For small amount, I usually do the mixing on a piece of alum foil which does not absorb or interact with the glue at all. The mixing tool is a piece of toothpick. I did not envision any mixing problem this way.

Really?????

Correct that not all are created equal but i disagree with the 1:1............

for some reason the glow end of this hobby is mostly unaware of the aerospace grade epoxy we use in the turbine side of the hobby. Hysol epoxy is a far superior product to anything Tower and most LHS have in the epoxy lineup.

9462 (white) and 9462F (gray) is an overnight (8hrs) 1:1 that is thixotropic (it doesn't sag/drip/run) so there's no need to add any fillers such as microbaloons, etc...after cure you'll pull wood/metal/fiberglass before you separate the glue joint.

E20-HP is a clear thixotropic with almost the same peal and tensil strength as the 9462 but a 20min pot life, it's a 2:1 ratio

E05-CL is a clear thixotropic high strength 1:1 ratio 5 min pot life.

the dispensing gun takes all the guesswork out of the ratio as it dispenses both equally and if you use the mixing nozzle it self mixes and you can apply it neatly like a calking gun.

You should never use anything LESS than 30 minute epoxy with microballoons.

5 minute epoxy doesn't set quite as hard as 30 minute epoxy, and you are slightly weakening things with the presence of the microballoons.

It is better to use 30 ( or even 45 minute ) set epoxy with a smaller percentage of microballoons, then allow 24 hours for everything to harden.

Agreed, but the 30 minute variety doesnt stay in place long enough to fill the gaps I described above. I can always fill in 30 minute epoxy afterwards

Will post pics when I can

Ameyam

It will not "stay in place" if it is too thin or if it cannot bind to the surfaces properly... in the latter case a bit of roughening up with sandpaper cures that.

If you are merely filling holes, without looking for strength, you can pour microballoons into the gaps then drip thin CA onto the powder.

Give the CA several hours to dry, then you can sand or work with the filled areas.

Just for fun mix up some epoxy, place it out thin, about 1/16 on wax paper. Now add some MBs and do the same thing. Let it set up for 24 hours. Now pull it off the wax paper and try to snap it in half. See what the strength of epoxy is for yourself. After you know you will be able to decide how and what to use on repairs. Epoxy may not be the best choice. I often use epoxy and a fill to smooth out the outside of a glass fuse but on the inside of the fuse I often use fiberglass and resin. A lot depends on the type of repair. I have a glass fuse on a pattern plane that requires repairs. The epoxy and MBs will just be a fill then sanded smooth, the real work will be on the inside and probably really ugly but strong.

While I agree with you about the Hysol products and I do use many of them at work, The average r/c guy is just not going to spend the extra money or make the additional effort to find it. They are going to buy what is at the the hobby shop or hardware store. This ends up being Tower, Devcon or any other low grade epoxy that is readily available. The truth is that many guys just don't build anymore and there are not alot of guys left to pass on knowledge. Just as seen here. One suggestion is to mix up some epoxy and snap it to judge strength. It's all about bond strength. The force it takes to peel the epoxy off a well prepped surface. Only once did I see mention of surface prep here and then it was just sanding with no reference to cleaning. Epoxy is just one of those widly mis-understood things we use in our hobby.

I never mix fillers with fast set epoxies for that very reason. If you are planning to use fillers, you need to use a slow set epoxy so that the epoxy has the time to be mixed and you still has time to add and mix in the filler. I would recommend using no faster than a 15 or 30 minute epoxy for that purpose. In my case, I routinely use West Systems extra slow hardener with the base resin to give me more working time with the epoxy so that parts can be repositioned as needed before the epoxy starts to harden

extra slow is the 209, it's great for huge layups but 206 (and even 205) are much better choices for parts and small layup jobs. the 209 can take up to a week before you can move parts, that's just too long to wait for those applications IMO.

+1

Even using the 209 hardener, I've never had to wait more than overnight with any build. The only time I ever had Wests fail was with 205 in a sub-50 degree garage. That being said, I normally work with spruce and birch plywood in my builds which includes many compound curves that I have to wrap ply around