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Old Nov 15, 2007, 08:04 AM
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carl rich's Avatar
Cincinnati
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Question
Covering; silkspan vs fiberglass and resin

I'd like to know which type of covering will give me a smooth surface for painting and strengthening a foam plane as well.

I've used 1/2oz FG with 2 part resin thinned with Denatured alcohol and got all the above. I don't like the horrible fumes.
I've heard of several methods of using silkspan but want whatever will make a foam jet smooth for painting and a little stronger too.

I've heard of guys using Poly Minwax, thinned white glue and Modge Podge from Micheals.
Please tell me what you have used and a step by step of how you did it. If enough guys do this in one thread we will have this answered for alot of people who are wondering the same thing.

thanks,
Carl
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Old Nov 15, 2007, 08:07 AM
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USA, PA, Pittsburgh
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Search for Herb's posts. He uses silkspan/white glue.
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Old Nov 15, 2007, 11:49 AM
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Las Vegas, NV
Joined Dec 1996
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Well I've tried several methods, not sure which is best still. I just used .75 oz cloth and WBPU (water based polyuretchane) to glass the Hobby People F-16. I did one coat for adhesion, then the next morning another thick coat of the baby powder and wpbu mix. I sanded that several hours later and it sanded fairly easily, much easier than epoxy, but the surface isn't as strong. There were still imperfections and waves and the thickness of the mix caused some valleys where the material seperated so I had to sand quite a bit with 220 paper dry. That night I sprayed with Zinsser Bin Shellac based white primer and wet sanded that a day later and it came out pretty nice. I painted with Testors gloss white and it looks great, but I just weighed it and it's gained about .4 oz for the fuselage My scale's only sensitive enough to go in .2 oz increments though. It took a lot of white to cover the under color, when I mixed the baby powder/poly mix i colored it with a drop of black and two drops of white paint, getting a dark greay color so when I sanded the final top layer of white primer I could see where I was sanding through. The surface looks much better than foam and it was easier to sand than epoxy but it's not as tough and I'm still not sure I like it better than epoxy. Even thin cloth and epoxy over foam can get dented though.

As for paper or tissue and thinned white glue, that's probably the least amount of work, after it dries a bit of sanding with maybe 320 then 400 grit and it's good to go. The paper will shrink around compound curves but for wings it's a disaster, I found that out on my GWS P-51, big time warpage. I haven't done a tissue finish just a couple of small test areas but it'd be lighter than heavier computer paper. I did the top of my Wattage F-22 in paper and it adds about .2 oz per sheet. Looks good though. Thinner paper would be enough. Sometimes the foam bead texture shows through, that might be more so with tissue but I'm not sure.

So, I'm not sure which method I like best. Paper is easiest and possibly the lightest since no primer is needed but in my experience the weight's about the same. Covering up the foam beads it the main thing, making it dent proof ends up making it heavy. My pursuit of a glass like finish made my Kyosho T-33 replacement fuselages heavy back in the old days, then when they crashed I'd pull off the skin and it'd be not very rigid at all. I'd say glass and wbpu is second easiest (except of the multiple coats) and glass and epoxy third (but the most durable of the three).
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Old Nov 15, 2007, 12:42 PM
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Simi Valley, CA
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I've had good results with 1/2 or 3/4 oz. glass & water based Polycrylic. Usually 3 coats is the magic number for getting a nice smooth finish. It won't quite be glass smooth but it looks great painted. With some sanding you can get a really nice finish on it.

Silkspan is okay. But, I think it's harder to work with than glass. I've had issues with wrinkles & bubbles. Glass seems to just soak up the PC & settle down on the foam.

Like Ed mentioned, it won't be dent proof. But, it will be a bit stronger & look a lot nicer.

-Mark
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Old Nov 15, 2007, 01:09 PM
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carl rich's Avatar
Cincinnati
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I have some 1/2oz glass and can get it readily at LHS. As far as multiple coats do you mean; first coat of wbpu goes on the dry 1/2oz fiberglass, allow to soak in and dry, sand, apply 2nd coat, dry, sand, apply third coat, dry sand, ready to paint?
Exactly what is the name of the WBPU used? I've tried a quart size can of wbpu for wood floors from Home Depot. I was not impressed. Could be because I only did one coat. Didn't seem to harden at all when dry. Was a light blue can.
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Old Nov 15, 2007, 01:10 PM
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This is interesting. Just found it. No idea why it didn't pop up when I did a search. The blue can is exactly what I used.
http://www.rcgroups.com/forums/showthread.php?t=192622

FYI, this is for the big 54" ws Sabre from Fly Fly that is on its way.
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Old Nov 15, 2007, 06:57 PM
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That's the stuff. I've used it to glass one of my HET F-20's. It's not as hard as epoxy but it's much easier to use, smells better & a lot easier to sand.

I do 1 coat let it dry, 2nd coat let it dry, 3rd coat the same & then sand it. You don't need to sand in between coats. But, the 3rd coat is the charm. By the last coat is when it really starts to leave a smooth finish.

-Mark
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Old Nov 15, 2007, 07:09 PM
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Mark, do you put fiberglass on with the first coat or are you only using the Polycrylic by itself?
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Old Nov 16, 2007, 09:28 AM
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Fiberglass goes on with the first coat.

-Mark
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Old Nov 17, 2007, 08:11 PM
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Someone mentioned some warping with FG and polycrylic or WBPU. I intended to cover the whole foam wing with FG and coat whole top in one piece. Think this would warp? Is it necessary to do one small square at a time?
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Old Nov 17, 2007, 09:08 PM
MYC
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I usually do the top and bottom of a wing at the same time. If you hold the wing LE up and drape the cloth over it you can position the glass how its going to lay and then mark it. I then cut the piece and do one wing at a time with about 1/2 to 1" overlap at the center for additional strength. This leaves no seams (except on the tapered TE) to deal with later. With this method I have not had any warping issues b/c the top and bottom dry at the same time.
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Old Nov 17, 2007, 11:23 PM
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Fresno CA
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Applying the glass with the weave at a 45 degree angle to the span of the wing will help to eleminate warping.

Dents can be removed by poking small holes with a pin then covering the area with a very wet paper towel and applying a hot monokote iron, remove the iron as soon as the water stops sizzling. This will also remove some wrinkles fron unwanted contact with the ground!

A little heat from a hot air gun will remove unwanted warps.

Hang out in the handlaunch glider forum for a while, you can learn a lot about F/G and WBPU wings and how to care for them ! Trust me those things pull some G's when launched and they use very THIN wings !

Blue Skies ..... R Dub
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Old Nov 19, 2007, 07:58 AM
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Chapel Hill, TN USA
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I used silkspan/poly on my Panther at 43"ws, epoxy/glass on the Cougar, 35" span. Both came out 30 oz AUW with same power/batt setup. But the Cougar's finish is much stronger and not as prone to hangar rash of course. Dents can still be problem with the poly, epoxy will stand up much better and if applied properly it is not any heavier.
Sorry, these are pushers.
J
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Old Nov 25, 2007, 04:08 PM
Fast, faster & fast again
North Hollywood, CA
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Beauty...

Quote:
Originally Posted by J Morgan
I used silkspan/poly on my Panther at 43"ws, epoxy/glass on the Cougar, 35" span. Both came out 30 oz AUW with same power/batt setup. But the Cougar's finish is much stronger and not as prone to hangar rash of course. Dents can still be problem with the poly, epoxy will stand up much better and if applied properly it is not any heavier.
Sorry, these are pushers.
J
Hey, remarkable job on your planes. Where did you get those pushers from? I love the way those birds look. How are the flight characteristics and what kind of speeds are you getting with them. I hope you had a fantastic Thanksgiving weekend. Thanks in advance for any info you can give me on those planes.

Jim
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Old Nov 25, 2007, 11:22 PM
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Thnaks Jim,
The Panther is from an old prop-in-the-nose jet plan by Pat Tritle. I think it is available from Fying Models Plan Service of Pat himself. Do a search in Scale forum and PM him.
I used the Panther fuse for the Cougar and then scratched the wing and flying tail from 3 views. Awesome fliers on LSSPJ and a APC-E 7x5 prop, 3s lipos. I think they estimated the Panther at abut 70 mph at Superfly. Cougar's a close second. They both fly like they are on rails.

J
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