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Empennage

Rudder Riveting – Day 2

I sent out a call to the SABC for some #10 dimple dies. David Mills replied with an even better solution – make your own! A very big thank you Dave. Your solution worked a treat!

I made my own #10 dimple die by drilling a #10 hole in a spare block of wood, then countersinking it. I used the AN5 bolt to check that the countersink was deep enough.

I then put the rib into position and placed the AN5 bolt into the hole. Using a spare bolt as a driving rod, I then whacked it with my hammer.

Voila! Two #10 dimples!

With my countersinking tool already set up, I countersunk the rudder counterweight and gave it a coat of self etching primer.

Whilst that was drying, I riveted the counterweigh rib to the rudder spar.

I then clecoed the counterweight skin into position and riveted that to the counterweight rib. Don’t rivet the spar yet. I was paid a visit by the Chief Dimpler and Chief Marker who wanted to give me a hand.

Here is a shot of the counterweight skin-rib rivets.

Next, I installed the counterweight and bolted it into position. There were no instructions as to torque settings. I checked the books and AN5 nuts usually have around 100 inch-pounds. Unfortunately I couldn’t get the torque wrench in the space to I just tightened up as firm asI could with 1 hand and applied some torque seal.

I noticed the rudder horn brace sitting on the bench. I scanned ahead of the plans and couldn’t find any mention of it so I assumed it must be installed with the rest of the bottom rib “and associated parts”. So I clecoed this in and installed riveted the horn to rib rivets. The rivets to the rudder horn are pop rivets so I’ll do them later.

The plans then called for the skins to be clecoed to the skeleton. As I was scanning the plans I noticed a comment about bevelling the edges of the counterweight skin to provide a smooth transition for the main skin. There was no mention of this in the instructions and I only noticed the comment on the plans by chance. As the counterweight skins were already riveted to the skeleton, I could only really file the edges carefully with my microfile. I didn’t want to use a sander or grinder with the spar so close. Once filed I gave the area a shot of self etching primer.

I then clecoed the skins onto the skeleton.

The instructions then called for the 6 rivets to be set for the skin-counterweight skin to be set, and the 3 rivets for the skin – counterweight skin – spar to be set. If you get as confused as I was, have a look at the photo below. You can see the middle 12 rivets holes in a 3×4 pattern. The top left 6 are the skin-counterweight skin rivets, which are the shorter ones. The upper 3 on the right are the longer ones for the spar.

Here is a shot of the counterweight skin rivets.

And here are the counterweight skin to spar rivets.

I then clecoed the tip rib into position and began riveting.

As I got to the rivets in the narrow tip, I had to switch from my squeezer to my rivet gun. Eventually, even the bucking bar couldn’t fit. I tried a few different things as a thin replacement bucking bar, but couldn’t find anything that was suitable. I eventually decided to modify one of my bucking bars using my grinder so that it could fit. I ground out the neck of tapered eng ad made it thinner as shown in the photo below.

This allowed me to set a few more rivets in the tapered section.

I was then able to set all but the most aft rivet using this modified bucking bar. For the aft rivet, I used a cleco clamp placed on the opposite flange and a flathead screwdriver placed on the clamp as a bucking bar. This was just enough to half or third set the rivet. I was then able to fit the modified bucking bar in to finish the job. Here is a photo of the tip rib rivets.

Finally, I was at the stage I wanted to and that was to bond the trailing edge together. I had to work fast and I was using to fast-setting tank fuel sealant so I didn’t have the time to take any photos until after I was done. First, I set up the rudder, trailing edge wedge, scraper, sealant tube, solvent (acetone) and lint free cloth on the bench so that I had everything ready and in arms reach. I then mixed the sealant. I had bought one of the 30-min fast setting sealant tubes that can be used in a standard caulking gun. Highly recommended although most was not used and I’ll probably throw away. Placing the trailing edge wedge flat onto the bench, I experimented with placing a small dob of sealant at various spacings along the wedge. Any of you about to do this, I would recommend a dollop in between every hole about the size of the letter “O” on your keyboard. I then used a scraper to spread this out thinly over the wedge surface. I had heard this sealant described as the stickiest stuff known to man. The description doesn’t do it justice. With one side coated, I then stood the edge upright on its thicker end and placed spring clamps on the edge of the bench for the wedge to lean on. I then applied sealant on the other side in a similar fashion to the first. I found this approach fairly effective althought I still managed to get a bit of sealant on my work bench. Far less than if I simply flipped the wedge over though. With that done, I slid the wedge into position (after checking that I had it oriented the right way) and started putting clecoes in. As I clecoed the edge, small amounts of sealant were being squeezed out in areas along the trailing edge and the rivet holes. Using lint free cloth soaked in acetone, I was able to clean the excess sealant off. Here is a shot of trailing edge bonded and clecoed to the ali box tube I had match drilled earlier.

Here is a shot of the trailing edge showing how straight it is.

It was then that I realised that I hadn’t riveted the skins to the spar. *face to palm* So I quickly ripped out the squeezer and set those rivets. I could reach all but a few of the rivets down the bottom on one side. I was running out of time in the shed so I decided to call it quits and set those later.

Build time today 6 hours.

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About gstrack

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

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