Flight, June 25, 1915.
THE JANNUS FLYING BOAT.
WHEN the Jannus brothers, Antony and Roger, who made their names as pilots of those successful flying boats built by the Benoist Company, announced last year that they were going to start on their own account, and design and construct flying boats, it was realised that their experience should result in the production of a very useful craft. It is not surprising, therefore, that now the first product of the Jannus firm has made its test at Baltimore it has more than fulfilled expectations.
Although the Jannus machine appears to follow the usual lines of flying-boat design, there are, as a matter of fact, many original features embodied in its design, mostly as regards construction. The principal objectives of the designers have been sea-worthiness, wide range of speed, quick assembling and dismantling, comfortable and clean accommodation for pilot and passengers, and general efficiency. As regards the former item, tests have shown that there is little to be desired in this respect. This has been brought about by the low centre of gravity and the large freeboard, as well as other points in the design of the hull. In addition, the special form of wing tip floats assists largely in this matter. These taper sharply towards the bottom, reducing the planing surface at high speeds, so that there is little or no pounding action on the wings. At the same time, when acting as floats, they quickly displace the water at an increased rate, and overcome any heavy side load.
The hull, which is of the single step type, is divided into two portions, a fore portion containing the pilot, passengers, engine and main planes, and a rear detachable portion carrying the tail planes. This possesses advantages not only in construction, but in facility for shipping. The control cables from the cockpit to the tail all pass through a steel conduit which protects them against the propeller breaking, whilst they are provided with the Jannus sister hook, which locks them together quickly so that their adjustment is not affected when the tail is detached. The fore portion of the hull has a beam of 46 ins. at the top, tapering to 38 ins. at the bottom. The latter is concave at the step, after which it is slightly convex, curving upwards at the nose. A turtle deck in the bows protects the pilot from wind and spray. Behind the pilot's seat is a wide seat for three passengers, who have plenty of leg-room - in fact, the cockpit is exceptionally roomy. Immediately behind is the engine compartment, which is isolated from all other parts of the boat so that any oil or grease is confined to this compartment. The engine, a 120 h.p. 8-cylinder water-cooled Maximotor mounted fairly high up in the hull, drives by means of a chain the propeller, which is situated at the trailing edge of the planes and is mounted directly on the boat, being quite independent of the planes. This is quite an important feature, for should the planes through any cause become strained, the propeller and engine do not get out of alignment, and, again, the planes can be taken down without interfering with the power plant. The rear portion of the boat tapers from the section of the fore-hull to a shallow vertical knife-edge at the rear.
The planes, which form a complete unit, are of rectangular plan form, having a span top and bottom of 45 ft. 10 ins., a chord of 5 ft. 6 ins., and a gap of 6 ft. The top plane is staggered forward about 18 ins. Perhaps the most interesting feature is the interplane strut construction. These struts are arranged in six pairs, the fore and aft struts of each pair being situated only some 18 ins. apart, and both are enclosed in a fabric covering. Each pair is thus effectively streamlined - a similar practice to that carried out on the Avro-Arrow scout and the D.F.W.-Arrow scout. Besides increased efficiency, this construction makes for strength, each pair of struts being braced by horizontal struts and wire bracing. The struts being mounted in the main spars, the latter are necessarily situated in the centre of the planes the same distance apart as the former, but being strongly cross-braced in between the spars, the whole frame is by no means weak; wood battens form the leading and trailing edges. A balancing flap measuring 6 ft. by 2 ft. is hinged to each outer extremity of the rear spars of both top and bottom planes. The tail planes consist of a fixed stabilising surface 12 ft. span by 2 ft. chord, to the trailing edge of which are hinged two elevators of 13 1/2 sq. ft. area each. In between the latter is a partially balanced rudder, connected with which at the stern of the boat is a small water rudder. The horizontal surfaces are mounted some 3 ft. above the boat. The control fitted is of the Jannus two-lever type, consisting of one lever operating the balancing flaps and another lever operating the elevators and rudder.
During the tests, which were carried out by Mr. F. G. Ericson and Mr. Antony Jannus, a total load of 2,200 lbs. was carried at a speed varying from 30 to 55 miles per hour with only 60 indicated h.p., so that with full power great things may be expected. The principal dimensions of the Jannus flying boat are: Span, 45 ft. to ins.; chord, 5 ft. 6 ins.; gap, 6 ft.; supporting area, 480 sq. ft.; length over all, 28 ft.; length of hull, 25 f t ; weight of machine empty, 1,665 lbs.; useful load, 900 lbs.; range of action loaded, 240 miles.