How to Repair Pulled Rivet on Lower Cowl

[RoundTwo]

I need to repair two rivets that connect the aluminum bow to the fiberglass cowl of my J. Both rivets are the outermost rivets. One has pulled all the way through and the other one isn’t through yet. Is this common?

So the question is how to fabricate an effective repair on oily fiberglass and have it blend in nicely.

I have a good bit of fiberglass experience with boats and even on thin glass on my Boston Whaler, so I understand the challenges. I’m thinking the fragmented area around the rivet will need to be cut back to good, oil free glass and then taper the edges to give lots of surface area for adhesion. From there, I’m not sure if the patch should be internal, for cosmetic reasons, or external for structural reasons. Since the rivet will be pulling in, an exterior patch will have a mechanical advantage over an internal patch.

Any firsthand experience/advice would be appreciated.

[Fly Boomer]

13 minutes ago, RoundTwo said:

I need to repair two rivets that connect the aluminum bow to the fiberglass cowl of my J. Both rivets are the outermost rivets. One has pulled all the way through and the other one isn’t through yet. Is this common?

So the question is how to fabricate an effective repair on oily fiberglass and have it blend in nicely.

I have a good bit of fiberglass experience with boats and even on thin glass on my Boston Whaler, so I understand the challenges. I’m thinking the fragmented area around the rivet will need to be cut back to good, oil free glass and then taper the edges to give lots of surface area for adhesion. From there, I’m not sure if the patch should be internal, for cosmetic reasons, or external for structural reasons. Since the rivet will be pulling in, an exterior patch will have a mechanical advantage over an internal patch.

Any firsthand experience/advice would be appreciated.

I don't have an answer, but it's a nicely worded question, and I'm looking forward to answers from others with experience.  I'm sure your experience added to that of others will produce some great suggestions.  I don't have any fiberglass experience, but my cowling sure seems to take a beating, and will need help soon.

[N201MKTurbo]

Your methods are spot on. You should read 43.13-1B, but their procedures are the same as yours. One thing to consider, fixing it on the inside will have less effect on the appearance, but to do it properly, you will need to remove the whole aluminum structure inside. At that point you are repairing all the rivet holes. Kind of a big job. If you do it from the outside you can just fix the bad holes, but you will have significant paint repair to do. Either way read the Mooney maintenance manual and be sure you use the correct materials.

[PT20J]

I believe Byron  @jetdriven has done this sort of thing and might have some ideas.

[N201MKTurbo]

If the hole isn't totally destroyed, you may get away with the next size rivet.

[EricJ]

+1 that AC 43.13 shows acceptable repair methods for fiberglass/composite construction.   A "scarf patch" like you are suggesting is among the methods described.   It's worth familiarizing yourself with the composite repair section in 43.13 so that you can reference it either in the repair records of if anybody asks or gives you crap about it.

 

[RoundTwo]

47 minutes ago, N201MKTurbo said:

If the hole isn't totally destroyed, you may get away with the next size rivet.

It’s kinda crunchy around the edges, so maybe a 1/2x13 bolt.

[N201MKTurbo]

1 hour ago, RoundTwo said:

It’s kinda crunchy around the edges, so maybe a 1/2x13 bolt.

It looks like you should fix it.

[carusoam]

Find Byron’s posts on the subject…  @jetdriven

He completely refurbed the cowling in his M20J…

Lots of details from what kind of resin and fiber to use in which location and how to add structure where…

Best regards,

-a-

[RoundTwo]

5 hours ago, carusoam said:

Find Byron’s posts on the subject…  @jetdriven

He completely refurbed the cowling in his M20J…

Lots of details from what kind of resin and fiber to use in which location and how to add structure where…

Best regards,

-a-

I’ve been waiting for him to stop by.