HS attach issue discovered!

[MK77]

Hi All,

Here's an issue I just discovered on the RV-7 project that I'm completing. Seems the previous builder broke a drill bit off in the fuselage while trying to drill the holes to attach the HS to the fuse. Looks like he then tried to drill the broken bit out, did more damage and didn't manage to get the bit out in the end. Here's a pic:

https://drive.google.com/file/d/1qu3...ew?usp=sharing

The hole doesn't go through the longeron but I have no idea how deep the drill bit is embedded. He re-drilled the hole in a new spot, but it's REALLY close to the bend in the angle. No room to get a nylock on, only a metal lock nut. You'd have to grind down a washer to fit. Here's a view from underneath:

https://drive.google.com/file/d/10Qj...ew?usp=sharing

To make matters worse yet, the hole that is drilled isn't exactly perfectly perpendicular and the bolt head is raised on one side when you put it in.

Thoughts?

MK

[lr172]

ideas sent via PM

[BillL]

This is a critical structural area, you might want to contact Vans on Monday. I would not leave that drill tip in there. Either drill a punch hole from the inside for a small pin punch or get it out with nitric acid. It won't eat the aluminum, but don't leave it unattended. A drop or two should be plenty. Rinse with mineral free water.

Worth what you paid for it.

[Larco]

An MS21042 nut might be good for close quarters if you decide the longeron is ok.
Larry

[nippaero]

Hi Matt,

Don't Panic! I had a similar issue with an RV-6 I am working on. The previous builder did not drill the holes in the correct location and the bolts did not go through the longhorns. I spoke to Vans and we came up with a solution that other builders have used.

This is a critical area and you want the HS to be securely attached to the longhorn/airframe.

I am going to make some brackets that will allow for a secure attachment. Look at the picture in post #6 of this thread.

http://www.vansairforce.com/communit...d.php?t=130785

I believe this was a common mistake in some of the early RV-6 kits because there was so much variation in builds before the pre-punched days. The hole to longhorn clearances were very tight.

I hope that helps. Good luck!

[MK77]

Thanks for the insights! I did contact Vans and they responded with a similar fix as some of the ideas mentioned here. Basically removing the rivets from aft deck / longeron on the affected side and riveting a 1/8" x 3/4" strap on top. Then re-drilling the attach hole thru that. In the process I'm going to try to straighten the hole a little so it's perpendicular and use a MS21042 nut.

Vans didn't say anything about trying to remove the drill bit. What's the concern with that?

Matt

[Andrew M]

Leaving the drill bit in is willful ignorance, although ignORance can be bliss sometimes. Generally good practices require removing and or blending damage prior to repairing, just so you know what you got.

[BillL]

Originally Posted by MK77

<snip> Vans didn't say anything about trying to remove the drill bit. What's the concern with that?

Matt

Unquantified, but the small holes and a sharp, hard, steel tip (dissimilar materials) in aluminum could affect a stress riser, and/or corrosion. So, I would take measures to remove it, smooth the hole, and then, move on.

You want that bird to be airworthy for a long time.

[RV7A Flyer]

Originally Posted by MK77

Vans didn't say anything about trying to remove the drill bit. What's the concern with that?

Matt

There's right, and then there's not right. Set your standards high...

[MK77]

Not really a matter of standards, I was more so concerned with doing more damage to the longeron in an effort to get it out (which the OB clearly did and STILL didn't get it out). Since it's not completely drilled thru the longeron I guess I'm hesitant to do more drilling from the bottom to try to extract it. Maybe the acid... or just carefully remove some material around it until I can grip it and wiggle it out then smooth the damaged area.