Flight, April 13, 1916.
THE BENOIST FLYING BOAT.
MODEL "C" TWIN ENGINED.
So successful has been the passenger air service between Petersburg and Tampa, Fla. (about 20 miles), which was inaugurated on January 1st, 1914, by the Benoist Aeroplane Co., that it has been found necessary to design a 'bus capable of carrying a larger number of passengers than did the standard Benoist flying boats originally used. Hence the large twin-engined flying boat, shown in the accompanying illustrations and scale drawings, and it must be admitted that its designer, Tom W. Benoist, has succeeded in producing a decidedly interesting machine of a type that is bristling with "knotty" problems. He has, furthermore, met with results in actual practice that have been extremely encouraging.
In the design and construction of the model "C" flying boat the usual Benoist practice obtains almost throughout, the only departures being those necessitated by the peculiarities of twin engine design and the large size of the machine. For instance, the power plant, which in this case consists of two 100 h.p. Roberts motors, is not located in the hull, as has always been a feature of previous models, but is arranged between the top and bottom planes. The boat is of the short hull type, as in previous Benoist models, though somewhat modified, the "business" portion of the boat finishing just aft of the main planes, the remainder of the boa merely serving to carry the tail. The length of the boat proper is 20 ft. 6 ins., and the beam is 5 ft. 6 ins , whilst the maximum depth of the hull is 3 ft. The step is located 13 ft. 6 ins. from the nose, being rather further back than is usually found in other designs of flying boats, viz., at the cg. of the machine. From the stern up to a point about 7 ft. from the nose the bottom is flat, after which it is slightly V-shaped laterally and curved upwards. From the nose to the cockpit is an inverted V deck. The cockpit is very roomy, measuring 5 ft. fore and aft, and seating six persons - three, including the pilot, in front and three behind. The latter seats are immediately in front of the main planes, so that all the occupants have an excellent view in all directions. The hull is built up in the usual way of first-grade clear mahogany, the sides being 3/8 of an inch thick, and the bottom consisting of two layers of the same thickness, except for the last five feet at the stern, which is made up of a single layer. The rear portion of the boat carrying the tail planes is to all intents and purposes a fuselage of rectangular section attached to the stern of the boat proper and sloping upwards. It is built up of four longitudinals and six sets of cross members, the whole being wire-braced and covered with fabric.
The main planes, which have a span, top and bottom, of 65 ft., are a development of those employed on preceding models, modified as to camber and construction to meet the special requirements of a machine of this type. They are made up of five sections as follows: A centre section 11 ft. span rigidly attached to the boat and carrying the two engines. Attached to the centre section are inner extensions measuring 14 ft. 6 ins., and to these are attached the outer extensions of 12 ft. 6 ins. In the centre section and the inner extensions the main spars are of spruce, with a cross section of 2 by 2 1/2 ins., and in the outer extensions they have a cross section of 2 by 1 1/2 ins. A "V" arrangement is employed for the interplane struts in the centre or boat section, which has the advantage not only of being extremely strong and rigid, but the absence of bracing wires between the two pairs of innermost struts allows a clear passage from the cockpit to the stern of the boat and to the engines, which can thus be inspected with the greatest facility. This arrangement also provides exceedingly strong and simple mounting for the engines, the cross pieces of the "A's" formed by each of the two outer pairs of centre section struts carrying the stout engine bearers. In front of each engine is mounted a square radiator through which projects an extension of the crankshaft for receiving the crank-handles for starting the engines. From the centre section outwards top and bottom planes are separated by four pairs of stout streamlined struts having a factor of safety of about eight or ten. The lower plane is set at a dihedral angle, the gap being 6 ft. at the centre and 5 ft. at the wing tips. This not only makes for stability, but enables the lower wing tips to be kept as far as possible out of the water, which is a matter of some importance with big span machines. Bracing is by Roebling 19-strand cable, the positive or carrying wires of the inner box section being 8/16 in. doubled and 8/16 in. single for the outer box sections. A neat method of attaching the cables to the turnbuckles, anchors, &c, is employed. Small brass ferrules are slipped over the cables when turned back to make the loop and soldered in place. The end of the cable opposite the turnbuckle is looped but not soldered or fastened permanently in the eyelet of the fitting, and the latter is provided with a small bolt which can be withdrawn by removing a cotter pin, it being thereby possible to make up all the cables on the bench and attach them in an instant, as well as to carry a supply of spare cables on board. All the wing fittings are made of sheet steel stampings spot welded where necessary, and the planes are covered with strong unbleached Irish linen treated with five coats of special Benoist dope and finished with two coats of Valspar.
Ailerons are hinged to the rear spar extremities of the top plane only, and floats are mounted under the lower plane just below the extreme outer inter-plane struts. A Dep. type of control is fitted, but any other system can be installed. The fuel tank, which has a capacity of about 30 gallons of petrol, is located in the boat immediately behind the cockpit As previously mentioned, two 6-cyl. Roberts two-stroke motors of 100 h.p. each are fitted, being coupled direct to 8 ft. 6 in. diameter by 5 ft. 6 in. pitch propellers revolving in opposite directions at 1,100 r.p.m.
The principal characteristics of the model "C" Benoist flying boat are :- Span, 65 ft.; Chord, 5 ft. 6 ins.; gap, 6 ft. to 5 ft. ; supporting area, 660 1/4 sq. ft.; weight empty, 2,400 lbs.; useful load, 1,300 lbs.; speed range, 40-60 m.p.h.; climbing speed, 500 ft. per min.
The Benoist machines have now acquired considerable interest for us in this country, as Messrs. R. F. Wells and Co., of 10, Elystan Street, Chelsea, have recently arranged for the British agency and to build them under licence.