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Author Topic: Double-Covering with SLC and Silkspan  (Read 1523 times)

Offline Kim Mortimore

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Double-Covering with SLC and Silkspan
« on: May 14, 2008, 09:04:48 PM »
In his T-Rex article in CLW, Brad Walker talks about double covering open bays with a layer of iron-on Super Light Covering film (SLC) from Phil Cartier, followed by a layer of silkspan using water-based polyurethane as a way to build open bay planes in places where dope fumes are not acceptable.  I would like to be able to build clear-painted colored silk open-bay planes in a non-fume area, and I'm curious if Brad's method might be adapted to silk-over-SLC.  This might solve the problems of over-shink, under-shrink, wrinkling, never-ending shrink, sizing removal, etc that go along with silk and dope.

Has anybody tried silkspan over SLC?  If so what do you think?

Is SLC a peel-off sticky-back material like Fascal, and if not, is any special treatment needed to get the edges to stick?  How about covering curves?

Does anyone know of a fuelproof, low odor, brush-on clear that could be used to fill the weave of the silk on top of SLC?      

Thanks,
Kim Mortimore 
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Offline Jim Thomerson

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Re: Double-Covering with SLC and Silkspan
« Reply #1 on: May 15, 2008, 10:43:17 AM »
There are several articles in Aeromodeller on tissue over mylar, which seems a good way to go.  Silk should work as well.  Gelatin has been used to fill silk. 
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Offline Mike Spiess

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Re: Double-Covering with SLC and Silkspan
« Reply #2 on: May 16, 2008, 07:31:48 AM »
This winter I built a Super Clown and wanted to use a silk skirt my wife gave. I experimented with a few balsa frames to see if Polycrylic would work. I found out that the silk had little or no shrink left in it. So what I did was cover the wing with a type of very light weight polyspan used by freeflighters I got from Cambles Custom kits. Then applied the silk over with Polycrylic. It worked very well. I attached the polyspan with one cote of Polycrylic around the edges then shrunk it. I didn't precote the blasa before attaching it. Becareful with the heat on polyspan as it's very thin and gets hole very quickly. Then I laid the wet silk over it and flowed polycrylic right on. Make sure the silk is touching the polyspan every where. If not you'll have some funny looking bumps.
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Offline Kim Mortimore

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Re: Double-Covering with SLC and Silkspan
« Reply #3 on: May 16, 2008, 01:26:34 PM »

Mike,
Did you use dope or other clear paint over the polycrylic?  My understanding is that polyurethane is fuel proof, but polycrylic is not.

Kim Mortimore
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Offline Mike Spiess

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Re: Double-Covering with SLC and Silkspan
« Reply #4 on: May 16, 2008, 01:42:29 PM »
Yes Kim I used some PPG StratoClear DCU 2082 something my son had left over from a project of his. I don't know if the Polycrylic is fuel proof or not I've never tried it. I have to say the wing came out very strong I was surprised. And the sun shines through it just what I wanted.
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You don't stop flying cause your get OLD
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Offline Bob Reeves

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Re: Double-Covering with SLC and Silkspan
« Reply #5 on: May 21, 2008, 01:22:35 PM »
I have done two ships with silkspan over SLC and discovered a few things in the process. SLC covering is a very thin plastic that has a heat sensitave adhesive.. You iron it on just like Monokote except use a lower temperature. I had trouble covering compound curves because if I tried to stretch it it would tear.. Think this is just a matter of learning how to use the stuff properly.. The saving grace to covering it with silkspan is you can piece and patch to your hearts content and not worry about the seams, the silkspan will cover them. Also sanding through the silkspan isn't as catastrophic as the SLC will keep you from creating a hole. Still not a good thing as you still need to patch the sand through but having SLC under it makes it allot easier.

The first time I used Brodak Butrate without doing anything to the SLC prior to covering. It actually turned out great except for one minor issue. The silkspan didn't stick to the SLC. I would probably never have known this if I didn't decide to cut out a section of the wing for a trim tab. SLC is advertised as being ready to paint but I think it still needs a wipe down with solvent and a once over with a scotch bright to be sure whatever you are putting over it will stick.

The second time I used Nitrate as everyone told me it was stickier. I've never used Nitrate in the past as I have never found a need to use anything but butyrate clear. I'll never venture into the nitrate arena again.. It was simply a disaster. Am sure it was me but after spending two weeks redoing what I had already done (several times) I'll go back to Butrate..

I still believe in this finishing method and will do it again using butyrate but with a scotch bright and solvent treatment prior to laying on the silkspan. The SLC keeps the dope in the silkspan which more than makes up for the added weight of the plastic. It makes filling and sanding easier and you end up with a silkspan finish that is almost bullet proof.

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Offline Steve Fitton

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Re: Double-Covering with SLC and Silkspan
« Reply #6 on: May 22, 2008, 06:39:06 PM »
Quote from: Kim Mortimore on May 16, 2008, 01:26:34 PM
Mike,
Did you use dope or other clear paint over the polycrylic?  My understanding is that polyurethane is fuel proof, but polycrylic is not.

Kim Mortimore

Polycrylic is very much NOT fuel proof.  I know this from experience.
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Offline john e. holliday

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Re: Double-Covering with SLC and Silkspan
« Reply #7 on: May 26, 2008, 07:41:17 PM »
Thanks Bob,  now I know how I am going to finish the "G Nobler".  Didn't take my kit out of the box, but, it looks great.  I know I can't build that straight and light.  Later,  DOC Holliday
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