If I'm using towerhobbies brand "30-minute" epoxy then once I mix it, how much time do I have before it becomes too sticky to use? Or how much time am I supposed to have to apply it and stick the parts together?

I know this seems like a dumb question, but I've mixed three batches so far while assembling my first ARF and it seems that I only have 15 minutes to use the mix before it becomes too sticky to apply or maneuver pieces into position. On the third batch I cooled the bottles down and it didn't seem to affect anything.

G'day Mate,
The trick to using Epoxy, is to only mix a small amount at a time, just enough for what you need, the larger the amount mixed, the more heat it produces, because of the chemical reaction, & the faster it goes off. This is true whether it is 5 minute, 15 or 30 minute, if you find that you need a bit more, if you didn't mix enough to start with, just mix another small amount to finish the job.
Also, hot weather, makes it go off quicker too, obviously.
So, for instance, you were glueing 8 pinned hinges into a wing for ailerons, 4 per side, mix enough 30 minute epoxy to use for 8 hinges, you won't need much, & stick the hinges into the wing side first, then let it dry, & mix another amount to use on the aileron side, it is better to mix a bit more, than to have it go off before you can use it.

15 to 20 minute pot life sounds about right for 30 minute epoxy. Remember that it 'sets up' in about 30 minutes, so its working life will be much shorter. It doesnt go from thin and workable to set up in .028342 seconds right at the 30 minute mark. it cures slowly until you simply cant work with it any more.

What he said.

I've heard "heating" it with something like your gun for covering material will allow to it "flow" better.. but I assume due to the heating it will go off quite quickly once removed from the heat.
Mike

For what it's worth:

Think ahead about everything you want to epoxy and get all parts test-fitted and ready. Have all your application tools ready. Then, mix your epoxy and work effeciently but quickly, don't stop to answer the phone. .

So just plan ahead and get everything set as quickly as you can. Using this method, I don't even use 30 minute epoxy, unless it's something I need some time to carefully set up clamps, etc.

Seems it always goes farther than the amount I mix up, I always end up throwing out a scrap of cardboard with a scrap piece of balsa as a mixing stick hardened onto it, with more epoxy than what ended up on the airplane.

To slow down the setting time and extend the pot life cool down the MIXED EPOXY.

However as everyone else says just mix small quantities and use as you need.

Buy a box of toothpicks and a pad of post-it notes. Mix what you need for a few minutes work. Discard toothpick and post-it.

I use wooden coffee stiring sticks and the small dose cups that hospitals use to dispense pills.. about a half ounce in size and just fine for mixing epoxy. I found the cups at a novelty store that sells party products. That way, you can mix only a small amount, less than a half ounce at a time, and use it right away. If you want to find out how long it takes before it becomes unusable, mix a small batch, put a stiring stick or a toothpick in the batch and wait a few minutes (keep an eye on your watch or clock). When you the batch gets the point where you cannot move the stick to the point where you cannot spread it out, then it's pretty much into the cure and unusable. Then you will know how long it will take for your particular batch of epoxy to cure.

DS.

What I use for holding the epoxy is those paper bowls you get a fast food restaurants to hold your squirts of ketchup. I use whats left of a push rod wire to mix the epoxy and also for the applicator. I twirl the rod in the epoxy to collect some then apply. This allows me to dab just a small amount where I need it and the rod is long so I can get the epoxy in those hard to reach spots. Clean up is easy - wipe off the wire with a paper towel, throw the paper bowl away.

Thanks everyone for your input. It is much appreciated.

Or, you could always use polyurethane glue instead. Stronger, lighter, nothing to mix, and much easier to work with IMO.

Using cups makes the situation worse, along with high ambient temperatures. Mix it on a flat suface and gather it with your application tool as needed. To measure lay it in lines the same length and thickness. With this method you will quikly learn how much you need for a certain length of glue line. Works for me.

if you do not have enough time with the 30 minute epoxy then you can try 60 minute epoxy it will seep onto the wood a bit more and make a stronger joint.

Need more information on this please. What polyurethane glue are you referring to?