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Empennage

Rudder match drilling

After a quick dash to Bunnings for some aluminium angle, I got back into the shed to start match drilling the rudder. I could only find 3m lengths which I couldn’t fit into the car, so I ended up grabbing some alum square tube which came in a 1.8m length instead. I needed this for the rudder trailing edge as a temporary straight edge and reinforcement to keep this edge straight when I rivet it.

I started by drilling a hole at one end in the middle of one face of the box tube. I then removed all the clecoes from the trailing edge, then aligned the hole in the box tube with the hole at one end of the rudder trailing edge. I then held the box tube flush against the trailing edge and match drilled the hole at the other end of the trailing edge and put a cleco in it to hold everything together. The trailing edge strip between the skins has a bit of play in it so the holes went out of alignment towards the middle. I resolved this by holding a cleco and using its prongs to move the strip into position in one of the holes in the middle of the trailing edge, then match drilling it and putting a cleco in it. The drill bit keeps everything aligned pretty well. Once I had the 3 clecoes in, I then repeated the process by putting a cleco in the middle of each gap I made between the clecoes until I had match drilled every hole. Here is a photo of the trailing edge match drilled.

I then match drilled all remaining holes on both skins. No dramas encountered here. Just be careful match drilling the holes close to the trailing edge. It’s easy to drill through to the flange on the other side and damage the rib.

Next, I had to pick out the horn brace and trim it. Here is a photo of one side trimmed.

The horn brace was too big to be able to use my band saw to cut it so I trimmed using my hand tools. Once trimmed I cleaned the edges and deburred as much as I could using my Scotchbrite wheel. The hard to reach areas I deburred using my microfiles. The plans then called for the brace to be placed into position and match drilled to bottom rib and rudder horn. Here is a photo of the brace match drilled and clecoed on.

I then had to fabricate some strips out of some alcad strip stock. This was fairly straight forward. I did the usual “measure twice, cut once”. The alcad is 0.032″ so I used my hand tools to cut this rather than my band saw. I was worried the saw would tear it.

We had a party to go to so I called it a day at this point. Build time 2 hrs.

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About gstrack

Husband and father of 2. Control & Instrumentation Engineer. Flying nut. Gadget geek.

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