A Comparison of Aircraft Fabric Systems

By Jeff Paulson, Overall Aircraft Services LLC

January 2011

 

A History of Fabric on Airplanes

The purpose of covering an airplane or airplane components with fabric is to give it shape and or to enclose it.  Fabric was the choice over other materials starting back with the Wright Brothers and still is in many cases. It was chosen because it is light weight, easy to repair and no special tools were required.  With a pair of scissors and a selection of needles anyone could cover an airplane.

 When higher performance airplanes with lots of horse power came along then fabric started to be replaced with aluminum.  Even on the early high performance planes, such as most the planes built for WWII, fabric was used to cover the control surfaces.  Fabric was used because it was lighter, easy to repair and less apt to flutter.

 FIRST SYSTEMS

The fabric system that was first used was Irish Linen and shellac. The Irish linen had a fine weave, was strong and available. The shellac was used not so much to protect the linen but to seal it.  If the fabric was not sealed, the wings and tail could not create lift. The air would just pass through.  

 The Irish linen and shellac worked on the first planes because they were light, slow, and typically had a very short time between repairs.  The problem with this system is that the shellac was not very durable. The shellac was brittle and  the movement of the fabric would cause it to crack.  If it was left out in the sun, the UV would go though the shellac and weaken the linen. As aircraft started to last longer, Irish linen and shellac were just not good enough. Something different had to be done.

 The next system that came along was Grade A cotton, that was heaver duty than Irish Linen, and nitrate and butyrate dopes. The fabric was sewn on, then sealed and painted with the nitrate and butyrate dopes.  Nitrate dope is stronger and adheres better to the fabric than Butyrate does.  Butyrate on the other hand weathers better.  Most times a couple coats of Nitrate was put on first to bond to the fabric and hold the finishing tapes on. Butyrate was used for the rest of the build up and color.   After a while it was discovered that, in most cases, Nitrate dope really was not needed and only Butyrate was used. This system was far superior to varnish and shellac.  When stored outside, cotton and dope would last 7 to 10 years before it had to be redone.  If the plane was stored inside it could last 20 to 30 years. Cotton and dope became the standard for aircraft covering and lasted through WWI and well past WWII.

 The biggest down side to cotton and dope is the flammability of the system.  In the history of the early airplane factories there are several cases where the paint booth caught fire or exploded. Several WWI fighters were brought down after tracer bullets caught the fabric covering the planes on fire.  Even a cigarette ash falling on a cotton and dope airplane could catch it on fire and destroy it.

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