can you use polyurethane for building up and filling in the grain on balsa before painting?
Iwas going to use butyrate dope, but poly is easier to get.


thanks


Dan

I've used poly for other things, and it would get pretty heavy. Depending on your application, VERY light fiberglass cloth works well, like .25 ounce. Mix in some of the microfiller balloons stuff in with the epoxy, and it will be even lighter. The microfiller stuff is like an extremely fine powder that when you mix it in with the epoxy, takes some of the epoxys place so it is lighter than the same amount of regular epoxy. It works well when fiberglassing something to paint, but it does make the epoxy weaker so it isn't good for cowlings and firewalls and such.

Polyurethane varnish is normally quite expensive, has poor filling properties, long curing time (12 hours between layers I think it was) and is potentially more hazardous to health than regular dope.

On the other hand, it is very resistant to scratches and most chemicals.

I have used it for fuel-proofing with great success. If thinned, its easily sprayed. You can also brush it on, however, the result will be heavier and not as good looking.

Polyurethane paint is excellent on top of fiber-glass mouldings.

/Bo

I have used water-based Polyacrylic - by Min Wax - with corn starch added and it is excellent!!!! Unlike dope, there is no odor. I suggest you put a coat of the Polyacrylic on without the corn starch first. Then a second coat with. Add enough cornstarch or the Polyacrylic to make it a little thicker than cream. This is a very hard material when dry so don't be afraid to sand initially with a coarse sandpaper - like 100 or 180.

RCPAUL

Do you not have lite fill in US. It is the same as the filler used on wall cracks but at 10% of the weight. Easy sanding so it all goes except for what is in the grain.[img]i/expressions/face-icon-small-wink.gif[/img]