How to get epoxy glue into narrow gaps/slots?
 

Hi all, Looking for some advice..

I have a model where the horizontal stab has loosened partly in its slot in the fuselage. Is there any way to get some epoxy glue into the narrow gap between the stab and fuselage? Thinking of using a slow cure epoxy and apply it into the gap by using a syringe with the largest needle available, but thinking the epoxy will be to thick to be able to be squeezed through the needle. Any tips/advice on this?

You can put the epoxy into a small plastic bag, push it into a corner and snip the tip off the corner. Pipe the epoxy in place the same way a baker decorates a cake. I use this method quite frequently.
https://cimg8.ibsrv.net/gimg/www.rcu...aded888e5.jpeg
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Also, warm the epoxy after mixing, and it will thin out. This does accelerate the cure time, so use the longest setting you can find. Can be bad when 5 min. sets in a minute or so....

A club member, who was an adhesives chemical engineer for 40 years, swears by thinning Gorilla Glue with acetone. The acetone flashes off quickly, leaving the straight glue behind. He says it also foams less - still makes a super strong bond that fills gaps, just isn't as prone to foaming out of the gap as much as straight Gorilla Glue. You can also then put electrical tape over the crack, to further minimize foaming out while it cures. (the black electrical tape will not get glued to the crack like masking tape might!).

Both good tips,,,

but, I'd probably just tape it all off with blue tape, mix some 15min epoxy and just push it into the gaps with a credit card, wipe it all down with some rubbing alcohol to remove extra epoxy, and remove the tape before the epoxy dries,,

Truth be told, depending on the size and configuration, I might just use medium to thick CA,, What kinda plane we talking about here?

Another alternative:

Applying what I learned from a modeler I worked with that may help here as well - he taught me a technique for getting epoxy into hinge slots using a plastic straw cut down to a couple inches; the shortened length of straw is squeezed together to fit into the narrow slot, epoxy is loaded into the open end and then gravity plus pinching the straw like a tube of toothpaste works the glue into the slot -

Yep, one of my sayings since entering the Composites industry 12 years ago. Ask 10 Composites guys how to do something and get 13 correct answers.

Here's answer #14. You can get 12 ml. syringes at Tractor supply for less then a dollar. Select the appropriate size needle for the job. With a large needle I like to drill small holes at 3/8" to 1/5" intervals. Use a thin laminating resin. Clamp if necessary,

You need to be careful with syringes. The syringes with the rubber plunger have some type of lube on them that can contaminate your epoxy.

Thanks all for your replies. Much good advice here. Large needle and some drilled holes seems resonable. Just have to test with epoxy first to see if it get through. Laminating resin sounds good. Guess Z-poxy finnishing resin will do?

Picture to show where I want the epoxy:

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When using syringes, pull out the plunger and clean both the plunger and inside of the tube with acetone or naptha before you use it. Alcohol can contaminate the syringe with plant fibers, adversely affecting the epoxy

I've never had a problem with lubricant contamination, but I suppose it's possible. Well that's not completely true. I got a covid vaccine that had Vaseline in in it. Still got covid, but my joints didn't ache. If you are worried, just clean the plunger before hand. While not a #1 choice, ZPoxy should still be adequate.

And, another alternative - pack the joint with baking soda, carefully wipe off/dust off all the excess, Then drip thin CA into the joint, soaking the soda. Any soda on the surface near the area that gets CA on it will set up rock hard, so only have it where you want it.
I use this technique to fill old firewall holes. It is so hard and strong, you can drill new ones into it, and even use a tap to cut threads in it.
I've even used a variation to restore rotting portions of my deck on my house. 5 years in rain/snow/sun (+100 to -20 below!) and still far better than the wood. Sounds silly, but actually much cheaper than the "wood rot restore" products at the hardware store.

Hi!
I would not use epoxy glue in your case as it is very tight surfaces on a plane like you have pictured.
I would use thin or medium Ca glue and accelerator!

Hi all,
Will just let you now that this one has been fixed and the plane flow several times :) I used some expanding PU glue which I applied to the area using a syringe with the larges needle available, just as in the picture I have added above. Worked nicely.

Happy flying :)

Thanks for telling how you fixed it -

Syringes and applicators are available on Amazon and they are inexpensive. They have become a standard part of my modeling tool box of tricks.

My way of filling up cracks and gaps is rather simple with use of any bonding agents thickened up to desired state by adding micro balloons or talcom powder, mixed on glass offcuts with the rice scewers, or round tooth-picks also used for easy application along the gap areas to push it into, help of index finger if needed comes handy also. Use of thickened up PVA glue, water based Liquid nails is lot friendlier, also lighter and easy to clean up than Epoxy.