Polyspan Covering
This may be deviating from the subject a bit (and a bit long-winded) but...
I bought some LiteSpan today at the LHS in my quest to have a super light 5-servo Herr Cub (flat wing with two HS-55 for built-up ailerons I added). I had on hand a roll of cub yellow ultracote, but decided it might be fun to go with a more 'traditional' (meaning liver-spotted, old fart, 1940's-type, more-pain-than-it's-worth) covering method.
It seemed a bit odd that I couldn't find anywhere on the label exactly how much LiteSpan material I was getting...hmmm...come to think of it, the packaging brilliantly disguises the 'yield'...what a fantastic marketing achievement! The price seemed decent ($3.50 or so for ??? sq. ft.), so I didn't complain and bought two packages. After unfolding the first pack, I found that it's probably not enough to cover the wing. Oh well. I thought that I'd pop one pack open, experiment with it, and see what it was all about.
After applying Balsarite to the test frame and 'kicking' it with a heat gun, I set my iron on low-ish. The LiteSpan seemed to stick pretty well to the Balsarite at low heat without wrinkling or deforming. After covering the underside and ends of the test frame and trimming, I recoated the edges (over the LiteSpan) with more Balsarite. I couldn't kick it with the heat gun, so a 20 minute (minimum) wait is needed. Applying the topside covering was fairly easy, and after sealing all of the edges, I slightly increased the temperature of the iron and shrunk out all of the sags (there weren't many since the test frame was flat).
I applied 21st Century paint to the covered surface to see what level of opacity I could achieve. I was very put-off by the results. It would take a TON of paint over the covering to get it to the point where it wasn't semi-transparent. Grrrrrr.......... Maybe if I primed the entire plane before applying the color coat, I would get what I was looking for...but at the expense of more weight which was EXACTLY what I was trying to avoid.
Remember that the test frame was flat. Covering compound surfaces with this stuff would require one to feather the LiteSpan by making lots of radial cuts, then applying more Balsarite, then ironing some down, trimming, then applying more Balsarite, then gumming up ones' iron...you get my drift?
OK, on to the durability tests. Can you say 'flunk'? I knew that you could. The LiteSpan is probably twice as durable as Japanese tissue...and 2x0=0. I seriously doubt that it would endure even the most minor of bumps without tearing. Applying a small amount of fingertip pressure to an open bay would require re-shrinking. No thanks.
My objective was to keep it light, but make it look good. Although I don't really like the glossiness of the Ultracote, THAT is what I'm going to use on this cub. The LiteSpan would require so much more paint that I believe that the differences in the final weight would be insignificant.
Consensus: If you have the patience and the time, don't give a hoot about the finish of your planes (I'm talking opacity here), build velvet-lined boxes to transport your planes in, and never actually touch your planes (without forceps at designated hard-points) this stuff is for you! Hell...if you want to play around with the LiteSpan to draw your own conclusions, I'll send you the remainder of the pack that I opened. SASE to me and it's yours.
Note: I don't consider myself to be a 1/2A guru by any means...I typically fly .40-size fun-fly profile, combat screamers, and some really sweet 1/4 and 1/3 scale aerobat stuff. Whatever the case, I try to keep it light!!! I have an EXTREME amount of experience with HLGs (where every gram counts), so I am fully aware of the lightness vs. durability travesty.
-Tom