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A geodesic airframe (alternatively, geodetic) is a type of construction for the airframes of aircraft. It makes use of a space frame formed from a spirally crossing basket-weave of load-bearing members[1]. The principle is that two geodesic arcs can be drawn to intersect on a curving surface (the fuselage) in a manner that the torsional load on each cancels out that on the other[2].
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Development
One of the earliest uses of a geodesic-style approach of construction in any military-used vehicle of any sort in modern times was that of the "diagonal rider" ships' wood hull strutctural element, first used by Joshua Humphreys in the first US Navy sail frigates initial American naval fighting vessels in 1794. The "diagonal riders" were included in these naval vessels' construction to reduce the problem of hogging in the ship's hull, and their resistance to hull deformation in a wood-construction ships' hull, much like half an aircraft's fuselage, were a possible precursor to similar diagonal members in a more complex geodesic form, in much later heavier-than-air aircraft.
The geodesic construction method was developed by the British aeronautical engineer Barnes Wallis, inspired by his earlier experience using geodesic wiring harnesses to hold the gasbags in his commercial airship design, the R100. Wallis used the term "geodetic" to apply to the airframe and distinguish it from "geodesic" which is the proper term for a line on a curved surface, arising from geodesy. The system was later used by Wallis's employer, Vickers-Armstrongs in a series of bomber aircraft, the Wellesley, Wellington, Warwick and Windsor. In these aircraft, the fuselage was built up from a number of duralumin alloy channel-beams that were formed into a large framework. Wooden battens were screwed onto the metal, to which the skin of the aircraft could be applied; linen stiffened with aircraft dope.
The metal lattice-work gave a light structure with tremendous strength[1]; any one of the stringers could support some of the load from the opposite side of the aircraft. Blowing out the structure from one side would still leave the load-bearing structure as a whole intact. As a result, Wellingtons with huge areas of framework missing continued to return home when other types would not have survived; the dramatic effect enhanced by the doped fabric skin burning off, leaving the naked frames exposed (see photo). The benefits of the geodesic construction were offset by the difficulty of modifying the physical structure of the aircraft to allow for a change in length, profile, wingspan etc.
References
Notes
Bibliography
- Buttler, Tony (2004). British Secret Projects: Fighters & Bombers 1935-1950. Hinckley: Midland Publishing. p. 240 pages. ISBN 1857801792.
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