Will drilling a hole in carbon tubes weaken them?

[skunkwurk]

Hi Guys,

My plane originally came with aluminum wing and stab tubes. I purchased carbon replacements to lighten the plane, the manual originaly called for a hole to be drilled and tapped for each wing panel and each stab half. I bought wooden dowels which fit the inner diameter of the carbon tube, I had planned on glueing a small piece in the corresponding tube, and then I intend to screw in a pre-tapped insert. I'm looking at this now and I'm starting to have second thoughts about possibly weakening the tube. Or possibly adding enough weight to the carbon tube to make this a moot point.

I've uploaded a image of what the threaded insert looks like. What's your guidance on this?

I appreciate your help in advance.
Sc

 

[Jetpainter]

I did the stab on my Carf Extra by gluing blind nuts in the carbon tube. But on those tubes the hole was very near the end, so I wasn't very worried about the tube breaking.

 

[skunkwurk]

I did the stab on my Carf Extra by gluing blind nuts in the carbon tube. But on those tubes the hole was very near the end, so I wasn't very worried about the tube breaking.

Thank you for the reply. Did the blind nuts go inside the tube in wood or directly into the carbon tube? Have a picture by chance?

My hole positions would be pretty far in on the tubes, that's what's worrying me.

 

[Jetpainter]

The blind nuts were epoxied inside the tube. I added milled fiberglass powder to the epoxy to make sure it stayed put.

To locate them I put it together and drilled through the stab hole into the tube till it barely went through both sides of the tube. That way I could use a long bolt that went through the one side of the tube into the blind nut then out the other side to makes sure it was in the right place and angle.

 

[skunkwurk]

The blind nuts were epoxied inside the tube. I added milled fiberglass powder to the epoxy to make sure it stayed put.

To locate them I put it together and drilled through the stab hole into the tube till it barely went through both sides of the tube. That way I could use a long bolt that went through the one side of the tube into the blind nut then out the other side to makes sure it was in the right place and angle.

Thank you.

 

[Bunky.F.Knuckle]

The further out on a CF tube the better. My Univ of Dayton crew experienced the same fate a few weeks ago. I warned them not to drill the tubes. They didn't listen, and as fate had it, wing tube broke on just a light impact to the ground. They just didn't drill a small 6-32 hole.... They went for the gusto. 1/4"!

 

[Jetpainter]

Yeah on mine they were only about 3/4" from the end and 3mm I believe. I've slept a few times since then and I never take them off so I don't remember.