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Author Topic: Doping Polyspn or Silkspan  (Read 441 times)

Online Mike Griffin

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Doping Polyspn or Silkspan
« on: January 08, 2020, 09:05:09 AM »
When covering open bays with Polyspan or Silkspan, I put several coats of either Nitrate or Butyrate on the material to make sure it is filled properly.  After that, is where the process gets a little unsure for me.  Should you make your final coat before priming, a coat of dope mixed with Zinc Sterate (spelling ?) and sand with fine sandpaper, then spray primer, sand carefully again and then shoot your color? Or, just carefully sand the doped open bay prime over the final dope coat, carefully sand and then shoot the color?

I would appreciate anyone who could share their process steps.

Thank you
Mike

Offline Randy Powell

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Re: Doping Polyspn or Silkspan
« Reply #1 on: January 08, 2020, 04:06:30 PM »
Well, I don't use filler coat .  Follow the Phil Granderson method. I put 3 or 4 unthinned coats of non-taunting clear over the silkspan then sand flat and smooth. I sometimes shoot an additional thinned coat on and examine (usually with a flash light with the overhead lights off) and touch up as needed. Then on to base color.
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Online Mike Griffin

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Re: Doping Polyspn or Silkspan
« Reply #2 on: January 08, 2020, 10:46:06 PM »
Well, I don't use filler coat .  Follow the Phil Granderson method. I put 3 or 4 unthinned coats of non-taunting clear over the silkspan then sand flat and smooth. I sometimes shoot an additional thinned coat on and examine (usually with a flash light with the overhead lights off) and touch up as needed. Then on to base color.

Thank you Randy
Mike

Offline Shorts,David

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Re: Doping Polyspn or Silkspan
« Reply #3 on: February 22, 2020, 05:44:33 PM »
Hi Mike and Randy and...

My first time using polyspan. I attached it around the edges with butyrate before reading from others that I should use nitrate. I shrunk it up very nice. Now...
Does this sound correct...

Option A: I can fill it in with some more clear butyrate and then sand. Then prime. Then color. Of course sanding along the way. Then clear again.  AND - should I fill with brush and  then switch to the gun to prime?
Does that work?

Option B: Can I just go to butyrate primer now and skip filling in with more clear?

Also, which top coat clear is best over butyrate? Should I just stick with the butyrate clear I'm using?

Thanks. I've asked so many people and written down notes, but then I feel dumb asking the same person the seemingly same questions over and over.
If I screw up a little, that's okay, this plane is my daughter's and mine is all framed waiting for me to figure my process out.

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Online Dennis Toth

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Re: Doping Polyspn or Silkspan
« Reply #4 on: February 23, 2020, 06:42:05 AM »
Mike, Dave,
If you are using dope as the basic finish (not auto paint) then once you get to the point of about 4=5 coats (could be a few more to get it drum tight) of 50/50 clear (I usually do 2-3 coats taunting - Sig super coat clear, 2 coats non - Sig lite coat or Brodak clear) then you can do a coat of butyrate plus zinc stearate (I get mine from Randy Smith) as filler (some add a few drops of black dope to get a grey tint) after which you sand smooth with 600, spray on a coat of 60/40 clear to seal, then go to block coat. I do not use rattle can primer with dope as they are acrylic lacquer based and dope do not stick to it well and acrylic lacquer can be heavy very fast.

Another option is to use Silver as the filler coats. With the silver you use it as the filler and block coats. The trick with silver is to let it dry hard before sanding. There are some videos on YouTube that cover this but the idea is to spray on silver, find dings, and off silver (600 paper) reapply silver - sand off repeat until satisfied with the surface then go to color.

Some use a block coat of Dianna Cream for light colors. Most important part of this method is to let the dope dry completely, especially the silver, before sanding. It seems that using Brodak or Randolph thinner gases off in a day or so, Sig takes a few days. Once done you can top coat with death paint (2K Max) and it is bullet proof.

Best,   DennisT

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