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Building Tips and technical articles. => Paint and finishing => Topic started by: rob biddle on July 19, 2009, 09:00:09 PM
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Hi gents,
I'ts been a fair lay off for me but I'm back into some serious building again and I hope everybody is doing well.
Currently I'm building a Brodak nobler which I hope to fly in advanced at the Aussie nats held between christmas and new years. The airframe is pretty well complete with a few little fiddly jobs to go before beginning the finish.
I plan on using the minwax pc method which has given me decent results in the past. This time I'd like to use polyspan for the open bays instead of plastic film and was wondering what is a good alternative to balsarite as an adhesive to stick it down. Balsarite is simply not available here (to my knowledge).
I guess nitrate dope would work but I was hoping to eliminate dope from the equation altogether. In the past I have used "Clag" brand water based kids craft glue to stick down silkspan, it is truly wonderful and super user friendly.
Any thoughts would be greatly appreciated. Thanks in advance,
Rob.
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Rob
SIG Stix It, will work on polyspan,I picked some up at Col Taylor Hobbies,Wagga
on my way back from Melbourne,Kelletts in Sydney may carry it.
Paul Allen
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Rob
Disregard Kelletts,I just checked your location,try some hobby
shops in Melbourne.Check out Hobby Cave on the net.
Paul Allen
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Rob
"Applying The Covering (Silkspan, Japanese Tissue, Sig Koverall, Polyspan) I have always applied one coat of Sig Nitrate dope unthinned to the bare wood sanding after each coat with 600. The reason for using Sig Nitrate is to seal the wood and create a base that the covering will adhere to. When using polyester coverings it is mandatory for proper adhesion of the covering unless you are using Sig Stix-it to adhere the covering to the framework. The first coat of dope on the polyester covering is always Nitrate followed by Butyrate. Butyrate can be applied over Nitrate but Nitrate will not go over Butyrate. Another advantage of Nitrate is the thick glue like characteristics. This comes in handy when trying to seal the fuzzy edges of Koverall before sanding and blending."
http://winshiprc.tripod.com/painting_techniques.htm
Here are some more good tips..
http://www.rcgroups.com/forums/showthread.php?t=170038
Here is the Starline site with it's tips on Polyspan.. this is how I have done my 2 planes that I have used this stuff.. weight wise it's OK .. the paint can build up quickly buy the finish is nice .. I still can make a plane lighter with silkspan. But I sure like the durability a whole lot more..
http://www.faimodelsupply.com/starline-polyspan2.htm
Jim
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There other solutions, but Nitrate Clear is hard to beat for Polyspan covering. Besides, how are you gonna adhere the CF veil reinforcement?
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All,
How above 3M spray can adhesive to adhere the polyspan? Not sure if it's available down under.
Rob,
What do you plan to paint the open bays with since you are trying to avoid dope and polyspan won't take water-based paints?
Kim Mortimore
Santa Clara, CA
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Butyrate dope worked fine for me.
A few coats on the bare frame, sand smooth, and dope to outline of the Polyspan. a bit of heat shrink as required, then more butytrate.
I wouldn't use 3M 77 on anything more critcal than paperwork inside a climate-controlled building.
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I applied polyspan using Baslaloc, a water based heat seal adhesive. Is that available? You apply a thin layer to the wood surface and after it dries, apply the polyspan with a covering iron, just like monocoat. After shrinking, I then sealed the polyspan with Minwax Polycrylic. Worked pretty well. Also, can you get some of the SLC film? It's a thin mylar film. You cover just the open bays with it and then cover the whole wing with silkspan attached with polycrylic. Just as strong as polyspan.
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Thanks heaps guys. There sure are a few options available.
I'm just in the process of knocking up a couple of test panels to experiment with. I didn't want to use dope initially just so I wouldn't have to brave the elements out in the shed but with a plentiful supply of Randolph nitrate on hand I will try that to begin with.
Ralph, I don't intend to use cf veil. I'm just going to use lightweight silkspan as Brad Walker outlined in his Flying Models (I think) article.
As to using mylar underneath silkspan, one bloke I know uses it to very good effect with traditional type clear finishes. I tried this on my last model (profile sukhoi) and unfortunately it was a wrinkly disaster, out of frustration it got stripped back and monokoted. Obviously the result of something I did wrong, I intend to attempt it again sometime when I'm not feeling chicken.
Thanks again,
Rob.