Monococque Sopwith Snail from the right |
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The Sopwith 8F.1 Snail was a small fighter developed in 1917-1918, with conventional and monocoque fuselages, but it was led down by its engine, and only two prototypes were built.
The first order, presumably for four aircraft, was placed on 31 October 1917. These aircraft were to have a conventional fuselage, built around a fabric covered framework, and to be powered by the A.B.C. Wasp radial engine, which was just entering its official tests in that month.
On 23 November 1917 two more aircraft were ordered, this time with a monocoque fuselage, using plywood to form the shell, bringing the total number of aircraft to six. Official interest in the monocoque had probably been triggered by the BAT F.K.22, designed by the Dutch aircraft designer Frederick Koolhaven, and which combined the monocoque fuselage with a similar radial engine, and a similar wing layout to the first Snail.
The first two prototypes, C4284 and C4288, were built at the same time.
The A.B.C. family of radial engines were not a success, and the Wasp was no different. The engine for C4284 wasn’t delivered until 18 March 1918. The second engine can’t have been far behind, as C4288 was displayed at Brooklands on 27 April 1918. By this point the problems with the engine meant that there was no interest in putting the Snail into production, but the two prototypes were sent to Martlesham Heath in May 1918. Their speed and rate of climb was good, but it wasn’t as manoeuvrable as the Sopwith Camel and handling at low speed was poor. C4288 was sent to Farnborough where the monocoque fuselage was to be studied, but the other six prototypes were never completed.
C4284: Conventional Fuselage
C4284 was built with a conventional fuselage. The wings had 5in of back-stagger, with the upper wing slightly behind the lower wing. The pilot sat directly under the middle of the upper wing, with a large cut-out above the cockpit and a small windscreen on the fuselage.
The A.B.C. Wasp engine was carried in a streamlined nose, with the heads of the cylinders emerging into open air.
The two fixed forward firing Vickers guns were carried on the upper longerons, and were almost entirely concealed within the rounded fuselage on either side of the cockpit. The muzzle of each gun was visible in a small trough just behind the engine, and it fired between two of the engine cylinders. Small chutes for spent cartridge cases and belt links could be seen further back on the side of the fuselage.
One side effect of the gun position was that the centre section struts were different lengths. The rear struts were shorter, and went the upper longerons, but the front struts were longer, and went down to the lower longerons, presumably passing to the outside of the guns.
The Snail could also carried a free firing Lewis gun mounted on the upper wing. On C4284 this was carried on the starboard side of the centre section fuselage. It could be moved in to allow it to be reloaded.
Three more serial numbers were allocated to conventional prototypes – C4285, C4286 and C4287. These were to have had the back stagger on the wing reduced to 3.75in. Some work began on C4285 and C4286, but neither were completed and were instead used to provide spare parts for the two prototypes.
C4288: Monocoque Fuselage
C4288 had a monocoque fuselage, built out of plywood. It had a elliptical cross-section, and its shape was provided by a series of hoops and four bulkheads to the rear. The plywood skin was nailed to the hoops.
The wings had more normal positive-stagger, with the upper wing 22in ahead of the lower wing. The pilot’s cockpit was moved back to the trailing edge of the upper wing, which had a smaller cut-out area at the back.
C4288 didn’t carry the fixed forward firing Vickers guns, and the forward part of the fuselage was neatly streamlined. It isn’t clear what guns the monocoque version may have been intended to carry.
C4284
Engine: A.B.C. Wasp radial engine
Power:
Crew: 1
Span: 25ft 9in
Length: 19ft
Height:
Empty Weight: 1,390lb
Maximum Weight: 1,920lb
Gross Weight:
Maximum Speed: 124.5mph at 10,000ft
Cruising Speed:
Climb rate: 9min 55sec to 10,000ft; 19min 15sec to 15,000ft
Ceiling:
Range:
Guns: Two fixed forward firing Vickers guns, one free firing Lewis gun
Bomb load:
Fabric covered Sopwith Snail
Monococque Sopwith Snail from the left