To Poly or not to poly... that is the question?

Inq

Elite member
I'm trying to improve my cosmetics of building. I got the oil-based Minwax polyurethane recommended here on the forum on the first plane, but it was always destined to be a mule. If it lasts ten flights, I'll be ecstatic. I didn't do any post processing after cutting out the pieces on it.

I'm working on my first plane of my design and I want it to look better standing still (also). I've actually been sanding the DTFB. Who knew you could sand the paper and foam with sandpaper? Another tidbit, picked up on the forum. Don't think I'd ever get to that one on my own.

While I'm sanding it, I thought how fragile the paper is, yet once the poly is on it... its almost like plastic (guess it is really). Are there any pros or cons one way or another why I should or should not poly the pieces before assembly? My thought is once poly'd I can do final sanding of the poly for a nice surface ready to paint without having to deal with the corners and hot-glue. However, I had to hot-glue a rubber-band wing protector on after the poly and I noted it had fallen off on the way to the landing field.

Thanks guys!
 

Foamforce

Well-known member
I'm trying to improve my cosmetics of building. I got the oil-based Minwax polyurethane recommended here on the forum on the first plane, but it was always destined to be a mule. If it lasts ten flights, I'll be ecstatic. I didn't do any post processing after cutting out the pieces on it.

I'm working on my first plane of my design and I want it to look better standing still (also). I've actually been sanding the DTFB. Who knew you could sand the paper and foam with sandpaper? Another tidbit, picked up on the forum. Don't think I'd ever get to that one on my own.

While I'm sanding it, I thought how fragile the paper is, yet once the poly is on it... its almost like plastic (guess it is really). Are there any pros or cons one way or another why I should or should not poly the pieces before assembly? My thought is once poly'd I can do final sanding of the poly for a nice surface ready to paint without having to deal with the corners and hot-glue. However, I had to hot-glue a rubber-band wing protector on after the poly and I noted it had fallen off on the way to the landing field.

Thanks guys!

I’ve seen others say that glue doesn’t stick to the poly, so assemble first, then poly. I can see the appeal of applying poly first though, so if you try it I’m interested to hear how it goes. I wonder if it will make cutting more difficult.

FWIW, my recent experiences with poly have been that it needs to go on thick to be waterproof. My first attempt was to apply it and then wipe off excess with a paper towel. However, when I painted after that, I got warping. My next attempt was to apply it thick with a brush and leave it alone. That appeared to work much better and I didn’t get any significant warping when painting.

Regarding painting, I’ve been airbrushing on cheap acrylic paint thinned with water. It covers the poly nicely but it does scratch pretty easily. It doesn’t fall off by itself though, so it’s adequate for my planes, considering that I’ll crash all of them eventually. PS, I’m not doing any sanding. That’s a particularly time consuming process and I feel that it works well enough without it. I’m not building very pretty planes though.
 
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Inq

Elite member
Regarding painting, I’ve been airbrushing on cheap acrylic paint thinned with water. It covers the poly nicely but it does scratch pretty easily. It doesn’t fall off by itself though, so it’s adequate for my planes, considering that I’ll crash all of them eventually. PS, I’m not doing any sanding. That’s a particularly time consuming process and I feel that it works well enough without it. I’m not building very pretty planes though.

Thanks for that! That was going to be one of my next questions. I spent about $25 on the foam-board, 3D plastic, Motor, ESC and propeller and servos. If I get three cans of spray-paint, I double the cost of the plane.

I've never used acrylic paint. Sounds perfect... I can easily clean the air-brush with water. It's water base? Does is rub off? Do you do a poly coat over it? Does it stink? Wife isn't very tolerant of my stinky antics. :rolleyes:
 

Foamforce

Well-known member
Thanks for that! That was going to be one of my next questions. I spent about $25 on the foam-board, 3D plastic, Motor, ESC and propeller and servos. If I get three cans of spray-paint, I double the cost of the plane.

I've never used acrylic paint. Sounds perfect... I can easily clean the air-brush with water. It's water base? Does is rub off? Do you do a poly coat over it? Does it stink? Wife isn't very tolerant of my stinky antics. :rolleyes:

I’ve tried acrylic paints from HobbyLobby, Dollar Tree, and Dollar General. They all seem fine. One thing I notice is that they have a kind of gritty feeling after application and they’re not shiny. It’s uniform and looks good enough though.

It doesn’t rub off with your finger, but I can scratch it with my fingernail. The bottom of my snowball has lots of paint rubbed off from extensive sliding over icy snow, but that was enough to cut deeply into the foam on the sides of the skids, so it’s not surprising that it removed paint too.

Yeah, the acrylic cleans up pretty easily. I do most of my cleaning by shooting water through my airbrush. I also back flush it by pinching the end with a paper towel while shooting water. I finish up by shooting a small amount of acrylic airbrush cleaner, although I’m not sure how necessary that is. I shoot it into the cleaning pot to reduce odor. I haven’t had to disassemble my brush to clean it yet, and these were the instructions from Badger airbrush, more or less.

I ventilate the basement room that I’m in and wear a respirator while I do this, but it doesn’t seem to have much odor. On the other hand, brushing on the oil based poly is pretty stinky, so I leave that in the garage to dry for 24 hours. That continues to smell a little for a couple days. In comparison I don’t even notice the acrylic.
 
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