APPLYING FABRIC

As with other covering materials, you need to be careful and neat with your application. I start with the tail surfaces to warm up before tackling the fuselage and wings. Place the control surface on top of the fabric and cut the fabric to size making it about an inch larger all around. Apply a coat of thinned (with 10 to 15% Acetone) Poly-Tak adhesive to the outer edges of the surface and let dry. You do not need to apply adhesive to the ribs. Because it dries very quickly, I pour the glue into a small container and work from there. You should only apply the Poly-Tak over several inches at a time or it may dry before you apply the fabric. As you become more familiar with the procedure you will modify the methods to suit you. I like to apply the fabric over the first coat of glue with another wet coat of glue so it can wick up through the fabric.

Don’t worry about getting out all the wrinkles or stretching the material tight over the airframe. The fabric will shrink more than enough, and it doesn’t bubble or sag as the temperature changes. It pulls smoothly over compound curves and won’t pull away later. Start at the top and iron down a small section of the fabric and allow to cool. Pull the fabric taught (but not over-tight,) and tack the fabric down at the bottom. Allow to cool and do the same to the left and right sides. Continue ironing down small sections and go around the perimeter of the surface. Use the iron to remove any large wrinkles and tighten the cloth slightly. Now turn the part over and repeat the process. Trim the covering to about a ¼-inch around the surface. Now slowly iron the cloth onto the edge all around. Cut the fabric with a hobby knife at any sharp corners and where

the cloth is glued to the fabric from the other side, use a small brush to apply Poly-Tak to the fabric, and press the covering into place.

After the fabric is attached to the airframe, heat the iron to 225°F and smooth the edges down. Then, increase the temperature in 25° increments to shrink the fabric. You can stop at any time the fabric feels tight enough. The Poly-Fiber will shrink 10 to 12% at 350°.

Once the surface is covered, I use a paper towel and some Acetone to remove any access glue from the outer surfaces.

For the wings, start on the lower surfaces. Again apply Poly-Tak around the edges but not the ribs or sheeting. As with the tail surfaces, tack small sections of the fabric down and work around the perimeter of the wing. At the tip, pull the fabric taught and apply heat to the outer edges. Continue tacking the fabric down every 12 to 24 inches at a time, until the fabric is completely tacked down. and apply heat to remove larger wrinkles and any loose fabric. But don’t use a high heat setting, this comes later.

For the fuselage, start with the bottom surface and then add the fabric to the sides. Finally, apply the fabric to the top of the fuselage. Again, where there are covering seams where one piece of fabric is glued to another, use a small brush and apply glue to the fabric overlap and press into place. Then smooth the seam with the iron.

Here’s the rudder placed onto a piece of the Poly Fiber cloth. When cutting the cloth to size, always use sharp razor blades.

Here you can see the covering overlay along the edge of the control surface.

Here the cloth has been cut to shape. Also I applied a coat of glue to the rudder.

Here the fabric has been tack down along the outline of the rudder.

For structures and hardware sticking out from the wing, balsa framework has to be add around them so the covering can be anchored in place around it.

Here the middle wing is having fabric applied to the underside. It is tack to the root end and then at the tip rib.

Here is the middle wing panel with the fabric applied and tacked down around the outer edges and tip.

The same technique is used on the ailerons for the top wing.

The same process is used for the elevators and horizontal stabilizer.

Here the control surfaces are covered and test fitted onto the fuselage.

Here is the slot for the tail skid. The covering is glued in place around the opening.

Here you see the bottom surface covering wrapped around the side longeron.

Here’s the fuselage side. Note the plywood side piece for the pushrod guide slot. Same thing is done for the rudder pull-pull cables.

Here the side covering is in place. The bottom edge wraps over the bottom covering.

Start covering the fuselage with the bottom surface.

Here the top covering is being tacked in place at the front and aft ends.

A trick for getting straight seams in the covering is to slide a piece of poster paper under the seam.

To seal the seam, use a small brush and apply Poly-Tak under the overlap.

The top covering is tightened with extra material hanging over the sides.

Then cut along a guide line with a sharp blade.

And press the fabric down and smooth it in place with your fingers. If there is any excess adhesive pushed out of the seam, clean it away with paper towels soaked in Acetone.