Minwax Spray - a faster, less messy way to waterproof foamboard?

[F2G2Corsair]

Hi everyone. I've been lurking on Flite Test for some time, and thought I'd share an idea I have. I've been experimenting with many waterproofing methods for my swappables, and I've come across a method I haven't seen used before.

I'm sure you've heard of using polyurathane minwax to waterproof a plane, but did you know they sell minwax spray too? I decided to try it on a few scraps of foamboard, and I've found it to be hit or miss, but when it works it's just as good as regular minwax. Typically I stand with the nozzle about a foot away from the plane and slowly circle the aircraft while spraying every last inch of it, which takes about 15 to 30 seconds, then I let it dry, flip it over and repeat. If you get too close the paper comes off the foam immediately and warps it, so be careful and practice a few times. I did this outside on a sheet of cardboard just so you know. I've found this method to be faster and cleaner than applying minwax with a brush (did you notice the Top Gun reference lol).

I noticed the Clear Gloss minwax spray doesn't require you to shake the can for 2 minutes before use, unlike the Clear Satin kind. I plan to use this method on my next build, a swappable Pizza Box Flyer.

One last thing, don't try using minwax spray in a windstorm. It was nice and convenient at first because the wind pinned the foamboard to a fence for me, but the moment the wind shifts it's gonna spray all over you lol! I was just lucky it didn't... And don't leave your plane out to dry at sunset, if the temperature changes it'll turn into a taco!

 

[adamd]

i was also wondering about the spray. if you got good results i might try the same on a foam board north-star i'm drawing up

 

[rorak]

From my understanding its the propellant in the can that makes the paper come off. If as you said you hold it a foot or more away the propellant evaporates before it hits the foamboard, also use lighter coats. I think Chad talks about it in the painting foamboard episode of Flite Test, Im assuming minwax uses the same propellant as spray paint.(I could be wrong)
Paul

 

[con244]

Did I misunderstand the application instructions of the canned stuff? I thought it was necessary to wipe the excess off to avoid too much added weight. Does spraying help keep the weight down?
Con

 

[rorak]

I would think you would still want to wipe it down, however I dont think much came off when I wiped mine down.
Paul

 

[con244]

With the addition of spraying thinners the spray on product would dry very quickly stopping you from wiping of any excess before it starts to dry which would leave a rough finish. Maybe over there in the cooler weather this may work but in the 110+F that we have here, I'm not sure the spray on would be a goer. Maybe in winter??? I though the whole idea was to actually soak the paper to make it waterproof. I have used spray paint on foamboard models with no problems and think that this is probably just the same but with a clear coat.
Con

 

[F2G2Corsair]

I haven't been wiping down the foamboard I sprayed with minwax, and I've repeatedly tested it by dunking it under a water faucet with no effect. As far as temperature goes, I've had trouble with rapid cooling at sunset causing warping, but I'll have to wait a few months before I can do high temp testing. I don't know if minwax spray is lighter than the brushing technique, but I would think it wouldn't be a big difference.