Stits lite painting and finishing

Model Airplane News, Feb 2002 by Benjamin, Bob

Adding details that

bring a model to life

Last month, I showed how to apply a heat-shrinkable abric finish to a model using the Stits Lite products from F&M Enterprises. This article picks up where we left off and shows how to add the final surface details and achieve a beautiful painted finish. Let's get started.

RIB STITCHING

It isn't absolutely necessary to simulate rib stitching, but many modelers enjoy including this detail on their fabric-covered scale models; of course, it's a must-do for scale contest work. I use a custom-made "stitch-shooter" that I assembled with an old syringe and a small-diameter metal tube from the hobby shop. I form the stitches with beads of Tacky Glue, which is available at most craft stores.

Every full-scale fabric-covered airplane is subject to FAA regulations that dictate how far apart the rib stitches on their flying surfaces must be spaced; you will have to research this information to find out what the correct spacing is for your model. On my Fly Baby, the full-size interval is 3 inches between stitches, which converts to 3/4 inch at 1/4 scale. After I've applied the first coat of Poly Brush and it has dried, I draw pencil lines spanwise on the wing. I place a stitch at each line and rib intersection. With a little practice, you can apply all of the stitches to the wing in short order. Try to make them all the same width.

PINKED TAPES

On full-scale aircraft, these pinked tapes (often called rib tapes) seal and protect the exposed portion of the rib-stitching cord; they have pinked edges to increase the gluing surface and to strengthen the glue bond. F&M Enterprises provides pinked-edge tapes made from the same Poly Fiber as the covering cloth is made of; the tapes are available in a variety of scale widths. Just as with the full-scale aircraft, the pinked tape on our models is attached to the wing with Poly Brush. Each tape wraps all the way around the flying surface, even if there is a sheeted leading edge and trailing edge (LE and TE) that is not stitched. This way, there is never an unprotected end to work loose and tear away in the slipstream.

EDGE TAPES

Applying these is the final step in the full-scale covering process; they seal all the exposed fabric overlaps and seams as well as the ends of the pinked rib tapes. All of the fuselage stringers and longerons should be taped over where they contact the fabric. Modelers who do not want to bother with rib-stitch detail may still want to use edge tapes for a finished appearance, as well as for the extra mechanical reinforcement they add. Edge tapes are characteristically wider than the rib tapes; on my 1/4-scale model, they are inch wide, and the edge tapes are 1 inch wide.

Edge tapes are applied to the TE first so that as you work your way around the wingtip and the LE, any overlapped seams in the tapes will face the rear. This gives them a neat appearance and makes the seams aerodynamically cleaner. To apply the tape, use Poly Brush and finger pressure to seal it into place. A top coat of Poly Brush seals the tapes after they have been attached. A final overall coat of Poly Brush should then be added after all of the tapes have been attached and sealed into place. Any last-minute touchups of unwanted raised edges or rough spots can be done with the heating iron set at a low temperature (about 225 degrees). This little extra effort makes a big difference in the final appearance of the finished paint job and is actually much easier than trying to sand down the odd bumps later on.

SURFACE PREPARATION

When all of the fabric and tape work is in place and has been sealed with at least two coats of Poly Brush, the entire structure is then sprayed with a coat of Poly Spray. On full-size aircraft, this aluminum-pigmented material both protects the underlying fabric from damaging ultraviolet rays and provides a uniform undercoat for the final painted finish. Poly Spray can be wet-sanded to a fine surface finish, or it can be left as is. Wet-sanding is messy but very necessary if you want to do a great finishing job with any fabric-- and-paint method. Use 400-grit sandpaper and plenty of water, and just dive in and do it. Then clean up and enjoy the results.

This is the time to add all the fine detail. Windshields can be added and masked off, and hatches and metal sheeting edges can be masked off and created with filler. After the underlying surfaces have been finished and sanded smooth, a coat of Poly Spray will show where you need to sand down any high spots on the fabric.

PAINTING

An entire article could be devoted to spray equipment. I use a DeVilbiss automotive touchup gun and a smaller Paasche airbrush for my finish paint work. Slits Poly Tone paint can be used with any good-quality spray equipment; it's the easiest paint to work with that I have ever used. It can be used with glow fuels that contain up to 15 percent nitromethane. Light colors should go on first; apply a mist coat first to provide some surface adhesion, and then apply a solid-flow coat followed quickly by another coat as soon as the previous one begins to dry.