B

bfilarsky

Active Member
I've got most of the work done on the rudder, but I can't quite figure out how to countersink/dimple the last holes on the ribs. I've been dimpling, then lightly countersinking all the others in order to make room for the dimple in the skin above it, but I can't get a dimple dye in there. I believe it .040" aluminum, and when I tested a countersink of the required depth on the same type, it went all the way through the metal. So, do I just go ahead and countersink it anyways (I'm afraid it will crack down the line if I do, they seem to be in a fairly high stress area) or is there some way I can dimple it?

Its the last three holes on either side of both the top and bottom rib:

 
Go for the vice grip dimpler, it works well for these holes. You may have to bend the flange out a bit to get it to fit on the last hole, but thats fine.
 
my solution

I bought I tool from Cleveland which worked for me. I is a straight piece of steel with a 3/32 female die in one end. You attached this to the benchtop with die end extending beyond the table top. Put the rib nose hole over the female die, insert the male die on the other side and smack it with the hammer. I got no distortion and a nice dimple.
 
I used a slightly different method

http://stjohn.openbar.com/airplane/2007/10/almost_done_with_the_rudder.html

If you don't mind grinding away a chunk of c-yoke, this option might work for you. One thing the photos don't show is that you need to clear the masking tape away from the mating surfaces of the dies, or you get to clean off compressed tape-goo later and you don't want to press it into the metal of the rib. Using this method, I didn't have to bend the flange at all. I guess this would be a roundabout, pretty-darned-expensive way of doing it, but I never got the vise-grip dimpler and I was already in possession of the mutant c-yoke, since that's the way it was when I got it off eBay.
 
I never had much luck with the pop rivet dimpler. You have to be able to get the nail to go through the rib hole, which is near impossible to do on the last hole (and the last two holes on the flap ribs, at least for the -9). Maybe my pop riveter needs too long of a nail to get a good grip.
 
Make the female die

I took a piece of 1/8 steel flat bar, drilled and countersunk it to use as the female die. Used visegrips on each side of the hole to be dimpled to hold it to the rib flange (protected the flange with small pieces of scrap). Put the male die on top, put an old 1/4" drive socket over it to protect it, and smacked it a couple times with a hammer. Couple turns with the countersink finished it.
 
If I recall at least the bigger part which has narrower gap is 0.032" stuff, right? So it might be countersinked as well and that would leave more room for riveting as well... no new tools needed.
 
There is an even easier method. if you take the 3" yoke squeezer and remove the female die you can make a decent looking dimple by just running the male die into the hole in the yoke. Go slowly and the dimple will come out fine. It's good for getting into tight to reach areas and dimpling thin skins.
 
Well, thanks for the other suggestions. I already blew $30 with Avery, and I won't be seeing the project again until next week (when I'll have the tool). Some good ideas for me to keep in mind, though!
 
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