I have had nothing but trouble with epoxy Glue. I used 5 min, 15 min, 30 min and after carefully mixing them 50-50, none of them set up. They came out soft after drying overnight. I bought these glues at a hobby shop, and considered taking them all back. I even tried mixing more hardener in the mix without success.
Will" Elmers Tightbond" be suitable for gluing stress joints, like wings, tail feathers, etc, and if so, is it fuel proof? Just needed to ask,
Thanks

Yes, Titebond is fine for high stress joints. Built many a plane with it.

IME, it is SOMEWHAT resistant to glow fuel, not very resistant to gasoline.

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On the epoxy issue...see you're in Oregon. How cold is it in the shop where you're working? Extreme cold can greatly lengthen the curing time of some expoxies, ime.

I've been using epoxy glue ever since it came out - 50 yrs anyway - never had any trouble with it setting up

Somethings wrong about the temperature and humidity

I've run into the slow setting epoxy also. A couple tricks for cold shop use. First mix more than you need, a small amount for some reason doesn't want to set as quickly even though you use the same amount on the joint. The other thing is to use a couple 100W bulbs e 6 to 8 inches above the piece to speed the cure. Sometimes, the stuff just is slow to kick off and I've had it go two or more days before it was cured. I've never noticed any weakness in these slow cure joints though.

Don

Don:
I tried the gluing process in my garage, cold , about 40 degrees,, then I moved the plane into the kitchen table, ( no wife to nag me)
but had the same problem. I have just about had it with epoxy. If it wont set like it says, then I'll use Tightbond. I have never had a problem with that glue. But I do worry about fuel and it's reaction to it on stress surfaces.
I make sure I mix epoxy throughly and even add a little more hardener, same result, goey mess, never sets up. Who knows???????

Try heating it with a heat gun. The heat usually accelerates the curing process.

Ken

You know, it's been a long time, but I have seen epoxies that are not to be mixed at 50/50. If you're using a 50/50 and you have the ratios right and mixed properly, it's unlikely to cause you these difficulties.

When I mix epoxy I usually use a paper plate. One thing that I have noticed is that my mixing is sometimes lacking, so I try to avoid applying the epoxy from the edges of my mix. I've found that if I'm going to make a mistake in mixing, the problem is always around the edges of my epoxy "puddle."

If you're at 40 degrees Titebond II is going to be a little troublesome also.

The temp and humidity will cause epoxy to cure at different rates as has been said. I haven't had problems like you are having but I'm wondering if you might be mixing it in something that might cause you a problem. For instance, I paint for a living and you don't want to mix epoxy or urethane type paints in something that has a waxed surface. The wax coating of the container can stop the crosslink reaction between the chemicals in the material you're mixing.

what pdm52956 said, if you are mixing in anything with a wax coating the epoxy may not set up properly. I have never had a problem with any of the epoxys not setting up properly, even if the mix ratio was off quite a bit. Temperature effects cure time a lot, the warmer the faster up to a point well above what a human can stand.

i also have epoxy soft set problems. i use hysol, polyurethane glue, weldbond, titebond, anything to avoid using epoxy, although i use it when i have to.

I go down to a restrant supply place and pick up a sleve of 1oz plastic cups, those cheep things that the take out resturants put condiments in. A sleeve of 100 cost me about $3.00. Them and a box of long round sticks, "hardwood aplicators" that came from a medical supply. Each epoxy get mixed in a new cup and with a new stick. No contamination at all, and the cost is about four cents per batch.

On the heat, you need to keep the epoxy below 140F. Cured epoxy starts to break down a 150F or so. I try to keep it down to about 120F maxum. At that temp, you can cure epoxy without a hardner, almost.

Don

I took the advice of campgems,.. I bought new paper plates, wax free type. I did tests today with 15 min- 30 min and 60 min with different glues. The hobby shop glue set up hard as a rock in the required time. The Ace Hardware Glue failed in set up time, and after 6 hours, the 60 Min glue is still tacky. So those will go back to Ace Hardware. Ace's 5 Minute and 15 min, worked ok. The tightbond epoxy set up after an extra hour . I was mixing these glues in Paper plates and it improved 98%. , the results were
not scientific, just at house temp. around 68-70 degrees. So I guess I'll be getting rid of plastic wrapping containers now. Other plastic may be ok, but I'll stay with what works for now.

Use 30 min epoxy

The 5 min has problems for most of us in modeling. Some say it is bittle and others say it is is not fuel proof. Others say it doesn't give them enough assembly time

I've heard that wax paper can foul an epoxy before. But in my experience its never been a problem and is infact, my preferred surface to mix a small dab of epoxy up. Most of the time I use small coffee stirrers (plastic straws) to mix with. For a larger batch such as when fuel proofing a firewall or tank compartment I use left over plastic pudding/yogurt cups and popcicle sticks.

Whenever I've had a "soft pour" where the epoxy either doesn't cure or comes out "rubbery" I now believe its the result of too much hardener. When I use a flat surface like a paper plate or piece of wax paper I make a small puddle of resin and then right next to it I make a small puddle of hardener. Then mix together thoroughly folding it over, scraping together, and stirring well. Practice a few times and when uncertain use just a tad less hardener than resin.

Its difficult to believe when I've used graduated measuring cups I've had the worst luck. Just eyeballing small puddles has been the most reliable. I also prefer 30 minute and 15 minute epoxy and use nothing faster now. I've had just as good results with Tower Hobbies brand as I have name brands but I only use those sold in hobby shops and not the hardware store stuff and I just flat out avoid the stuff packaged in double-barrel syringes.

I'm much more confident than I used to be yet always have a feeling of relief when an epoxy takes a good set. And when I'm going to hang an engine of 1hp or more on it and me stand in front of it to start it up I want a good epoxied firewall keeping that prop in check.

Practice with small batches and see if you don't start to feel better about it.

Regards,

Clay

It funny, w8ye, I use 5 minute for most everything. I don't use the ace brand, but Devcon 5 minute. The short pot life is an issue, but I've goten to where I can time the project to not run into kick off problems. doing the dubro flat hinges, I limit myself to 5 slots maximum. That is enough to get the hinges in one aileron on a 4*60 size plane, Not the wing and aileron, but all of one part. I use the Devcon 5 minute for fuel proofing the engine and tank area, I mix up an ounce or more, then add alcohol to it to thin it out. Even though it is thin, you have to watch the time or it kicks off on you.

Brittle epoxy is a sign of to much hardner. Sticky epoxy could have used some more, but it will eventually harden OK, some times taking over a couple days if it is cold.

Ive used epoxy quite a bit over the last 20 years. I've used it for inlaying Opal in rings, making Opal doublets and then getting out of that business and back into RC, I've used a bunch of expoy in building.

Things I've learned. Buy small amonts. The little tubes cost more per OZ, but unless you are going to use up a tube in a couple months, it will save you greif vs buing the large containers. An unopened set of foil tubes will last for several years. I've still got a couple from when I had my store which closed in 99. They are the Epoxy 330 and Epoxy 220 brands and although they may be a bit slow in kicking off now, they are still good. Once opened though the life goes down hill quickly.

I've also found that the longer the epoxy pot life, the better bond and the stronger it is. When I was faceting gemstones, I ran out of 5 mintue epoxy, but the hardware store across the street had it. I ran over to pick up some and discoverd they had a 60 second epoxy. WOW that would increase my productivity by a bunch, or so I thought. I picked up a set and dopped up some stones to facet. What an expensive experment. The stuff did kick off in about 60 seconds. Great. However, the bond to the stones was awful. In addition to not bonding to the stones, the cured epoxy had the hardness of a pencil eraser. Very flexable. Not good at all for precession faceting

My stock Epoxy now is Devcon 5 minute and Devcon 30 minute. I've never had an issue with either when mixed right and given enough heat to kick off completely. If I am in a building frenzy, I get the larger bottles, but after a couple months I expect a bit of problems with slow cure and kick up the heat a bit.

One last thing, using Epoxy over CA, if the Ca hasn't had a few hours to finish off will sometimes cause the epoxy to not cure correctly. Just keep that in mind.

Don

I've used epoxy since I think the late 50's

I've always used 30 min

All these years all I've read in Magazines and on the Internet is that 5 min is brittle and not fuel proof.

I wouldn't know, I never used 5 min.

Are all these people wrong?

One thing that I've noticed, don't make the mistake I once made. I mixed 30 min epoxy with 2 hour hardener (maybe vice a versa). Lousy is the only way I can describe how it came out.

Some of them may be wrong. It depends on their experience. I doubt that any of the reports are intentionaly mis-statiing the facts. I'm just passing on my experience. As you don't and haven't used 5 min, how can you state it is brittle and not fuel proof when so many others have had success with it, including myself.

Don

So this is why the faster 5 min epoxy is not as good as the 30 min? Penetration & bond?

Though I've used epoxy for many years, I'm afraid I don't have as much over all experience with it as you do.

I had to reinforce my Tribute 3 weeks ago. I used epoxy but I guess I didn’t make the correct mix. After 24 hours it was still like rubber. I placed the plane on top of our oilheater (+ approx. 45 degrees Celsius) for 4 days, and it finally became hard.

I was recently told, that it is no longer allowed to use epoxy glue on 1:1 scale planes made of wood. They must use white carpenter glue (I don’t know if that’s the right name), because the epoxy glue doesn’t penetrate into the wood – even under pressure - like white carpenter glue does.

Of course you will have to use epoxy glue where you have fuel or have to glue wood and another material together. (Araldit 24 hour should be even better than epoxy and never use Araldit 30 minutes). In that case, it’s advisable to make a lot of small cuts with a sharp knife in the wood, to get the biggest surface as possible. Sand paper will not make the surface rough enough.

Its advice able to have glue that’s flexible when it’s dries up (elastic glue sealants?). The longer it takes to dry up, the more flexible it is – so I was told.

When it comes to white carpenter glue, I was only able to find one type of glue here in Denmark that dries up flexible. The name is Casco Trælim Vinter 3303. Here is the data sheet translated to English with Goggle Translate:
http://translate.google.com/translat...state0=&swap=1

(The Danish word “limfuge” is “glue sealants” in English – correct me if I’m wrong).

http://www.cascoadhesives.com/

I don’t know anything about glue from RC manufactures.