Dimpling accident....

HighSchoolBuilders · #1 03-11-2009, 10:54 AM

HELP! I accidentally damaged (crack) the side of a hole with my C-Frame when dimpling, right next to the hole to be dimpled. Now I have a damaged hole and I don't know what can I do. I read a fellow builder's log and he opt for a new skin. I wonder if there is a way to fix it, short of buying a new skin.

Thanks!
Hank

Jamie · #2 03-11-2009, 11:02 AM

What skin is this?

frankh · #3 03-11-2009, 11:02 AM

Drill 2 extra extra holes either side of the damaged one,

The fix will be stronger than the original..You can put a rivet in the damaged hole for appearances sake.

Frank

HighSchoolBuilders · #4 03-11-2009, 11:05 AM

It's the RV-8, HS801PP.

The line of holes is fwd/aft oriented, do you mean one hole fwd and one aft of the damaged hole?

Thanks!
Hank

airguy · #5 03-11-2009, 11:19 AM

Welcome to the "extra hole" dimplers club - I can almost guarantee it won't be the last one you do! We've all got a few of those...

llavalle · #6 03-11-2009, 02:07 PM

Or use a DRDT-2 instead of a regular C-Frame. Use a manual squeezer instead of an air powered one... It'll take more time but you have less chances to end up doing this...

Don't get me wrong, I would trade my manual squeezer for pneumatic one any day... I'm just trying to convince myselft that buying a pneumatic squeezer is a bad idea

flion · #7 03-12-2009, 08:19 AM

There's a couple of ways to fix this. A new skin might be the easiest, if most expensive approach. Or, you can put a couple of rivets on either side of the hole (yes, fore and aft in this case). That will mess up the rivet spacing but will be safe. If you do this, flatten the bad dimple and drill out/deburr to remove the crack; then use filler to cover it up before you paint. Don't simply fill it with a rivet; that crack needs to be removed.
The other option is fussy but will leave you with a rivet in the right place. Flatten the dimple and drill out/deburr as before. Scuff the flange slightly around the rivet hole and the inside of the skin. When you assemble the skin for riveting, use Hysol adhesive to patch here. Before the Hysol sets, smooth it to match the skin (it's tough to sand later). When gluing aluminum like this, use naptha to keep everything really clean or the bond will tend to lift. When the Hysol sets, re-drill the rivet hole and countersink for the rivet. Sand the remaining Hysol to match the skin (if you smoothed it carefully and the patch hole is not large, you won't have a lot of sanding to do). Then, set the rivet. The Hysol should be sufficient bond to replace the rivet and, once painted, you won't know that the rivet isn't actually set into aluminum.

HighSchoolBuilders · #8 03-13-2009, 08:22 PM

Thanks for the advices. I opt for a new skin, cost $80 + $120 next day shipping to NYC, just happens to be in NYC on a 48 hours layover, will hand carry it back to Hong Kong.

I am sure it will not be the last dimple mistake I make, the tips will come in handy in the future! Thanks!

Hank

RScott · #9 03-14-2009, 01:31 AM

You don't need the DRDT-2. Put the male die on the bottom, put the hole over the die, hold it in place and give it a whack. The male die will hold the skin in place as long as you hold the skin down.

I have screwed up plenty of times on my plane (probably more than my share) doing the slow build wings and the tail section. This is one mistake I haven't made--so far. And you don't need at DRDT-2 to avoid making the same mistake again.

airguy · #10 03-14-2009, 09:39 AM

RScott is correct, the DRDT-2 is not magical (though I happen to love it myself). I find my best results using the DRDT-2 (and same would apply to the C-frame) with my dies reversed from his description. If you place the male dimple die on the bottom, you will have a tendency to drag the sheet metal across the male die while positioning, scratching the surface. It's purely cosmetic, but a lot of people want to avoid that. I place the male die on top, and use upward pressure on the skin to hold it in place on the male pin while dimpling. Drop it down and move to the next hole, raise it and hold it while dimpling. This worked better for me on the larger skin pieces, and no surface scratches. I can see that this technique would work better with the DRDT-2 with it's slow lever action than the C-frame which you are striking with a hammer, though.

To each their own...