carrollcw

carrollcw

Well Known Member
crack.jpg


Building an RV7. The picture is of the bend tab on the left elevator next to where the trim tab goes. It is from the step where you bend the lower tab, then bend the upper tab over it. I accidentally bent it too far inboard and ended up with a small crack. I have straightened the bend back out and wonder what are my options at this point.

I have no illusions of building a perfect/flawless airplane, just a safe one. I can accept some cosmetic flaws.

My thoughts are I can either:
1- leave it as is, and rebend in the proper location (closer to the wing root) - probably not a good idea

2- stop drill it (basically make the pre drilled hole large enough to cut out the crack) and rebend (accept the cosmetic flaw)

3- stop drill, cut the tabs off and make a riblet (lots of work!)

4- order a new skin (even more work and $$$)

What do y'all think?
 
Paul Dye helped give me some of the above ideas, but recommended I ask the forum! Better to have hundreds of minds than just 2!
 
For what it's worth...

I vote #3. The extra work is minuscule in the context of the whole plane (though be careful on using this logic... in aggregate it can get you in trouble). #1 doesn't seem good, as you've said. Because you've re-bent it already and would have to do so again, I don't feel good about #2. If you're going for a show plane, by all means go with #4, but that's probably not required for a safe solution.

Whatever you decide, you can be sure that this is not the first challenge you will face, and when you overcome it, remember that you did overcome it when you run into the next ones!

Disclaimer... I am not an aeronautical engineer and my opinion is nothing more than that, an opinion. Don't take my word but make your own decision.
 
File

I would take a small round file and enlarge the existing relief cutout to capture the crack. Follow that line as if the existing notch was that big to begin with. Do the same to the mating piece to keep things "looking" right. As an experienced sheet metal guy, the question I ask myself is "what does it do, and what happens if (or when) it breaks". That particular 1/4" of material doesn't do much, and as far as of how it works, as long as the crack is cleaned out and it doesn't recrack when you bend, you should be golden. This kind of "blend repair" gets done regularly in the certified world.
 
I agree that opt 3 is a good option. However, I don't think this part really bears any load, so a riblet might be overkill. Furthermore, since I am not too concerned with the look (especially since this is the bottom of the elevator) opt 2 seems to be sufficient.

If I did opt 3, the other issue would be if I left the riblet flange oriented so I could buck standard rivets, the riblet would not sit flush on the edge. On the other hand, if I turned it around so that it sat flush on the edge, I would have to use pop rivets (not very aesthetically pleasing). Either way, it wouldn't look right.

What to do....
 
Andrew, that is kind of what I was thinking with opt 2. Thought I could probably clamp it to my drill press and enlarge the hole to encompass it. I doubt the rebending of the metal is a big deal since it isn't load bearing.
 
Andrew M said:
I would take a small round file and enlarge the existing relief cutout to capture the crack. Follow that line as if the existing notch was that big to begin with. Do the same to the mating piece to keep things "looking" right. As an experienced sheet metal guy, the question I ask myself is "what does it do, and what happens if (or when) it breaks". That particular 1/4" of material doesn't do much, and as far as of how it works, as long as the crack is cleaned out and it doesn't recrack when you bend, you should be golden. This kind of "blend repair" gets done regularly in the certified world.
Click to expand...

Took the words right out of my mouth. This is exactly what I would do. Verify with Van's to be sure.
 
Andrew M said:
I would take a small round file and enlarge the existing relief cutout to capture the crack. Follow that line as if the existing notch was that big to begin with. Do the same to the mating piece to keep things "looking" right. As an experienced sheet metal guy, the question I ask myself is "what does it do, and what happens if (or when) it breaks". That particular 1/4" of material doesn't do much, and as far as of how it works, as long as the crack is cleaned out and it doesn't recrack when you bend, you should be golden. This kind of "blend repair" gets done regularly in the certified world.
Click to expand...

Yep. What I'd do.
 
Andrew M said:
I would take a small round file and enlarge the existing relief cutout to capture the crack. Follow that line as if the existing notch was that big to begin with. Do the same to the mating piece to keep things "looking" right. As an experienced sheet metal guy, the question I ask myself is "what does it do, and what happens if (or when) it breaks". That particular 1/4" of material doesn't do much, and as far as of how it works, as long as the crack is cleaned out and it doesn't recrack when you bend, you should be golden. This kind of "blend repair" gets done regularly in the certified world.
Click to expand...

Paul gave you several good options but he is also wise enough to know that within the larger group of experienced people someone may have an even better idea. Do this!
 
I managed to crack mine in the same place. I'm a #3 kinda guy. According to my notes, the construction of the riblet and installation took me an hour.

850910688_uPkSK-L.jpg
 
#2 or #3 would be my choice. You'll probably want to do the work to enlarge that hole and capture the crack anyway, so do that first and see what the result is. If it looks good, bend the tab. If you don't like the result, remove the tab and make a riblet.
 
Crack Repair

My friend [he's a structural mechanic] and I were riveting the aileron spar to the skin. We hung it by the counterbalance pipe, but it cut the wire. Made a nice dent and small crack in one corner at the trailing edge. I was envisioning new skin and all the work to rebuild the aileron again. He just straightened out the dent and stop drilled the crack. Sure it's a flaw, but it's safe.
 
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