Is this that 'Polyurethane glue' some of you guys are using ?.

Haven't tried it on any foam yet, but did attempt to glue some coroplastic together with it and wasn't impressed with the results.

Maybe I got the wrong stuff ?.

I haven't tried that brand, but I've used Elmer's "Probond" with very good results on foam. If you moisten the area with a little water before you apply the glue, it will foam up when it cures and fill any gaps. It's very good on regular styrofoam -- I don't know about using it on EPP foam or anything else.

Neil

It is not the brand that I use but looks like it should be OK.

My ployurethane glue does not work on smooth plastics that well.

I glued the center plastic pieces on my little Hornet foam wing. I sticks to the foam with a vengeance but the plastic surface needs to be made rough.

No, that's not the one I have. I have Elmers Probond. I think what you have is regular wood glue, but I'm probably wrong..

..a

I have used Probond as well. It works well but takes a long time to dry and requites clamping/taping. I'm going to try 3M 77 spray adhesive next.

Charles

A good test is to dribble some of the Titebond in a paper cup and spray some water on it. The glue should foam up to form a creamy colored foam. It usually takes about a 30 to 45 minutes for Elmers Pro Bond to foam up, and about 3 to 4 hours to harden up. I usually wait overnight before I fly with any Probond repairs. If you don't use water with the probond it can take longer to dry.

Probond is not really a glue. It is a water activated poyurethane foam, that just happens to really stick stuff together like glue. So use the water!!!

It is sooooo much ligher than epoxy, and very strong. Roughing up slick surfaces helps. Even works on fiberglass too.

Gordon

Originally posted by Plane Crazy
A good test is to dribble some of the Titebond in a paper cup and spray some water on it. The glue should foam up to form a creamy colored foam.

Yup, thats exactly what this stuff does.

Although the 'rough up' plastic to plastic bond wasn't what I was expecting, a balsa to plastic joint was surprisingly tough.

I'm going to try some balsa and foam test pieces.

Its beginning to sound like the same stuff.

I think it's essentially the same stuff, Bill. Polyurethane glue. Can't be too much difference besides brand name.

mw

Hi,

I have also been using the stuff, however!

While both are called "Probond" the Polyurethane is much different. The PU (sorry) is not water soluble and requires solvents for cleanup. I tried some water with it. Does not mix at all.

It also has a list of health hazards on the label!
Contains diisocyanates and can cause breathing problems, skin rash, chest tightness etc. according to label. Onset of symptoms may be delayed, which could cause real panic as you might not associated them with the glue you used some time ago. I tried it, didn't like it and threw it out as too hazardous. CA is bad enough

I use the "Probond professional strength wood glue". Sandable and paintable, very fast setting.
great for finishing /hardening foam with silkspan.
Makes a hard rigid surface.
Easy water cleanup/thinning and no health hazards.
Seems to be quite water resistant once dry, by label says it won't take prolonged immersion.
If the model is subjected to prolonged immersion, I figure that the strength of the glue joints will be the least of my worries!

Also much cheaper than the PolyU glue.

Sands nicely when really dry ( 24 hrs)

Cheers,
Dave

Here's my 2 cents worth on PU glues...

There were (possibly still are) 2 formulations
of Titebond polyurethane glue. The original was
very viscous. About 1 1/2 years ago they came out
with a formula that is much runnier and seems to
foam more aggresively when exposed to moisture.
The newer type comes in a squeeze tube that is
nominally stored inverted. I prefer the latter
as it spreads easier. It will foam *very* quickly if you mix in enough water. The down side is poor shelf life. That's why I'm starting to like Probond, it seems to pour almost as easily as the
newer Titebond, but seems to last longer in the
bottle (good for a slow builder like me).

Polyurethane is one of the strongest wood glues you can use. Not only does it foam to fill gaps, but it penetrates the wood for a very strong bond. Epoxy just sits on top. Works well on styro foam too (white, blue and pink).
Virtually nothing glues coroplast well, but if you run a flame over the surface it makes it more chemically active. CA is the best for coro.

The picture looks like you got a builders tube to be used in a caulking gun. Hard to get small quantities out if that is what you have. PU is activated by moisture, so regular bottles usually harden within a year of opening. The caulking tube at least keeps air out.

Rick.

PS There is also polyurethane varnish which is a different fish.

I've used the stuff with great success on coro, at least in open areas, like the spar... The trick is to rough the plastic and clamp...

Small areas, I prefer Goop...

As far as setup time and gluing, if you want it to fill an area, Like in a spar-cutout in a foam wing, add 1-2 drops of water per 2 Tsp of glue and mix it like epoxy.... Sets up firm in just under 2 hours... I normally cover the joint with waxed paper to make it easier to smooth out when the glue over-expands...

Definitely keep it off the fingers and clothes... There's no getting it out of clothing...

I don't use epoxy on foam, except with fiberglass... This stuff is amazing...

Dave W.
I saw your post on covering with wood glue and silkspan. Picked up some Elmers Probond prof. wood glue at Wally World. Am building blue foam cut IL-2 Stormovik parkflyer and thought about covering with green tissue and this glue. Did a test piece last night and it warped the foam pretty bad. The wing is undercambered and only 1/4" thick. How do you keep the warps out? Covering both sides at same time might work but I wasn't going to cover the bottom. I may have to stay with Polycrylic.

In my experience Elmer's Probond gives a very strong bond, like a foamy epoxy, but it doesn't grip smooth plastics and metal as well as porous surfaces. Works great on white foam. I haven't glued coro since I built a US Aircore trainer, but IIRC that plane used clear silicone caulk/sealant for wood-to-coro and contact cement to bond coro-to-coro. The contact cement worked great, but I don't recall what brand I used.

Shoe Goo is a handy adhesive-of-last-resort (especially when you need a flexible bond) but I believe it's solvent-based so be cautious and test first.

Shoe Goo or works great on EPP, it's about the toughest glue I've ever seen once it dries. It stays a bit stretchy, will not let go, and won't break either. For a permanent EPP bond it works fine, the drawback is drying time and it's consistency, it will run when too thick and doesn't tack up enough to help with construction. It will eat styrene based foams.

I've used epoxy for spars and joining wing halves, and of course white, pink, or blue styrene foams. For wood work with lite ply's and such, I go epoxy or CA.

The adhesives I find myself using more and more are contact cement and 3M77 spray mount. EPP/coro/nonstyrene only. The 3m is basically contact cement in a spraycan and with the smooth control you can get with a spray application, it's very workable. For mock up and preassembly, or doing scale outlines in foam, the 3m is the stuff. A light mist on a piece of epp, a pattern or template, etc and you can tack it and untack it to other pieces as needed. for final assembly, give each side a moderate mist and let them sit 5 minutes, when you put them together make sure you've got them where you want them cause they're not coming apart again.

When doing wings/spars for foamies and full assembly of the wing I haven't used anything but 3m or contact cement to place the spar or build the wing.

There is CA in the spar iself, since I'm doing kevlar wrapped CF/Balsa spars doped with CA. They come out very light, and are easy to install, you don't need a channel in the wing, you just cut the whole core spanwise where you want the spar. Then glue the spar to one side of one half, glue those two to the remaining side to complete the panel, this game *must* be done with the wing beds to provide alignment! Then cap top and bottom of the spar channel with balsa strips pushed into the slots, then sand those flush, and your spar area goes totally flush on both sides,

It's pretty slick and you've got an ultrastiff CF spar under it too. my EPP cub's 48" spar weighed 12g, and it hauls a s600 direct drive with 7 nicads, video gear, fully articulated landing gear, and foam wheels through all kinds of insanity and the spar stays true. I think the wing came out at 6 oz covered, no servos.

But in general, I just keep using that 3m, and by the time you cover your foamy, the 3m is plenty, plenty strong.