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Large Hole in HS

jhearnsberger

Active Member
We accidentally dimpled the skin just below the stringer. It was cracked and had to be drilled and dimpled to a size 4 rivet. A friend suggested putting a small piece of metal on the bottom of the hole before riveting. My rivet folded over on me and after drilling it out I now have a hole that is about 3/16" in diameter with an 1/8" crack or tear on the right side of the hole. A very small crack on the bottom of the hole and on the left.

I have wondered about drilling the hole out to 5/16" or 3/8", putting a small strip of metal beneath the hole and put a flush rivet through on each side of the hole, then covering the ugliness up with bondo before painting??

Any suggestions would be appreciated.

hole_in_hs.gif
 
Jake,
One solution would be to epoxy or proseal in-place a small, thin (say .016, but any scrap will do) piece of aluminum to cover the hole on the inside and then use micro (epoxy and microballoons) to fill the hole on the outside. Don't use Bondo. Once sanded and painted you'll never know it was there.
 
I have wondered about drilling the hole out to 5/16" or 3/8", putting a small strip of metal beneath the hole and put a flush rivet through on each side of the hole, then covering the ugliness up with bondo before painting??

I would do this and then do what Todd said for the filling instead of the bondo.
 
We accidentally dimpled the skin just below the stringer. It was cracked and had to be drilled and dimpled to a size 4 rivet. A friend suggested putting a small piece of metal on the bottom of the hole before riveting. My rivet folded over on me and after drilling it out I now have a hole that is about 3/16" in diameter with an 1/8" crack or tear on the right side of the hole. A very small crack on the bottom of the hole and on the left.

I have wondered about drilling the hole out to 5/16" or 3/8", putting a small strip of metal beneath the hole and put a flush rivet through on each side of the hole, then covering the ugliness up with bondo before painting??

Any suggestions would be appreciated.

hole_in_hs.gif

Not the end of the world. Your plan to drill it to a nice round (deburred) hole, then back it with a riveted aluminum strip is fine. Fill it with micro/epoxy, not bondo. A couple of reasons - micro/epoxy doesn't shrink over time like epoxy. Also, it's lighter (which won't amount to much on this application, but on the entire project might add up to a little weight savings).
 
Not the end of the world. Your plan to drill it to a nice round (deburred) hole, then back it with a riveted aluminum strip is fine. Fill it with micro/epoxy, not bondo. A couple of reasons - micro/epoxy doesn't shrink over time like epoxy. Also, it's lighter (which won't amount to much on this application, but on the entire project might add up to a little weight savings).

I agree but I would use something a bit heavier than .016 material. You want the patch to be stiff and stable to prevent filler from breaking out over time. A thicker patch in this small of a size will hardly be much weight difference.
 
filler breaking out?

After drilling the hole to 3/8", the stringer covers up a tenth of the hole. I have the plate butted up against the stringer with a dimpled hole on each side.

There is a hairline space between the stringer and the plate.

Are you saying that the filler could break out over time?
 
It's possible, but not likely with such a small area, especially if you steer clear of Bondo. Also, don't bother filling in the hole until you're working on something else like your fairings, where you need to mix up a batch of filler or Micro, otherwise most of what you mix up will go to waste.
 
Not your father's Bondo

I would like to hear from others like me who have used Bondo (lite) and have had no problems after 830 hours of flying. I think the stuff is getting a bad name from people who have never used it.
 
I would like to hear from others like me who have used Bondo (lite) and have had no problems after 830 hours of flying. I think the stuff is getting a bad name from people who have never used it.

I agree. The auto body fillers have come a long way over the last 25 years.
 
I would like to hear from others like me who have used Bondo (lite) and have had no problems after 830 hours of flying. I think the stuff is getting a bad name from people who have never used it.

I agree. I've seen lightweight types of Bondo that used the blue catalyst go for years & years without a sign of shrinkage or cracking. And it's still not cracking or shrinking.

L.Adamson --- RV6A
 
Proper bondo usage is all about using a quality brand (more expensive; you get what you pay for...) to start with, and not expecting it to do something it is not designed for. Follow the mixing instructions, apply only to a clean and properly prepared surface, mix correctly, and keep the film build to a minimum, and you will be fine.

That said, in this application I would still use an epoxy/micro/flox mixture to repair this hole.

Brad Simmons
Airframes Inc.
Milan, TN
 
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