flickroll

flickroll

Well Known Member
My -8 has close to 350 hours on it. It will be going to Glo Custom the beginning of Dec for paint :D , so I am busy taking care of details that need to be fixed prior to the journey to Glo. On the rear canopy, the filler over rivet heads of a number of the rivets that connect the skirt, canopy and canopy frame together is cracking at the exterior of the fiberglass, creating a small 'circle' around where the rivet is embedded. I did not build the airplane, but suspect the rivet heads are covered with epoxy/micro. I have thought of a few options to repair:

1. Using a small Dremel bit, grind out the filler material over the rivet head. Use flox or epoxy/cabo to refill.

2. Grind out the filler, drill out the rivet, replace the rivet with a new pop rivet, and refill with flox or epoxy/cabo.

3. Grind out the filler, drill out the rivet, tap the frame for 6-32, and install screws with locktite on the threads. Then refill with flox or epoxy/cabo.

4. And yet another idea is instead of flox or epoxy/cabo in the above examples use 3M Structural Adhesive which is every bit as strong as flox but remains somewhat flexible. It ain't cheap....around 40 bucks for around 10 oz. This stuff was used extensively during the construction of the canopy of my Christen Eagle II, and I never had working rivets like this.

I am inclined to do #1 above (although maybe with 3M), thinking a stronger filler than epoxy/micro will not crack later. I know this is not the first airplane that this has happened to. Opinions on the best (most permanent) repair welcome!

Thanks
 
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repair

I'm with you on this one. go for #1. I don't see the need to replace the rivets unless there is a problem with them. you are going to have the same issues bonding on new rivets that you have now. so ya dremil them out scuff the head of the rivet with the dremil a little give a wipe with acetone or mek after you clean e'm up. you might try putting some milled fiber in your mix with the micro balloons. it gives it some tooth having those glass fibers in the mix. just a pinch for like an ounce or two. also I have had really good luck bonding epoxy to metal by wetsanding with resin and 80grit. don't know if you want to go through that much trouble doing every little rivet like though.
good luck
Erik
 
Easy fix

This is the process I used to "secure" the rivets on my cowl where I had riveted the mounting strips for Skybolt fasteners. The same process would work in your situation.

Scuff the area of the rivet and an area about 1" wide. Fill the rivets with epoxy and micro filler. Use 5 minute epoxy to speed the process. Once cured block sand flush. You can also use a catalyzed filler because of the next step.

Get some 1" wide thin glass cloth. www.cstsales.com. Cover the rivet line with the glass cloth and epoxy. Only use enough epoxy to fill the weave. You can use ply peel if you want. When cured block sand the edges and sand the cloth lightly. Feather in the edges with epoxy and micro filler or Rage or Evercoat 416.

This shouldn't take much if you used thin cloth. Sand and fill as necessary.

These rivets won't be a problem with this method. It took longer to describe how to do than to do it!!!
 
Forgot to mention....the skirt already has PPG K36 primer on it. Since this primer has a catalyst, I think all I would need to do is scuff sand the primer before doing repair work. I do like the idea of using a light cloth over the rivet line - I have some 1.45 oz stuff I got from Spruce. Done carefully with peel ply should result in a good repair with minimal work.
 
The fundamental problem sounds like working rivets. Lots of ways to patch over the top of them, but might it be best to address the fundamental problem first?
 
Dan's right

DanH said:
The fundamental problem sounds like working rivets. Lots of ways to patch over the top of them, but might it be best to address the fundamental problem first?
Click to expand...

I forgot to address this part. If indeed you have rivets that are "working" they must be locked down first. The best method utilizes Cyano acrylate glue. Commonly known as CA. I always have it for my RC stuff anyway.

If you have a hobby shop nearby, get a small bottle of thin CA. Ask if they have "foam safe," CA. If so, get that. Wick in a VERY small amount around the rivet head. I would also purchase some accelerator. This makes instant glue more instant, for lack of better description. I like the aerosol version from Great Planes. After applying the CA, spray the rivet with the accelerator. Since the rivets are close you could do 2 or 3 at a time. The accelerator will make the glue cure instantly.

Use the CA sparingly. When done the rivets aren't going anywhere.
 
Dug into a few of the rivets today. There is no filler over them, just K36 primer. I suspect the rivets themselves are OK, especially where they are squeezed in the canopy tubing. I think the root cause of what is happening is the skirt and canopy flex a little, so over time the interface between the rivet head and the skirt has fretted ever so slightly. The area where I have the biggest issue is the rear of the skirt, and the skirt used to 'buzz' in this area at high airspeeds before I applied fuzzy velcro to seal it. This high frequency buzz most likely caused the fretting. If the CA is a good cure for locking the rivet heads that would certainly be an easy fix to stop further cosmetic issues. Light glass cloth over the whole shebang would really lock everything in. Comments anyone?? Thanks
 
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