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.

What goes together, must come apart

Wed 21st Nov 2hr 20

Completed R-918 attach strips, fitted and match-drilled them to R-901 skins and R904. Disassembled the rudder and began "DDEP" (Deburr, Dimple, Edge preparation)

Ken Scott replied to an email I had sent Yesterday to Vans support. He says I should replace the HS-902 spar on which some of the countersinks are too deep but the others three spar halves can be used. He also suggested two additional rivets through the skin and stiffeners either side of the double-holes created by mistake when dimpling the stiffeners. I don't like this as I believe the eye will be drawn to the anomaly in the rivet pattern. However the part is very cheap and as I am having a HS-902 shipped across anyway, there will be no additional postage or packing charge. Once they arrive, I can completely eliminate that ding. I also copied my examiner Mick Bevan on this correspondence and he concurs.

Yesterday evening was also the monthly meeting of the SAAC. I always bring a notebook along to record all the useful information and contacts that I get. Yesterday, I got a lead on a torque screwdriver that can handle the very low torque values necessary for the AN3 bolts in the central HS hinge brackets - 20-25 inch pounds. Charles O'Shea also took me through the builders manual that I will be completing with Mick Bevan.

I had already cut the bottom attach strips to length as they come from the same piece as the R-917 shim. As George Orndorff recommends, I cut the two R918 attach strips from the ends of this piece, leaving more than enough for the R917 in the middle. This evening, I cut off the angled ends that butt up to the rudder brace and filed and polished the edges.

They are held in place initially with side-jaw clecos (you need the longer 1" type to reach) and then clecoed as the holes are drilled. The lower holes are not drilled at this stage. The plans simply specify "2" approx spacing" - one of the few places I have seen the abreviation "approx" anywhere on these plans.

Taking the rudder apart took a while as there were so many clecos but that is because I had the stiffners clecoed in as well. I also deburred the skins very lightly.

No photos this evening - The camera is acting up and just could not be persuaded to perform.