Dollar Tree Foam Board Waterproofing

[Daniel Kezar]

I was thinking one of the flite test videos instructed not to use the waterbase poly? But that was being applied over the stock paper on DTFB, not tissue. Im surprised to hear the application of poly does not help the paper adhere to the foam. I thought it would soak thru and make a better stock paper to foam bond, but I have not personally tired it. I have not heard anyone mention using the minwax poly in the spray can verses brushed on either, but thought this may be an option.

i know this is an old post, however, i was wondering if you have tried the different minwax's yet. i want to waterproof my planes so i can fly in the winter but i do not want to risk ruining them.

 

[Jetcrafter_2000]

Just the waterbased stuff

 

[Daniel Kezar]

Just the waterbased stuff

i was thinking more along the lines of the other video they did called "minwax your plane" or something like that. in that they just put it over the existing paper and specifically said use non water based because it will delaminate the paper.

 

[Psychron]

Don't you love it when you get a video not specifically addressing your question? The answer is, if you're replacing the white paper with the kraft paper, use the water based. If you're simply wanting to keep the existing white paper, the oil based will not delaminate your board and is what you'd use as a first coat on your paper. Despite all that I heard the hot glue won't stick to the polycrylic so they've advised in previous videos to waterproof your planes after building. I've got a couple built and I've actually just thinned the paint with windex and sprayed right on the paper without any issues. The one thing I do though is coat every exposed edge with hot glue to hold those paper edges down to prevent de-lamination later on or while painting.

 

[Merv]

My question is, is it the paper backing that doesn't like the water, or is it the actual foam, or both?

The paper does not like water but it's the adhesive that is the weak link. The adhesive that holds the paper to the foam will let go long before the paper is wet enough to be damaged. Some wet the paper to help remove it from the foam, when damp, it peals right off. Moisture will not hurt the foam.

The water based poly has enough moisture to release the adhesive. The oil based poly will not release the adhesive.

Myself, I cover my planes with colored packing tape. The tape is fast, cheap and water resistant. I have flown in wet conditions (rain, dew) with out any ill effects. If I were flying off the water, I'd use oil based poly to completely water prof my plane.

 

[Brett_N]

Thinned PVA glue (about 70% water to glue) "painted" over the DTFB paper (1) - Makes the paper stick, (2) increases foam rigidity and (3) waterproofs once it's all dry. You can also peel the paper off if you want. Or, for ultra-strength, peel the original paper off, and then laminate 2 layers of brown "construction paper" or "painters paper" using the 70/30 PVA glue mix. This is a common practice for guys that hot-wire cut foam. Once it's dry, paint it however you want.

Oh - PVA is carpenters glue - you can buy a gallon of it cheap. Elmers white glue also works but not as well as the yellow stuff. TiteBond Quick and Thick is my only building glue anymore, and TiteBond 2 is the cheap stuff I use for laminating.

Packing tape also works incredibly well. I found it easiest to use the tape method BEFORE doing any gluing and folding.

If you go with oil based poly, make sure you wipe on - wipe off. Or you will have a plane that falls apart

 

[Jmoore541]

I am new to building with dollar tree foam for airplanes, but has anybody tried fiberglass resin? Unless is eats the foam, it seems that the paper would act like the mat and you would get a ton of strength. A stereo guy named Steve Meade has a fiberglass resin that just uses the ultraviolet light from sunlight to cure it and I wondered if that would work.

http://www.wccaraudio.com/smd-produ...d-sunflash-uv-activated-resin-1-us-quart.html

So I have tried this exact recipe for a rc boat I was making and the resin literally ate right through the DTFB with no paper on it. Idk about the resin you referenced but the typical repair kit you can buy most places did