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Stiffy glue

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apburner

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Am wondering what you folks use to glue stiffy into a coupling. I am building a 7.5 E-bay from LOC Precision and am concerned I will get it stuck in the wrong place so a good long pot life glue would be preferable. I am thinking either a 20 minute finishing epoxy from Bob Smith. Or gorilla glue. I could just slather it into the coupler and then spread it with a card very thin. Dampen the stiffy and slid into place. I am leaning toward the gorilla because it expands as it set also.
 

rharshberger

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Use the epoxy, and a balloon to provide expansion of the stiffy against the coupler.
 

rharshberger

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+1 on the epoxy. Not sure about the balloon.
For some reason I was thinking that Loc Stiffy's were diagonally split on one side. If the aren't then just coat both pieces with epoxy and slide together making sure a little bit is getting pushed out ahead of the stiffy that way you know that there is no dry joint. Wipe off the excess when finshed. If worried about the stiffy slipping before epoxy has cure a section of maskong tape will cure that.
 

dixontj93060

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To be honest, I'm not understanding any of these responses, much less the question...

A stiffy coupler is meant to fit inside a regular coupler. Just brush on some 30 min. (or longer) epoxy on both the outside of the stiffy and the inside of the regular coupler. Insert the stiffy and position it so you have equidistant overlap of the regular coupler on each end of the stiffy. Use alcohol to wipe excess epoxy away. Sit aside to cure.

Now if you are not talking about a stiffy coupler and are instead trying to "stiffen" a regular coupler then you may try doing a layer or two of fiberglass and laminating epoxy. You can use a balloon to hold the fabric in place--I have before, but don't really use the balloon anymore. I simply wait until I get a partial cure in the epoxy and wipe off excess epoxy with a rag dampened with alcohol while also pressing fabric securely on the inside of the coupler.

If you are talking about neither of the above and maybe are trying to install a stiffy coupler directly into an airframe--don't do it. Even with Gorilla glue your alignment and overall strength of bond with that big of a gap would be highly suspect.
 

sharkbait

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I believe he said he's building a Loc 7.5" E-Bay, and wants to know what type of adhesive to use to install the stiffy tube inside the coupler tube.

With Loc tubing, you can also use almost any good wood glue. I'd personally reccomend TiteBond Wood glue. Nothing wrong with using epoxy either though. Scuff up the inside of the coupler and the outside of the stiffy with some #120 grit sand paper, apply your glue in a thin layer to both surfaces and slide it in until the stiffy is centralized in the coupler. Wipe up any excess glue with a damp paper towel and let dry. Take some CA SuperGlue and apply a soaker coat to the edge rims of your coupler and stiffy to protect the ends and keep them from fraying. You can also go a step further to toughen up your E-Bay by light sanding the outside of the coupler tube with #220 paper and apply a thin layer of laminating epoxy to the outside of the coupler. Let it soak in & cure and then sand it for fit with #220 & then #400.
 

sharkbait

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Another little tip while you have the laminating epoxy out, put a coat down on the tops of your E-Bay bulk plates. It will make cleaning them up after flights much, much easier.
 

dixontj93060

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I believe he said he's building a Loc 7.5" E-Bay, and wants to know what type of adhesive to use to install the stiffy tube inside the coupler tube.
OK, I guess I was thrown off by the whole balloon discussion...

As sharkbait said, epoxy or wood glue. You really don't want to use Gorilla glue as you will get foam expansion and hardening where you least want it, at the ends of each coupler right where you need your bulkhead to fit. Best to keep that area as "clean" as possible.
 

bobkrech

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TiteBond wood glue. For gluing fiberboard to fiberboard, all you need to use is wood glue. Epoxy or anything else is not going to make it stiffer or stronger.
 

jd2cylman

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While I am a big fan of TiteBond for all things cardboard rocket related, I think this might be one time I think epoxy would be better (and is also recommended by LOC). I've heard of and experienced myself premature bonding when installing couplers using wood glue. If that sucker sets before the stiffy is in the correct place, game over. Get new couplers and try again...

Adrian
 
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AlfaBrewer

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I've epoxied them in before. I had to do a repair and was able to strip the stiffy out and reuse the coupler. That indicated to me that the epoxy didn't get any penetration into the paper. If memory serves, it was 5 minute, which may have been the cause of the lack of penetration.

I've used wood glue. Lots of wood glue. Use one smooth motion to press the stiffy in. If you stop, you'll be buying a new coupler and stiffy.

I've used polyurethane glue (Gorilla glue). Dampened both surfaces and applied a decent layer that a skimmed with a hotel key card.

All of them work, some may be better than others. Some are definitely easier than others. As a side note - don't turn your key card in when you check out of a hotel. They are super handy for spreading wood filler, glue, epoxy, Bondo, whatever.
 

rharshberger

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TiteBond wood glue. For gluing fiberboard to fiberboard, all you need to use is wood glue. Epoxy or anything else is not going to make it stiffer or stronger.
However as the OP stated in his post, having the Stiffy seize at the wrong point during insertion into the coupler was the reason he was asking about other adhesives. I will admit I love using TB II as much as possible during builds but but when it comes to couplers, Stiffy's, or some of the Estes MMT's that are built as an assembly and inserted, epoxy is usually my first choice. I'm not sure epoxy between cardboard is going to be any less strong than wood glue since both are stronger than the cardboard they are bonding.
 

Coop

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I'd go with an epoxy there, if nowhere else. That's a lot of cardboard to ask wood glue not to bind up on. Epoxy will give you the working time to get the insert into the correct position.

Later!

--Coop
 

samb

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I'll add one (small) voice for Gorilla glue here. I've used it on couplers and motor mounts up to a LOC Doorknob size (54mm/7.6 inch airframe). I've mentioned before that I'm limiting my exposure to epoxy and I find the polyurethane glue an adequate substitute. I rarely add additional moisture beyond the ambient humidity. I don't think you'll go wrong with either one.
 

apburner

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I'll add one (small) voice for Gorilla glue here. I've used it on couplers and motor mounts up to a LOC Doorknob size (54mm/7.6 inch airframe). I've mentioned before that I'm limiting my exposure to epoxy and I find the polyurethane glue an adequate substitute. I rarely add additional moisture beyond the ambient humidity. I don't think you'll go wrong with either one.
I must admit I was a little surprised at the lack of answers on polyurethane glues. I have used it on RC planes with great success and with the expanding it does I was thinking that this would make the two papers of the coupler and the stiffy soak up the glue nicely and really bond well. Good to see there is a contingent of folks using it. I think I will go against the grain and try the Gorilla glue as an experiment. If it doesn't work I can always get another coupler and stiffy. Lol.
 
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