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Getting epoxy in a hairline crack

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Old 06-25-2017, 02:33 PM
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Eaglepilot2
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Default Getting epoxy in a hairline crack

As the title states. Does anyone have a good way to get epoxy into a hairline crack? I have a vertical stab that I need to do. My first thought is to heat it so it's very thin, but was wondering if anyone had a better way, or a sure way to make sure it's deep enough for good coverage.
Thanks for any help.
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Old 06-25-2017, 02:57 PM
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Dealt with it by slightly reducing Zap finishing resin with denatured alcohol , use a piece of G-10 as a squeegee . Let gravity do what it does .
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Old 06-25-2017, 02:59 PM
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Ca would be better for a hair line crack I would think, but using something like a game card or thin credit card and go back and forth over the crack would force the glue in. Then clean the area of excess being careful to not get anything in the crack.
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Old 06-25-2017, 03:04 PM
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The problem I have with ca is that it has a mind of its own about where it goes and runs and its non foregiving .
We've all likely had that experience .
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Old 06-25-2017, 03:50 PM
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Quote:
Originally Posted by jetmaven View Post
Dealt with it by slightly reducing Zap finishing resin with denatured alcohol , use a piece of G-10 as a squeegee . Let gravity do what it does .
I don't like thinning epoxy when it doesn't have enough exposure to the air for the thinner (alcohol or something else) to completely evaporate. If the solvent can't evaporate, it makes the epoxy jell-like and weaker.

I would heat the epoxy slightly and work it in back forth with a squeege as suggested. Use at least 30 minute epoxy to give you enough working time...

Bob
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Old 06-25-2017, 03:55 PM
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My experience with reduced finishing resins has been excellent , it cures as it should , sands well and does not become
gummy .
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Old 06-25-2017, 04:14 PM
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Thanks for the suggestions. I should have mentioned it has a foam core, so CA isn't really an option. I can flex it enough to open it about 1/16" at its widest and it tapers down to little or no opening on each end. Looks like there may be several ways to do it, just need to work it in.
Thanks again for all your help!
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Old 06-25-2017, 04:18 PM
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Use medium viscosity Foam Safe CA.
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Old 06-25-2017, 04:21 PM
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If you can flex like that, use a syringe and force it into the crack, when you relax it the excess will ooze out and then just clean up.
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Old 06-25-2017, 05:02 PM
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Quote:
Originally Posted by big fred View Post
If you can flex like that, use a syringe and force it into the crack, when you relax it the excess will ooze out and then just clean up.
I actually thought about that, but how difficult is it to get it in the syringe, and what kind of syringe would you recommend? Just wondering if I can draw epoxy into the syringe.

Last edited by Eaglepilot2; 06-25-2017 at 05:17 PM.
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Old 06-25-2017, 07:07 PM
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Quote:
Originally Posted by jetmaven View Post
My experience with reduced finishing resins has been excellent , it cures as it should , sands well and does not become
gummy .
Is that when using it as a finishing resin? If so, then yes, you can thin it like that when you spread it on a surface. In that application, the solvent has time to evaporate before the resin cures. In a structural application like bonding a crack, it may not.

If you thin 5 minute epoxy like that, you will find that it does not cure hard because the solvent doesn't get out before it cures. The same thing happens with a longer curing epoxy if thinned in an application where it is not well exposed to the air for the solvent to evaporate.

Also, I'm not sure that finishing resin is the best adhesive for a structural repair... YMMV

Bob

Last edited by rhklenke; 06-25-2017 at 07:09 PM.
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Old 06-25-2017, 07:08 PM
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Quote:
Originally Posted by Eaglepilot2 View Post
I actually thought about that, but how difficult is it to get it in the syringe, and what kind of syringe would you recommend? Just wondering if I can draw epoxy into the syringe.
Just go to the farm supply store and you can buy some 3cc syringes and needles. It takes an 18g minimum needle to put epoxy through so just get a few of those needles. You may want to consider trying the catheter from an IV needle, it's just the little sleeve that sits over the needle and is left in place when an IV is started. Barring that, use your Dremel with a sanding drum to flatten out the taper on the end of the needle.

To get the epoxy in the syringe, just leave the needle off and pull it into the syringe then put the needle on it an push the air out. Try and get syringes that do not have the hub lock, they come both ways.
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Old 06-25-2017, 07:13 PM
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I'd just open the crack and glue it with hysol. The small tips would probably force it right into the crack.
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Old 06-26-2017, 02:17 AM
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I'd use hysol as well.
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Old 06-26-2017, 02:58 AM
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Use some 30 min epoxy. Heat it with a momocoat blower. It will become waterlike. It can then be put in a syringe and injected into the crack. Be sure to do this with of lots of ventilation.
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Old 06-26-2017, 06:31 AM
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Thanks for all the suggestions. I'm sure I'll be able to get it done after all your help! Guess I'm headed to the farm supply store!
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Old 06-26-2017, 08:17 AM
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What is the structural component of this vertical fin?
If the structure is the foam then you can just get some epoxy in there and it will be strong as new. If it is foam with a fiberglass covering then just butt gluing it back together is not going to be strong enough.

You can heat most epoxies to make then thinner, heat will also dramatically reduce pot life so be ready, your 30 minute epoxy once warmed up may only give you 5 minutes.
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Old 06-26-2017, 08:27 AM
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Its balsa sheeted foam core and glassed. Once glued, I do plan to reinforce the joint with some cloth and the usual blending for repaint.
Thanks
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Old 06-26-2017, 08:33 AM
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If you are conna reinforce it with cloth and repaint why are you worried about the CA getting everywhere? just CA it, reglass it and be done with it. Could be lettin' the paint dry by now......
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Old 06-26-2017, 08:40 AM
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Quote:
Originally Posted by Terry Holston View Post
If you are conna reinforce it with cloth and repaint why are you worried about the CA getting everywhere? just CA it, reglass it and be done with it. Could be lettin' the paint dry by now......
I suppose you're right, but I guess I'd feel better knowing the foam was bonded also. I suppose I'm more paranoid than most people.
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Old 06-27-2017, 08:24 PM
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I would use Hysol.. mix it with 20 percent more hardner.. then dilute with dn alcohol.. use a rubber glove so you won't get skin oil on it and work it in.. then wipe clean with alcohol

place a fan on it, no heat.. come back tomorrow.. it will be hard and solid.. BTDT
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Old 06-27-2017, 08:34 PM
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you get syringes at any pharmacy I use them for work on plastic models.
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Old 06-28-2017, 10:46 AM
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Quote:
Originally Posted by gooseF22 View Post
I would use Hysol.. mix it with 20 percent more hardner.. then dilute with dn alcohol.. use a rubber glove so you won't get skin oil on it and work it in.. then wipe clean with alcohol

place a fan on it, no heat.. come back tomorrow.. it will be hard and solid.. BTDT
I like that hint, I've always wondered about thinning Hysol. How about using the one hour stuff instead of the 9462?
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Old 06-28-2017, 11:05 AM
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Quote:
Originally Posted by Zeeb View Post
I like that hint, I've always wondered about thinning Hysol. How about using the one hour stuff instead of the 9462?
no.. it won't penetrate the glass..
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Old 06-28-2017, 11:42 AM
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You can also mix your epoxy,then add acetone to desired texture,(almost water thin) then apply with a fine haired brush. Then wipe of with lightly with a soft cloth.
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