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Apr 10, 2011, 11:11 AM
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Leightweight Brown Paper Covering wbpu/glue


I have three planes to cover - two are balsa sheeted wing and balsa fuse and is a complete foam plane. I want to achieve some strength and a surface that when painted, will shine without adding a considerable weight. I've looked at a lot. Liquid sheeting, silk, glass, etc. Epoxy and glass is not an option - just to heavy. I've read tht silk is can be just as strong and weigh less. Also, not interested in packaging tape. In this thread, I want to concentrate the disucssion on brown paper cover techniques. I am looking to lightweight brown paper packing paper (u-haul) and either wbpu or glue. I am looking for the best method to achieve a lightweight, strong paintable surface that will yeild an excellent finsih. A few questions:

1. What are the best methods so seal the balsa and foam?
2. Wbpu or glue - pros cons?
3. What is your technique.

Thanks in advance for you time and information.
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Apr 10, 2011, 02:26 PM
Master of the figure 9
Old Man's Avatar
I have covered foam models with both wpbu/paper and resin/glass, the resin/glass models always come out lighter. I used phone book paper because it was lighter than brown paper.

Paper covering will add much more weight than resin/glass when done properly. It is very easy to add a ton of weight with the Wpbu becasue is saturates the paper were resin goes between the fibers in the glass cloth.

I built two identical Mig 21's, one with wpbu/paper covering one with resin/glass covering. The resin/glass covered Mig weighed 12oz less than the paper covered model.

Good luck I will be watching with interest.

David
Apr 10, 2011, 04:31 PM
Registered User
SGM (light) grade silkspan and 50% wbpu thinned with water. What weight FB cloth did you use?

howell
Apr 10, 2011, 07:45 PM
Build more, websurf less
FlyingW's Avatar
Rocket,

I've used paper from brown paper lunch bags and also 3M postal wrapping paper with great success. I apply it with Titebond-II mixed about 50-50 with water. (I think it adds strength, but I always add wood spars to the foam wings anyway.)

Apply small pieces no bigger than 9x9 inches, or whatever you can fit in a paint roller tray. I think you can get as big as a 8x8 or 9x9 inch piece from a single lunch bag - buy a bag of 50 - it will last a few wings.

Mix the glue and water in the paint roller tray. Then dip the piece in the glue mixture and work the glue through it and to all spots front and back. Then squeegie most of it off with your fingers. Then position it on the wing and smooth it in place with your fingers. Then wipe it off a bit with a paper towel and let dry.

Keep plenty of paper towels around to clean the drips and your hands - they will begin to stick to the wing as well if not kept clean. Since it's all water-based, it doesn't smell and it is pretty easy to clean - just don't let it dry before trying to clean it. And do not do this operation anywhere in the house without a drop cloth and while wearing old clothes - it makes a lot of drips.

Do pieces on the top and bottom of the wing at the same time - the paper shrinks a little when it dries and will warp the wing if you do only one side. I usually work from the tips in towards the root. Then I use strips of the heavier paper over the leading edge.

Prepare only enough glue/water mixture to do about four pieces - usually the top and bottom on each wing panel. Let dry overnight. Then repeat with the next section in.

It takes few days to finish a wing, depending on the span.

The results are a realistic looking (kind of like panels lines) and relatively smooth surface. It is also suprisingly strong and light, and add a coat or two of water-based polyurethane to seal it.

While I've made a couple of wings that look good with the brown color, I did use thinned latex house paint on another wing and it came out well. I suppose you could spray paint it with something like Krylon after you sealed it with the wbpu.

Good luck.

Paul
Apr 11, 2011, 02:32 PM
Registered User
Thread OP

Great Info


Thanks for the great info. David, what method are you using to achieve such a lightweight glass finish? Also, can lightweight silk be substituted for the glass? Really nice work Paul. One of the planes is an old Sig Mustang 450 that I am going to build as an electric conversion and really want to keep the weight down. Silk and resin/poly - what are your thoughts?

Johnny U.
Apr 11, 2011, 06:13 PM
Trapped in California
foamflyer's Avatar
http://www.foamflyer.info/papercover.html

I've successfully used white copier paper.


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