F712 Bulkhead to F779 Skin Problem... Grrrrrr!

I am having one of *those* days... I think I would have been better off mowing the lawn than touching the airplane today.

Anyway, the other night I riveted the F712 bulkhead to the F779 Tail Bottom Skin. I didn't like the way some of the rivets looked so today I decided to "fix" them. Can you see where this is going? The problem I had is that the rivets didn't set correctly on the dimple. While the shop head was uniform, it was offset to one side or another and a bit of the edge of the dimple was showing on many of the rivets. The picture below points to examples of what I am talking about, but it may be hard to see the exposed edge of the dimple(s).

Earlier today I set out to remove and replace those rivets that exhibited this issue, and things quickly went from bad to worse. The rivets drilled out fine, but the replacement rivets came out worse than the first, and they needed to be drilled out as well. So now I have a 3 holes that are enlarged (stretched) but not ragged or egg-shaped. I will not try to replace them a third time, as the holes being slightly enlarged, are causing the rivets to tip. Sigh.

Sooo... what to do? I was ready to throw the assembly into the street earlier, but I've calmed myself down somewhat. I would prefer not to use Oops rivets here as this is where the VS and Tailwheel will mount and a collection of Oops rivets in one location gives me some concern. I've thought about just enlarging all the holes to 1/8" and using some -4s, but the spot kind of has me mentally beat right now, and I don't want to see any of those rivets go south on me (sad, but true). That leaves me with the option of drilling out the remaining rivets (3) and enlarging all the holes to 1/8" and using some 3212-4-2 CherryMax rivets here (edge-distance is fine). That is, unless anyone has a better suggestion or reason I shouldn't do that. Anyone?

Thanks for listening -- I feel better now.

Brad,

Personally, I wouldn't worry too much about those few rivets. The big issue with a rivet that is slanted to one side is over time, with vibrations you will "smoke" the rivet (basically it will rotate). A few bad rivets have never brought an RV down!

If you must fix it (which I know you must!), why not drill it out to a #30, dimple the skin and bulkhead in place, and squeeze a AN426AD4-4 there? Another thought is to keep everything a #40 and make some doubler shims to go inside the bulkhead.

Hey Mike, thanks!

I was editing the post when you responded. I don't know why I am having touble with these seemingly simple rivets, but I am. I guess the area has me somewhat mentally beat, and I am just concerned about the possibility of those -4 solids going bad on me too. I'll think about it. I've hung it up for the day, and I will revisit this tomorrow.

THANKS!!!

this is where a non swivel set will pay off

i guess you squeezed these, i did mine, and with the same results. after drilling them out a time or two i went to -4's. however after learning what i did on the canopy i've found the fixed flush rivet set works way better than the swivel once you gain some skill. and before anyone starts a war over this i understand completely that the swivel is easier to use. especially for beginners and helpers, but on curved surfaces this is what you get. the fixed set really shoots the most beautiful rivets ive seen. (shop heads that is) thats a .040 IIRC so if you have to drill it out to -4 and machine csk the skin the go from there. good luck and may the rivet gods shine on you.

Why not use 7/64" rivets? The heads are the same as standard 3/32" rivets.

http://www.vansairforce.com/community/showthread.php?p=137802#post137802

That's a tough skin to work with. I did ok where you are at now, but when I match drilled F779 to the side skins, some of the holes came out ovaled. I ended up drilling them out to -4's on all the F779/side skin common rivets. It's not really noticable and can only be stronger. I was able to dimple them normally because I was still in the normal drill/deburr/dimple process.

Ovaled.... did I just make a new word?

Brad-
I have a couple there that aren't perfect, and I was using AN426-4's from the start. For a few of the holes on the F711 bulkhead that are almost impossible to buck with the tailgear weldment in, Van's said no problem using some pulled rivets, but recommended CherryMax instead of the CS4's just because the taildragger takes a lot of abuse down there.

You could try the old trick of pre-squeezing a 3/32" rivet until it fits the hole. Use a hand squeezer and probably a 0.5 longer rivet.

Thanks!

Thanks for the tips guys. If nothing else, it makes me feel better to know I am not alone.

Captainron, thanks for the tip. I ordered a 1/4 lb of them from GAHco this morning. I can see them coming in handy in this area. I certainly don't think I will need that many, but I'll do a good deed and share them with some local builders.

Cytoxin, yep I squeezed them. I am a big believer in the fixed flush set as well, I've probably done 90% of my flush riveting with it, and I just might use it for round #2 (see below).

Unfortunately, yesterday didn’t turn out much better than Saturday. I drilled out the remaining three rivets, enlarged the holes and dimpled for -4s. Upon close inspection of the parts, I had some very tiny cracks around one hole in the bulkhead, and one hole in the skin. They didn’t penetrate all the way through the material, but as we all know you can only see a small portion of the crack with your eyes. I am unwilling to take chances here so a call to Van’s this morning has new parts on their way. Oh well, getting it done right is more important to me than getting it done quickly.

Thanks again!