Category Archives: Empennage

Riveting the rudder frame together

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Bottom rudder frame

Started riveting the rudder frame together tonight…the frame goes together pretty easily. Van’s calls out optional LP4-4 blind rivets to attach the rudder brace and control horn. I wouldn’t know how to buck solid rivets here, or even squeeze them unless there’s some way to get a longeron yoke in there. Perhaps it’s possible to change the construction order and rivet the brace and horn together first. Whatever…

A fuzzy rudder counterweight

I also riveted the counterweight skin to its lower rib and then to the spar. That was enough for one day!

Primer

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More carcinogenic primer

Despite a cold day (4C/40F) the primer went on well. I found some instructions on the web for my cheapo Harbor Freight HVLP spray gun, and they helped quite a bit.

Mmmm…primer!

And here are the rest of the primed parts. It’s time to rivet!

Back to the rudder

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After a brief interruption for a wedding (Ellen’s and mine!), it was back to the rudder. This weekend’s tasks were to countersink the trailing edge wedge, prepare a piece of angle stock to hold the trailing edge straight, and finally, debur and dimple the skins.

Countersinking the rudder wedge

The first step in countersinking the TE wedge was drilling the holes to final size. I borrowed a technique for this from my friend Jim Piavis, match-drilling and clecoing the wedge to a flat surface – in this case, the hollow-core door I use as a work surface. Match-drilling into the door leaves a nice, accurate hole for the coutersink pilot. That, in turn, helps keep the countersink from chattering and chewing up the hole.

Dave’s pudgy hand. Note the wedding ring!

Here’s the end result. The process worked, and the wedge looks good. Another test-fit of the skins and wedge was encouraging. Next step – match drilling one rudder skin to a piece of aluminum angle per Vans’ instructions. I fastened the angle to one edge of the work surface for some added stability. Once assembled and prosealed, the trailing edge will be held straight when clecoed to the angle.

Drilling the wedge

The end result will look something like this…except with both rudder skins clecoed to the angle.

The wedge of doom

The horizontal stab is complete!

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The horizontal stab is complete!

Not too many problems here, except that I had to work a bit getting the remaining #30 rivets to fit in the frame. After some problems using the thin-nose no-hole yoke on the vertical stab, I seem to have mastered the art of using it.

Because the no-hole yoke is thinner, it flexes more as the squeezer ram develops more force when moving toward the end of its stroke. This flexing was causing slanted and/or cleated shop heads when I first used it on the vertical stab. By using a longer (1/2 inch) flush set the squeezer engages the rivet with slightly less force, not deflecting the no-hole yoke as much but still with enough force to form a good shop head.

Here’s another picture, this time without the blue plastic. Van’s recommends removing it to prevent corrosion…so I did.

And here’s one more picture…I like that shiny alclad!

Just about ready to pitch my Avery rivet height gauge

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With the first tech counselor visit complete, it was time to start on the horizontal again.

Whitney was looking for things to do, so I put her to work pulling clecos and inserting rivets. We got the top of one stabilizer riveted. Once again, the pneumatic squeezer came in handy. The only problem with using the squeezer is that a little finesse on the trigger is required. It’s very easy to slam the rivet in place rather than gently squeeze it. Also, an adjustable set is a must-have item for the squeezer.

One more thing…I’m just about ready to pitch my Avery rivet height gauge. The plans call for -3.5 rivets, which Avery’s gauge says is too short, i.e., not enough rivet shank protruding from the hole. I tried one -4 rivet which was the right length according to the gauge. That rivet was harder to set; the shop head tended to ‘cleat over’ and become lopsided. The rivets called out in the plans made almost perfect shop heads.

Lots of progress in the last three days

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Rudder clecoed together

Lots of progress in the last three days. Got the rudder clecoed together, then trimmed and fitted the R710 rudder brace that goes between the rudder horn and the lower rib. The brace has holes punched in it to indicate where material should be trimmed away for fitting, but the plans don’t say explicity to cut to the centerline of these holes as when trimming stiffeners. I cut and trimmed to the hole centers, and found that I was a little short on edge distance when match-drilling to the rib sides. I called Van’s – again – and they said that due to the loading on this part, a little reduction in edge distance would be ok.

Rudder trailing edge clecoed together

I clecoed the AEX wedge in place to get a rough estimate of how well things are fitting together. It’s not perfect, but it’s straight enough to give me some confidence that the trailing edge will go together during final assembly. After this check, I match-drilled the skins. Then came fabrication and fitting of the 0.032″ strips that will hold the lower rudder cap. Finally, I disassembled everything and began deburring/edge finishing rudder parts.

Preparing the counterweight ribs

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The next step is preparing the counterweight ribs and fitting them to the counterweight skin and spar.

Counterweight skin fitted to spar

I had to spend an entire evening trying to get this skin fitted correctly. I eventually found out that the skin wasn’t bent correctly at the factory and while I was able to get the skin fitted, the incorrect bends made the leading edge of the counterweight slightly skewed. Van’s says it’s ok, and I decided to use the skin as-is. The skin can be easily checked for a correct bend by simply setting it down on a flat surface with the skin sides vertical. If the skin’s bottom edges sit flat against the surface, it’s probably ok.