M.Goodall, A.Tagg British Aircraft before the Great War (Schiffer)
Deleted by request of (c)Schiffer Publishing
SOPWITH hydrobiplane Type ST
At the end of April 1913, instructions were issued to the works to build one aircraft to Contract CP37570/13X3726, for delivery to the Isle of Grain by 11 October 1913, at a cost of .4,000. The machine was partly built at the works of Hamble River, Luke & Co. and was finally assembled at the Sopwith premises at Woolston. The nacelle was recorded as 'delivered' in February 1914, but the aircraft was canceled before final delivery could be made. The engines and wireless equipment were removed and returned to Farnborough and Calshot respectively. The airframe was held at Woolston for structural testing by loading with sand and was reported to be still there on 7 August 1914. The aircraft was reported to be 'still on order' in the list of 'HM Aircraft, Built, Building or under Repair.' for July 1914. This large aircraft was identified by Serial No.61 and was to carry the pilot and wireless operator side by side, with a gunner in front.
The layout was of a large three-bay pusher biplane with a further center section bay within the width of the tail booms. The top wing, made in halves and joined on the centerline, was of greater span than the bottom, and had extensions supported by struts; the tips were tapered and rounded off. The tail booms were parallel in elevation and tapered in plan to the tail. The control surfaces consisted of ailerons on all four wings, a large rudder with curved leading edge forming a balance area, and a semicircular tailplane with elevators, mounted on the top booms.
The two engines were mounted side-by-side in the rear of the nacelle, driving a single pusher propeller on a separate shaft, by triple link chain drives. Separate radiators and header tanks were provided for each engine at the extreme rear of the nacelle. The pilot and wireless operator were seated side by side just ahead of the wing. The nacelle tapered to a knife-edge at the front with the decking sloping down; above this a pillar mounting was provided for the Vickers 1 1/2 pounder gun, which was to be the subject of the trials.
The large twin floats, with single steps, were mounted on separate chassis under the center section bays; a cylindrical tail float, with tapered ends, supported the tail.
Power: Two 120hp Austro-Daimler six-cylinder inline water-cooled driving by chains and shaft a 12ft diameter four-bladed pusher propeller.
Data
Span top 80ft
Span bottom 70ft
Chord 7ft 6in
Gap 6ft 9in
Area tailplane 65 1/2 sq. ft
Area elevators 37 1/5 sq. ft
Area rudder 30 1/2 sq. ft
Length 44ft 6in
Height 13ft 10in
Main floats 20ft long: 3ft 9in beam: 2ft.9in deep
Weight 5,230 lb.
Tail float 8ft 9in long: 1ft 6in diameter
Speed 55mph.
Endurance 5hr
H.King Sopwith Aircraft 1912-1920 (Putnam)
Possible Twin-engined Gun Bus
In the chapter on 'Pushers and Gun Buses' mention is made of a seaplane known in the summer of 1913 as 'the 80-ft. span machine', and in this regard these points are stressed: (1) That Sopwith appear to have built the largest British aeroplane of its time, and (2) the company's early use of increasingly powerful engines ('in the 200 h.p.+ bracket’).
By reason of this second fact - the single engine concerned being a Salmson (Canton-Unne) no allusion is made to the apparent thought that was given to the fitting in this airframe of not one, but two engines, these being Austro-Daimlers ('Austrian-Daimlers' as they were termed) of 120 h.p.
But whatever the facts of this matter, it is worth remarking that at about the same time (1913) the Vickers company was busy with designs for a pusher aircraft (and actually made and tested floats for it) from which it was proposed to develop a twin-engined gun carrying machine. Had it materialised, this proposed machine would have probably been only about 10 ft less in span than the '80-ft.' Sopwith.
Whatever claim Sopwith may have had to large dimensions in early aircraft, however, a supplementary one (for twin engines) might now be cautiously advanced, though the description given of the Cobham triplane bomber in its own chapter 'the only multi-engined Sopwith to be built' - appears to stand inviolate.
The 'Possible Twin-engined Gun Bus' (as this present note has been prudently headed) was intended to carry wireless, in addition to one or more guns; and the prudence exercised with regard to its powerplant, and to the remote possibility of the aircraft itself having actually existed, is warranted by the fact that the gun-carrying seaplane No.93 appears to have had a single 120 hp Austro-Daimler, as noted under 'Pushers and Gun Buses'.
Further, the (nominally) 200 hp Salmson (Canton-Unne), which might conceivably have delivered 240 hp, was sometimes regarded before the 1914-18 War as being, in effect, 'two engines in one', as witness this comment of 1914: ‘The fourteen-cylindered [sic] 200 b.h.p. design consists of two groups of seven cylinders acting upon a one-throw crank, the junction of the crankshaft being made in the common crank-pin between two big-end pin cages. This fourteen-cylindered engine is noteworthy as it acts upon a six-stroke and not upon a four-stroke cycle, the valve cams being in consequence specially arranged, and the cam-shaft driven at one-third, and not one-half, of the crankshaft speed. This is done in order to obtain working impulses at equal angular intervals of crankshaft revolution with two seven-cylindered groups operating all on one extended crank-pin ...'
Small wonder that such a fascinating - as well as a powerful - piece of mechanism should appear to have captivated the Admiralty, and that official interest should have been transmitted to their new aircraft-builders, Sopwith. Therein may conceivably lie the background to this present note, though the Navy had long since had an introduction to twin-engined aeroplanes, for Cdr C. R. Samson had flown in the Short Triple Twin during 1911; thus an installation of two Austro-Daimlers in 1913 would have presented no drastic technical departure.
