Horizontal Stabilizer -- Use a Doubler?

So I had to drill out (again!) a rivet in the inboard nose rib-doubler-spar-shim-main rib joint. I've had such a problem getting these rivets set and getting the parts to lay flat and not clinch, but I finally figured out that they're better squeezed, and to squeeze them you have to install them before installing the attach angle just inboard of them (which, once installed, pretty much forces you to buck, and bucking through all those parts requires a pretty high driving pressure, which I think is what's been giving me trouble).

Anyway, in the process of getting the rivet out, I must have nicked the side of the hole in the nose rib flange that mates to the doubler; it's just a little bit oversized, and only in one small spot where it goes to 0.137" for a #30 nominal hole. (The hole in the doubler got some dings around it, too, possibly while I was getting the rivet out of there.)

Van's says insert a rivet and build on... but that I could install a doubler on the nose rib flange (which I interpret to mean adding an 0.025" sheet (same thickness as the nose rib) the size of the nose rib flange with holes drilled to match). My questions for the group are:

1. Would you use a doubler here? Why or why not?
2. If I were to use a doubler, what length of rivet should I use? I reason that I should use a 4-8 rivet because the parts to be riveted together (0.025" doubler + 0.025" nose rib + 0.125" spar doubler + 0.063" spar + 0.040" shim + 0.025" main rib) are 0.303", which would leave a 0.197" bucktail, and this exceeds the 1.5D (1.5*0.125"=0.1875") shown in the big diagram in Section 5 of the manual... but that's the same rivet length without the doubler, so...

Pictures (album at https://imgur.com/a/rCBg9pn):

The troublesome hole!
The corresponding hole in the spar doubler, if it matters.

Thanks for your help, everyone.

Doubler

NotMuchofaStall said:

So I had to drill out (again!) a rivet in the inboard nose rib-doubler-spar-shim-main rib joint. I've had such a problem getting these rivets set and getting the parts to lay flat and not clinch, but I finally figured out that they're better squeezed, and to squeeze them you have to install them before installing the attach angle just inboard of them (which, once installed, pretty much forces you to buck, and bucking through all those parts requires a pretty high driving pressure, which I think is what's been giving me trouble).

Anyway, in the process of getting the rivet out, I must have nicked the side of the hole in the nose rib flange that mates to the doubler; it's just a little bit oversized, and only in one small spot where it goes to 0.137" for a #30 nominal hole. (The hole in the doubler got some dings around it, too, possibly while I was getting the rivet out of there.)

Van's says insert a rivet and build on... but that I could install a doubler on the nose rib flange (which I interpret to mean adding an 0.025" sheet (same thickness as the nose rib) the size of the nose rib flange with holes drilled to match). My questions for the group are:

1. Would you use a doubler here? Why or why not?
2. If I were to use a doubler, what length of rivet should I use? I reason that I should use a 4-8 rivet because the parts to be riveted together (0.025" doubler + 0.025" nose rib + 0.125" spar doubler + 0.063" spar + 0.040" shim + 0.025" main rib) are 0.303", which would leave a 0.197" bucktail, and this exceeds the 1.5D (1.5*0.125"=0.1875") shown in the big diagram in Section 5 of the manual... but that's the same rivet length without the doubler, so...

Pictures (album at https://imgur.com/a/rCBg9pn):

The troublesome hole!

The corresponding hole in the spar doubler, if it matters.

Thanks for your help, everyone.

Click to expand...

If Vans says no doubler is needed then don't complicate matters.
If you're having difficulty getting parts to stay together, use the rubber tube method.
Also, pre-squeeze the rivet a tiny bit to keep it from shifting.

No way would I use a doubler there. That hole is barely out of spec it would appear.

no doubler

Hi Will,
As per the other comments, I also don't think you need an extra doubler, it will just make things more complicated than is necessary, that hole really doesn't look too bad and the rivet will fill it when set.

But I would suggest practising gun riveting with some various scrap aluminum to develop the technique, we all had to learn this. There are lots and lots of similar rivets later on in the build that cannot be reached with a squeezer and you just have to use the gun and bucking bar. You could practice with different length rivets, varying the air pressure, try different weight bucking bars etc. until you can do it consistently, and then do the real parts.

That trick of using a small piece of rubber tubing on the rivet tail works very well to help bring the parts together without clinching, so practice that too.

As others have said, no doubler.

If this is where I think it is, I messed it up also, though I also oversized the hole pretty badly and had to go up to a -5 on it. At that point I just went with a Cherry Max rivet, which was OK'd by Vans. You'll find squeezing in that area tough as the squeezer wants to interfere with the rib angles - it's kind of a "V" shape in there, yes? I talked to another builder about it, and he bent the ribs to the appropriate angle after the rivets were set.

NotMuchofaStall said:

...0.025" doubler + 0.025" nose rib + 0.125" spar doubler + 0.063" spar + 0.040" shim + 0.025" main rib) are 0.303", which would leave a 0.197" bucktail, and this exceeds the 1.5D (1.5*0.125"=0.1875") ...

Click to expand...

That's a lot of math there! Are you aware of tools like these: One Piece Rivet Gauge? That tool will allow you to quickly stick a rivet into the hole and determine the proper length without having to do all the algebra (which I would get wrong).

Thanks everyone for the sanity check! No doubler it is.

For the record, I have successfully drilled out dozens of rivets without much difficulty once I got the hang of it (and the proper tools)! I?ve actually finished most of the rest of the empennage short of closing things up (I?d like a tech counselor to look things over before I close anything that can?t be inspected in service), and I?m coming back to the HS. I had successfully bucked five of the six 4-8 rivets in this location using a rubber washer around the bucktail end, but the sixth rivet had too much of a gap between the shim and spar web, and it would not come out for love or money despite getting the factory head off cleanly. I ruined a bunch of parts in the process of drilling it out. So I resolved to squeeze these six rivets if I could, in the interests of minimizing chances of ruining more parts.

In good news I have lots of scrap parts to practice on for later.

Put a rivet in it and move on.