Vintage Piper Restoration

Tips and experiences from the shop at Stanton Airfield


A similar inspection of the aluminum wings and related parts is also a must. Johnson explains, “The aluminum spars on the J-3 ailerons had significant corrosion under some of the hinges. It appears these hinges were not removed for a long time including at the last recovering.” He noted the matting surfaces on the hinges were not rusted, yet the aluminum under them was badly corroded.

Cleaning, painting, and new fabric

Johnson says, “After making needed repairs to the fuselages all the steel parts were cleaned down to bare metal using media blast.” He went on to discuss different types of media and grit used for cleaning and the importance with selecting a material not too abrasive as to damage the tubing. Once cleaned all the steel parts were immediately cleaned and painted with an epoxy primer.

“Even a short period of bare steel in a humid environment, or the fingerprints from handling the bare parts will be enough contamination to start the rust process,” Johnson says. Today’s epoxy primers withstand environmental conditions much better than the old paints and are compatible with the fabric cements used to attach the fabric to the steel tubing. Also, there are approved corrosion inhibitors available for flushing and coating the inside of steel tubing if you choose.

There are a few different types of synthetic fabric available today and approved with a supplemental type certificate (STC) for use on vintage airplanes. The covering material used on both these airplanes was Ceconite. Hank Geissler, A&P mechanic and Stanton’s primary dope and fabric person, says, “All of the covering systems available today have pros and cons and your choice is dependent upon what kind of finish you want. I’ve used most of them and just happen to like using Ceconite fabric with Randolph Aircraft Products nitrate and butyrate dope.”

After the fabric is installed and heat-shrunk, two coats of clear nitrate dope were applied. “One thing I like is to spray all the dope onto the fabric to eliminate brush marks, and I adjust the thinning percentages depending on which coat I apply,” says Geissler. Next is rib-stitching, adding fabric tape to the wings, along with all the extra layers of fabric added to corners and other areas where the fabric directly touches the structure underneath.

Then one more coat of clear butyrate and a series of butyrate coats with silver pigment added to protect the fabric against damage caused by sunlight. “We lightly sand in-between coats with 280 and later 320 grit sandpaper. Before the final color I like to paint all the fabric parts with a white base coat first. It seems to provide a consistent base and enhances the final color. I used three coats of color with a 400 grit sanding after the first and second coats.”

Geissler ends by saying, “Most people develop their own individual techniques and these are mine.” He goes on to say, “Don’t think the final color coats will cover imperfections; they won’t. You need to be careful and neat all the way through the process.”

 

Stanton Sport Aviation Inc. is a full-service FBO providing pilot training, airplane rental including tailwheel and LSA, maintenance, restoration, and aircraft storage, located at Historic Stanton Airfield in Minnesota. Stanton Airfield is a shareholder owned private airfield open to the public providing a place for recreational and sport aviation enthusiast to enjoy aviation. AMT editor Ron Donner has been a volunteer and member of the board of directors for more than 10 years. More information can be found by visiting www.stantonairfield.com.

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