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Author Topic: Polyspan  (Read 904 times)
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Crabby
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« on: August 24, 2017, 06:21:56 PM »

I have been a long time Esaki user, and would like to try some Poly Span on my next bird, the Guillows Bullet or the Comet Pepper. Questions: how do you apply it, what heat source shrinks it best, and how do you color it? Does one need to consider a different method of framework to allow for the shrinking? I am just doing a little recon before I jump into the deep end never having swam Grin Also You guys who like to use esaki over mylar I would like to hear about that as well.
I am laying in the sack getting over back issues, and getting very itchy to start butchering balsa again. I need to add some covering techniques to my arsenal, if I am gonna fly outdoors in Florida.
« Last Edit: August 24, 2017, 06:38:15 PM by Crabby » Logged

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gossie
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« Reply #1 on: August 24, 2017, 06:47:30 PM »

I've used Polyspan a few times, and it's great stuff for larger models.......Power models in particular.......Esaki for me on small or lightweight models though thank you.

I dope the frame several times with 50/50 dope and thinner, sand back each time with very fine grit paper to remove any bumps.
Cut the Polyspan oversize, lay it on the frame and using a small brush & run acetone or lacquer thinner through the Polyspan onto the frame so it re-wets the dope and grips the Polyspan.
I always put it on shiny side DOWN for good grip to the frame.
You can pull it out to make a nice smooth job of it before the dope goes off, and re-wet it of course if need be.
When it's done I run an ordinary clothing iron over it quickly and that shrinks it ready for a coat or two of thin thin dope, and then I either paint it with a rattle can or use coloured tissue for decoration.
Suggest do not sand the Polyspan when it's on as that lifts the fibres.

Hope that helps.
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Flyguy
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« Reply #2 on: August 24, 2017, 08:30:08 PM »

I would strongly advise against using polyspan on anything under 40", I made that mistake on my 34" Jabberwock and it added way way too much weight, believe me it would be way too heavy for the Comet Pepper. It's great for Wakefield wings, but anything smaller than that is a mistake, in my view - for ex I used it on my Coupe and would only use Mylar on that now, it's overkill.

I use polyspan lite (from Mike Woodhouse) on the fuselage only, then give it two coats of 50% nitrate, yes it's still porous but it doesn't matter for the fuselage. I just rub the frame with glue stick and then place it on, pull it smooth, let it dry and trim, then shrink, I like to just hit it with a heat gun. I really like it, you can work with it and it's the one thing I can get a perfect job with everytime (Mylar is trickier). If you don't want to get polyspan lite (seems like it's only available overseas), then I'd go with tissue, or maybe tissue over mylar, or even a light silk, just for the fuselage.

I wouldn't use polyspan lite for the flying surfaces though because it's too porous and there's no reason to add weight with a lot of dope. I use 1/3 mil Mylar for the wing, 1/4 mil for stab and rudder, again attached with glue stick, that's it, then just spray it with a coat or two of paint. That's very light yet tough. I used to think that Mylar doesn't add any strength but that's not true, I stuck 1/3 mil mylar on a floppy wing and it was pretty damn stiff after shrinking. Another interesting thing I noticed on landing is that tissue seems to get sliced easily by the astroturf, I think because it's stiffer, whereas the mylar actually seems to hold up better, doesn't slice, maybe some dents but you can shrink those out.

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Crabby
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« Reply #3 on: August 24, 2017, 08:53:20 PM »

Guys, when you speak of heat gun do you mean the wife's hair-dryer or the red one all the bald guys use?
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« Reply #4 on: August 24, 2017, 09:59:43 PM »

Your wife wouldn't have any hair if she used the heat gun as a dryer! It gets much hotter than a hair dryer, here's one, though you can probably find them on amazon or elsewhere:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHZ16&P=ML  Once you get practice you'll be surprised that you can get away with incredible heat to get those stubborn wrinkles out! I also have irons, but I just use those to smooth the edges, I'm a heat gun fan for all the surfaces.

Bald guys use a red hair dryer?
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Crabby
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« Reply #5 on: August 24, 2017, 11:14:24 PM »

Ha Ha Ha hence the distinction "heat gun" vs hair dryer! An inside joke we used in my old job as a Graphic production supervisor, I used it so long I forgot the difference. The GM was bald and we had a red hot sob heat gun that resembled a hair dryer. We would laff and say Vinnie (the bald guy) f'd up and used it instead of a hair dryer... you had to be there. But
It's a scenario where fiction morphs into fact especially when you have had many screamingly funny anecdotes where a guy who was really upset over his hair loss (he was a real jerk ) was the the butt of our inside joke... I am tearing up right now thinking of his very chrome done! Ha ha ha! RIP  Vinnie! You bald so & so! God bless! If you weren't such a jerk we'd a laid off!
« Last Edit: August 24, 2017, 11:28:05 PM by Crabby » Logged

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« Reply #6 on: August 25, 2017, 01:30:19 AM »

Sorry for that last response... I swear it's the pain meds I am on... if I could delete it I would... anyway what thickness Mylar am I gonna order, and can I use Design master florals on it? I am worried that it's translucency will show my spray pattern...?
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Tapio Linkosalo
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« Reply #7 on: August 25, 2017, 02:14:02 AM »


I use a covering iron for all my covering work, both attaching and tightening, and for Polyspan, Oracover and mylar. Just adjust the heat properly.

When working with polyspan, note that there is a shiny side and dull side. Always cover shiny side out, as the dull side takes a lot of dope to tame all the hair sticking out. You do not want to apply that much dope onto the covering.

For coloring, I cover my wings, then apply a few coats of dope until the finish is good, then apply cover with ordinary spray can paint. A final layer of sprayed lacquer finishes the surface. We are talking about F1B / F1H sized models here, I would not use polyspan for smaller models.
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« Reply #8 on: August 25, 2017, 10:16:53 AM »

Just to pass forward my experience with 5 micron Mylar covering and temperatures.

Everybody told me low heat for sticking the thing on the frame, high heat to shrink. But nobody told me what's low heat and what's high heat. So when I started the first time I set the iron on about 120°C to stick it and 150°+++ for shrinking. Afterwards I was surprised that the whole wing had terribly warped  Angry  Sad  :'(
So on the next wings I turned down the temperatures to about 50°C for sticking and 100-120°C for shrinking. That gives me nice tight coverings without any warping.

BTW, I prepare the wood in a similar way as Gossie, 2-3 coats of diluted sanding sealer or dope, what's nearest on the working table, and fine sanding in between with 400 wet and dry sanding paper. Then 2 coats, on the underside of concave sections also 3 times, with a product I find here called Pattex (similar to Evostick), a mastic glue. Diluting a lot, no more than 25% glue and 75% mastic thinner, thin like water!

As tools I use only a small iron like the Coverite 21st Century Sealing Iron on the Tower Hobby pages with temperature control.

Urs

PS: on top of the Mylar I put normally Esaki with dope (little), because the appearance of the plastic covering is not my preferred one.
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Mike Thomas
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« Reply #9 on: August 25, 2017, 06:06:58 PM »

I use polyspan lite (from Mike Woodhouse) on the fuselage only, then give it two coats of 50% nitrate, yes it's still porous but it doesn't matter for the fuselage..............I wouldn't use polyspan lite for the flying surfaces though because it's too porous and there's no reason to add weight with a lot of dope.

I have some of Mike Woodhouse's polyspan lite, and it is very porous. However, it may work well as an alternative to mylar under Esaki tissue. Perhaps light enough for a Coupe wing. Has anybody tried it?
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Flyguy
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« Reply #10 on: August 25, 2017, 08:35:39 PM »

Sorry for that last response... I swear it's the pain meds I am on... if I could delete it I would... anyway what thickness Mylar am I gonna order, and can I use Design master florals on it? I am worried that it's translucency will show my spray pattern...?

I would get 1/4 mil for the stab/rudder and 1/3 or 3/8 mil for the wing. Design master florals work really well on Mylar, 2 light coats is usually plenty. If you want it to look like tissue, use the holiday red I note in my Pacific Ace building video, you would think it was Japanese tissue if I didn't tell you, it's flat and has texture, also the purple pansy from my Comet Pepper building video has a lot of texture and really looks like tissue, I have a modeler friend who saw it awhile back and he thought it was tissue. But I've also experimented with some of the 'just for flowers' colors, which are more transparent and are basically dyes. I was hesitant earlier but now I like the way they look, the Lanzo Cabin is a good example. So it depends on what kind of look you want. It's pretty forgiving with respect to spray patterns, just get a somewhat even light coat on it, don't blast any particular area too close, and it kind of smooths out nice when it dries. I've tried almost, but not quite yet, all the colors in the floral series, I mention most of them in the videos so that you can see what they look like (and I can keep track of it myself!).

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Crabby
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« Reply #11 on: August 25, 2017, 10:01:04 PM »

Are you doing any prep work to deal with the static electricity change in the Mylar?
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« Reply #12 on: August 25, 2017, 10:47:06 PM »

Nope. I just lay out a foot or two of paper towels. You can then roll out the Mylar nice and flat on that and trim with scissors. Then I glue stick the frame, sit that down, pick up the Mylar with two hands, hold it relatively tight though it doesn't really matter, and stick it down on the frame. You can then pull up parts, or just pull on it, or do whatever to get it relatively smooth. I tend to treat it like tissue and still try to get any wrinkles in the span direction. If I'm not sure they'll shrink out, you can actually give it a little test blast with the heat gun, that will usually tell you if you'll be able to shrink them out later when it's dry. Then let it dry, trim, shrink, and, if I have to, do the edges with an iron. Some have asked for a video of my procedure, but it's embarrassing because it's really primitive - lay out on paper towel, rub glue stick on frame, pick up and lay on Mylar, that's basically it!
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Crabby
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« Reply #13 on: August 26, 2017, 12:00:39 AM »

Nothing beats doing, and I would be if I wasn't laid flat most of the day, so I have the luxury of baiting fellow Hip-Pocketeers for info. So nothing to do but wait for a few rolls of Mylar. I have been using the floral sprays for a while, just this will a first with anything other than Esaki. I have a half dozen planes in triage, and a few unfinished projects that will be put on hold, in favor of a Pepper, or an Arrow.
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« Reply #14 on: August 26, 2017, 04:01:14 AM »

Interesting thread, I've been interested in this stuff as well,  hope you get feeling better Crab.  I'd love to see your next project.
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Crabby
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« Reply #15 on: August 26, 2017, 08:52:46 AM »

Thanks Steve, I'm finally paying the price for my suicidal and fanatical approach to sports, work and life in general. I had several coaches and bosses who I would have gladly fought a running chainsaw for, and finally the worst perpetrator turned out to be me. I have several abnormalities in my lower lumbar area resulting in sciatica, and periformis syndrome. Now I am being forced by the maker to now stop. It a matter of whether or not I want to return to a full life again. Trust me even the simplest things are finally being granted back, but I am on a slippery slope to be sure. Sorry, I feel like if you or anyone out there feels like a coward because you can't physically do something, see a shrink before you cripple yourself!
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« Reply #16 on: August 27, 2017, 12:20:12 PM »

I used polyester tissue or polyspan if you prefer with shiny side in once and never again.  It went hairey without sanding and when I applied paint (sprayed) it looked awful.  I use diluted pva brushed onto the framework and so far - several models   - some diesel powered and washed with detegent spray - are still sound after 3 or 4 years at least.  The last one I did, a Mamselle I painted with fairly cheap Acrylics from a sort of art shop and admittedly it is electric powered the paintwork is still good even though it has got wet a few times so acrylic adheres to polyspan OK.
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