Spraying the silver Poly Spray makes a real change to the wings. Three coats are applied until there is no obvious light showing through. An auto inspection light was placed beneath the wing and the lights were turned off in the garage. If any light penetrated the fabric then it had to be recoated again. Between coats, Poly Fiber advises to use their special “Paint Cleaning Chemical” which is wiped on and off. This removes any sanding residue, dust or dirt before the next coat is applied without harming the base finish.
The silver finish is actually fine granules of aluminum suspended in a clear Poly Based mixture. The sprayed aluminum needs to be very lightly sanded between coats until smoothed out before the final paint color is sprayed. If the pinked ears of any tapes stand up or if any taped edge is rough the fabric can be lightly sanded and the fabric recoated.
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Finishing Tapes, Gusset Tapes and Inspection Rings were attached per the pencil line locations by first coating the affected area with a brush coat of Poly Brush, then brushing the tape and the affected area with more Poly Brush while pressing the fabric tape into the wet glued zone. Wet tapes are essential and it is easy to see when a tape is wet or has areas not wet. The Poly Fiber Instructions are excellent and this Blog is not meant to replace them or even supplement them. Needless to say, their instructions include much greater detail on how the process works. The tape attachment was followed by heat smoothing the pinked edges of the tape down into the Poly Brushed surface until they were smoothed out and there were no standing ears or rough edges.
When the brushing and heat smoothing process is finished then you move to the spraying process. This required me to relocate both wings to a spray booth which is my garage with a lot of drop cloths. I used my wing rotator fixtures (Harbor Freight Engine Stands) to rotate the wings with the other end attached to a sling contraption. When any of the Poly Fiber coatings came in contact with a plastic drop cloth they make for a very sticky floor. When I tried to walk across the plastic drop cloths my feet would stick to it. The solution was to use a cotton drop cloth on the floor. Another item that needed protection before spraying the wings were the aileron and flap brackets, the wing strut connection brackets and any other protrusions – so these were carefully taped off.
After two spray coats of Poly Brush the wings took on a very ruby red glossy appearance. The next phase is the protection coat of Poly Spray which is the UV silver coat that protects the fabric from the damaging effects of the sun.
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The most important finish of a fabric covered airplane is the sprayed on silver finish. These multiple coats of silver are basically aluminum particles suspended in the vinyl chemistry to protect the fabric from the harmful effects of the Sun. There is usually a minimum of three coats of the Poly Spray material needed to bury the fabric in metal. A work light is placed behind the fabric to inspect if enough silver has been applied to totally eliminate any light penetration through the fabric. The silver/fabric material is carefully sanded with 320 / 400 grit sandpaper between coats.
The next spray coats will be a White Poly Tone Color that is used as a base finish prior to spraying the final classic 146 J3 Yellow. The White is needed to cancel the gray tone of the silver otherwise the Yellow color would be a greenish and hideous color.
Attaching large sheets of sticky medium weight Polyester fabric to the sticky Poly Tak edges of the fuselage frame became a two person job. The objective is to attach the fabric before the Poly Tak glue starts to set up and dry while also leaving enough time to get the right amount of slack in the fabric for shrinking allowance. Too little slack could deform the metal frame during shrinking and too much slack could result in a saggy skin.
Side walls of the fuse were covered first, then shrunk and trimmed. The Belly panel was attached next and overlapped the side walls. The roof panel was attached last. Fabric tapes were attached on the edges and over the stringers using Poly Brush as the glue. Poly brush coats were then brushed on next over the entire fabric surface. Poly Brush coats were then sprayed on as seen in the photos above.
The Turtle deck had its own spray booth and is shown with tapes attached. There is no “Red Tint” on the fabric finish since the “Untinted Poly Brush was used.
The next step will be the Silver Coats using Poly Spray for UV Protection.