Waterproof Your Airplane

by FliteTest | September 24, 2014 | (20) Posted in How To

Peter developed a cool way to waterproof your foam board airplane. You might have seen the results of this technique in our Planes: Fire Rescue episode.  

The coating will vary in smoothness based on how many coats you apply and how much sanding you do.

You'll need Water Based Minwax Polycrylic, Brown Kraft paper, and Baby powder. 

The key ingredient to this trick is Water Based Minwax Polycrylic. 

Cut the paper to size and coat it with the Water Based Minwax Polycrylic before applying to your airplane.

Also, brush on the Polycrylic to the fuselage of your foam board airplane.

The each coat dry and sand with 220 grit sandpaper. 

Peter recommends that you only use this technique on the fuselage of your airplane, not on the wings.

Adding some baby powder with a 1 to 1 ratio to your Polycrylic will give you a nice sand'able coating.

Be sure to share your tips in the comments and join in on the discussion in the forum HERE!

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COMMENTS

animan on September 24, 2014
Nice idea! For planes like the F22 (which I have build and destroyed 4 ), this would be great to pre-do 2 dollar tree panels first, lightly sand, no paint, build F-22 using those 2 dried panels., then re-coat and do final coats and painting.
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Rhudson1960 on September 25, 2014
Sounds like a good idea. It may also help to flatten those bowed and twisted sheets of DTF. I'll have to start a new project to try this out. I have a water-based acrylic from another manufacturer to try. (cheap too, from a $ store)
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FoamFlyinFool on January 31, 2015
well how did it work out and what was the brand u used ???
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steadfast4life on September 26, 2014
Great Idea. No more paper peeling off depron problems. This definitely looks more sturdy and professional.
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sailorJohn on September 25, 2014
Thanks Peter ,I've had my own ideas but this will go into my bag of tricks. We need a special name for all of Peter's great information!
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animan on September 25, 2014
I contacted the manufacturer of this DTFB and they admit to using a less expensive glue, and they had no motivation for us RC people to upgrade the glue on this product, even after I explained the cost/benefit for this industry..
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HorrifiedPilot on September 26, 2014
I love the airframes that peter makes. They look pretty legit.
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pintokitkat on September 24, 2014
As far as I can find out, Minwax, which is sold over here under the name of Ronseal, does not do a water based polycrilic to buy in the UK and I suspect, the EU.

Apparently Ronseal used to sell it years ago, but it was only available to the trade in 1000 litre lots, or something equally as useless to us modellers.

Unless, of course, you know different...
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seansgrandad on September 25, 2014
Reading the interweb I see some advice that "Water borne polyurethane is sometimes called polycrylic". Don't know how accurate this information is though! The name change might be one of those marketing /environmental/PC/blurbspeak things😑
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CJGFX on September 25, 2014
Yes you can get water based varnish in the UK and EU. I've never seen the Minwax brand, but there are others that do the same job. I use V33 waterbased varnish here in Frnace and it work great. Looking on the B&Q website you can use B&Q Quick Dry Clear Satin Interior Varnish 750ml Product code:03203842. You simply need to look on the tins and make sure you can clean brushes with water and the drying time is very quick, in the B&Q case 30mins. Though in my experience on a sunny day it's more like 10mins on foam. If you on doubt buy a small pot and try it on a scrap piece of foam. As well a paper you can use fine cloth too or fine fibre glass cloth. Where I fly has no nice grass for landing on, only rocks and gravel. By adding a cloth layer to the base of planes make them really stand up to punishment..
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Pumpster on September 24, 2014
Great tips!!! I was wondering how Peter got those nice surfaces. Can't wait to try it on my next build,
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Arend on September 25, 2014
more of a meta comment I suppose, but Peter appeared much more relaxed on screen with Josh S. together and the flow of the whole episode was much better than Peter's earlier ones.

And please make the build video for the C119 boxcar soon, my kids so want to put a teddybear in and see it fly!
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CJGFX on September 25, 2014
PLEASE PLEASE PLEASE Peter can we have the plans for the 'Dipper' water plane........
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maue on September 25, 2014
Ditto. Can we please get plans on both planes. I like how much presence they have in the sky.
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Yogenh on September 25, 2014
Me too I would love to have the Dipper
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dshugard on October 17, 2014
me too I'm looking for a water plane
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perpetualn00b on June 23, 2017
it looks like a modified mini guinea pig
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HilldaFlyer on September 27, 2014
Peter, great information and I was waiting for this. I have a couple of questions that you may be able to answer given your experience with this technique.
1) You mentioned that you don't do wings... why not?
2) I've experienced warping issues with flat surfaces (FT-22 wings) after treating with oil-minwax and paint. Does this resurfacing cause warping of flat surfaces?
3) Have you tired to recover a sheet of DTFB before cutting out and gluing? How about after cutting but before gluing?

Thanks - great technique.
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NO49 on October 1, 2014
Polycrylic is not water based polyurethane (wbpu), it's an acrylic varnish, it smells the same as acrylic latex house paint (polyurethane has a different smell). Minwax actually makes polyurethane (both water based and oil based) as well... it's a separate product from their Polycrylic. But, wbpu will be interchangeable with polycrylic in this application. So will another product I use and love... Deluxe Materials Eze-Kote. All three products can be used with light glass cloth to fiberglass or "glass" foam and balsa planes for a sand-able paint-able tougher surface with minimal added weight. Even without actually glassing, guys have been mixing baby powder with Polycrylic or wbpu to finish foam planes for years... just Google the words Polycrylic and baby powder and watch all of the results you'll get ;)
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PropSpinner on September 24, 2014
Next on FliteTest, Building a Seaplane. :-)
Good job guys!!
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maue on October 1, 2014
I second. Sea plane :D
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animan on September 25, 2014
Just did some testing using this method on the DTFB and the water based coating. It works BUT does not solve the number one issue with this foam board, adhesion. The original paper and this new technique still does NOT adhere to the foam. This is the biggest downfall of this foam. After a crash or hard landing, the foam separates from the paper and this causes structural weaknesses. I have found the only glue that really Sticks to this foam is foam safe instant glue, and to re-glue a whole sheet is not practical from a cost point of view.
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sailorJohn on September 30, 2014
Would this work as well on insulating pink or blue foamboard.
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tinkerbill on October 2, 2014
Common sense says it should work on almost any type foam , due to the fact that it is water-based! Adhession might vary with the particular type of foams though. As always, do a test on a small piece first. It saves material and PIBS (pain-in-butt experiences)!
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tinkerbill on October 2, 2014
Along this same topic, has anyone tried using a thinned mixture of Elmer's carpenter's wood glue on the foam from DT? If so, with or without paper? If without paper, has it been used with some very thin polyester or other silk-like coverings? Reason I ask is I was blessed with a whole bunch of this glue for free. If I don't get a good answer in a reasonable amount of time, I might do some experimenting on my own and report back. ;)
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sailorJohn on December 1, 2014
Learning to use Peter's method--- Tip Keep a pin or monocote woodpecker on hand as you will get air bubbles as coating dries-- couple of pin pricks and smooth it down with finger or wet brush and all's well
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lr on March 15, 2015
tinkerbill,
I've used 60 lb kraft paper with Titebond 3 to reinforce a Radian. (I think that's made of Elapor, isn't it?) Works nicely and is pretty smooth even if you don't sand it. Very easy to put on. Thin the TItebond with a bit of water so it brushes out nicely. I'm not sure how much, might be up to 50 percent. Paint on the paper until it's pretty well saturated. Then put some on the foam. Brush and squeegee the paper in place. A credit card works, as I recall. It's ok to brush on some more at this point, but be sure to squeegee it off. If you wait a week, it might be waterproof, but it's pretty strong as soon as it's really dry. Titebond 3 is supposed to be waterproof, or at least very water resistant after a week, but I was only going for reinforcement.

I also used that paper with epoxy to sheet a foam wing. It was a little heavier than it should have been for a hlg wing. 40 lb kraft might have been better, but I don't know where to get it in small amounts. For epoxy, spread out the epoxy on the paper and let it soak in for, say, 5 minutes. Then scrape it off and do the other side the same way. Get it all scraped off, then vacuum bag it to the wing. Seems to be very tough.
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pistolpete1982 on May 14, 2015
Anybody try doing this to wings? Why do they say not to?
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joshuaparker on July 10, 2015
I seen another video on this from some other guy on youtube.He used a glue and water mixture. Has anyone tried that before maybe the Flitetest crew.
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TurtlesThatFly on August 8, 2016
What if I cover the foamboard first, then cut it?
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Waterproof Your Airplane