Finishing Foam

Tony Albence gives the original wing a light scuff sanding before starting in with the filler.

 

Once upon a time, in a land across the sea, there lived a little foam ice chest. Deep in its heart, the ice chest dreamed of flying like the birds. Lo and behold the wizard of ARFs visited the ice chests village. The foam ice chest begged the wizard to let it fly. With a whoosh, a boom and a blinding flash of light, the ice chest was transformed into an electric 40-inch Tiger Moth model airplane that did indeed fly with the birds.

Fill any molding points or other surface defects with lightweight filler, then sand smooth before covering with the silkspan.

However, the Tiger Moths skin still looked like the skin of an ice chest. It was soft, easily damaged and not very pretty. It could fly, but it was definitely an ugly duckling. Enter Tony Albence, an artist from the land of Delaware, here in the US of A. Tony has been using a process with only common modeling supplies that transforms such foam models. Here is how he helped the pitted, ugly duckling become a durable, smooth-surfaced swan.

Brush a light coat of thinned glue on the foam airframe.

THE MAGIC BEGINS

Using 220-grit sandpaper on a sanding block, remove all molding marks, seams and bumps. When done sanding, wipe the surface first with an anti-static laundry sheet that has been through your dryer once and then a damp cloth to remove all the debris. Fill in all the big holes, depressions and ugly molding marks with lightweight spackling. Finally, give the surface a final sanding to a smooth finish when the spackling is dry.

Then smooth on a piece of silkspan after moistening it with water.

Now for the real magic! Make a mixture of Titebond II alphatic resin glue and water. The mixture should come out to the consistency of light cream; a smooth brushable blend. Pick a part of the ugly ducklingwing, tail or fuselageand coat one surface. Do not attempt to coat the entire model at one time! While the glue mixture is still wet, apply a piece of medium or light weight Silkspan, available from SIG manufacturing or your local hobby shop. Pre-cut these pieces, large enough to cover each section and allowing for a 1/4 to 1/2-inch overlap around the edges.

Work out any bubbles or wrinkles before it starts to dry.

You will also want to prewet the Silkspan before you apply it to help it lay out smoothly. Lay the piece you are about to use on a towel and give it a heavy mist with water from a spray bottle. Let this water soak into the Silkspan while you are applying the glue to the foam part. You want to get the Silkspan wet, but not dripping like a napkin rescued from the swimming pool. The water loosens up the Silkspans fibers and will greatly increase its ability to conform to the contours around the wing tips and other curved areas.

Carefully brush a second coat of thinned glue onto the silkspan, working it around the edges to create an overlap with the piece coming from the other side.

Lay the silkspan onto the glue-coated foam and smooth out all the wrinkles using your fingers or a brush. Dont hesitate to cut some slits in the Silkspan to help wrap around the wing tips and other edges with compound curves. Blot with a paper towel to remove the excess glue mixture. After it is all smooth and bubble-free, brush on another light coat of your glue/water mixture and set it aside overnight.

When working around a complex curve like at the wing tip, cut slits in the silkspan and overlap them as you wrap around the contour.

When the glue is thoroughly dry, trim the silkspan around the edges using a new #11 blade or single-edge razor. You will be surprised at how tough the dried paper is to cut. Lightly sand the surface and smooth the edges using 320-grit sandpaper.

A light sanding once dry will remove any ridges.

Cover all the remaining parts of the model using the same process. A total of two or three coats of the glue and water mixture will provide for a smooth hard surface. As most of the weight of the mixture is water that evaporates, this process adds very little actual weight once dry. If you apply the silkspan smoothly and sand the surface carefully with 320 and 400-grit nothing more is needed.

This closeup shows off the smooth surface and excellent gloss finish provided by this technique.

FINAL FINISH

For color, a very light coat of acrylic craft paint thinned with water works well. We are using Craft Smart acrylic paint. If you cant find that brand at your local art supply store, buy a bottle of what they have and do some tests on some scrap foam. For a high-gloss finish, use gloss craft paint thinned about 50 percent.

Basic acrylic craft paints are all you need for this process. I look for sales to buy mine.

When the gloss coat, some decals, and lettering are applied, a beautiful swan will appear. The finished Tiger Moth shown here gained just two ounces. As you can see here in the photos, Tony Albence is also taking another humble foam Tiger Moth to a completely new level. After smoothing the surface with Silkspan he is now following that with a masterful paint job. Finally, remember to fly three mistakes high, and only make two, and dont forget to send us photos of your finished model.

 

 

Tony is going all out on this second airframe, replicating a unique full scale color scheme. Hopefully this model will be completed and flying by this summer.

Visit www.find.flyrc.com/071105 to view more photos of this project!

Links

Silkspan, distributed by SIG Manufacturing, www.sigmfg.com, (800) 247-5008