural varnished surface. Steel spools with side thrust and ground friction arms are used on which to wrap the rubber absorber cord, and guard or check cables allow the latter to absorb up to six times the weight of the machine. Any additional load in landing is transmitted direct to the struts through the cables. The front members of the inner and outer U's are connected by tubular steel tie-rods, and braced by double steel cable, the rear members being braced with single cables.
The engines - which are, we believe, 90 h.p. Curtiss eight-cylinder V-type - are mounted on steel tubing beds with wood vibration breakers and with V-type bracing having all ends pin jointed. By removing six main pins, the cowling, radiator and engine may be withdrawn as a complete unit - an important feature in connection with commercial air services. The main engine bolts do not pierce the tubing bed, being rings with studs. The radiator is supported by a felt pad, and is tied from the top to prevent fore and aft movement. As a safeguard against fire all structural members are of steel with the exception of the wood vibration strip. The entire cowling is of aluminium, and is in five detachable sections. It is possible to work around any particular part of the engine with ease, and without removing any but the one section of the cowling. These sections have the hinge joint type connections, which will take up all wear and not allow the cowl to become loosened.
In order to minimise the danger arising from fire, the main petrol tank is carried below the fuselage. From the main tank the petrol is delivered to two centrifugal pumps, which force it under pressure to a main control box in the fuselage, thence to the desired engine gravity tank. By means of this control box petrol may be delivered at any pressure or by gravity. The petrol system for each engine is entirely separate. For long distance flights extra petrol can be stored in the fuselage in 5-gallon cans, and poured into the main tank through the filler whilst in the air ; in ordinary filling, petrol is poured into the tank from outside the fuselage. All pipeline connections are of the olive and special fabric-lined moulded rubber hose.
After the trials of the "Wampus-Kat," G. G. Budwig, the test pilot, gave the following report on its general performance. The machine is very easy to fly, take off and land. It flies naturally, and is very stable. But little control is necessary at any time, even in rough air, and it makes natural turns to either right or left, and makes them equally well flying level or in a climb. When stalled the ship recovers quickly, and settles slowly with no tendency to spin or fall violently. The horizontal balance is the same whether loaded or empty, flying level or gliding; the addition of load does not apparently change her climb to any great extent. The glide is good, and she keeps her speed at a small angle. The general controllability under all conditions is excellent. When one motor stops or is shut off abruptly, the machine turns toward the dead motor very slowly, and there is ample time to stop all turn with the rudder.
It flies level on one motor at 2,400 ft. with 90 gals, of fuel and one passenger, at 1,500 ft. with same fuel load and two passengers. (This with the engine revs, at 1,300, about 100 under normal, due apparently to unsuitable airscrews.)
The principal characteristics of the "Wampus-Kat" are :-
Span 50 ft.
Span with wings folded 22 ft.
Chord 5 ft. 5 in
Gap 6 ft. 8 ins.
Overall length 30 ft. 10 ins.
Overall height 11 ft.
Dihedral angle 1 deg
Wing section R.A.F. Mod. A
Total area wings (including ailerons) 484.9 sq. ft.
Area of ailerons (4) 41.25 sq. ft.
Area of tail plane 36 sq. ft.
Area of elevators (2) 23 sq. ft.
Area of fins (2) 10.30 sq. ft.
Area of rudders (2) 19 sq. ft.
Total h.p. 180
Weight of machine empty 2,611 lb.
Weight of machine fully loaded 4.015 lb.
Weight of fuel and oil (4 1/2 hrs.) 540 lb.
Weight of pilot and four passengers 800 lb.
Weight/sq. ft. 8.23 lb.
Weight/h.p 22.3 lb.
Speed range (sea level) 45-90 m.p.h
Climb in 10 mins. (full load) 3.500 ft.
Ceiling 11,600 ft.