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Rudder trailing edge question

Desert Rat

Well Known Member
Hey All,

I'm building a new rudder to replace the one I got with a used kit that had some dents in it. Also, not really a deal breaker, but on that one it looked like the T.E. wedge hadn't been countersunk enough and the dimples weren't nesting all the way. This was a bad assumption on my part, because I have the same issue on the new one.

I've countersunk the holes in the wedge until they're knife edged (searching VAF leads me to believe this is acceptable in this application) and in fact have wallowed out a couple of the holes while trying to push my luck.

I'm not thrilled with this result. I've ordered a new wedge as well as the jig from Cleveland tools so that I can make sure the countersinks are dead nuts on with the surface of the wedge.

Does anyone have a suggestion for making this fit better or is this as good as it gets? I was planning to use 3M tape to stick this together for riveting, but if there are gaps like this, I might be better off using pro seal? I hate the idea of using pro seal as a band aid on this, so if there's a trick to this I'm all ears.

https://photos.google.com/share/AF1...?key=RDlpTlpyZGs3Q1Z5dDRvbEYtb2RqVnlEaEY3dnNB
 
The problem with countersinking the holes on both sides of the AEX extrusion is that you lose the pilot hole which keeps the countersink concentric. As you said, the countersink from both sides results in a knife edge in the middle of the AEX. My solution was to use a piece of sacrificial 1"x 1" x 1/16" angle and clamp the AEX to it. The angle maintains the pilot hole for the countersink, so ensures concentricity. This should allow the skin dimples to all fit properly in both sides of the AEX. I used Proseal with a small roller applied to the mating surfaces. Also clecoed the skin/AEX/skin to the angle to keep it straight while the Proseal cures.
 
The problem with countersinking the holes on both sides of the AEX extrusion is that you lose the pilot hole which keeps the countersink concentric.

You are right.
That is why there are details in Section 5 of the construction manual giving some tips and suggestions on how to do the countersinking on the AEX wedge.
 
You are right.
That is why there are details in Section 5 of the construction manual giving some tips and suggestions on how to do the countersinking on the AEX wedge.

So section 5 suggests that a countersink should be around .007 deeper for a dimple than for a flush rivet. That doesn't seem to be deep enough here. Since I've got a new wedge coming anyway, I just kept going with this one to see what it would take and it's more like .014 deeper than flush. By the time I get this to pull up reasonably tight, the holes are oversized almost big enough for a #30 drill bit shank to slip through.

Are you guys really going that deep to get this to look right?
 
Proseal

The problem with countersinking the holes on both sides of the AEX extrusion is that you lose the pilot hole which keeps the countersink concentric. As you said, the countersink from both sides results in a knife edge in the middle of the AEX. My solution was to use a piece of sacrificial 1"x 1" x 1/16" angle and clamp the AEX to it. The angle maintains the pilot hole for the countersink, so ensures concentricity. This should allow the skin dimples to all fit properly in both sides of the AEX. I used Proseal with a small roller applied to the mating surfaces. Also clecoed the skin/AEX/skin to the angle to keep it straight while the Proseal cures.

Same here. Left it clekoed till the proseal was fully cured then riveted.
Remember the Proseal will take up a little space either side. Same for a layer of tape if that's the chosen solution.
 
So section 5 suggests that a countersink should be around .007 deeper for a dimple than for a flush rivet. That doesn't seem to be deep enough here. Since I've got a new wedge coming anyway, I just kept going with this one to see what it would take and it's more like .014 deeper than flush. By the time I get this to pull up reasonably tight, the holes are oversized almost big enough for a #30 drill bit shank to slip through.

Are you guys really going that deep to get this to look right?

The .007 deeper is for a very specific reason based on testing.

I have serious concerns about double that amount.

I have written extensively here in the forums, in the past, why the .007 dimension is specified. A search on countersink depth for dimples will probably find it.
 
Secret

Just a little secret. After dimpling the skins, i touched the inside dimples with a sanding block so the two skins? dimples had more clearance.
 
Thanks for the replies everybody. FWIW, I sent the mother ship the same question with the same photo a couple of days ago and they responded late yesterday that it doesn't look out of the norm the way it is, but that I might break the edges a little if I wanted to try to get them to lay down better.

Since I've already got another wedge coming, I'm going to play with this a little more, but it seems like the feedback I'm getting her and from Vans is that this is going to be a case of good enough vs. perfect.
 
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