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Aviation History
1961
1961 - 1683.PDF
FLIGHT. 787 23 November 1961 A photograph taken during the initial stage at Lasham; the 80ft span dwarfs all con- ventional sailplanes Southampton's Man-powered Aircraft THE idea of designing a man-powered aircraft arose during amaths lecture in the spring term of 1960. Design workbegan in earnest the day after finals at Southampton Uni-versity in the following July. By the end of September the project design was complete, and a report was submitted to the Man-Powered Aircraft Group Committee of the Royal Aeronautical Society, in the hope of receiving financial help which had beenannounced by the committee as being available. Support was given to the project by Prof Richards and the department of Aeronauticsat Southampton, and detail design and planning was started. Construction started in January 1961 and was finished in September.Meanwhile, a promise of a grant of up to £1.500 was received from the Royal Aeronautical Society in February, and without their helpthe achieved rate of progress would not have been possible. Since early September trials have been carried out at LashamGliding Centre, with Derek Piggott, the chief flying instructor, as pilot. After many ground tests and "hops" the first real flight tookplace at 4.30 p.m. on Thursday, November 9, 1961, at Lasham, as reported in Flight last week. The flight was seen by a number ofindependent witnesses, who were almost as surprised as the designers. The flight speed was fairly constant during the climb, thus showingthat the height was achieved by propeller thrust and not by using kinetic energy attained during the ground run. The flight wasthus a true unassisted take-off and flight under man-power alone. The design work started with horsepower tests on members of alocal cycling club. A reclining seated position, taking the reaction of the leg thrust on the back and leaving the hands free to applycontrol movements, was found to be satisfactory both for power output and control, and also proved to be comfortable. The resultsof these tests confirmed the work of Dr Wilkie, as reported in the Journal of the Royal Aeronautical Society (August 1960). Theseresults also meant that a fuselage with low frontal area and good forward vision could be constructed. A conventional high-wingmonoplane was chosen, rather than a helicopter (which is less efficient), or an ornithopter (about which little is known), the aimbeing to have an aircraft flying as soon as possible. Although the aircraft relies on ground effect, it was considered that a low-wingconfiguration would gain little, and increase the problem of tip clearance while the aircraft was on the ground. Conventional materials, i.e.. wood and fabric, have been used inpreference to some of the newer materials such as plastics, because of the great difficulty in using the latter efficiently. For example,Durestos could have been used for the spars, but for the curing process required. However, a limited use of expanded polystyrenehas made for the tips of the flying surfaces. The horsepower required for level flight depends on wing area,weight. CL and CD. Variations were played on the size and (g: Iliffe Transport Publications Ltd 1961 shape of the wing and other structure until what appeared to be theoptimum design was found, requiring about 0.4 h.p. to be exerted by the pilot to sustain steady level flight. Since there seemed to be no obvious advantage in a two-seater—except for power continuity—a single-seater was preferred, on account of its simpler configuration. A major consideration in thedesign was ease of construction with a minimum of jigging. Wind-tunnel tests on a -,J,;-scale model were carried out at full-scale Reynolds number, in order to check the drag and to measure lift and pitching moment. After suitable fillets had been added toimprove the flow at the pylon/wing junction, the measured lift and drag agreed closely with the calculated values. As mentioned inlast week's Flight, a two-dimensional wing section was made in order to develop a practical method of wing construction. Thissection was subjected to a large number of structural and aero- dynamic tests, and from these the construction used in the actualwing was evolved. It was found possible to maintain laminar flow up to 60 or 70 per cent of the chord by careful smoothing of theleading-edge profile, using ,7, in balsa sheet covering up to 20 per cent chord. BY THE DESIGNERS For ease of transport and ground handling, the wing was madein three sections. Two spars were used, as this simplified the problem of jigging and incorporating aerodynamic twist. Thespars were made from laminated spruce with girder webs, and were joined by cross-bracing to form a torque box resulting in a wingwhich was extremely stiff in torsion. The ribs were of the girder type made in spruce and balsa, as this proved to be the lightest formof construction. Conventional ailerons were constructed integral with the wing and detached later, thus avoiding a separate aileron jig-All the metal fittings were bonded to the wood by Araldite epoxy resin, and elimination of bolts resulted in a great weight-saving.The remaining structure is entirely glued using Cascamite urea- formaldehyde synthetic resin. The construction of the fin and tail-plane is similar to that of the wing, the whole surfaces being made to move to improve control and simplify construction. For thefuselage a basic slab-sided box section with light fairing was chosen for ease of construction: and, in any case, the fuselage is very smallcompared with the wing, so that any improvement to be gained by using a more elegant shape was not considered worthwhile. Thenose fairing is removable to allow the pilot to climb into the seat, which was placed between the front and rear wing spars to obtainthe correct e.g. position. The pilot is well protected against injury, since the spars are the strongest part of the structure.All the main loads due to landing, the drive mechanism and the propeller thrust are taken on a light-alloy structure to which thewing and fuselage are bolted. The framework has been consider- ably modified as a result of initial undercarriage difficulties. It nowconsists of a 27in racing cycle wheel at the rear and a 9in light-alloy at the front. The latter is sprung and is free to castor. The most severe problems have been met with the drive mech-anism. It consists of a ^in Renold chain to drive the back wheel from the pedal cranks, and a twisted flat steel belt to drive thepropeller shaft from the back wheel. The belt, which is 0.008in thick spring steel, is joined by two rows of spot welds and annealedin the region of the weld. In order to increase the coefficient of friction, and hence reduce the initial tension required in the belt, itis coated with "belt-stick." A flexible shaft drive is used at the top of the pylon to tilt the thrust axis through a small angle. Thepropeller is permanently geared to the back wheel, which can free- wheel relative to the pedals. This may influence the output by thepilot, but is a precaution against possible shock loads on landing. The propeller has a light-alloy tubular spar and sheet metal ribs.The space between the ribs is filled with solid balsa, bonded to the ribs with epoxy resin. Tests under full-scale conditions were madeon the propeller in the low-speed section of the 7ft - 5Aft tunnel at Southampton University. The cruising speed for the propeller is
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