Mixing Epoxy - RC Groups
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Sep 16, 2001, 08:32 PM
Registered User

Mixing Epoxy


Now that I am starting construction of my Wingo, does anyone have any tricks to mixing 5 minute epoxy? I guess I am usually not getting the mix quite right because it hardens, but has kind of a tacky surface feel long after the hardening time is up, although the bond seems to be strong enough. Is this a problem with the volume of the two components or how well mixed they are?

What I did was try to dispense equal length beads from the two tubes, then mix them together using a small wooden stick. It's hard to get the beads equal in volume because the two components aren't equally viscous and one of them spreads more than the other.

How exact does the mix need to be?

I am also planning to use some plastic knives as mixing and spreading tools. Does anyone have any favorite tools to make the job easier?

I am a rank beginner at this so apologize if I am asking the obvious.

Thanks,
Allen
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Sep 16, 2001, 09:26 PM
Rehab is for quitters
LuckyArmpit's Avatar
The 5 minute epoxy I have is from the LHS. I use equal amounts
of resin and hardner. If you use too much hardner, it sets up alot faster. For large surfaces, I use a plastic knife as you. But for small jobs, I just use a toothpick.

Dave...
Sep 16, 2001, 10:19 PM
EDF Head
Haldor's Avatar
The epoxy will harden up in ~5minutes but it wont reach full cure before 60mins. The epoxy can feel rubbery right after it start to harden, 5-10mins. It will feel tacky for atleast 30mins.

Time to harden and time to fully cure are two different things so I'd say you're not doing anything wrong.
Sep 16, 2001, 10:22 PM
Registered User
FlyingKiwi's Avatar
I just use an old ice-cream container lid (polyethylene) - the epoxy doesn't bond to it, so you can peel off the old set stuff and keep re-using it. To mix & apply, I just use some scrap 1/4" wide strips of MDF - just snap off the tip to get a new edge. Beacuse it is long, you can use the side of it to spread, or use the end to apply in spots - seems to work ok. As for proportions, I've never once measured - just squirt a couple of blobs about the right size and go for it - a little bit quicker or slower doesn't matter - just have everything setup before you do the mixing!!!

Cheers
Andrew
Sep 16, 2001, 11:18 PM
Space Coast USA
hoppy's Avatar
Allen,
If you haven't glued the body together yet, go to Walmart and get some 30min epoxy. It will give you time to mix throughly, apply, position the parts, and tape them together with masking tape. Pull the tape off after the epoxy has set. The 5 min sets to fast.

The secret to epoxy is mix, mix, mix. Ice cream sticks work well. Keep folding the material over it self, stir, fold.
hoppy
Sep 17, 2001, 02:06 AM
Tacoma, WA, USA
William A's Avatar
Ditto what Hoppy said, its hard to throughly mix amounts any larger than a finger nail size with the 5min stuff.

For mixing and apply small amounts w/ the 5min stuff, I got a large bag of popsicle sticks at the dollar store.

For larger surfaces that demand a more uniform layer, I use 30min stuff, mix w/ the sticks and apply with a small disposable brush(the metal handle kind).
Sep 17, 2001, 11:49 AM
Registered User
Thanks for all the advice. I did manage to get the fuse together with the 5 minute epoxy, but in retrospect I agree that it would have been easier with the 30 minute. I have been using plastic knives and small wooden sticks to apply it. I think I will get some 30 minute epoxy to attach the plastic fuse cover since that needs to cover a large area that might be hard to mix and apply in less than 5 minutes.

I think my previous problem (with it staying tacky) was due to not mixing it completely. In the last couple of batches I spent extra time mixing it and it seems to set a lot more solidly.

Allen
Sep 17, 2001, 11:58 AM
Registered User
Get a box of tongue depressors and vinyl gloves from the chemist, perfect for mixing and spreading, and with a glove on you can smooth off with a fingerwhilst protecting yourself from some pretty nasty chemicals.
Sep 17, 2001, 05:25 PM
Registered User
What nobody has stated yet ..is that 5 minute, 30 minute or whatever time...is "The working time" that is the amount of time you will probably (temp. makes a difference)have to use the glue as a flowing, positionable substance. The "Cure " time is a totally different thing...(again related to ambient temp.) It may be an hour or sveral or a day or so for all the chemical bonds to complete.

(I know a lot of you already know this stuff but a newbie might not)

Jim
Sep 18, 2001, 08:58 AM
Registered User
Quote:
Originally posted by SCRIV
Get a box of tongue depressors and vinyl gloves from the chemist, perfect for mixing and spreading, and with a glove on you can smooth off with a fingerwhilst protecting yourself from some pretty nasty chemicals.
'Course you may get some funny looks buying this stuff.
Sep 18, 2001, 11:51 PM
Registered User
Mike C's Avatar
I bought a big bag of popsicle sticks from Walmart for a couple of bucks in the craft section and they work great. I use a lid from a coffee can to mix on. When it hardens you can flex the lid and the epoxy just pops off. That was a tip from someone here. Give it plenty of time to set up.
Sep 19, 2001, 12:56 AM
Registered User
Thanks for all these great hints. I got the popsicle sticks, throw-away brushes, and 30 minute epoxy (for the large areas). It helped a lot. Another thing I found was some small, throw-away plastic cups (about 1 ounce size) with graduated markings. That way, for larger mixes, I put, say, 1/4 tsp of epoxy and 1/4 tsp of hardener into the cup. The cup makes mixing easy, and works especially well with the brushes.

Allen


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