Epoxy question
 

I did a small mistake, I have an ARF GP Cessna and the wing is in 3 peases, left, center and right. I was putting the left and right wings to the center section, and accidentally grabbed the 5 min eboxy instead of 30 min :(... Now the wings are glued to the center-section (wich bolts the wing to the fuselage). Knowing that fact that 30 min epoxy is much stronger than 5 min.
Do I need to take it apart and re-glue it with 30min, or is it ok to run with it that way?

If I have to take it apart, how should I do that? [&o]

thx, Regards. E

RE: Epoxy question
 

You will be fine. In a case like that they call for 30 minute epoxy to allow you enough time to get your parts joined and lined up properly more so than the strength aspect.

RE: Epoxy question
 

So I don´t have to wory about loosing my wings?

RE: Epoxy question
 

You're going to hear both opinions, I'm sure. IMO, I'd re-do them with 30 minute epoxy if that's what's called for in the instructions.

If you do decide to redo the wings, then it shouldn't be too difficult to take these wings apart. Get a covering heat gun, and go over the joints slowly to heat them up. As they get warm, wiggle the joints carefully until they start to loosen up...with a bit of patience, you'll be able to pull them apart....the heat will soften the epoxy. Once they're apart, do some sanding to remove the old epoxy and clean up the joints, and then re-glue them using the "correct" epoxy.

You may have to do a bit of recovering around those joints as well, as the heat may damage the existing covering.

RE: Epoxy question
 

I share the opinion of OldScaleGuy, and would not put myself through the trouble of separating the pieces and re-gluing. If you got a solid bond of 5-minute epoxy, it would take a serious amount of strain to pull one piece off the other. More than likely the wood would break before the joint would separate. I presume you're not going to be putting your Cessna through any maneuvers that would present more than a few G's to the wingtips, so fly with confidence and enjoy your model.

With all due deference to gboulton, it would have been better to use 30-minute epoxy. But if you are not experienced with de-bonding cured epoxy, I think the risk of screwing up the de-bonding and re-gluing process is a lot worse than just flying normal non-aerobatic sport/scale style, especially considering the joints in question are half-way out on each wing, where the flight stresses will be less than in a wing joining two halves at the center.

RE: Epoxy question
 

Epoxy, like every other type of glue, soaks into the wood fibers. the longer the soak, the stronger the bond, typically, which is why your isntructions called for the 30 minute epoxy. Since it's not a plane that's going to see terribly high stresses, like a much faster or aerobatic plane would, I think you're fine with what you have.

RE: Epoxy question
 

i agree with leaving it alone you are risking messing up what you have,if you are worried you could add something like fiberglass reinforcement but i wouldn't bother personally.when i first started building kits i never used anything but 5 minute epoxy and never had anything break due to stress

RE: Epoxy question
 

Speaking of IMO this is horrible advice. Debonding epoxy is a pain in the rear, not to mention all the extra work associated with the process (heat, wiggle, sand, reglue, recover). There's a good chance you will break a rib at the bond joint and then you can add rebuilding to the list.

The five min will be fine, just remember to use 15-30 min in the future as it will give you more "cure time" to get your parts lined up
correctly as Old Scale Guy mentioned.

Darren

RE: Epoxy question
 

Even if you seperate the parts glued together with 5 min. epoxy, you would never be able to remove the 5 min. epoxy from the parts epoxied. There would always be a layer of 5 min. epoxy sealing and seperating the 30 min. from the wood in the joint. In my opinion, this process would likely decrease the strength of the second glue job to less then the initial 5 min. epoxy bond.

gboulton is certainly entitled to his opinion. However, I would not hesitate to fly the plane as is and wouldn't worry about the strength of the 5 min. epoxy bond one bit.

RE: Epoxy question
 

Ditto! The 5 min has soaked into the wood somewhat and you will NOT soak any more Epoxy into the wood by de-bonding the 5 and using 30.

If you are truely worried about it, (I wouldn't be) then remove some covering at the glue joints and re-inforce with fiberglass tape. This will also give you the opportunity to add some customization to your plane as well by re-covering the wing joints with a contrasting color.

RE: Epoxy question
 

In my eyes it comes down to the type of joint you are dealing with. If it's a lap joint then I agree with the majority - Leave it alone, it will be fine. You'll destroy the wing before the glue joint fails. If on the other hand, it's a butt joint then I would side with the "take it apart" faction. Sand the surfaces well to remove the 5 minute - it hasn't penetrated so much that you can't remove the majority of it and reglue with 30 minute. My limited experience (limited because I don't like 5 minute epoxy), 5 minute tends to remain soft when cured and I wouldn't trust it where bending is present.

RE: Epoxy question
 

I vote with the "let it be" crowd. If you got it together properly you'll only break something trying to seperate it. The wing saddle may take 10g or so in a snap roll, but there is little flexing. Little advantage to the 30 minute (IMHO) in that application beyond time to work.

I use 30 or 45 minute for everything. I'm patient and usually don't build in a hurry, and I feel it is stronger partially because it has longer to permiate into the wood and you can mix longer and leave it set to "kick" so I believe the results are more consistant. Used to keep an assortment, but I end up with my brush stuck in kicked 5min mix just before I get that last little dab on. :)

RE: Epoxy question
 

Not that I am an expert but this should be ok, If you are really worried about the stress involved then why not glass the joints.

Personally I have a very simple way to avoid this kind of mistake, I only use 30 minute epoxy.

James

RE: Epoxy question
 

I guess I don't see anything wrong with having 5 min. epoxy on hand for times when it is useful and it is useful in my estimation. However, if you are easily confused by the two, by all means only buy one, or the other. ;)

RE: Epoxy question
 

If you were able to work fast enough to get it together straight--and it's not twisted--then leave it be.

The dihedral braces are doing all the work. All the epoxy does is fill in the voids. I've glued the horizontal stab on a small 40 size ARF with 5 min before. Had to work fast, but it held up for about 300 flights before a deadstick led to me stuffing the airplane. The stab was still glued solidly in place. All that joint is--is a flat piece of balsa glued onto 2 pieces of 1/4" balsa and it's constantly trying to seperate itself when you push and pull the elevator stick.

With a wing joint--you have a dihedral brace. The brace fits in the pocket. Thats what it keeping your wings from folding in a high G turn. Not the epoxy. All the epoxy does is keep it from wiggling inside the pocket and keeps the the wings from sliding outwards and away from the dihedral brace.

Leave it be and go fly it. You'll be fine.

RE: Epoxy question
 

Assuming you have the wing segments lined up properly, 5 minute should be fine. After all, 5 minute epoxy is still stronger than the wood it binds.

DaveB