This business about recovering every few years comes from the old days of covering with cotton and linen. That’s ancient history. Today, all covering is done with heat-shrunk polyester fabric. With proper application, today’s fabric systems last 20 to 30 years, even outdoors.
There are really only three basic systems, and they all start with heat-shrunk fabric:
- CECONITE FABRIC (Ceconite is a fabric brand), applied with nitrate and butyrate dopes. Randolph dopes are also widely used on Ceconite. Dope is easy to repair and has been around since aviation began.
- POLYURETHANE. These are two-part polyurethane systems using automotive coatings with flex agents added to reduce cracking of the dried paint. Major brands are Superflite II and Air Tech. Their finishes are high gloss, but are hard to repair and must be sprayed with the precaution: urethane spray mist is very toxic.
- POLY-FIBER. The “Stits” system, using Poly-Fiber fabric and all-vinyl coatings. Our vinyl coatings do not support combustion. See the Poly-Fiber page here at our site for more information.
If you got a price quote on each of the three systems, you’d see that they all total about the same. Only the cost per can is different. For instance, dope costs about £55.00 a gallon, Poly-Fiber is about £80.00 a gallon, but you need twice as much dope as Poly-Fiber. The urethanes can get as high as £200.00 including catalyst and flex agents. Here you use fewer gallons, but at a much higher price. No matter which system you use, the final cost for the fabric, tapes, coatings and paint is about the same. Cub sized airplanes usually run about £4,000 to £4,500 in materials. A Stearman will run about £7,400 in materials. An Ultralights may cost as little as £1,000 to £1,500 in materials, depending on the size of fabric components.
Most of the aeroplanes covered today are done by owner/builders. Fabric covering is easy to do; it’s just time consuming. Your LAA Inspector will usually supervise your work for a reasonable fee, then sign the paperwork and logbooks if you do a good job that meets with his approval. Ask around at your airport, or in your LAA Strut. Have a chat with your Inspector. We offer training and free advice here at Aircraft Coverings Ltd.
This has to be done by a Licenced Engineer or an Approved Organisation, but have a word with them. Most will be pleased with a helping hand and may even let you do it under their supervision.
Get a copy of the Poly-Fiber manual (available from us), also available as a free PDF download on this site. There are 135 pages of easy-to-follow instructions on basic fabric covering. Over the past 30 years, thousands of aircraft have been covered by following this manual. Better still, come to the Poly-Fiber sponsored workshop at the LAA Rally. If you can spare a weekend, you will come away with all the knowledge and skills you need. Or come & spend a training day with us – Details can be found under the “Training” tab.
When Cubs rolled off the line, they had 75 pounds of Grade A cotton and dope on them. A Ceconite and dope finish on that same Cub will weigh around 50 to 60 pounds. A Cub covered in Poly-Fiber has 40 to 45 pounds of finish weight. A Cub painted with urethane can get pretty heavy if you lay on the thick coats. Urethane is not known for its light weight. Ultralights can be done in as little as 12 to 15 pounds.
If you have the luxury of working on it eight hours a day, you can finish in a month or so. Of course, this all depends on your work habits, speed, and expectations. Most people do it during a winter season of weekends and evenings.
No. Pick a system and stay with it. Mixing and experimenting can result in disasters of all sorts. Unless you have a degree in organic chemistry, a full lab, and the time to test your experiments, we recommend you stay conservative. Remember, you’re going to ride in this aeroplane.
Lift acts like a giant vacuum cleaner, exerting a peeling force on the top of your wing. You have to do something to hold your fabric on other than just gluing it. Pop rivets, screws, clips, and rib lacing are designed to secure fabric for long service lives. Rib lacing is kindest to the rib structures, and it’s really pretty easy to learn. It takes only about five hours to lace a wing. This is great insurance and it costs very little. Yes, you have to rib lace. But it is really a piece of cake to do. Glue alone does not hack it.
We don’t recommend it. Urethane paints designed for automotive or other hard substrates just don’t last long on fabric. They are fine paints for stiff, non-flexing surfaces, but were never designed to last for years on vibrating, flexing fabric. Be smart and use something designed from the start for fabric. Nothing is more disappointing that cracking paint over perfectly good fabric. And there is no easy remedy. You can’t strip it. You have to recover.
Since 2001, the FAA has required that fabric covered aircraft (at least the fabric parts) be painted only with topcoat paints tested and approved on an STC. Use of any other topcoat paint will void the STC and airworthiness of the aircraft. Up to 2001, the STC’s “ended with the silver”, and any type paint was legal to use. This is no longer true. Over the years, increased use of brittle automotive or industrial paints caused enough cracking and delamination to cause the FAA to rethink approving untested topcoat paints over fabric. Failed topcoat paints expose polyester fabric to sunlight and UV damage. As of the latest revision of the Poly Fiber STC Procedure Manual (revision 21, September 2006), only the following topcoat paints are approved on the Poly Fiber STC: Poly Tone, Aerothane, or Randolph Ranthane. All three of these paints have long service lives over fabric as well as an FAA Parts Manufacturing Authority (PMA), which allows their application on certified aircraft. For instance, a J-3 Cub must have only Poly Tone, Aerothane or Ranthane over the fabric parts, but you could use enamel or anything else over the struts, cowl, fairings, etc. The keyword is FABRIC.