Epoxy for repairs and oops

I have seen a bunch of threads refer to using epoxy to make minor repairs, sometimes I have read the term structural epoxy.

Some examples of repairs are: filling an over countersunk hole and redrilling, or filling it with epoxy, then setting the dimple and rivet wet (to fill the void), or when using a doubler on a enlarged hole, setting the rivet with epoxy wet so that it fills any void.

I assume you want something rigid, but not so rigid that it is brittle and will crumble when the parts invariably expand and contract.

I'm looking for what are the specific epoxies people are talking about when doing the above types of repairs. Sure there is the clear 5 minute stuff at the local store, but is that appropriate?

Thanks!

i never really used jb weld much before i saw a u tube with pretty extensive tests for adhesives. since then i will use it for small ''touch up''. i have used it with micro bubbles and flox. my main concern has been a good bond and strong enough to not develop cracks. way easier than getting out the scale and then throwing away 90% of west systems epoxy you mixed. jb is made to set up very slow [hours] so that probably contributes to its good performance.
years ago , before airplanes, it was recommended to me to fix a crack in the casting of an inboard/outboard. it held for years, never leaked a drop of water.

I know of a couple structural epoxies that are used. My mentor uses one and I use the other. He's tested them and verified their strength with his test coupons and mine.

3M 2216 B/A

and

West Systems thickened G/Flex. We haven't tested the unthickened version.

The prep we're using has been significant abrasion and a solvent wipe.

The spec sheet mentions that 2216 B/A is suitable for acrylic, too, with a slightly different prep and somewhat lower strength.

If you plan to use either, you should download the data sheets and instructions and safety information first.

Note that filling a hole and attempting to drive a rivet with the epoxy still wet will probably lead to a bad rivet that might even be glued in. Not recommended. I never rivet a wet joint. Not ever.

Let the epoxy cure first. However, a better plan in general is to make another rivet hole, a good one, nearby and just make a cosmetic fill of the damaged hole.

Dave

Thanks guys so far.

Why not wet? Isn't that how we do the fuel tanks with sealant? Riveting wet would mean all of the excess is squeezed out and all that remains is "filler".

The place where I would want to use it has no room for another hole.

You could just go up a rivet size. No one will ever see it.

Carl

Ender said:

Thanks guys so far.

Why not wet? Isn't that how we do the fuel tanks with sealant? Riveting wet would mean all of the excess is squeezed out and all that remains is "filler".

The place where I would want to use it has no room for another hole.

Click to expand...

The OP was discussing an oversize hole, and riveting it with the hole filled with epoxy and then the rivet, wet, is a good way to get a buggered up rivet. As Carl suggested, go to a larger rivet.

This isn't at all a fix for an oversize hole. Even if you rivet it cured, that's a non-structural joint, because epoxy has a drastically lower bearing strength than aluminum. Here, the goal is not to make it seal against fuel, it's to develop shear strength, a totally different thing.

In your case, better call Van's support and ask for advice.

Dave

Thanks for the replies.

Going up a rivet size isn't an option due to edge distance. This is on one of those one rivet flanges that is on a curved edge of a bulkhead.

Talked with Vans and they agreed on the doubler, they didn't say anything about Epoxy.

Where the epoxy idea came from was a big jet AnP. They suggested an epoxy in order to fill any void left over. It's not meant to be structural, just to keep everything tight as the metal expands and contracts over time.

I guess what you folks are saying is that when someone has said to use a structural epoxy in other posts, they mean something that is filled, cured, sanded, and redrilled - as opposed to doing anything wet.

I do understand your point about not doing it wet, essentially there is no way to get that rivet out once its cured in the future if anything were to happen.

Ender said:

I have seen a bunch of threads refer to using epoxy to make minor repairs, sometimes I have read the term structural epoxy.

Some examples of repairs are: filling an over countersunk hole and redrilling, or filling it with epoxy, then setting the dimple and rivet wet (to fill the void), or when using a doubler on a enlarged hole, setting the rivet with epoxy wet so that it fills any void.

I assume you want something rigid, but not so rigid that it is brittle and will crumble when the parts invariably expand and contract.

I'm looking for what are the specific epoxies people are talking about when doing the above types of repairs. Sure there is the clear 5 minute stuff at the local store, but is that appropriate?

Thanks!

Click to expand...

I think this depends on where the fiberglass part. On thin part around the empennage, you can reinforce the fiberglass with a small round ~ 1" dia layer on the back side. The hole can be refilled using a mixture of epoxy and cotton flox. This will make the hole as strong as the fiberglass surrounding and you can redrill and countersink dimple. Aircraft Spruce is having a 50% sale of West System epoxy at the moment. The 5 min epoxy from HomeDepot should be okay for small holes but for anything bigger that requires more layup, you should be using the slow epoxy.