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Will Womack

Well Known Member
The plans call out an optional blind rivet CS4-4 to attach the rudder control horn support bracket to the skin and bottom rib. However, the solid rivet callout is 3-4. For those that used the optional rivet, did you enlarge the holes to 1/8" (from 3/16")?? This doesn't seem right to me.

Thanks in advance.
 
Will,

I believe the CS4-4 is correct, but you'll need to decide now whether you will use the solid or blind rivets, both for hole and dimple size.

On my -9A I planned on using the CS4-4's there, but didn't think to enlarge these holes nor use the larger dimple dies. Now I can't use the blind rivets, but last night managed to get a bucking bar in through the brace hole for the two middle rivets.

I'm now trying to figure out how to get a bar on the front and back rivets inside the horn. The forward one is tricky because the nut plate interferes a bit, and the rear one is simply in a tight corner.

Anyone have suggestions on a bucking bar I can get in there with?

Mike Behnke
RV-9A Empennage
Andover, MN
 
I believe the plans allow you to use LP4-3's there. I wussed out and did that, but I also did it on another rudder with the longeron yoke just fine.
 
jcoloccia said:
I believe the plans allow you to use LP4-3's there. I wussed out and did that, but I also did it on another rudder with the longeron yoke just fine.
Click to expand...

LP's aren't flush (lo-profile "dome" rivets). CS's are (CounterSunk) and are flush.

DWG 7 calls out "AN426AD3-4 (CS4-4 OPTIONAL) ALL R-901 SKIN TO R-904 BOTTOM RIB TO R-710 HORN BRACE RIVETS"
 
As usual, you're right Dan. I was talking about the rudder horn to horn brace rivets. I wussed out on the ones in question too, though, and used CS4-4's :D
 
John,

When you installed the CS4-4 do you remember if you enlarged the holes early on, or after dimpling. I don't think it is really an option for me now. Unless I were to enlarge the holes and redimple. Not sure how well that would work out.

Would probably be a whole lot easier to head over to the tool crib and try and borrow the longeron yoke :D
 
110 degrees

I'm pretty sure CS4-4 have 110-degree heads. I personally would dimple the #40 holes, then enlarge to #30, and then run the deburring tool in each hole a few times until the CS4-4 sits flush. It's a combo of dimpling and c-sinking to get it "mostly right" while removing as little material as possible.

Somewhere out there you can find 110-degree countersink cutters, but in my opinion I wouldn't waste the money. Even Van's makes note of this in their construction manuals in various spots, that the CS4-4 isn't a perfect fit in a 100-degree dimple/c-sink, but it's a compromise that we can live with.

Call Van's if you're unsure.
 
dan said:
I'm pretty sure CS4-4 have 110-degree heads. I personally would dimple the #40 holes, then enlarge to #30, and then run the deburring tool in each hole a few times until the CS4-4 sits flush. It's a combo of dimpling and c-sinking to get it "mostly right" while removing as little material as possible.

Somewhere out there you can find 110-degree countersink cutters, but in my opinion I wouldn't waste the money. Even Van's makes note of this in their construction manuals in various spots, that the CS4-4 isn't a perfect fit in a 100-degree dimple/c-sink, but it's a compromise that we can live with.

Call Van's if you're unsure.
Click to expand...

This is pretty much EXACTLY what I did because I didn't realize until later what a pain those last couple of rivets are. I think the rivet was still a little proud was I was done because I didn't want to cut too much (just a couple of turns), but if I remember right it gets covered by the fiberglass tip, or at least a reinforcing strip of glass anyhow (assuming you're going for the "smooth" look). It looks a little funny, but seems to be functional non the less.

Speaking of when to drill/dimple stuff, I've been pre-drilling and dimpling many of the tip attach holes in the elevators. It's already pretty tight in some spots even before I rivetted the skin, so I figured it might be downright impossible after rivetting. Am I the only one who's doing this, and is there some potential gotcha' that I'm missing?
 
I had the same problem last week. I tried using solid rivets there and dont have a longeron yoke... yet. Anyway i tried riveting them and got really bad results... so i just drilled out the rivets. enlarged then countersunck the holes a little with the hand thingy. The pop rivets seem to sit pretty flush.

David
 
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