I read quite a few posts about Polyurethane glue, but I don't remember anybody saying anything about how it sands. I'm considering using it on my next build. I am aware about the "squeeze out/foaming" factor. That or I'll just use some of the "new" wood glues. It's been at least 15 years since I've done any building.[]

Why don't you just use the "traditional" adhesives/glues that have been proven successful for decades?

Here's what I use:

"CA," Gap filling and the thinnest one.

5 minute Epoxy.

30 minute Epoxy.

Certainly other items can be used, for other tasks, that follow the basic framing up of a balsa and plywood model.

Hope this helps, but my guess is this will be a long Thread.

I have not used it for new construction because of it's exspansion. I don't want parts moving around.
Excepton the pin style hinges. It's great there. I have not tried to sand it.

I have used it for repairs in those hard to access places and when parts don't fit tight like they use to.. It's great for that.

Idon't like CA and only use it for hardening threads.

Try Tite Bond II or Gorilla wood workers glue. I prefer Gorilla which sets up quicker.

I also like to use Super Phatic. It watery and wicks in like CA. Water cleanup and no smell.

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Test it on some scrap balsa first - the polyurethane stuff I used was horrible to work with afterwards. It foams and cures when exposed to moisture, more moisture and it foams more - and very difficult to sand. I strayed and learned my lesson, stay with the tried and tested wood and superglues.

Cheers

Bundu

These models were framed up using only CA, 5 minute Epoxy and 30 minute Epoxy.

I just started building a few others, I'll get photos.

Very nice work. I need to look into that "Super Phatic Glue". Who sell's it?

Does it add much weight?

Every HDWE store, Home Depot, and your local Hobby Shop.

I trad at my local HS whenever possible. You can also purchase stuff from Tower Hobbies. A day or two and the box arives at your door.

It's important to keep the money in the Hobby whenever possible.

Adds no weight worth talking about.

Photos of your build, that's the proce you have to pay for the Thread.

Charles

The glue is good for fire walls , landing gear blocks, wing bolt blocks and such. To frame up a plane with, no. Unless you have a way to hold everything in place, because as the glue expands it will move things around. What ever is glued with that stuff has to be clamp together.

Thanks!!

Ken

Hobby Lobby sell Super Phatic.  It's nice but pricey like CA.

Using polyurethane on pin hinges only takes a drop or two.

I put water in the hole.  Move it around with a pin to brake and surface tension.  Then scoop up a bit on the pin and smear it around the hole.
Then push in the hinge.  Of course coate the center hinge portion with vasaline. 

Polyurethane glue has it's uses as mentioned earlier.

It's almost impossible to sand after it cures. The foam is hard and has the appearance of honeycomb

<span style="font-size: larger;"><span style="font-family: Comic Sans MS;">Hi kenh4397. I wouldn't recommend Polyurethane glue if you are working with Balsa or other wood types in airplane construction. It is generally harder than most materials used in the construction of R/C planes. It <u>is </u>however</span></span> <span style="font-size: larger;"><span style="font-family: Comic Sans MS;">friendly to foam construction, and it's waterproof. C/A's tend to eat foam, and hot glue is risky. Epoxy is even harder than Polyurethane. One of the key things to remember in using Poly-U is "Less is better"! unless you have serious gaps or a very rough surface to bond, you want to keep the film of glue as minimal as possible simply to avoid excessive squeeze-out. I use an exacto blade (preferrably a new one) to trim excessive glue, making careful multiple passes to trim the excess. Since Poly-U takes a while to cure, you have some time to wipe off squeeze-out which can also help to minimise the problem.
One problem with carpenters glues (white, yellow or beige) is that they are not really waterproof. That type of glue will turn back to liquid if exposed to water for even a few minutes, even if the parts have been glued up for a long time! I nearly lost an R/C boat that way once! As for working with Balsa, why not stick to C/A's, they've been used for years and come in a variety of consistaneys from super thin to thick like honey and even the slow ones will set virtually instantly in contact with a wet surface, or with accellerators. For plastic parts, certain plastics like plexiglass or lexan will bond well with the right acrylic thermal cement, which by the way works quite well with wood.</span></span>
<span style="font-family: Comic Sans MS;"><span style="font-size: larger;">Hope you find this helpful.</span></span>

Poly U has it's place in modeling IMO. I use it to sheet foam wings, hinge pins, and when gluing sheeting to wing ribs and such. Remember it foam to about 4 or 5 times its size. Use the foam to you advantage and allow the expansion to fill small gaps that white glue, epoxy or CA would not bridge. Do not use it for structural parts such as landing gear areas and engine mount areas. It also is not very good for stick building. It is sandable, but harder to sand than your balsa. It also is not as strong as white glue , ca, or epoxy.
I don't use ca at all hardly, [gives me an allergic reaction] but I do use all the others.
Good luck and best wishs.