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Damaged RV-10 Horizontal stab - how to fix?

Rick RV-4

Well Known Member
Horizontal Stab got dropped and damaged the leading edge beyond repair. Two ways to fix:

- Start all over and completely rebuild with all new parts, or

- Drill out all rivets, and disassemble the structure as necessary, then redo with new skins.

If I do the second option, any concerns with the structure being weakened after drilling out all those rivets? I’m pretty good at drilling out rivets, but some holes are going to wind up slightly bigger.

Thanks in advance for your thoughts.

Rick
 
Horizontal Stab got dropped and damaged the leading edge beyond repair. Two ways to fix:

- Start all over and completely rebuild with all new parts, or

- Drill out all rivets, and disassemble the structure as necessary, then redo with new skins.

If I do the second option, any concerns with the structure being weakened after drilling out all those rivets? I’m pretty good at drilling out rivets, but some holes are going to wind up slightly bigger.

Thanks in advance for your thoughts.

Rick

If it were me, I would do the second option. The structure won’t be weakened by drilling out the rivets. If that makes you nervous, Set a bunch of rivets in a spare set of parts, then practice drilling them out. It really isn’t that difficult. If for some reason you do make a mistake, make sure you have some oops rivets on hand. They are a slightly larger diameter rivet.
 
I agree with Bob and would proceed with disassembling and buying replacements for the damaged parts. Depending on how much of a whack the drop was, I'd suspect that in addition to skin, you might also have some other bent internals - such as the leading edge ribs, and I'd make sure to run a laser sight or straight end down the spars. I recommend waiting on ordering parts until you have the the damaged portions disassembled.

I've been there; my left wing got backed into by a hangar neighbor not paying attention. I'd look at it as an opportunity to do a better job the second time around...ok, probably not helping :cool:

I do recommend having some NAS1097AD, aka "oops" rivets on hand. As you are practiced at removing rivets (flush rivets are a breeze once you've done about 10 in a row...), it'll come apart easy enough and hopefully won't need more than a few of them. I also get Bob's sentiment to not use them for each hole, however, the NAS1097 series simply has the same head as the AN426 rivets, but with the next larger diameter shank, so there is no strength reduction when done properly and would not be concerned if I had several of them in a row, although it's good goal to try and avoid that though :D

My tip for easier flush rivet removal is a Starrett 18A Automatic Center Punch, or a comparable one, to enlarge (or recreate) the drill dimple in your flush rivets for an extra aid on being on center.
 
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Thanks all,

I think I’ll at least start with option two and I appreciate your advice on having the oops rivets on hand. I’m thinking I’ll at least need new nose ribs but will wait to order any parts until I assess all of the damage. If anything looks even questionable I’ll punt and go with option one.

Thanks Ron, Bob and Bob!

Rick
 
If it was mine, I would probably replace the entire HS as there are a lot of rivets to be drilled out and they are harder on thinner parts like the ribs.
This way, I would never worry about it or have second thoughts years down the road.
 
For what it’s worth, I damaged the trailing edge of the left elevator on my 7A. I considered re-skinning it but I ended up re-building from all new parts. The only parts I re-used were the steel horn and the trim tab.

My go-to consultant on all things RV related said he thought there would be way to many enlarged holes in the sub-structure after removing the skin.

Even though I was planning to build using the new parts, I started by removing the skin on the elevator. After removing the skin, I was glad that I had orders all new parts. There is no way I would have wanted to re-assemble the elevator using the old sub-structure.

I know the HS is a much bigger job than an elevator, but when you are done you won’t have any doubts about integrity of the HS.
 
My 2 cents....

Riveted airplane structures with damage are repaired all the time.

The key is in how (at what skill level) the repair is done.

Example-
The phrase "drill out rivets" should not be done literally when parts are intended to be reused. Section 5 of the manual gives details on removing rivets in a way that will not risk enlarging the holes with drill bit. Using that procedure would be the first step in a quality repair.
 
My 2 cents

As a barely average builder (myself, not you)- I would build a new one. I dropped by rudder when hanging it by myself and chose to build a new one. The second one is much better than my first. Second time around is so much easier.
Cal
 
It is best to use a drill size that is one (or two) sizes smaller than the original hole. Get a #42 drill, set a depth stop and center punch lightly each rivet before you drill them off.
 
#40 drill
Drilled at low speed monitoring that the drill is centered. Slight wrist motion as the drill is at the intersection of the rivet head and body. They pop right off. Use flush cutting wire cutter to remove shop end.
 

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My 2 cents....

Riveted airplane structures with damage are repaired all the time.

The key is in how (at what skill level) the repair is done.

Example-
The phrase "drill out rivets" should not be done literally when parts are intended to be reused. Section 5 of the manual gives details on removing rivets in a way that will not risk enlarging the holes with drill bit. Using that procedure would be the first step in a quality repair.

Seconded. I would add to that:
  • If you are "twisting" a rivet out, I have found it is sometimes necessary to relieve the tension / friction on the shank of the rivet by drilling a hole all the way through. A #51 drill has worked well both as a "1 rivet size down" drill bit for AD3 rivets, and as a "reasonably safe" drill size for drilling through. Reasonably safe in that as long as you stay centered on the rivet shank, you should not gouge the edge of the hole.
  • If you are punching a rivet out, you want to back the hole with something that will support the sheet around it - like a bucking bar with a hole / depression drilled into it. Also "punch" is likely too strong a verb here. You want to tap on it just hard enough to remove it.
 
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Nothing stops you from spending an hour drilling out rivets to see how you do, then making the decision based on an inspection of the parts.
 
I had to replace the spar in the HS of my Dad's 8. (Long story.) I drilled out rivets and reused most of the existing structure. In my case with the strategic use of a 2 or 3 cherry max rivets I was able to avoid disassembling it completely which saved a lot of time. Point here is to think a little bit about your specific repair as sometimes there are shortcuts.

As others mentioned, center punch every rivet before drilling. Spend the money on new high quality drill bits. Practice on scrap first. Try to just go deep enough to pop the heads. Protect the part as this makes way more chips than drilling out prepunched holes during assembly.

You will get VERY good good at drilling out rivets and be able to do it quickly and accurately....which is not a bad skill to have. I'm repairing a Baron currently and saved myself nearly $1000 by drilling a part out of a salvage plane this weekend. I never would have attempted this previously.
 
Go slow and remove the skin(s). THEN evaluate any parts that might need to be replaced in the spars and ribs.

Chances are you may have a few misses and that's what oops rivets are for.

If you don't push too hard when drilling and don't drill all the way thru, you can use a similar diameter sized tool such as a old punch that has been ground down and with just a small wiggle, snap the head off the rivet.

Grind down a pair of wire cutters so one side is flat and you can grab the other side of the river and pull it right out.

Remember it's OK to make the skin hole bigger since you are replacing the skin. It the rib/spar underneath that you do not want to enlarge. Again, if you do, oops rivet it.

And the HS spars are quite a bit of work compared to a re-skin.

You-Tube has a video on removing rivets.
 
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Drilling rivets

I drilled my HS apart. No oops rivets.
You've received tons of excellent advise.
Here's my method...
-Use an auto punch to center punch every rivet you plan to drill. Make the punch mark nice and clean
-Use a bit 10 units smaller, #50-51. Start slow and walk back to center as needed early. Drill the center almost all the way through.
-Use a drill stop with #41 to drill only as deep as the rivet head
-Pop the heads off.
Some rivets will drop out so be ready with clekos. You don't want more stuff damaged. A modified auto punch ground down to dimension will knock out quite a few shanks.
Use a bucking bar and punch to remove remaining stubborn rivet shanks. I have bars made for the job with a hole to fit over the shop head. Second person is needed. Resist the urge to punch without a support. It will bend things.
 
Thanks guys!

I will certainly try the rivet removal and rebuild route, and if it just doesn’t go well, I’ll salvage what I can or rebuild with all new. This is my second build so I’ve replace quite a few rivets. This should make me even mo better at it!
 
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