Penance for old sins

Sun 16th Dec 9hrs 30min

Countersunk HS-902-L spar and prepped edges. Cut replacement R-915 A&B stiffeners and match-drilled to rudder skin. Prepped R-915s. Made replacement HS-908 attach angles.

I did the countersinking of the HS-902 spar flanges to accept the skin dimples. This was the part where I had ruined the original part so I took it easy, making sure that the head of a size 3 countersunk rivet fitted down completely in the countersink so that it does not stop a fingernail drawn across the rivet. On this occassion I was careful to get it just right but I am not entirely certain that the skin dimples are fitting down enough, even if the rivet heads are okay. However, Vans support said clearly that the countersinks need to be set deep enough for the relevant rivets, not the dimple that sits into it.

The rudder is one of those areas where it is hard to arrange to drill through the parts that have already been match-drilled into the new parts. The skin is very floppy, even with the stiffeners clecoed to it. So, sespit what I said last Thursday, I drilled through the new part into the old. I seem to have got away with it as all the holes seem fine.

I was not happy with the second set of HS-908 attach angles. They were infinitely better than the first set but still a little smaller than the designed dimenions so, as I was having other parts sent, I decided to sport the $5 for the short length of angle required. This time, I marked very carefully and stayed well away from the lines with the bank saw. I then used a hand file and digital calipers to come right down to the exact dimensions required. Finally, I rounded off the corners to match the full-size drawings. They took a surprisingly long time as the 9 HS902/7 attach holes have to be drilled and then the angles have to be match-drilled to the HS-907 doubler and HS-902 spars. In the case of the left attach-angles, I only drilled the location hole and then did the remaining drilling throught the already match-drilled holes in the spar and doubler. Naturally, I clamped a straight edge across the two angles to ensure their bottom webs are in the same plane.

Eventually, I was happy that my HS-908s are spot on and all the other little 'oops' to date had been cleared up. Pity abut that trim tab.