I recently bought a Super Cub LP RTF (made of Z foam) by Hobby Zone. Icrashed it and broke the plastic firewall. I bought replacement parts at Hobbytown, and knowing I was a beginner and needed help, they recommended Zap Goo pt-12 adhesive (which they sold me). For some reason I got nervous about it and called them back. They then recommended I try it first on some of the foam in the packing material. When I did, the foam from the packing immediately started to melt.

Since then, I have talked to Hobbytown twice, Hobby Zone tech reps twice, and even the tech rep for the company that makes Zap Goo. I have been told use the Zap Goo, don't use the Zap Goo, use a medium CA, don't use a CA, and in the end, the people at all three places ended up saying they didn't know what to tell me, except that I might just have to keep buying stuff and scraping some foam off the engine block (I really don't want to cut my plane up) to experiment with.

It makes no sense to me that these tech experts can't tell me what to use. The problem is that foam-safe CA apparently is a permanent bond, and I need a flexible bond (which nobody seems to know a product that is flexible and foam safe) because Ineed to be able to replace the firewall again (if I damage it again) without tearing up the foam. I have been told that Zfoam would probably not be the same consistency as the styrofoam I experimented on, but none of these people can guarantee me that whatever I use won't eat the Zfoam too. I saw a video by the plane designer and he talked like you don't even have to use foam-safe adhesive on this plane!

Is there anyone out there that has ever had to use a flexible adhesive on Zfoam, who can tell me what to use, and is really sure of it? I would really appreciate the help.

I have a T-28 trojan that I pretty much broke into a bunch of pieces.  It was all put back together with hot glue and it worked really well.  I also used epoxy on it, as well as foam safe CA.  I even used Elmers glue once because that was all that was available where I was, it worked too.

I have used all of the above mentioned glues on my Super Cub, T-28, Corsair, J-3 etc. The best glue I've found so far for foam is UHU Creative Film & Foil. It is sold in Europe as UHU Por. and some hobby shops here in the U.S. also sell it. You can order it online from Saunders-usa.com. It does not dry hard and brittle like C.A. but retains a very slight amount of flexibility and is very strong. 

The titebond II that everyone builds wood planes with also works good on foam. The hotglue or epoxy will make it heavy if you use a lot of it.

Or good old 2 part epoxy.

Thanks for all the replys so far!  So much more helpful than the rep responses.

gorilla glue

Any of the epoxys work quite well and do not add much weight if you put it on thin.  There is no need for a heavy coat.  Gorrilla glue also works well if you have a way of clamping or holding parts together while it cures as it foams up and tries to push the parts you are gluing apart.  Foam safe CA also works well.  Carpenters glue or Titebond may be a problem unless you can leave it set undisturbed for 24 hours or more as the inside areas are sealed off from the atmosphere when the outer areas start to cure.  Thin joints work out okay with the Titebond.

elmers white glue or epoxy is what i use. both work fine. no need  for anything more expensive

3M77 spray adhesive works for butt gluing foam blocks or panels together. I've used it for veneering balsa or ply to foam, too.

I've been using polyurethane glue (like Gorilla glue or Elmer's Ultimate Glue). I paint it on one side of the break, and then fit it back together. I tape it together with scotch tape or packing tape so the foaming action doesn't push it apart, as Rodney mentioned. I don't spray any water on the joint unless I need some gap filling, since that will cause it to foam much more.

In fact, if you need some gap filling, you can mix some poly glue with a couple drops of water, and it will foam up into a foamy paste, and you can gob it into the areas you need filled. Just beware, if you mix in the water, it foams up and cures much quicker, so you have less working time than you would have otherwise.

I don't know what Zap Goo is, but I do know Shoe Goo has a solvent that will eath styrofoam.

For a flexible glue, as mentioned above, the UHU foam glue can be found at most craft shops.

AND it makes the repair seams disappear which does not happen with most of the other glues.

Just use a lot to permeat the sections to be repaired fully.

Wipe off any excess that dribbles out when you push the parts together, and immobilize until dry.

Well the <span id="prodTitleBrand">Super Cub LP RTF</span> <span id="brandName">by HobbyZone is made out of what they call is "Z" foam. On page 28 of your manual it states that any CA is ok on your wing and fuselage. That Zap Goo will probably work fine. I recently cracked up a ParkZone Radian (also made of "Z" foam), broke the fuselage in half and the wing halves had all sorts of breaks. I asked the same question, and even originally bought "foam safe" CA. But with further research, found out that regular CA works just fine and maybe even be prefered. I used Dave Brown Regular Thick Ca on one side of the break, with a spray of activator on the other side. When I put the broken pieces together I had minimal what I call "ooze out". But great adhesion and no melting foam. The Z foam is not like foam you would find in something like the packaging material the plane came in or a foam ice chest. My Radian had a serious crash where most would consider totaled. But I'm sure I'll be able to complete the rebuild and it will fly again. Good luck to you.</span>

Oh and I also wondered about aliphatic glues like Elmers. The problem I see with Elmers is that with the extended break I had, I was worried that the glue would dry and seal around the outside of the break, not allowing air to get to the inside of the break, making an ineffective repair. So I'm not sure Elmers or any aliphatic glue would be the best choice.

With Epoxy, although it generally sticks and bonds to almost anything, I'm not sure it would to the "Z" foam. Have you ever mixed some epoxy on the lid of a coffee can? When it sets or hardens, you can peel it right off. I fear the same with the "Z" foam.

RC560, canopy glue will also work, as long as the break isn't too thick and air can penetrated the bonding areas. I plan to partially skin with cut fabric softener sheets and Pacer Formula 560 canopy glue over the break lines to give added strength.

So that's why I settled for regular Thick CA. I try not to use a lot of CA because of cost and fumes, but it seems the best solution. At least for me.

Tom,

Thanks for the info on your Radian repairs. I've got a broken tail boom on my Radian, and have been debating whether to use my old standby, poly glue, or try Elmers, CA, or other glue.

Sounds like regular CA will work well.<br type="_moz"/>