Aircraft fabric covering

Aircraft fabric covering is a term used for both the material used and the process of covering aircraft open structures. It is also used for reinforcing closed plywood structures. The de Havilland Mosquito is an example of this technique, as are the pioneering all-wood monocoque fuselages of certain World War I German aircraft like the LFG Roland C.II in its wrapped Wickelrumpf plywood strip and fabric covering.

Early aircraft used organic materials such as cotton and cellulose nitrate dope; modern fabric-covered designs usually use synthetic materials such as Dacron and butyrate dope for adhesive. Modern methods are often used in the restoration of older types that were originally covered using traditional methods.

The purposes of the fabric covering of an aircraft are:

Pioneering aviators such as George Cayley and Otto Lilienthal used cotton-covered flying surfaces for their manned glider designs. The Wright brothers also used cotton to cover their Wright Flyer. Other early aircraft used a variety of fabrics, silk and linen being commonly used. Some early aircraft, such as A.V. Roe's first machines, even used paper as a covering material. Until the development of cellulose based dope in 1911 a variety of methods of finishing the fabric were used. The most popular was the use of rubberised fabrics such as those manufactured by the "Continental" company. Other methods included the use of sago starch. The advent of cellulose dopes such as "Emaillite" was a major step forward in the production of practical aircraft, producing a surface that remained taut (eliminating the need for frequent re-covering of the flying surfaces)

The air battles of World War I were mainly fought with fabric-covered biplanes that were vulnerable to fire due to the flammable properties of the cloth covering and nitrocellulose dope. National insignia painted on the fabric were often cut from downed aircraft and used as war trophies. The German aircraft designer Hugo Junkers is considered one of the pioneers of metal aircraft; his designs started the move away from fabric covering. The highly flammable mixture of fabric, dope and hydrogen gas was a factor in the demise of the Hindenburg airship.

By the World War II era many aircraft designs were using metal monocoque structures due to their higher operating airspeeds, although fabric-covered control surfaces were still used on early mark Spitfires and other types. The Hawker Hurricane had a fabric covered fuselage, and they also had fabric covered wings until 1939. Many transports, bombers and trainers still used fabric, although the flammable nitrate dope was replaced with butyrate dope instead, which burns less readily. The Mosquito is an example of a fabric-covered (madapollam) plywood aircraft. The Vickers Wellington used fabric over a geodesic airframe which offered good combat damage resistance.

An interesting case of ingenuity under wartime adversity was the Colditz Cock glider. This homebuilt aircraft, intended as a means of escape, employed prison bedding as its covering material; homemade glue and dope made from boiled millet were also used by the prisoners in its construction.

With the development of modern synthetic materials following World War II, cotton fabrics were replaced in civil aircraft applications by polyethylene terephthalate, known by the trade-name Dacron or Ceconite. This new fabric could be glued to the airframe instead of sewn and then heat-shrunk to fit. Grade A cotton would typically last six to seven years when the aircraft was stored outside, whereas Ceconite, which does not rot like cotton, can last over 20 years.