My First Dimpling Error (a familiar tale)

[goatflieg]

The day I have dreaded has arrived. Ths morning I made my first major mistake on an aircraft part. I've read accounts of other builders making this same mistake, and swore it wouldn't happen to me... I even devised a strategy to avoid it. But my strategy failed.
I had finished deburring all the horizontal stabilizer parts, and was beginning to dimple the skins. I thought I'd start with the hard parts. I wanted to see how many of the center rib leading edge holes I could dimple with the C-frame table before I had to resort to using the rivet puller and close-quarters set. Other builders had made the mistake of punching unwanted holes when the dimple die came astray of the rivet hole. I thought I'd avoid that mistake by carefully locating the male die into the hole, then pre-loading the female die to sandwich the piece firmly in place before striking with the mallet. Well... it came astray anyway... and I ended up with a punched and dimpled hole just adjacent to the one that should have been dimpled.


Fortunately, this happened on the bottom of the skin, so whatever corrective measures I make won't be glaringly obvious to the appearance of the aircraft. As I see it, I have several choices:
1. I flatten the errant dimple, dimple and rivet the correct hole and leave the error as is... or perhaps fill it with bondo, liquid metal or welding before painting.
2. I leave the errant dimple, dimple the correct hole, drill a corresponding errant hole in the rib, and rivet both holes.
3. Order a new skin, re-drill, deburr and hope the holes match the ribs and spars.
My biggest concern is the proximity of the holes. They're very close together, and I'm sure that complicates the situation. I did some more research here to see if other builders' errors were similar to mine and what corrective measures they took. I read many accounts, but I did want to share this situation with my compatriots before deciding on my own plan of action.
Well, I knew it was coming... and I'm sure there will be more mistakes in my future. Build and learn... that's what it's all about.

[Mark Dickens]

Since both holes are so close to each other, neither has the right edge distance. What I'd do (and perhaps this is me only) is that I'd flatten both out as well as I could, use neither one of them, redrill the rivet hole in an adjacent area with correct edge distance and use that for the rivet. Whether you patch it up with some JB weld later on is up to you. The main thing is to make sure that both holes are deburred so they don't propogate a crack later. Moving the rivet over another 3/8" won't hurt anything at all.

My bet is that with a little artful touch up, no-one would ever know the difference later.

Edit: Or just skip the rivet...the plane won't fall from the sky.

[wirejock]

I have never made that error! I have some ocean front property for sale too.
EDIT
Mark makes a good point. It also depends on what is going on with the substructure. If the rib is dimpled, I would use the matching hole. If not, I would do as Mark mentions.

That said, I just happen to have Vans response should it happen.
In my case, flatten the errant dimple, dimple the correct hole then drill two new holes through the substructure part on either side equally spaced and observant of edge spacing. Abandon the errant hole and fill at painting.
I do not use the c-frame spring. I have a heavy truck tire wheel chock I use for holding skins down on the male die.
YMMV and please ask Vans to get a specific answer to your build for your files.

[goatflieg]

Sent a detailed email to Vans with photos; awaiting their reply. I don't use the C-frame spring to hold the dies together. I physically hold the plunger down... and now I TRIPLE- CHECK to make sure it's where it's supposed to be. Just finished using the close-quarters dies, following their instructions carefully. They did a fine job. Ahh, hindsight.

[az_gila]

Originally Posted by wirejock

...
I do not use the c-frame spring. I have a heavy truck tire wheel chock I use for holding skins down on the male die.
....

I don't use the C-Frame spring either, but prefer to work the other way around and use the male die on the moving part.

When the nipple of the die is in the hole you know everything is lined up - gravity keeps it there.

The extra work manually holding the moving part up when relocating to the next hole is a small penalty to pay.

[Robert Anglin]

We turn the dies around and put the mail in the base and the female in the mandrill. Lay the skin on two 2X4's covered with carpet. Pick the skin up from hole to hole so you don't mare the face of the skin. Then bring the mandrill down to each hole as we see the mail die has been placed in each hole. Takes a little longer, but gives you a little safety check on each hole.
I would flatten the odd hole. finish the correct hole out, just as you would without this Bo-Bo, move over to the good side of that hole and pop another hole with edge distance, put the skin on with the two good holes and pooky up the odd flattened hole after. Pro-seal will hold well. If you like, just put a dab at the site of the odd hole, on top of the rib as you cleco the skin to the rib. Let that drop set with a peace of Skotch tape over it while you rivet the skin on, then dress it up later as you wish. Just what I would do, you mite like something other. Yours as always. R.E.A. III #80888

[Flyin'Bryan]

As Mark and others have indicated, the holes on the flatter parts of the factory pre-bent skins work best with a table or flat surface on either side of the C-Frame to support the skins on either side of the hole, put the male die in the holder and the female die in the ram. Then I hold them together as you have described, making absolutely certain that I have enough pressure to hold the ram firmly against the male die before I strike the ram.

As you know from my blog, I am a stickler for details, and some are missing from previous posts:

1. When you get to the curved parts of the skins, things get more difficult. The skin has a tendency to lift itself off of the male die due to the spring action of the bend in the skin.Then trying to get the hammer in position to hit the ram can get interesting as well. I think a helper is best in these situations to hold the skin while you focus on the ram and the hammer.You did not mention what type of table or support you are using for the skins

2. I have sworn by Cleaveland Tool's close quarter dimple die tool and have used it extensively for rib dimpling and skin dimpling in the areas where the LE curves begin. Sounds like you may have had success with the pull rivet solution and that is fine too.

3. I agree with wirejock to flatten out the dimple, but here are some details about that. If possible,and with a helper as necessary, use a back rivet plate under the skin, and make sure it is positioned correctly under the skin. Then use your flat rivet set with low pressure on the rivet gun and tap it a few times to remove the bad dimple. Your next decision depends on if you already dimpled the ribs or not, as others have pointed out. The holes are usually too close together, so you may have to drill some new holes on either side of the bad+good holes for proper edge distance, again as others have stated.

4. Don't use JB Weld to repair the old hole. Debur the bad hole as necessary after flattening out the dimple in the old hole and leave it for painting prep work later.

5. Sorry I did not reply yet to your comment/question on my blog from a few weeks back. Answer: Yes I am going to Airventure this year. Yes I will be there all week. Send me a PM or I'll reply to your build log email. I would love to say hi while you are there, especially if its your first trip to the big show.

Patch er up and build on.

[goatflieg]

I sent an email with photos to Vans Tuesday, didn't hear from them... so I called, and they said they responded... but I never got an email. I think they were confusing me with someone else, because they get a LOT of those, as you can imagine. It's no big deal... I'll flatten the bad one out and dimple the good one. He said it wasn't really necessary to straddle the error with new rivets, but I could if I wanted. I was planning to use the backrivet plate, but I think I'll carefully (and LIGHTLY) flatten it with a small hammer, rather than using the rivet gun. I've already experienced how easy it is to stretch aluminum sheet with one of my practice projects. Bryan, good to hear from you... I'll send you a PM.