Hi guys I'm Laminating a set of wings with 1/32 ply on pink foam cores. The question I have is what glue or epoxies to use. Thanks

If you're going to use weights to press the cores in their beds, then any laminating epoxy will work. I use a generic brand similar to West Systems.

If you're going to vacuum bag the wings, you can use Gorilla Glue. I prefer the yellow, not the white glue. The stuff expands quite a bit, so you only need a very thin layer on the skins. You can also use laminating epoxy when you vacuum bag, but the Gorilla Glue is a little bit lighter and cures in just a few hours.

-Keith

Oh, and do NOT use any kind of polyester or vinylester resin!!!!!! Unless, of course, you want a melted puddle of foam.

I don't know how to vacuum bag yet so I'm going to use the weighted system. Is is a good idea to use 30min epoxies or better to use the two part epoxies that I use for fiberglass work, it takes about 24 hours to fully cure.

Thanks for the help Keith

Definitely use the epoxy that you would use for fiberglass. Yes, you have to wait overnight for it to cure. But the extended working time means you can get everything positioned just right.

The large amount of 30minute epoxy you'd need would kick off so fast, that I doubt you'd be able to apply it and get everything weighted down before it's too late. And then the neighbors down the street would wonder what you're cussing about.

That is a true statment. The only good think is that if I lay it up say tonight I really don't have any time to mess with it till Wednesday or Thursday. Thanks again Keith.

Originally Posted by kpeevyhouse

Definitely use the epoxy that you would use for fiberglass. Yes, you have to wait overnight for it to cure. But the extended working time means you can get everything positioned just right.

The large amount of 30minute epoxy you'd need would kick off so fast, that I doubt you'd be able to apply it and get everything weighted down before it's too late. And then the neighbors down the street would wonder what you're cussing about.

Do you have a Tap Plastics up there? Their Superhard 4-into-1 has worked well for me, and I've seen the Marine Grade used to good effect as well.

From what I understand their epoxy is re-labeled Jeffco resin.

I know for balsa skins, 3M77 works great. not sure that it'd work for ply. If it did then you wouldn't need to bag or weight the cores- spray on both surfaces, let tack up and press on!

Greg

I prefer the quicker, thicker epoxies for skins. The slow cure epoxies tend to be thinner and can be soaked up into the wing skins making for a weak bond between the skins and the cores. Adding some thickening agent will help OR sealing the wood with some polyurethane should do the trick too. Another issue I've run into is having the skins move when using slow cure epoxies. You weight everything up and over a few hours stuff slides around.

So to summarize, I prefer a little quicker setting epoxy. I also like the yellow gorilla glue.

Also for a better bond, score the wing skins and the cores. I use VERY rough sandpaper (40 grit) on the skins. Just rub em slightly to rough em up a bit. I rub the cores ever so lightly with some 80 grit too. I've never had a wing delam doing this. But using thin slow cure epoxy on untreated skins and cores I have had those delam.

BTW, 3M-77 works great on balsa skins, but I don't use it on plywood.

I've used 3M77 on 1/64 ply over foam cores. Works great.

Do not forget: 3M77 is a contact cement. Where you make contact, it stays. Just a word of warning.

The only precaution I've heard (reads as not experienced myself) when using 3M77 on ply, is that ply tends to Super Heat more than balsa and 3M77 tends to release with heat, therefore you could delaminate your wing with a nice Sunny Day, by having it sit out in the Sun.

Originally Posted by TomFlyer

Do not forget: 3M77 is a contact cement. Where you make contact, it stays. Just a word of warning.

That is so true.

I do have some gorilla glue lying around here, that is what I used on my Mini Macchi skins, they were 1/64 ply.

Originally Posted by chip.greely

The only precaution I've heard (reads as not experienced myself) when using 3M77 on ply, is that ply tends to Super Heat more than balsa and 3M77 tends to release with heat, therefore you could delaminate your wing with a nice Sunny Day, by having it sit out in the Sun.

What chip said. Had a little better luck with Southern's Sorghum, but did have one delam at the PSS Fest a couple of years ago, so not using that anymore either. We are bagging the skins on with epoxy now.