What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

This may end being my most expensive mistake yet

gotyoke

Well Known Member
I got careless with my C-frame and made a figure 8 in one of the fuel tank skin holes where a rib attaches. I carefully drilled it up to #30, deburred as much as I dared, then re-dimpled #30. I noticed cracking in that hole and deburred more as much as I dared. This is the result. Still some cracking, it seems.

6C0E085D-BA51-4FB1-9668-BE9214D359C3.jpeg

Most importantly, I already have a support ticket into the mothership for repair suggestions. I am doubtful I have enough edge distance in the rib flange for an AD5 rivet.

What have others done to repair this kind of thing, or is it irreparable? A tank skin is kind of expensive, but I image the shipping could be even more expensive for a component this size.

What say you, oh wise random people on the internet?
 
Last edited:
I would wager a guess the fox is going to be to put a rivet either side of this one, and either put a Oops rivet in this one, or a -4 and build on.
 
In addition to the crack, when I zoom in on the picture it looks like the hole is knife edged. No way that's going to be up to snuff with respect to structural integrity unless it's upsized again.

I think that Taltruda is spot on with what you're going to get back from Vans.
 
Fuel tank skin

I did the same thing. It's an expensive mistake. Cost me around $300 with shipping to get a new fuel tank skin but there was no way I could get a peace about it otherwise. Added it to other mistakes. Three times I got a figure 8 out of the C frame dimpler where I could reach with anything else. :cool:
 
i am not familiar with the build of a tank but i have flown 2 planes i have built so here goes.......is it possible to modify the part that attaches here? some wording about not enough edge distance on a flange? modify that part so it has the edge distance?
 
Structurally you can put in another 2 rivets, one either side of the hole and build on. However, the crack needs to be filed out or stop drilled and the edges of the rivet holes rounded. Then you have to see if you can seal the tank.
If it was me I would be ordering a new skin.
 
I'd order a new skin.

For the C-frame, I like to put the male die on the bottom, so that I can positively locate the hole. Then whack! and done.

Dave
 
FWIW....

Buy a new tank skin. It's a fuel tank. I would always be dreading the impending leak if I were to try to salvage that.
 
Over time I've pretty much make my mistake decisions based on is it safe? if not, reorder immediately. I've done difficult rivets that were marginal and replaced them. also had some that were marginal and left them but replaced them a day or two later. Also had one or two that were left as that was the best I was going to do without buggering up the whole thing. There was a day or two that I did one or two rivets in a session and it felt like a triumph. Strive for perfection and do your best.

As far as your fuel tank, even if you could get a clean hole I would probably replace it since another hole in the tank is not great. Yeah, it's an expensive mistake, but in the grand scheme of things, not very significant in total cost.

Good luck.
 
Best practice

For the C-frame, I like to put the male die on the bottom, so that I can positively locate the hole. Then whack! and done.

Dave

^^^ This ^^^

Just need to be careful scratching the skins when you move them into position...
 
If you are painting, drill it out completely, make an inside patch sealed with pro seal and rivet the patch. Fill the hole and build on.

Or get a new skin.
 
If you are painting, drill it out completely, make an inside patch sealed with pro seal and rivet the patch. Fill the hole and build on.

That should be just fine. If you look at the quality of the tank construction on the QB tanks that come out of the Philippines, you wouldn't think twice about repairing that!

-Marc
 
good advice

For the C-frame, I like to put the male die on the bottom, so that I can positively locate the hole. Then whack! and done.

That mistake simply won't happen if you dimple with the male die on the bottom.
 
That mistake simply won't happen if you dimple with the male die on the bottom.

That is, in fact, exactly what happened. I was using the male die on the bottom. Some of these rivets require stretching over the piece and holding back the top skin out of the way, all while holding the ram down with one hand and striking with the other. Higher than normal levels of coordination and attention are needed to pull this off, and for one hole, I got careless.

No part of building an airplane is mindless, I'm finding. Well, except perhaps edge deburring with fine-grit sandpaper. But even then...
 
I’m wondering why it cracked. If the hole is deburred, dimpling won’t crack it. You’ve heard enough people saying “buy a new skin” so I won’t pile on. :)
 
My experience

I’m wondering why it cracked. If the hole is deburred, dimpling won’t crack it. You’ve heard enough people saying “buy a new skin” so I won’t pile on. :)

My experience is that my pilot hole was too small (3/32" instead of #40) and the dimpling cracked the hole. In this case it was not a tank skin so I filed the crack away and put two rivets in between original location.
 
Just Throwing This Out There…..

“The art of building is learning how to fix mistakes…..”

Everyone should, of course, do what makes them feel best - but don’t feel like you always have to order a new part if what you have is no longer “perfect”. Just about anything can be repaired!

I serve up, as an example, this fuel tank on an RV-6 that has over 4,000 flying hours since the builder discovered that he’d cut two left hand fuel tank skins instead of a right and a left. Easily fixed with a patch the size of a fuel tank filler and some rivets. “Back in the day”, this is what builders did!

No, you won’t use the exact same method to fix a single mis-dimpled rivet, but just about anything is fixable…..

243E17FB-D9A2-45D6-BAD8-48C029C05176.jpg
 
Back
Top