Aircraft dope is a plasticised lacquer that is applied to fabric-covered aircraft. It tightens and stiffens fabric stretched over airframes, which renders them airtight and weatherproof, increasing their durability and lifespan. [1] [2] The technique has been commonly applied to both full-size and flying models of aircraft. [3] [4]
Doping techniques have been employed in aircraft construction since the dawn of heavier-than-air flight; the fabric of the ground-breaking Wright Flyer had benefitted from doping, as did many of the aircraft that soon followed. [5] Without the application of dope, fabric coverings lacked durability while being highly flammable, both factors rendering them far less viable. [5] By the 1910s, a wide variety of doping agents had entered widespread use while entirely original formulas were being regularly introduced in the industry. [2] Typical doping agents include nitrocellulose, cellulose acetate and cellulose acetate butyrate. [6] Liquid dopes are often highly flammable; nitrocellulose, for instance, is also known as the explosive propellant "guncotton". Dopes often have colouring pigments added to facilitate even application, and are available in a wide range of colours. [7]
Dope has been applied to various aircraft fabrics, such as madapollam; [8] in more recent decades, it has also been applied to polyester and other fabrics with similar fine weave and absorbent qualities. [9] Reportedly, polyester fabric coverings have become an industry-wide standard, the use of both cotton and linen fabrics have effectively been eliminated. [5] In addition to changes in the materials that dope is applied to, the methods of application have also been refined to reduce shrinking, improve adherence and increase lifespan. [10]
By the 1910s, it was recognised that, while the practice was highly beneficial, certain types of doping agents posed a risk to workers' health. [2] While acetate and nitrate-based dopes were believed to pose little risk by themselves, the volatile compounds to dissolve them prior to application were poisonous. The medical profession across several nations became aware of this threat just prior to the First World War, and promoted the need for adequate workplace ventilation as a mitigating measure in factories where doping was performed. [2] In the United Kingdom specifically, studies were performed into the potential health impacts of various dopes, concluding that those produced to Royal Aircraft Factory specifications rendered them less liable to result in illness than several others. [11] Investigations into health concerns surrounding dope were also conducted during the Second World War. [12]
Due to more powerful engines and advanced aerodynamic techniques, the use of aluminium (and subsequently composites) supplanted fabric as the primary material used in the aviation industry by the latter half of the 20th century. [5] Various light aircraft, including gliders, home-built kits, and light sport aircraft, have continued to use fabrics. Thus doping techniques continue to be employed, albeit to a lesser degree than at the dawn of aviation. [10] [13] There are several covering methods that do not use dope coating processes, as alternative treatment methods have been devised. Identical materials and techniques must be used during maintenance as had been employed in construction, thus traditionally-built aircraft continue to use doping techniques throughout their operating lives. [5]
Numerous accidents have occurred as a result of incorrect use of doping techniques. Examples of common mistakes include mixing it with other chemicals, its use on the wrong fabrics, or its application to contaminated or improperly prepared surfaces.
During the investigation into the 1930 R101 airship disaster, it was determined that improper doping practices had resulted in the fabric of the airship having become brittle and easy to damage. [14]
Among the hypotheses for the 1937 Hindenburg airship disaster, the Incendiary Paint Theory, presented by Addison Bain, [15] is that a spark between inadequately grounded fabric cover segments of the Hindenburg started the fire, and that the spark had ignited the "highly flammable" outer skin doped with iron oxide and aluminum-impregnated cellulose acetate butyrate (CAB), which remain potentially reactive even after fully setting. The hypothesis has been disputed.
On 27 April 1995, 91-year-old aircraft designer, builder and significant figure in the homebuilt aircraft movement Steve Wittman and Paula Muir, Wittman's wife, were killed when their Wittman O&O Special broke up in flight due to delamination and separation of the wing fabric, resulting in wing aeroelastic flutter. The US National Transportation Safety Board investigation determined that the layers and types of doping that had been used on the aircraft did not have "the best adhesive qualities" and referred to "the Poly-Fiber Covering and Painting Manual" for proper processes to use. [16]
Nitrocellulose is a highly flammable compound formed by nitrating cellulose through exposure to a mixture of nitric acid and sulfuric acid. One of its first major uses was as guncotton, a replacement for gunpowder as propellant in firearms. It was also used to replace gunpowder as a low-order explosive in mining and other applications. In the form of collodion it was also a critical component in an early photographic emulsion, the use of which revolutionized photography in the 1860s.
Aviation includes the activities surrounding mechanical flight and the aircraft industry. Aircraft includes fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air craft such as hot air balloons and airships.
Celluloids are a class of materials produced by mixing nitrocellulose and camphor, often with added dyes and other agents. Once much more common for its use as photographic film before the advent of safer methods, celluloid's common contemporary uses are for manufacturing table tennis balls, musical instruments, combs, office equipment, fountain pen bodies, and guitar picks.
Lacquer is a type of hard and usually shiny coating or finish applied to materials such as wood or metal. It is most often made from resin extracted from trees and waxes and has been in use since antiquity.
In biochemistry, cellulose acetate refers to any acetate ester of cellulose, usually cellulose diacetate. It was first prepared in 1865. A bioplastic, cellulose acetate is used as a film base in photography, as a component in some coatings, and as a frame material for eyeglasses; it is also used as a synthetic fiber in the manufacture of cigarette filters and playing cards. In photographic film, cellulose acetate film replaced nitrate film in the 1950s, being far less flammable and cheaper to produce.
Cellulose triacetate, triacetate, CTA or TAC is a chemical compound produced from cellulose and a source of acetate esters, typically acetic anhydride. Triacetate is commonly used for the creation of fibres and film base. It is chemically similar to cellulose acetate. Its distinguishing characteristic is that in triacetate, at least "92 percent of the hydroxyl groups are acetylated." During the manufacture of triacetate, the cellulose is completely acetylated; whereas in normal cellulose acetate or cellulose diacetate, it is only partially acetylated. Triacetate is significantly more heat resistant than cellulose acetate.
A film base is a transparent substrate which acts as a support medium for the photosensitive emulsion that lies atop it. Despite the numerous layers and coatings associated with the emulsion layer, the base generally accounts for the vast majority of the thickness of any given film stock. Since the late 19th century, there have been three major types of film base in use: nitrate, acetate, and polyester.
Dip coating is an industrial coating process which is used, for example, to manufacture bulk products such as coated fabrics and condoms and specialised coatings for example in the biomedical field. Dip coating is also commonly used in academic research, where many chemical and nano material engineering research projects use the dip coating technique to create thin-film coatings.
The Hindenburg disaster was an airship accident that occurred on May 6, 1937, in Manchester Township, New Jersey. The LZ 129 Hindenburg was a German commercial passenger-carrying rigid airship, the lead ship of the Hindenburg class, the longest class of flying machine and the largest airship by envelope volume. It was designed and built by the Zeppelin Company and was operated by the German Zeppelin Airline Company. It was named after Field Marshal Paul von Hindenburg, who was President of Germany from 1925 until his death in 1934. It caught fire and was destroyed during its attempt to dock with its mooring mast at Naval Air Station Lakehurst. The accident caused 35 fatalities from the 97 people on board, and an additional fatality on the ground.
Sometimes dubbed the Golden Age of Aviation, the period in the history of aviation between the end of World War I (1918) and the beginning of World War II (1939) was characterised by a progressive change from the slow wood-and-fabric biplanes of World War I to fast, streamlined metal monoplanes, creating a revolution in both commercial and military aviation. By the outbreak of World War II in 1939 the biplane was all but obsolete. This revolution was made possible by the continuing development of lightweight aero engines of increasing power. The jet engine also began development during the 1930s but would not see operational use until later.
Aluminized cloth is a material designed to reflect thermal radiation. Applications include fire proximity suits, emergency space blankets, protection in molten metal handling, and insulation for building and containers.
The two Hindenburg-class airships were hydrogen-filled, passenger-carrying rigid airships built in Germany in the 1930s and named in honor of Paul von Hindenburg. They were the last such aircraft to be constructed, and in terms of their length, height, and volume, the largest aircraft ever built. During the 1930s, airships like the Hindenburg class were widely considered the future of air travel, and the lead ship of the class, LZ 129 Hindenburg, established a regular transatlantic service. The airship's destruction in a highly publicized accident was the end of these expectations. The second ship, LZ 130 Graf Zeppelin, was never operated on a regular passenger service, and was scrapped in 1940 along with its namesake predecessor, the LZ 127 Graf Zeppelin, by order of Hermann Göring.
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.
British Celanese was a chemical company based in England. Formed in 1916, it survived as an independent company until 1957 when it became a subsidiary of Courtaulds.
Cellulose diacetate, sometimes called diacetate, is a synthetic polymer made by treating cellulose with acetic acid. It consists of two acetyl functional groups on each unit of D-anhydroglucopyranose of the cellulose molecule. It was first developed in the United States.
Camille Edouard Dreyfus was a Swiss chemist. He and his brother Henri Dreyfus invented Celanese, an acetate yarn. He founded The Camille and Henry Dreyfus Foundation in honour of his brother.
Henri Dreyfus was a Swiss inventor of the modern weaving loom. He and his brother Camille Dreyfus also invented Celanese, an acetate yarn.
Raymond M. Stits was an American inventor, homebuilt aircraft designer, aircraft mechanic and pilot. He designed the Stits SA-2A Sky Baby, which was the world's smallest aircraft in 1952, developed the Poly-Fiber aircraft fabric covering system and was the founder of Experimental Aircraft Association Chapter 1.
The conservation and restoration of film is the physical care and treatment of film-based materials. These include photographic film and motion picture film stock.
Fossil preparation is a complex of tasks that can include excavating, revealing, conserving, and replicating the ancient remains and traces of organisms. It is an integral part of the science of paleontology, of museum exhibition, and the preservation of fossils held in the public trust. It involves a wide variety of techniques, from the mechanical to the chemical, depending upon the qualities of the specimen being prepared and the goals of the effort. Fossil preparation may be executed by scientists, students or collections personnel, but is often undertaken by professional fossil preparators.
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 Doping Techniques |