Hi,

Polyurethane glue expands while curing and I've had some spill over onto coroplast.

When I want to remove the excess, I currently I scrape with a knife, or use a plastic scouring sponge, but it does not do a very good job.

Does anyone know a better way to remove the polyurethane glue from coroplast?

Thanks for your help,

Wayne Miller

The trick I have found that works very well when using polyurethane glue is to go back and remove the excess from expansion with in 30 to 45 minutes. At this point in the curing process it is still soft enough to pick out but not sticky enough to cause a mess. (you can touch it with your finger and it's not sticky) I usually use and Xacto or razor blade to lightly score the lines I want to keep and then pick it out.

If you have the room around the work piece, knowing that this type of adhesive is going to expand, try using packing tape to control it. In other words, apply the glue to one surface, moisten the other with water, and mount them together as required. Take small strips of packing tape (pre-cut for the space available and ready to use) and with a putty knife or other thin straight edge, apply the tape over the joint. There will be a little expansion under the tape but most will be at the ends. Do not cover or try to stop the expansion out of the ends, as it has to expand somewhere. This controls and limits the expansion and you only have to pick the excess from the ends of the tape in about 45 minutes to an hour (dependent on humidity in the air). Let the glued joint cure overnight and gently remove the tape. You will find a nice clean, slightly bevel filled joint that is extremely strong and light.

If it has already cured, you're going to work at it. In my first few projects, I made test pieces trying to learn how much is enough and how much is too much as well as a satisfactory cure time for easy removal. I let one test piece cure overnight and even went as far as to use the Dremel with a small sanding drum to grind out some of the excess. Not and good method but if this is where you are now, you may have no choice. Just use a slow speed, light touch and grind away small amounts at a time so as not to hit the structure you were gluing together.

I just watch it and keep wiping it down with alcohol and paper towels. Like the idea of using some kinda tap on it also.

Make up a couple of test peices with some scrap material, coraplas, balsa, foam or what ever you are working with. Work out the bugs before you start on the actual project piece. The packing tape is great as it has enough sticking power to hold back the expansion of the glue but still allows it ooze out at the ends. Thus making the clean up much easier.

If you can catch it while still a bit wet....grab the wife's nail polish remover...
IT WORKS GREAT!
(primary ingredient is Acetone I think)

And your plane smells lemmony fresh!!

CrazyHerb

Hi,

The glue has already dried.

What I have done is taken a wood chisel. laid it almost flat on the fuselage and slowly "bumped" the hardened glue and taken most of it off. All that is left is a very thin, faint yellow layer and I'm still trying to figure how to get it off. Any ideas?

In the future I'll use your ideas of masking first and removing glue while still soft. I was also wondering if I could coat the coro first with a light coating of vaseline or something to prevent the glue sticking - has anyone tried this?

Any other ideas to remove the light yellow hardened film would be greatly apreciated.

Thanks for your help.

Fly4Fun,

Wayne Miller

According to the brand I use, "Gorilla Glue", "remove cured glue from your work piece with a chisel, scraper or sandpaper." I know this is not what you wanted to hear but once this stuff is completely cured it's pretty tough. But you already know that.

At this point, I would consider sanding the thin film with some medium to fine sand paper. Try to feather out what ever you can't get completely off. Then, I know you're gonna hate this part, hit it with a little spray paint of a color that matches exactly or completely contrast the color of your coraplas. Try to get a color that's opaque so that it covers with one or two very light coats. You don't want to add any more weight to that coraplas that you absolutely have to.


With the contrast color you can tape off some flames or any type of random or symetrical pattern so that your new color scheme looks intentional.

I used to work at a factory where we used expansion foam to pack the instruments we made. That foam is similar to the foam made by curing polyurethane glue I think.
That foam was total murder to remove! Sometimes a drop would drip out onto something we didn't want it on(like the instrument case!) and it would take hours to deal with it.
We tried many chemicals and methods until we discovered 'Oil-Flo Saftey Solvent'.

This stuff worked amazingly. I don't know if it will work for polyurethane glue, but I think that it is a staple now days at auto detailer places, so maybe if you find a place that details cars, they may put some on a rag for you.

Be aware tho, that you need to test the stuff on scrap cloro-plastic first- the oil flo attacked some plastic we tried it on, yet left most totaly un-scathed..

Here's a link google turned up..

[link=http://www.bigrocksupply.com/cgi-bin/webc.cgi/st_prod.html?p_prodid=691&p_catid=28]oil flo[/link]

Hi Mclintock,

I've searched the web locally, but couldn't find the stuff listed, I'll have to stop by the local suppliers and see if I can dig some up.

I did see something called Goop Off (or something like that) that removes tar etc. and I may try it.

I also read on another forum that raw fuel will soften the stuff, so I'll try that as well - but I've never had it soften when flying so it will be interesting to see if it works.

Thanks for your help.

Fly4Fun,

Wayne Miller

It's COROPLAST...don't worry about the yellow and GO FLY IT!
hehehe...

Hi CrazyHerb,

Your right and normally I would, except coroplast is new to me and I'm trying a couple of unique things such as building a full airfoil using 1/2 pink foam ribs, with 1/4 in. dowels as spars, and stiffening the wing to tail section with foam. Looks good so far! Its coming out lighter than the normal coroplast plane and will be like the UltraStik.

I would like the balsa flyers to be impressed, so want it as neat as possible.

By the way, the raw glow fuel does soften the polyurethane and makes it much easier to scrape off.

I'll keep you up to date.

Fly4Fun,

Wayne