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Feb 27, 2019, 07:40 PM
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psychedvike's Avatar
Thanks hoppy for including the link to the video. I'd also like to thank you for starting the post in the first place. This method of covering foams has work so well for me for many years and I've had so much fun building too many planes to even mention. I am in you debt.
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Feb 27, 2019, 08:16 PM
Space Coast USA
hoppy's Avatar
Thread OP
No, thank you for the video.
May 08, 2019, 04:46 AM
Entropy is happening!
Jim.Thompson's Avatar

Paper/PVA sheet.


Good thread Hoppy, thanks for starting it.
I did a very quick and simple test over the last couple of days to see if I can make a paper/PVA glue sheet.
I just used a roll of scrap laminating film that I had collected from the printers as the base on which to make it. I started with a sheet of printing paper, wet it out with glue/water mix without measuring ratios. I let that dry, then the next day added a sheet of newspaper, similarly wet out with glue and water.
I continued and added another two sheets and let the entire thing dry for a day and night.
The result is encouraging; I have no doubt that a paper/glue sheet can be made to any thickness desired for a particular application. I'll measure the thickness of this sample piece, but at a guess, it would be around 200/250 microns.
One application that is running through my mind, is to make a curved sheet to take the place of sheeting of the "D" box between the spar and the leading edge of a built up wing. My last two built up wings were made using the so called "laser method", consisting of foam ribs all hot wire cut together, build the top structure, then cut the entire assembly off the board and continue to build the bottom structure. Quick, light and strong.
I figure that paper/PVA might have a role to play in a very light built up wing structure for a thermal glider. I want to avoid using balsa as much as possible due to cost and allergy problems.
The covering could be 30 micron laminating film, or like you have done, more paper?
The laminating film is very nice to use and cheap.

Jim.
Jun 04, 2019, 12:13 PM
Scratch builder

What I've leared


Some posts here talk about alternatives to newspaper and/or Titebond. I'd like to share what I've experimented with in regards to these alternatives.

There is a product I found marketed in the dry wall world. It is called "Fibafuse". It is a mat fiberglass strip 2-1/16 wide by .014 thick. My tests indicated it weighs 1.5 oz./sq. yd.

I thought finally, a fiberglass I can buy locally without spending more than $5!!

I tried it over foam with the intent of increasing the torsional strength of my foam core wing.

I used both Titebond 50/50 and Ploycrylic (blue can) with equal results. The fiberglass is itchy to work with as you would expect. I can imagine that there are two groups of dry wall guys, those that swear by it and those that swear at it LOL!

Anyway, I found it to be at least as strong as newpaper but it was thicker and heavier.

I also tried some polyester fabric that I found to be lighter, at .92 oz./sq. yd. Titebond and Poly as well.

It was not near as strong as the newspaper and its strength was dependent on which way you laid the weave. So this was not better either.

Coffee filters have been tried by many, I found them to be noticeably less stiff for torsional strength than newspaper but they were lighter. Same glue: Titebond and Poly.

I also tried Pellon 830 easy pattern, a product used in sewing. It was very nice to use like the newspaper, but it soaked up a little more glue.

So initially, it starts out at .7 oz./sq. yd. but ended up as heavy as newspaper. This isn't a bad thing, just a characteristic typical of many of the "span" type coverings.... but of course it is locally available to many.

It is not as strong as newspaper but it doesn't warp due to being 100% polyester. This stuff would be my choice over coffee filters because it is one big sheet.

So... I like some others that have posted, I am back to newspaper.

The only thing I like to do different is, after soaking it with water, I squeegee it with my fingers, and then I like to blot the paper enclosed in a paper towel. I change towels at least once until I don't see any more water on the towel.

This gives me a uniform wetness from piece to piece as I apply. I do not use a credit card to smooth and squeegee because there is very little to remove. Instead, after smoothing and adjusting with my fingers, I blot the applied paper with another fresh paper towel.

My theory is that it pulls the glue up through the paper as any extra moisture is removed. It also allows me to press the paper "into the foam". This eliminates any possibility of tearing or "pulling" the paper and leaving stressed areas or tears as I found I tend to do with a credit card.

I think it is worthwhile to read what other people have tried and didn't work so well for them. Perhaps your needs are different and what didn't work for them, sounds perfect for what you are doing.
Jun 04, 2019, 02:36 PM
Space Coast USA
hoppy's Avatar
Thread OP
Good show Ken. I'll have to try the "paper squeegeeing'. Seems like a good idea.
Jun 04, 2019, 06:09 PM
Entropy is happening!
Jim.Thompson's Avatar

My first attempt using paper and PVA glue.


I covered the compound curved wing tips on my new Spacewalker this way.
They turned out ok; one has some very slightly raised bubbles, but you have to look for them to see them.
This job would have been very difficult to do with fibreglass and epoxy resin. Also, it would have turned out much heavier.
I will be using this more. I too like the newspaper.
Jun 04, 2019, 10:01 PM
Space Coast USA
hoppy's Avatar
Thread OP
Bubbles on the underside? That happens.
Jun 04, 2019, 10:37 PM
Entropy is happening!
Jim.Thompson's Avatar
Quote:
Originally Posted by hoppy
Bubbles on the underside? That happens.
I am guessing that this phenomena might be ameliorated by careful squeegeeing the wet paper first, as Ken points out above.
I did not take a lot of care with my technique and I'm sure it can be improved.

I even have the temerity (or just plain cheek) to consider building a large thermal glider using newspaper covering. Maybe, just maybe, paper/PVA over open framed construction....................
Was it you Hoppy who mentioned you had done this in the past?

Jim.
Jun 05, 2019, 08:48 AM
Scratch builder
Hoppy, I hold the paper strip vertically over the sink and lightly pinch it with my index and middle finger. I Slide my fingers downward several times turning the paper as necessary to get good coverage. Then I lay it in the paper towels to blot.

My latest experiment showed that laying the same width paper strip over the top and bottom of the foam core at mid chord is stronger than wrapping a single strip twice as wide around the leading edge.

The two separate strips act as the flanges of an "I" beam and as with "I" beams, the further apart, the better.

I expected the "D" tube type wrap to be better but it's not.


Jim, I would think thin overlapping strips would be best on compounds, the tighter the curve the smaller the strip.

Tearing the paper with the grain will feather the edge for better blending than cut strips.
Jun 05, 2019, 09:43 AM
Registered User
Things I've learned over the years;
Pelon 830 is erm Shite.. Poor at everything I've tried it for.
Newspaper is cheap ubiquitous.mostly heavy and weak though it turns to paper mache with too much moisture
Thin (paint store masking paper is both thinner lighter And stronger.
I simply lay the paper strips or whatever shape piece of paper fits best without incurring wrinkles that will need sanding out later. Used to sheep dip the paper bits in a watered glue tray. No longer, I just apply, then brush on the glue media... It soaks thru nicely.
Also found that Many 5 to 10 layers of Masking paper /glue makes for a defacto molded plywood skin. Similar to a glass/epoxy or poly resin one without the chemical horrors..
However; It Is necessary to prime surfaces with watered white glue and let dry.. Prior to paper covering or it Will develop bubbles and delaminate.
Papering.. Does add weight...But when done with some small experience.. the resultant rigidity is like a Surfboard..
I've seen one fellow who uses printer paper and fits it in imitation of ali skin panels
With excellent results, seemingly the weight isn't an issue for his models.
Lotsa choices, clearly, easiest is to experiment tho to find what suits/pleases. there is No single best technique.
Jun 05, 2019, 11:08 AM
Scratch builder
What brand is the masking paper you use? Maybe it is here in the states as well?

I don't really use "newspaper" but rather the packing paper available from Wal Mart; others include U haul and Blue Hawk at lowes.
Last edited by KenSt; Jun 05, 2019 at 11:15 AM.
Jun 05, 2019, 11:44 AM
Registered User
tspeer's Avatar
Quote:
Originally Posted by KenSt
What brand is the masking paper you use? Maybe it is here in the states as well?....
I use masking paper as well, like this brand.

I've also used printed bond paper, applied with WBPU instead of glue. I then iron on 1.5 mil laminating film for a light finish that adds to the strength and stiffness.
Jun 05, 2019, 12:49 PM
I Look, Listen, and Learn
Timbo383's Avatar
Quote:
Originally Posted by KenSt
What brand is the masking paper you use? Maybe it is here in the states as well?
It could be the same stuff I got at Home Depot, 1 foot wide and about, I don't recall, 25 or 50 feet. Thin but tuff.
Jun 05, 2019, 01:35 PM
I Look, Listen, and Learn
Timbo383's Avatar
Double post.
Jun 05, 2019, 03:13 PM
Scratch builder
Yes, Trimaco is quite easily found. I sent them an E mail asking the weights of their general purpose and premium green paper. No response yet.


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