Spitfire in my workshop. David Glen BSc (Hons) MSc: Model Maker, Journalist David Glen

Wing root fillets (upperside)

Wednesday, 26th April, 2017

After a winter of inactivity, the model has progressed during the past month or so, my reward for a period of sustained work on it, despite this year’s chilly spring temperatures. What is more, my web log is up to date – possibly for the first time since I began it!

The overall procedure for the upper fillet panels is much the same as that described in my last entry, so I will leave the pictures to speak for themselves and focus instead on the crowning element of the fillet assembly, which is the V-shaped capping strip that reinforces its trailing edge.

At first sight, this might seem a challenge too far, yet it speaks volumes of what can be achieved with annealed litho plate and crude tools, primarily fingers and thumbs.

I started by cutting two parallel strips of litho plate, each about 1.5-in. wide. Being small, these must be annealed with care or they can easily succumb to the torch and shrivel at the edges and corners.

The strip, cut to over the required length, is offered up along the curved trailing edge on the model and pinched between finger and thumb progressively and evenly along its length. At first it yields quite easily then tightens as the metal resists further stretching. Another annealing and more pinching follows, and slowly the material yields and the angle of the V closes up. Simultaneously, by firmly pressing down with the thumbs along the trailing edge curvature, the piece is coaxed to conform in that dimension also.

As the shape develops it helps to use sharp scissors to trim off the excess aluminium from the width of the piece, because the narrower it is the more workable it becomes. The final final scale width of the strip is approximately 13 mm and this line can easily be scribed top and bottom along its length using dividers on engineer’s blue dye. The finished profile is achieved with the scissors and a flat file, although great care is needed to avoid the softened piece becoming distorted.

It is inevitable during the forming process for some minor lumps, kinks or even creases to develop, but this is not fatal, since they can be erased with a little more annealing and some careful burnishing work using a hardwood dowel or the handle of a file. For these finishing touches it is best to tape the workpiece down onto the model. The final task, of course, is to mark and trim the piece at both ends before it is fixed in place with contact adhesive and then further finessed with abrasive papers. The ensuing rivet detail acts as belt and braces, because each rivet is fastened with a tiny blob of cyanoacrylate glue.

 I have gone into some considerable detail in describing this single operation only because it is a perfect illustration of how, with care and perseverance, seemingly extreme shapes can be formed relatively easily in litho plate.

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The paper template in use during marking out of the third skinplate in the fillet sequence along the top of the wing root. The template is marked with horizontal and vertical datum lines so that it is always replaced in precisely the same position. The sharp eyed may notice a glaring error. I have left the little door over the ground power socket off! Hopefully, I will be able to scribe it through at a later stage, for once the contact adhesive is dry there is no chance of removing the lithoplate panels without very considerable damage.
The next plate along during marking and cutting. Note how the line is transferred using many vertical pencil strokes. The line along the top of the wing does not need a template since it can be cut with a straight edge.
The fifth plate, demonstrating how the vertical cut is achieved using a carefully orientated strip a litho plate as a guide.
The same skin plate while waiting for the contact adhesive to become touch dry.
Emplacing the screw fasteners takes great patience and care. I use a burr in a mini wheel brace to help cut the countersink holes
The finished capping strip as described in these notes. Its challenging shape is formed with very simple tools.
A near perfect fit. The blue dye is to aid marking out the width of the piece.
Once glued in place most minor imperfections can be removed with abrasive paper, then the work can be marked and drilled for the rivets.
Job done. Only the leading edge panel on either side remains and the wing root fillets are complete. But this must wait until the lower leading edge skin panels are installed.
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