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Noin
10-27-2005, 03:39 AM
I have just finished painting my Estarter with craft type acry;ic paints and an airbrush. I now want to apply some polyurethane to the foam for a clean shell like surface. My problem is I don't know what polyurethane to use. What one can I buy that will not eat the foam. I know poly urethane by itself will not eat the foam but I find the stuff that comes in liquid form to thick to spray through my airbrush and I don't know what to thin it with that will not eat the foam. As for the polyurethane in the spray can, I am not sure if the propelant or any added chemicals would eat the foam. What have you guys used to solve this problem?

qban_flyer
10-27-2005, 03:49 AM
Krylon Fusion comes in clear and it is foam friendly as long as you spray it from about 18" away from the foam. Two or three thin coats is all you may require, though you'll know how much your model will need.

I sprayed my E-Starter with Michael's acrylics via an air brush too using pastel yellow for base color with medium cobalt blue trim a la Cessna Skylane. I did not add a clear coat to the plane since I wanted to keep it as light as possible.

I have used Krylon Fusion and Short Cuts on Blucor foam and so far nothing detrimental has happened to the foam.

hoppy
10-27-2005, 04:47 AM
Any water-based PU gloss floor/furniture finish will work. Thin with water if needed to spray. Another finish commonly used is polycrylic. That also is a water-based furniture/floor varnish available at hardware stores.

Another technique is to cover with 1 1/2mil clear and colored packing tape. This adds a glossy surface which also strengthens the foam. It can be iron on smooth. http://www.fast-pack.com/colored_tape.html

Covered with tape -

timocharis
10-27-2005, 05:23 AM
The clearest I've used is the water-based Varathane. Excellent finish. The Minwax Polycrylic is very, very close so if that's what your local store carries, go for it. They both are best brushed on, then sanded very lightly (use 400 or 600 grit). Better control than sprays, in my experience.


Dave North

qban_flyer
10-27-2005, 06:04 AM
Another technique is to cover with 1 1/2mil clear and colored packing tape. This adds a glossy surface which also strengthens the foam. It can be iron on smooth. http://www.fast-pack.com/colored_tape.html

Covered with tape -

Nice taping job there, Hoppy, mighty nice.

qban_flyer
10-27-2005, 06:07 AM
The clearest I've used is the water-based Varathane. Excellent finish. The Minwax Polycrylic is very, very close so if that's what your local store carries, go for it. They both are best brushed on, then sanded very lightly (use 400 or 600 grit). Better control than sprays, in my experience.


Dave North

Do you thin it or apply it as it comes from the can? Also, how thin a coat do you brush on the surface?

I like the brushing idea as it leaves no over spray behind.

Noin
10-27-2005, 01:29 PM
I like to spray on my finishes, as I find I have a more even coat. Thanks for the replies guys. I will go out today to check the local hardware stores.

KenS
10-27-2005, 01:43 PM
I asked a general question about airbrushes here: http://www.wattflyer.com/forums/showthread.php?t=2062

Thanks for the input about the finish, I had forgotten all about it, I assume it's for light waterproofing from the morning dew?

Noin
10-27-2005, 02:20 PM
Actually I don't like the finger prints and flat finish you get on bare foam or foam that has an acrylic finish only. With a PU finish it will be easier to clean and also have a slight gloss to it. I know I could get a high gloss but I think that would take to many coats of PU and add to much weight.

Vyceroy
10-27-2005, 06:23 PM
i use Minwax wbpu with great results .. i just apply it with a 1-2 inch foam brush on small models and a 3 inch on larger ones ..

qban_flyer
10-27-2005, 07:31 PM
I like to spray on my finishes, as I find I have a more even coat. Thanks for the replies guys. I will go out today to check the local hardware stores.

If you are looking for Fusion or Short Cuts clear by Krylon the only place where I was able to find it in my area was Ace Hardware.

KenS
10-29-2005, 04:40 AM
HMMM..It's a toss up between 2 brushes now, the Badger Cresendo or the Badger 155 Anthem...they are basicly the same price.
The Anthem is a 1 variable needle setup, the Cresendo comes with 3 needles....oh the decisions one must make arghhh...:eek:

qban_flyer
10-29-2005, 05:11 AM
HMMM..It's a toss up between 2 brushes now, the Badger Cresendo or the Badger 155 Anthem...they are basicly the same price.
The Anthem is a 1 variable needle setup, the Cresendo comes with 3 needles....oh the decisions one must make arghhh...:eek:

Have you checked them out on Tower's site? They have enough Badgers in there to drive anyone bonkers!
:p
http://www2.towerhobbies.com/cgi-bin/wti0001p.pgm?Q=1&I=LX8163&P=7

http://www2.towerhobbies.com/cgi-bin/wti0093p?&C=RJA&P=7

Big_Bird
10-31-2005, 01:44 AM
About how much weight would you estimate that Min-Wax Polycrylic brushed on a GWS Corsair would add per coat? Would it give any dent protection? This would go on over Wally World acrylic water based craft paint.

Ken

Steve
10-31-2005, 01:19 PM
I would vote for the polycrylic water based stuff in a spray can. I would be careful though. I built a GWS Beaver once and used some .5ozFG and the water based poly. I was a great finish, but the plane was way too heavy when I was done. Not a problem if you have a beefed up power system, but a BIG problem if you plan to fly stock.

I can see a light spray of poly to keep off the prints and smudges on the foam, but a "shell like" finish sounds very heavy IMHO and might be a problem on an e-starter which has a rep for being tail-heavy in the first place.

Big_Bird
11-01-2005, 01:10 AM
Steve, thanks a lot for the advice. I think I'll just leave the clear coat off.

Ken

hoppy
11-01-2005, 02:20 AM
36" of 3"wide 1.6 mil 3M 3699 clear packing tape weighs between 0.1 and 0.2 oz. Provides strength, a smooth glossy look, and grime protection. I use it on all leading edges and the bottoms.

Steve
11-02-2005, 12:04 AM
I agree...where would we be without clear packing tape?! Why a fella couldn't build a decent plane without it... :-)

KenS
11-02-2005, 01:12 PM
Well I wound up getting a Badger Crescendo 7 pc. from e-bay for 55.00
So I guess another adventure begins:P

timocharis
11-03-2005, 05:40 AM
qban: I just use the varathane/minwax straight up. You can thin it a little, but too much water and it doesn't work right any more.

Weight added is a question of technique. If you brush on thinly, then sand it back, you'll only add a few grams. If you ... well, you get the idea.


Dave North