Countersink Too Deep

[mdredmond]

Ugh. I've had this kit for four years but I'm still a beginner. Forgive, please.

Countersinking horizontal stabilizer spar flanges. Everything is great except that on the outboard hole on the rear spar, the cage slipped a bit and I countersunk too deep. The hole isn't visibly enlarged, but the countersink goes deep enough that there is a sharp inside edge.

My primary concern is safety but even if it's safe, if there will be cosmetic consequences (ripple in skin, for example) I'd rather replace the spar than not.

I've e-mailed Van's but can any of you comment on this?

Thanks!

[rv72004]

Youd have to ask Vans, but what about clecoing the skin on with a bonding filler inbetween. When it has set , you rivet? Almost a shim , but only in the countersink?

[Phil]

I'll bet you're going to be fine..

I'm guessing this is for the AN426-AD3 rivets??? The ones that hold the skin to the spar?

If so, you might be able to drill the hole out to a #30. If you have an oops rivet (1/8" Rivet - with a 3/32" rivet head) you can pop it in and no one will tell the difference.

Another option is to go ahead and make it a regular 1/8" rivet. No one will ever notice and if you're paranoid that they will, you can put some filler around the rivet and sand. That'll remove all visible references around that hole.

Phil

[Mel]

Not one person will notice a 1/8' rivet.
If they do, and ask you about it, your answer should be, "Didn't you do yours that way?"
BTW, Use a 1/8" at the same place on the other side just for symmetry.

[N941WR]

Matt,

Since you are building a real RV-9 and not the training version, I'll let you in on a little tip.

I used AN426AD4-? to rive thte F-779 in place. I figured with the extra loads that part would see, the bigger rivets might be a good thing and Van's didn't have a problem with that change.

[mdredmond]

Phil/Mel -

Thanks for the responses. Assuming Van's says it's okay, that's what I'll do - drill to #30 and use an oops rivet.


There are two issues with the hole: First, it's got a sharp inside edge. Second, it's too deep.

Drilling to #30 will solve the first problem. As for the second, I wonder if I should dimple some really thin stock and put a shim in the hole?

@Bill: What is the F-779? I don't have my blueprints with me.

[flion]

I'd fill the countersink back up with a little epoxy or Hysol and then re-drill and re-countersink. You can still drill it out to #30 to give the rivet a better bearing surface on the shank but the filler will make a more exact shim than trying to match it with thin aluminum.

[mdredmond]

I'd fill the countersink back up with a little epoxy

Not a bad idea.

I just got off the phone with Gougeon Brothers (West System) and the tech guy there said to use their G/Flex 655-K product, NOT their 'normal' 105 System epoxy. He said the G/Flex product is completely machinable and can be drilled, countersunk, tapped, etc. where the 105 product will simply shatter. Something about Tensile Elongation percentage.

I'm so overthinking this...

So now I've made my mistake on the plane and there won't be any more ;-)

[scard]

Originally Posted by mdredmond

Not a bad idea.

I just got off the phone with Gougeon Brothers (West System) and the tech guy there said to use their G/Flex 655-K product, NOT their 'normal' 105 System epoxy. He said the G/Flex product is completely machinable and can be drilled, countersunk, tapped, etc. where the 105 product will simply shatter. Something about Tensile Elongation percentage.

I'm so overthinking this...

So now I've made my mistake on the plane and there won't be any more ;-)

You are way over thinking it. Stick a piece of hardware (rivet) in the hole and be done. This one rivet isn't going to make it fall out of the sky.

[mdredmond]

Originally Posted by scard

Stick a piece of hardware (rivet) in the hole and be done. This one rivet isn't going to make it fall out of the sky.

I know. But at this point I want to avoid any cosmetic issues.