Aircraft Fabric Covering
   HOME

TheInfoList



OR:

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 Monocoque ( ), also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word ''monocoque'' is a French term for "single shell". First used for boats, ...
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 Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor pe ...
and
cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell w ...
nitrate dope; modern fabric-covered designs usually use synthetic materials such as
Dacron Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foo ...
and
butyrate The conjugate acids are in :Carboxylic acids. {{Commons category, Carboxylate ions, Carboxylate anions Carbon compounds Oxyanions ...
dope for adhesive. Modern methods are often used in the restoration of older types that were originally covered using traditional methods.


Purpose/requirements

The purposes of the fabric covering of an aircraft are: * To provide a light airproof skin for lifting and control surfaces. * To provide structural strength to otherwise weak structures. * To cover other non-lifting parts of an aircraft to reduce drag, sometimes forming a fairing. * To protect the structure from the elements.


History


Early use

Pioneering aviators such as George Cayley and
Otto Lilienthal Karl Wilhelm Otto Lilienthal (23 May 1848 – 10 August 1896) was a German pioneer of aviation who became known as the "flying man". He was the first person to make well-documented, repeated, successful flights with gliders, therefore making ...
used cotton-covered flying surfaces for their manned glider designs. The Wright brothers also used cotton to cover their
Wright Flyer The ''Wright Flyer'' (also known as the ''Kitty Hawk'', ''Flyer'' I or the 1903 ''Flyer'') made the first sustained flight by a manned heavier-than-air powered and controlled aircraft—an airplane—on December 17, 1903. Invented and flown b ...
. Other early aircraft used a variety of fabrics,
silk Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the ...
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 Sago () is a starch extracted from the pith, or spongy core tissue, of various tropical palm stems, especially those of ''Metroxylon sagu''. It is a major staple food for the lowland peoples of New Guinea and the Maluku Islands, where it is c ...
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)


World War I/Postwar

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.Goldenbaum, Jon: ''Aircraft Fabrics - Wrapping it up'', AeroCrafter - Homebuilt Aircraft Sourcebook, page 31-34. BAI Communications. National insignia painted on the fabric were often cut from downed aircraft and used as
war trophies __NOTOC__ A war trophy is an item taken during warfare by an invading force. Common war trophies include flags, weapons, vehicles, and art. History In ancient Greece and ancient Rome, military victories were commemorated with a display of captu ...
. The German aircraft designer
Hugo Junkers Hugo Junkers (3 February 1859 – 3 February 1935) was a German aircraft engineer and aircraft designer who pioneered the design of all-metal airplanes and flying wings. His company, Junkers Flugzeug- und Motorenwerke AG (Junkers Aircraft and ...
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 Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
gas was a factor in the demise of the Hindenburg
airship An airship or dirigible balloon is a type of aerostat or lighter-than-air aircraft that can navigate through the air under its own power. Aerostats gain their lift from a lifting gas that is less dense than the surrounding air. In early ...
.


World War II

By the World War II era many aircraft designs were using metal
monocoque Monocoque ( ), also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word ''monocoque'' is a French term for "single shell". First used for boats, ...
structures due to their higher operating
airspeed In aviation, airspeed is the speed of an aircraft relative to the air. Among the common conventions for qualifying airspeed are: * Indicated airspeed ("IAS"), what is read on an airspeed gauge connected to a Pitot-static system; * Calibrated ...
s, although fabric-covered control surfaces were still used on early mark
Spitfires The Supermarine Spitfire is a British single-seat fighter aircraft used by the Royal Air Force and other Allied countries before, during, and after World War II. Many variants of the Spitfire were built, from the Mk 1 to the Rolls-Royce Grif ...
and other types. The
Hawker Hurricane The Hawker Hurricane is a British single-seat fighter aircraft of the 1930s–40s which was designed and predominantly built by Hawker Aircraft Ltd. for service with the Royal Air Force (RAF). It was overshadowed in the public consciousness b ...
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 Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "li ...
is an example of a fabric-covered (
madapollam Madapollam is a soft cotton fabric manufactured from fine yarns with a dense pick laid out in linen weave. Madapollam is used as an embroidery and handkerchief fabric and as a base for fabric printing. The equal warp and weft mean that the t ...
) plywood aircraft. The
Vickers Wellington The Vickers Wellington was a British twin-engined, long-range medium bomber. It was designed during the mid-1930s at Brooklands in Weybridge, Surrey. Led by Vickers-Armstrongs' chief designer Rex Pierson; a key feature of the aircraft is its ...
used fabric over a
geodesic airframe A geodetic airframe is a type of construction for the airframes of aircraft developed by British aeronautical engineer Barnes Wallis in the 1930s (who sometimes spelt it "geodesic"). Earlier, it was used by Prof. Schütte for the Schütte Lan ...
which offered good combat damage resistance. An interesting case of ingenuity under wartime adversity was the
Colditz Cock The Colditz Cock was a glider built by British prisoners of war during World War II for an escape attempt from Oflag IV-C (Colditz Castle) prison camp in Germany. Background After the execution of 50 prisoners who had taken part in the " Gr ...
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.


Introduction of modern materials

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. Early attempts to use these modern fabrics with butyrate dope proved that the dope did not adhere at all and peeled off in sheets. Nitrate dope was resurrected as the initial system of choice instead, although it was supplanted by new materials too. One fabric system, developed by Ray Stits in the United States and FAA-approved in 1965, is marketed under the brand name ''Poly-Fiber''. This uses three weights of Dacron fabric sold as by the brand name ''Ceconite'', plus fabric glue for attaching to the airframe (Poly-Tak), fabric preparation sealer resin (Poly-Brush) and paint (Poly-Tone). This system is not dope and instead uses
vinyl Vinyl may refer to: Chemistry * Polyvinyl chloride (PVC), a particular vinyl polymer * Vinyl cation, a type of carbocation * Vinyl group, a broad class of organic molecules in chemistry * Vinyl polymer, a group of polymers derived from vinyl ...
-based chemicals. Ceconite 101 is a certified 3.5 oz/yd2 (119 g/m2) fabric while Ceconite 102 is a 3.16 oz/yd2 (107 g/m2) fabric. There is also an uncertified light Ceconite of 1.87 oz/yd2 (63 g/m2) intended for ultralight aircraft. This method requires physical attachment of the fabric to the airframe in the form of rib-stitching, rivets or capstrips, which are then usually covered with fabric tapes. In addition to Poly-Fiber, a number of other companies produce covering processes for
certified Certification is the provision by an independent body of written assurance (a certificate) that the product, service or system in question meets specific requirements. It is the formal attestation or confirmation of certain characteristics of a ...
and
homebuilt aircraft Homebuilt aircraft, also known as amateur-built aircraft or kit planes, are constructed by persons for whom this is not a professional activity. These aircraft may be constructed from "scratch", from plans, or from assembly kits.Armstrong, Kenn ...
. Randolph Products and Certified Coatings Products both make
butyrate The conjugate acids are in :Carboxylic acids. {{Commons category, Carboxylate ions, Carboxylate anions Carbon compounds Oxyanions ...
and nitrate-based dopes for use with Dacron fabric. Superflite and Air-Tech systems use a similar fabric, but the finishes are
polyurethane Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane is produced from ...
-based products with flex agents added. These finishes produce very high gloss results. Falconar Avia of
Edmonton, Alberta Edmonton ( ) is the capital city of the Canadian province of Alberta. Edmonton is situated on the North Saskatchewan River and is the centre of the Edmonton Metropolitan Region, which is surrounded by Alberta's central region. The city anch ...
,
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
developed the Hipec system in 1964 for use with Dacron fabric. It uses a special Hipec Sun Barrier that adheres fabric directly to the aircraft structure in one step, eliminating the need for the riveting, rib-stitching and taping used in traditional fabric processes. The final paint is then applied over the sun barrier to complete the process.Hunt, Adam & Ruth Merkis-Hunt: ''Finishing With Hipec'', Kitplanes June 2001 pages 70-74. Belvoir Publications. ISSN 0891-1851 Newer systems were developed and distributed by Stewart Systems of
Cashmere, Washington Cashmere is a city in Chelan County, Washington, United States. It is part of the Wenatchee– East Wenatchee Metropolitan Statistical Area. The population was 3,060 at the 2010 census. The population was 3,157 at the 2018 estimates. Hist ...
and Blue River (Ceconite 7600). These two systems use the same certified dacron materials as other systems, but do not use high
volatile organic compounds Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a t ...
, using water as a carrier instead, making them safer to use and less environmentally damaging. Many ultralight aircraft are covered with pre-sewn envelopes of 3.9 oz Dacron that are simply screwed, bolted or laced into place. These are produced in a wide variety of colours and patterns and are commonly flown untreated or with an anti-
ultraviolet radiation Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
finish to resist sun damage. Lanitz Aviation introduced a new process in 2001 manufactured in Germany under the trade name Oratex6000. Oratex has received a European
EASA The European Union Aviation Safety Agency (EASA) is an agency of the European Union (EU) with responsibility for civil aviation safety. It carries out certification, regulation and standardisation and also performs investigation and monitori ...
Supplemental Type Certificate (STC), Canadian STCs, and a US STC. Oratex differs from previous systems, which all require the application of many layers of special coatings (many of them toxic) along with the time, skill, equipment and safety precautions necessary to apply them. Oratex6000 is simply glued to the airframe and then shrunk tight and does not require any coatings.


Covering processes


Traditional methods

Traditional covering methods use organic materials, such as
cotton Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor pe ...
. Once the aircraft structure is prepared by sanding, the material is applied using dope as an adhesive. Rib-stitching is used on faster aircraft types and especially on undercambered airfoils to ensure that the fabric follows the aircraft structure. The distance between stitches is reduced in areas affected by the propeller wash. The covering would then be treated with tautening dope to remove wrinkles and increase structural strength, finish coats often containing aluminium powder would serve to protect the surface from ultra-violet light. Large fabric panels of the World War I era aircraft were often laced together through
eyelets Curtain grommets, used among others in shower curtains. A grommet is a ring or edge strip inserted into a hole through thin material, typically a sheet of textile fabric, sheet metal or composite of carbon fiber, wood or honeycomb. Grommets ar ...
to ease access to the internal structure for maintenance. Some disadvantages compared to modern methods are the relatively short service life of the covering due to biological effects such as
mildew Mildew is a form of fungus. It is distinguished from its closely related counterpart, mould, largely by its colour: moulds appear in shades of black, blue, red, and green, whereas mildew is white. It appears as a thin, superficial growth consi ...
and the labour required to achieve the end result.


Modern methods

Modern covering methods follow the traditional method with minor differences. Synthetic materials are used, covering is adhered to the structure using dedicated glues. The shrinking process is achieved by applying an electric iron or
heat gun A heat gun is a device used to emit a stream of hot air, usually at temperatures between 100 °C and 550 °C (200-1000 °F), with some hotter models running around 760 °C (1400 °F), which can be held by hand. Heat ...
. Once the covering is tight, rib-stitching is again used for heavier or faster aircraft. Cosmetic finish coats are usually applied, except in the case of Oratex which normally receives no coatings. A side effect of using modern covering materials on wooden structured aircraft is that due to the much longer life the structure remains covered and un-inspected for much longer time periods, this has resulted in special periodic inspections being mandated by aviation regulatory bodies. With both methods of covering it is normal for the aircraft to be re-weighed after renewal of the fabric to determine any change in mass and centre of gravity.FAA AC.43.13, p. 243.


See also

* Aircraft dope *
Homebuilt aircraft Homebuilt aircraft, also known as amateur-built aircraft or kit planes, are constructed by persons for whom this is not a professional activity. These aircraft may be constructed from "scratch", from plans, or from assembly kits.Armstrong, Kenn ...
*
Radio-controlled aircraft A radio-controlled aircraft (often called RC aircraft or RC plane) is a small flying machine that is controlled remotely by an operator on the ground using a hand-held radio transmitter. The transmitter continuously communicates with a receiver ...
, on which either doped-on fabric or prepared iron-on fabric (using heat from a clothes iron for adhesion and shrinkage) can be used for a covering material.


References


Notes


Bibliography

*
Federal Aviation Administration The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic ...
, ''Acceptable Methods, Techniques and Practices-Aircraft Inspection and Repair, AC43.13.1A, Change 3.'' U.S Department of Transportation, U.S. Government Printing Office, Washington D.C. 1988. * Taylor, John W.R. ''The Lore of Flight'', London: Universal Books Ltd., 1990. .


Further reading

* * *


External links


Fabric covering techniques
{{Aircraft components
Fabric Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not th ...