I'v been building models for how long and what did I do last night but screew things up again. Some how didnt add egnouf hardener to my two hour expoxying of two wing halfs. Now I cant seperate them, however when I looked at the tray I mixed it all up in the mixture was kinda soft. Im thinking of drilling a few holes around the joining area and injecting it with thin CA. Since I cant seperate the two wings this seems like my only viable option. Anythoughs people? Thanks!

Add a little heat, and give it another day. It should harden. Also, keep it someplace warm.

You can also use your heat gun, and take the epoxy off. Heat it up good and slide the parts apart, then heat it more and get all the epoxy off and do it over. You don't want to fly it with weak epoxy.

I would start like Mike said first and put it in a heated room and give it another day and see if it gets hard. It won't be full streanght, but will be good enough, if it doesn't, then remove it all and do it over. Drilling holes and putting in CA won't give you any streangth.

Don't do it half way and have it come apart. Take the time to do it right.

If you add heat - take it apart - don't rely on extra heat to harden epoxy.

It will cure with extra heat but looses a LOT of strength. You may/may not notice it on a model - but I started using epoxy in the building of full scale wooden and fiberglass boats and adding heat totally destroys the strength of the epoxy "if" you didn't add enough hardener.

Remember heat is a *byproduct* of the actual chemical process of the epoxy curing. The heat will speed up the process etc...but the heat will not cure the epoxy only part without the hardner to supply the necessary chemical reaction.

I cant remove the halfs, there is also a joiner use of plywood. Too much into the halfs to get them apart. This is a nightmare ahhhh.

If you can't get them apart, and there is a substantial plywood dihedral joiner in there, I would suggest that you fiberglass the center section with fairly heavy glass (like 6 oz.) and slow dry epoxy. Then fly it. Many of the older "jet style" pattern planes relied on only the glassed center to hold the two halves together and they held up to high speeds and pretty high "G" forces.

Clair Sieverling

Dangit Man, if you can't get it apart with heat and pulling on it then it's probably plenty strong enough to fly. maybe not but if you use the glass cloth and some 30 min epoxy?? I'd fly it myself.

Miloh.

HOLD ON THERE........
Before you start ripping things apart give the original glue job some time. Unless you were drastically short of the amount of catalyst (hardener) the epoxy will reach a full cure with intended strength. If your mix from the night before was still tacky, look at it in another day or two. Even with a significant lack of hardener, the epoxy will reach full cure...just takes more time. Also, those joined surfaces you can't see are not as soft/tacky as the stuff in your mix pan.
Heat may speed cure but it would take low/long exposure to help. The safest way to use heat would be something like putting the assembly inside a closed up car in the sun on a hot day. Generally, the epoxy will start to lose strength at close to 300 degrees and by 350 it's history.
Jim

Listen to Miloh. Borzak is way wrong on his info. An epoxy gets all it's strength from the resin. The hardener is just a catalyst to cure the resin. In the building of simple model airplanes of wood or plastic, there not exotic epoxy adhesives used. Most recommend a 50/50 mixture of resin to hardener. But the same epoxy mixed 90/10 would eventually cure with equal strength with enough time.

No wonder boats don't fly.

I tell you what you do then.

Make 3 exact jigs to text the above "theory" and see what happens.

1. Epoxy the first one with 90% epoxy and 10% harderner of an epoxy labaled 1:1 and see how long it takes to cure...if it cures.

2. Epoxy the 2nd one with the same mixture of 90/10.

3. Epoxy the 3rd one with 50/50.

After the first day heat the first example with your heat gun.

After the 3rd day "if" the first two have cured to touch (may/may not still be tacky depending on your climate). Then do what all good people do who want to find out about strength - do a destructive test. Odds are the first 2 will break loose at the epoxy line and the 3rd example will break the wood.

Remember to use a large enough piece of wood with an adequate glue line to put some actual stress on the joint.

Remember your talking about the wing joint of a plane here - not a servo tray.

When your done come back and post the results.

It's the assbackwards example of people who put MORE hardnerer in thinking the epoxy will cure harder/faster/better etc.. it won't.

Also remember that heat is "generated" by the cure - heating is not what causes the cure - but rather a chemical reation between the hardner and the epoxy. If it was the other way around you could simply spread epoxy with no hardner and apply heat from a heat gun to cure -- you can't.

If you want to find out some real "facts" about epoxy and ultimate strengths of glued connections check out the West Epoxy systems website they have some wonderful examples of what happens when you don't mix per instructions...

Will it hold? - Probably .... but why not guarantee it with a good glue joint. Ultimatlely it's up to you to decide if you want to trust YOUR airplane to a faulty epoxy joint

Whatever you decide to do - be VERY careful heating epoxy to speed up the cure (yes heat speeds up the cure but can't replace missing hardner) as adding heat is the number one recommended (by manafactures) way of REMOVING epoxy. So that right there tells you adding heat is not a very good thing to do.

Borzak!!

Your correct in the scientific sense. I to have extensive experience with west systems epoxy being in the boat business.
All I was trying to say is in this particular case if the man can't get it back apart by heating and pulling, purposely trying to break the joint at the glue it's most likely strong enough to fly.
Remember this joint is there to keep the wings together not protect it from water infiltration.

Miloh.

JRPNDE is essentially correct. as long as you don't exceed about 300 degrees, you will not weaken the bond. Epoxy bonds are a polymerization process and once done ( regardless of speed) the strength is the same. Yes, mild heat accelerates the cure time and so the comment, add heat, is good advice and will not weaken the joint if done in moderation (less than about 300 degrees).

I would poor hardner into a drug syringe and using the needle squirt it into areas that you can get at.

Job done