Flight, December 1936
A "MINOR" in METAL
Initial Effort by a New Concern: First Details of the C-W Cygnet Minor: Stressed-skin Construction: A Projected "Twin"
STRESSED-SKIN metal construction is no longer the expensive peculiarity of high-powered transports
and military types; there is a definite trend, particularly in America, toward light “private-owner” models built on this system. We may count ourselves fortunate that a few enterprising souls have had the foresight to study the possibilities of stressed-metal covering as applied to the smaller types, and among these Messrs. C. K. Chronander and J. I. Waddington, partners in C-W Aircraft, whose works are in Montrose Avenue on the Slough Trading Estate, are deserving of special commendation for producing Great Britain's first completely metal-covered light aeroplane.
As C-W Aircraft is a title not previously met with by readers, let us explain that policy is directed by Messrs. Chronander and Waddington, and that Mr. J. A. Heron is the chief engineer. These three are quite conversant with the most recent practice in stressed-skin construction, and hope to have the Cygnet flying in January. They are talking of delivery of production machines by Easter.
The Cygnet Minor ("Major" when any of the "Major" engines, such as Gipsy Major, Cirrus Major, Villiers-Hay Maya or Menasco Pirate are fitted) has been planned as a two-seater side-by-side machine for private operation or club training. A second passenger may be accommodated if the fuel load is reduced from 20 gallons to 8 gallons. The machine is fully aerobatic.
The low, cantilever wing has two main spars with booms of R.R. 56 alloy and light diaphragm ribs stiffened up with members of "bowler-hat" section. Torsional and shear leads are taken by the duralumin skin covering, but bending loads are taken by the spars. It is claimed that the wing, including ailerons, flaps and controls, weighs only 2 lb. per square foot. It is constructed in three sections: two outer panels and a centre section of seven-foot span and twenty-inch depth, which houses the fuel tanks. The comparative shallowness of this portion facilitates entry to the cabin. Attachment to the fuselage is effected by four bolts, the root-end fittings being straps of D.T.D.54 85-ton steel; there are no machined fittings.
With the centre-section spars as a basis, the sides of the cabin portion are built up. Fore and aft of this section are welded structures, the front one, of course, accommodating the engine mounting, and the rear one serving as an attachment for the rear end of the fuselage, which is of unusually small diameter. It is likely that in production models the welded portions will give place to monocoque sections.
A "Tadpole" Fuselage
Stringers of Z section and built-up frames feature in the after portion of the fuselage, to the rear end of which the tail unit is attached by eight bolts. The small cross-section of the rear part of the fuselage is said to confer aerodynamic and structural benefits, and merges with the wings through the medium of fillets of unorthodox design, the shape of which is seen to advantage in the accompanying drawings. This means that both in plan form and side elevation there is a very pronounced “slimming off.”
All control surfaces are metal-covered and of quite surprising lightness; the elevator weighs 3 1/2 lb., and the rudder 4 1/2 lb. The basic structure of the one-piece tailplane is similar to that of the wing.
The construction of the monocoque portions and the skinning of the wings has been simplified by the use of pop rivets and the employment of a special adaptation of a standard type of a riveting gun, which, it is claimed, enables the riveting to be done 20 per cent, faster than by normal methods. Countersinking features on the leading edges of wing and tailplane.
For riveting the skin on to members which cannot be drilled completely through a drill has been devised to make an "undercut" hole in the solid metal, enabling a pop rivet to be inserted and the head to be formed inside the undercut. A pantograph device has been developed (for the satisfaction of inspectors) which shows, four times actual size, the contours of the hole.
Flaps of high aspect ratio are incorporated having 24-gauge skin with triangulated ribs of light channel section. Operation is through a torque tube by a manual control with a spring servo device which automatically pulls down the flaps to 15 degrees for take-off. This spring bias also helps to keep the flaps closed in normal flight. The maximum depression is 60 degrees, permitting, it is estimated, a landing speed of 35 m.p.h.
A 6 1/2 in. travel is provided for in the Dowty single-strut undercarriage. The legs are carried in welded steel sockets attached to the front spars. The brakes are of the differentially operated Bendix type.
A single central column between the occupants and twin sets of rudder pedals permit dual control, although for specialised training work the manufacturers visualise two complete sets of controls.
Bias on fore-and-aft trim is effected by a spring in the elevator circuit, one end of which can be moved on either side of a fulcrum so that plus or minus or zero bias can be obtained at will by the operation of a tell-tale knob on the control column. The aileron and elevator controls travel in conduits in the centre of the cabin, lids being provided for inspection.
The two sets of rudder pedals are linked with a parallel motion, so that only the pedals are normally visible. One set can be removed in a few seconds, leaving the passenger's space free from excrescences.
Production Cygnets will be upholstered by Rumbold in any colour or style desired. Doubtless, Mr. Rumbold will find his task of soundproofing considerably simplified by the absence of flat panels. Rhodoid panels of quite unusually large proportions, coupled with the good location of the seats in relation to the wing, should benefit outlook.
The seats are fully adjustable for height and leg-length. Smith's instruments are grouped on the centre and left of the facia board, where they are visible to pilot and passenger. To the left is a capacious locker and map tray. A patented design of exit, hinged about the front side members of the cabin enclosure, is incorporated.
The windscreen is of the forward-sloping variety, for which aerodynamic advantages and visual benefits in rain are claimed. It also facilitates entry and exit. Behind the seats is a large baggage space which can, as already mentioned, be used for the carriage of a second passenger. A large step is inset into the trailing edge of the wing, being spring-loaded to reassume the contour of the surface when not in use. Smoking will be permitted in the 50 cubic-foot cabin, the ventilation of which is controllable.
The prototype Cygnet Minor is being fitted with the new Cirrus Minor of 80-90 h.p., but an alternative unit is the Pobjoy Niagara III. As already mentioned, any of the "Major" series of engines can be fitted, giving a considerable increase in performance with, presumably, a certain reduction in range. A Pobjoy will actually be installed in the prototype after tests with the Cirrus.
It is hoped to market the Cygnet Minor with Cirrus Minor engine at about ?795.
In the light of experience gained during the construction of the Cygnet a small twin-engined monoplane known as the Swan has been planned. This model should prove suitable for feeder-line work or as a "luxury" private-owner's type. It is believed that, utilising a number of components (including the rear fuselage) of the Cygnet, this could be marketed at a very attractive price. The prototype has been designed round a pair of Villiers-Hay Mayas, but engines of a new model, manufactured by the same company and rated at about 170 h.p., will be alternatives, and would give a maximum speed of 180 m.p.h.
C-W CYGNET MINOR
Two-seater Cabin Monoplane 80/90 Cirrus Minor
Span 34 ft. 6 in.
Length 24 ft. 2 1/2 in.
Height 6 ft. 0 in.
Wing area 185 sq. ft.
Tare weight 850 lb.
Disposable load 600 lb.
Gross weight 1,450 lb.
Maximum speed 125 rn.p.h.
Cruising speed 110 m.p.h.
Landing speed (with flaps) 35 m.p.h.
Take-off run (with flaps) 75 yd.
Landing run (with flaps and brakes) 60 yd.
Standard range 600 miles
Ceiling 20,000 ft.
Service ceiling 18,000 ft.
Flight, September 1937
SWAN and CYGNET
Advance Details of the C. W. Swan Light Transport and the Production-type Cygnet
All being well the Swan should fly in about a year's time. Meanwhile Cygnet production is proceeding steadily, a batch of twenty of these intriguing little two-seaters having been ordered. All will be powered with the 130 h.p. Gipsy Major I and, embodying aerodynamic and structural refinements suggested during trials with the prototype, should be capable of 150 m.p.h. The upholstery will be by Abbey Coachwork. One of the more prominent alterations has been made in the seating arrangements: there is now a single bench-type seat and a central control column. If need be dual sticks can be easily arranged on the cross-shaft. There is space for two large, specially designed suit cases and accommodation for golf bags down the "tadpole" tail quite apart from other space behind the seat.
The screen (in two half-spheres with no flats - made of Plastilume-moulded acetate sheeting) and roof portion of the production machines will blend more smoothly with the general lines. A standard dash arrangement has been evolved; this has a central panel and two lockers. The panel is hinged at it's base for inspection of the leads. Special instruments or a Sperry panel can be arranged on the pilot's side in place of the locker.
The latest Cygnet has its flaps in two portions, there being no central section as on the prototype. Mechanical operation is specified. Another change is the introduction of double the dihedral (now 10 deg.), making for better stability. The rudder and wheels will be larger than on the prototype.
A South African trip has been arranged for the Cygnet demonstrator which should be finished in about three weeks.
The manufacturers are highly enthusiastic about the results they have obtained with Noral NA57S strain-hardened aluminium alloy for structural parts and skin surfaces. This material, produced by the Northern Aluminium Co., Ltd., is claimed to possess high resistance against corrosion, to have adequate strength combined with ductility and to be comparatively cheap.
Apart from their work on the Cygnets and the Swan, C. W. Aircraft are taking in some substantial sub-contracts at their new works in Oxford Avenue, Trading Estate, Slough.
The general lines of the C. W. Cygnet are well shown in this Flight photograph, which also shows how the screen is arranged with quite a pronounced sweep-forward. The cleanness of the cantilever undercarriage noteworthy.
From a three-quarter front view the Cygnet has somewhat squat, though not unattractive lines. The prototype machine is fitted with a Cirrus Minor engine.
STRESSED SHIN IN MINIATURE. Capt. Hubert Broad flies the new C.W. Cygnet for the benefit of "Flight's" photographer. As will be seen there is a certain amount of cleaning up still to be done, but with a Cirrus Minor engine the Cygnet has a cruising speed of well over 100 m.p.h. and an 800-ft.-a-minute climb.
As flown in the King's Cup Race, the new C.W.A. Cygnet has the Cirrus Major 150.
THE CYGNET MAJOR: The new C.W. Cygnet with a Gipsy Major engine, shown here in the act of being taken off by Mr. Wynne-Eaton at Hanworth, is one of the King's Cup entries. In the race the machine, which has been modified in certain details, will be flown by Mr. Charles Hughesdon.
The G.A. "Cygnet" Two-seat Light Cabin Monoplane (130 h.p. D.H. "Gipsy-Major" engine).
Side-by-side seating, with a centrally disposed control column, is a feature of the Cygnet. This Flight photograph gives an idea of the "entry area"; there is a similar door on the starboard side. In the machine are the two directors of the company, Messrs. S. I. Waddington (nearest camera) and C. R. Chronander.
FOR THE KING'S CUP: The redesigned cabin and new moulded windscreen certainly improve the appearance of the Cygnet Major, which is now flying at Hanworth. In the cabin are Messrs. Waddington (nearest the camera) and Wynne-Eaton, who is carrying out the tests.
It is likely that the rear fuselage portion of the Cygnet will be simplified in production. This view shows the component for the prototype
A rib and elevator in Noral, which material is being extensively employed in the production Cygnets.
The two main Flight sketches show the salient internal and external features and the remainder indicate structural methods.
The basic construction of the monocoque fuselage is founded on built-up frames and "Z" section stringers..
The Cygnet accommodates pilot and passenger and has liberal stowage for luggage and sports gear. It will be seen that the seat now extends across the cabin.
C-W Cygnet Minor Cirrus Minor Engine
Stressed-skin in miniature: the CW. Cygnet Minor, which should shortly be flying.