Regular readers may remember that I was unhappy at the way that the thin steel channel that forms the middle two ribs of the fin had straightened between the braze points.http://tailwindbuild.blogspot.com/2008/07/24th-july-2008-fin-complete.html
Discussing this on the Yahoo Tailwind forum led to the conclusion that I had under bent the ribs leaving them in tension so when they were heated whilst brazing they bent at the heated points and returned to straight between them. This will be something to watch when I do the horizontal stabilisers and wing tips.
To improve the profile of the fin, I decided to add a thin layer of resin and micro-balloons which could be sanded to a smooth curve. First the channels were roughened with the sand-paper to provide a key for the resin. Then two pieces of scrap aluminium with the protective plastic still on to act as a non-stick membrane were used as "shuttering" held on with spring clamps and a stiff mix of resin and micro-balloons added where required.
Once dry the filler was sanded to profile to produce the smooth curve required.
Whilst I had the filler out, the joints between the rear of the ribs and the trailing edge were also filled to remove the lip caused by the thickness of the folded trailing edge and the joint between the trailing edge and the tail-light fitting faired in. Should get a nice smooth covering now.
