Step 6 – How I Cover Balsa Wood RC Planes
At the very end of last weeks post I featured a photo of the Hawklett in the bare wood state apart from the Anti-Glare panel and the motor access panel. In this post I propose to take you through the process of how I cover Balsa Wood RC Planes.
This is perhaps one of the most rewarding tasks as by the end the model has turned from a dull bare wood airframe to a glowing colourful thing of beauty (if done well!). The job requires the use of some basic tools that I will go through with you before I get started.
Essential Tools for Covering
The images here on the right show the basis of my adaptation of the original RAF trainer version of the Hawk jet on which this model is based.
I am using a heat shrink polyester material to achieve this scheme. This type of covering is available from various companies. Most reliable model shops and suppliers will stock it.
Being a heat sensitive product an appropriate heat source is required to adhere it to the surface of the balsa wood. There are two options one of which is necessary whilst the other is desirable but not essential.
The options are either a dedicated modellers electric heat iron with temperature control or a domestic electric clothes iron. The former is the best option as it can be used to access more confined spaces and is specifically designed for the job. Having said this, it can be done with the domestic iron but not so easily.
In addition I use modelling pins, a soft cloth pad, scissors and a scalpel with new blade. To aid accurate cutting I also use a 1M straight edge, a short ruler and a plastic transparent set square.
When using a blade and straight edge to achieve a true straight line cut in the polyester material it is necessary to have a good cutting base. I use a compressed fibre board with cork laminate attached to the top side. The cork takes cutting from the blade and is self sealing as the blade passes over it. A good alternative is a sheet of plate glass which does not blunt the cutting edge of the blade.
Cutting Heat Shrink Polyester Material
Covering films are supplied in widths that vary from 26ins (0.66M) to 1M. It can usually be purchased in multiples of 3ft or 1M lengths either in pre-packed sheets or cut from the roll.
Having ordered and received delivery of the two colours I had decided to use, I planned out the best way to cut the necessary panels to cover all top, side and bottom surfaces of the fuselage and fin, the panels required for the tops and bottoms of the wings, stabilizer, ailerons and elevators.
This is quite an exercise in logistics but if done well can save a considerable amount of wastage. Having said this, it is necessary to allow a good margin around all panels to enable them to be gripped and stretched gently over the surfaces before pinning in place.
Preparing To Cover The Surfaces
My preferred method is to cover the largest areas first followed by the smaller areas and individual parts. When using multiple colours it is advisable to apply the light colours first followed by the darker ones.
The first thing to do is to clean the surface using a ‘tack’ cloth. This ensures that there are no bits on the surface to show through the finished covering. After removing the film that protects the adhesive, I lay the material over the surface to be covered and gently stretch it into position. I hold it in place using modelling pins located at strategic positions.
Whilst doing this the shrinking iron has been heating up ready to start attaching the covering to the surface. I test the temperature by placing a very small piece of material, adhesive side up, on the shoe of the iron and if it starts to curl up and wrinkle the temperature is correct. Most Covering materials will attach to a balsa wood surface when the iron temperature is at around 150 to 170 degrees Celsius.
Attaching & Shrinking
With the covering pinned in place the first step is to run the shoe of the iron all the way around the edge so that it adheres to the wood. Once firmly held in place, I slightly increase the temperature of the shoe so that the material will start to shrink when it is moved steadily over the surface.
I try to keep the shoe just above the surface to avoid scratching the high gloss finish. Moving slowly the covering will shrink with the applied heat. Using the soft cloth pad I follow the shoe, gently rubbing the covering down on the surface to eliminate air bubbles and cause the adhesive to adhere to the wood. Any small wrinkles can be removed by re-heating the surface and gently rubbing the surface down with the soft cloth.
Once the complete area has been shrunk into place the excess material can be trimmed off and the edges smoothed down with the hot shoe. Corners need to be carefully trimmed so that the covering can be sealed across them. Curved edges, such as wing tips, need to have a surplus of covering left. This allows it to be pulled over the curvature whilst shrinking down with the shoe. Initially this technique takes a bit of practice to perfect.
Where two colours overlap, having first sealed the underlying covering, the first part of the top covering to be sealed is the actual join line. Here I touch the sole of the iron gently on to the overlap to tack the edge down. I take care not to apply to much heat so that the edge does not shrink way from the intended join line.
Having completed this tacking I seal all of the other edges before shrinking the covering down to the surface. I take care not to run the iron sole over the join line as the softened adhesive could cause the edge to shrink back from its intended position.
With just the ailerons and wing underside centre section to cover, she’s beginning to look much how I envisioned when I first chose the colour scheme.
Next week I hope to have finished these small tasks and installed the receiver, ESC, Lipo retaining straps and linked up all of the servos. I have to say that as an example of building balsa wood rc planes, this project has given me as much pleasure as I anticipated it would.
I do hope you are enjoying following this post and may be encouraged to have a go yourself at some stage. There is nothing more rewarding than the feeling of achievement and pride when the finished article takes to the air.
My website www.rookiercflyer.com is available for those needing help getting started in our wonderful hobby. Please feel free to share this post and the previous five posts with anyone you think would appreciate them.
Talk next week,