CVN-71

I'm building my first airplane kit. Yes I love building, they'll be no ARF's for me. Anyway I mixed upsome epoxy to mount the stab and fin. After letting them sit for 3 days I went to pick them up and look at my fine work. OK not so fine the stab came off and the epoxy was just tacky at best.
So here's my question, How do I get the old epoxy off so I can re-do it? I've just got a gummy mess back there and I HATE IT.
Please help a newbie to airplane kits.

Thanks
Randy

tuwood

hmm, ok I have a dumb question; did you mix the hardener with the resin?

I'm not sure about the best way to get the non hardened resin off, but a heat gun works on cured (hard) epoxy. I know alcohol helps thin out the resin when using it for things like fuel proofing but I'm not sure if that will mess up the wood.
I'll defer to the more experienced to assist on that matter.

tashley

My Feedback: (9)

Since it's still gummy you can more than likely scrub it off with a little alcohol and a lot of patience. Then you need to find out why the batch didn't kick off. Mismatched quantities of part A and part B, old epoxy, adding alcohol to thin before being mixed properly?

CVN-71

Guess I'll start rubbing..[] This was my fault. After fuelproofing the fire wall I mixed up another bacth in one of the same cups. I think I just got the mixture off. I can tell ya that wont happen again.

Square Nozzle

My Feedback: (1)

Denatured alcohol should remove the uncured mess with no trouble. A word of caution, the mix ration on various brands of epoxy varies. I use West Systems exclusively and the ratio is 5 parts epoxy to 1 part catalyst. A lot of the hobby type epoxy is 1 to 1. Be sure you use the correct ratio.

For general construction in areas not subject to fuel contact use alaphatic resin glue like Tite Bond or Elmers wood glues. Epoxy will not give you a stronger joint. The wood will fail long before the glue joint, with either glue. We typically use epoxy in the engine mount area, firewall, tank area and wing center section if you are using fiberglass to reinforce it. Resin glue everywhere else.

Teachu2

My Feedback: (133)

You can use a credit card to scrape off the majority of the mess, then wipe with denatured alcohol. It doesn't need to be perfectly bare wood - just do the best you can. Use properly mixed fresh epoxy and it'll absorb and cure the rest.

tashley

My Feedback: (9)

Unless I'm mixing large amounts of epoxy like West finishing resin I just use a flat surface like a cofffee can lid, paper plate, etc.. Then I can see well enough to get my portions right.

CVN-71

Thanks guys. I'll get some denatured alcohol and get it off. I used mesuring cups, but like I said I had mixed in one earlier and it might of had some left in it. You can bet this next batch will be mixed PERFECT..
Thanks again for the input.

Randy

mstroh3961

My Feedback: (4)

Randy, Do a test batch, and spread it out on a piece of news paper. If it sets up properly your good to go.

saramos

I would recommend using a fresh mixing cup for every batch. Old epoxy mixed with fresh epoxy can do weird things. I get 1 oz, and 2 oz plastic cups at a chain called Smart & final. And for when I am out, and need a few really really cheap, I have lunch at the local taco/burrito shop and pick up a couple of extra cups from the salsa bar.

Scott

CVN-71

I use the little medication cups from my LHS. Just did'nt have anymore when I did this part. Went a bought 50 cup last night. Funny thing though when I got home last night after work I went to the shop to look(cry) over the pieces and start to clean the old epoxy off and it was dried(cured) on both pieces.
So no I have another question. Now that this epoxy has dried up do I still need to get it off, or will the new batch I mix up this weekend stick or bond with the old?

Thanks
Randy

BillS

Randy,

I would not destroy the previous work. However I would consider putting toothpick dowels in the stabilizer and fin structural areas as just in case reinforcement.

Bill

Square Nozzle

My Feedback: (1)

I would simply sand the glue surfaces with 100 grit or courser sand paper and re-glue it. Just roughen it to kill the gloss and remove any wax residue from the cured epoxy.

Then when you fly it, ask everyone to stay back and keep their eyes on the plane.

Intruder38

I've been building for a few years and, in that time, I've had share of "tacky" epoxy. I also found that very rarely did I ever need a lot of the stuff to do what I needed done. Somewhere along the line I discovered/learned/heard (not sure which applies here) that for smaller amounts if I drew two adjoining circles on a piece of paper, filled one with resin and one with hardener, I got a perfect mix every time (and I could test the cure of the epoxy on what was left over). I use coins from a dime to a half-dollar to handle the amount of epoxy I need for any particular application. A hole template works for larger amounts on those rare occasions when I need more.