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  • August 17, 2019, 09:56:59 AM

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Author Topic: Refinishing over silk covering  (Read 406 times)

Online Dennis Toth

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Refinishing over silk covering
« on: February 09, 2019, 08:01:54 PM »
Guys,
I've been working on a patch on my El Diablo that is silk covered with a mostly clear finish. The patch had to be a full panel and because the ship is several years old the color has faded a bit. This makes the patch look well like a patch. So I'm thinking about refinishing the whole wing and go with a paint finish. The problem is it is finished with clear death paint. I was thinking of just recover over the base silk with another light silk cover. This would give a good base to then apply paint.

Has anyone done a double silk finish or covered over an older base covering?

Best,    DennisT

Offline Dan McEntee

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Re: Refinishing over silk covering
« Reply #1 on: February 09, 2019, 08:16:07 PM »
    It wouldn't take a whole lot of effort to sand everything off, or even use paint stripper to remove the top layers of clear, let dry thoroughly, then sand some. In laying the new layer of silk over the death paint, you probably get some react or lack of adhesion to the old clear death paint, and you'll have to do it all over again anyway. Just get things prepared on a day when you have all the time in the world to do it, and just sand it all off or strip it. I think you'll be happier with the result, and you will probably not be able to tell the old patch.
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Offline Avaiojet

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Re: Refinishing over silk covering
« Reply #2 on: February 10, 2019, 06:28:30 AM »
Quote
Has anyone done a double silk finish or covered over an older base covering?

Dennis,

Yes, I did something similar.

I actually did this to the ARGO 2 except I removed silkspan, not silk. Same process.

I mention the removal of the silkspan covering and the replacement of silk at the ARGO 2 Build, I believe it's over at CFC Graphics vendor's corner.

You probably seen it but forgot.  ;D  LL~

You do not have to strip the entire wing to bare wood, you'll have to do unnecessary tasks like cleaning everything up and refilling the grain again to prep for the new silk covering, so, keep this in mind.

The grain is already filled so why disturb it just to do it again? As I did with the ARGO 2. These areas were fine on the ARGO 2 and your areas are fine also.

As you know, I now apply silk dry using a CA method which I was instrumental in developing and perfecting from many years plus hours of experiments and tests.  LL~

A method you have perfected also, you know it works well and saves a bunch of time, so applying your new silk will be easy and less time consuming. You have already done this process before using CA.

FYI. On the ARGO 2, I only cut out the open bays and left all sheeted areas untouched, including the cap strips.

I suggest you do the same and leave all sheeted areas alone.

Send me an e-mail or call and I'll fill you in.

The "Jet"

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Avaiojet Derangement Syndrome. ADS
 Please visit my updated Website! www.cfcgraphics.com  If you're Trolled, you know you're doing something right.  Alpha Mike Foxtrot.  Owner of CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder."  "No one has ever made a difference by being like everyone else."  Marcus Cordeiro, The "Mark of Excellence," you will not be forgotten.  I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King.  "Ya gotta love it when a plane comes together."  Proverb 11.9  "With his mouth the Godless destroys his neighbor..."  "Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane." David McCellan, 1980.

Online Dennis Toth

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Re: Refinishing over silk covering
« Reply #3 on: February 11, 2019, 06:43:05 AM »
I get the remove old finish approach or cut out open bays. The reason for even thinking about doing a recover is that the patch I applied looks well like a patch. The El Diablo is somewhat like an I beam style wing in that there is no leading edge sheeting just ribs and half ribs with cap strips. Since the current finish is clear over blue silk and the blue has faded over time (ship is 4 years old) the new patch is darker. Also, I degreased the surface and did a light sand and use CA to adhere the silk. This worked well as I could pull it tight and smooth. The CA does fill the weave so you get a little color difference under the clear dope which makes it look like a patch.

I found some information on a clear adhesion promoters (Dupli-Color CP199 Clear Adhesion Promoter Primer) that is used to get paint to stick to plastic and other surfaces and though this might do the trick. It would allow just a top cover with a light non structural covering that could be painted to give a better look. I don't think the silk is adding more than 1/2oz and it is the structural part that keeps the wing stiff. Maybe just the AP over the base and repaint. Has anyone used an adhesion promoter under dope?

Best,   DennisT

Offline Dan McEntee

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Re: Refinishing over silk covering
« Reply #4 on: February 12, 2019, 08:27:05 PM »
    I don't know why you would want to add another material to the stack you already have? The death paint is bad enough but I didn't know you used CA to apply the silk patch. I think that is probably the worst way to attach a covering. The glue will wick up the fibers and stop. The CA dries rock hard and does not have the same flexibility that the dope you applied the silk with originally. It may have filled the weave some, but where the CA stopped will make for a hard line where the silk will tear easily the next time its stressed, because it doesn't have the same pliability that the dope does. If you sanded it at all, you probably sanded away some of the silk also, since the glue is so hard. This also changes the texture of the whole area where the CA flowed and it will take any new paint differently that the surrounding area. If you decide to try the adhesion promoter, you will be adding another different material to the mix and you don't know how it will react with what is there already. I have never heard of any one using it on a model, even on fiberglass, which would be a somewhat similar use to using it for painting plastic. I would think that he promoter has some sort of solvent in it to etch the plastic to allow paint to have better "tooth" to lay down on plastic properly. and it may not like the death paint , or the dope you put on top, or worst yet, both!
   I would just get out the sandpaper and sand all the death paint clear off. then lay on some clear dope just to be sure you have a good substrate again, then lay your new silk over that, or maybe just spray on some color over the original covering and patch. That process is all something that you know will work.
   Type at you later,
     Dan McEntee
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Online Dennis Toth

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Re: Refinishing over silk covering
« Reply #5 on: February 15, 2019, 10:56:51 AM »
Dan,
Some good points that I will keep in mind. I am leaning toward just the paint refinish. I will do some tests of the adhesion permoter on the piece of removed silk section to check for compatablity. I have put some clear dope over a small section that has the DP on it and it has gone on smooth and seems to be holding pretty good. Again I will do a tape pull test to see if it stays on after it gases off a week or so.

As far as the CA holding the patch, yes it sticks it down to the sanded DP. Since I only use a small drop to "pin" it in place then dope the rest it still remains flexible, the weave is not completely filled with the CA but is does wick into the silk a little. Dope on top seems to hold and shrink the patch drum tight. Only real issue is the color difference with the old faded blue vs. the new blue patch.


Best,   DennisT


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