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Mar 02, 2019, 01:11 PM
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Painting Sig Koverall


I have completed covering my 1/6 scale Stearman PT17 with Sig Koverall, and have applied three coats of nitrate dope to seal the fabric. The plane is now ready for the finish color coat. Before I start this I need some advice on what kind of paint or dope should be used for the final coat. I have read that butyrate dope should be used, but I have read that it will "shrink forever". I have also read that automotive paint, Rustoleum, and Kryton can also be used (which would require that a primer coat be applied to the fabric), but that these paints will chip, flake, and peel over time. So, the question is---what is best to use--paint or butyrate dope? I would certainly like to hear from the experts on this. Also, I plan to use five different colors (red, blue, yellow, black, and white) which will require masking. I have read that masking tape used over butyrate dope will cause the dried dope to come off when pulling off the tape. I would appreciate comments on this.
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Mar 02, 2019, 02:16 PM
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I've used butyrate dope, latex, Klass Kote, and Nelson's (which is no longer available, but System 3 is the same thing, though not in so many colors) over Koverall sealed with nitrate dope. All worked fine; if you use latex you need a top coat of something fuelproof if you are using glow fuel.

Rather than using masking tape, which can pull some dried finishes off, I use Tamiya tape right along the edges and then drafting tape over that (but a little back from the edge). You can find Tamiya tape in the plastic-modeling section of your LHS. It's a good idea to pull the tape off before the coat you've just applied dries (or cures) completely. This is sort of a pain because you then have to apply new tape between coats.
Mar 02, 2019, 03:28 PM
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gene6029's Avatar
Sailorpete, I have used both Butyrate over the nitrate over Koverall, and latex house paint over the Koverall. Never had any issues of my paint pulling off with the tape. The Chipmunk in my avitar was Koverall and latex house paint. The plane is close to 10 yrs old and still looks like new. As far as the Butyrate shrinking over time, the people most worried about it are those that cover with silk or silkspan, afraid of it tearing years down the road. The Koverall is pretty tough stuff, i cant see it tearing over time. Another worry is as the dope shrinks it could cause warping. I have been using Butyrate dope for many years and have not had it tear or warp any of my models, and i use both silk and silkspan on a regular basis. Surface prep is the key to your paint not pulling off, along with how the paint is applied.....Gene
Mar 02, 2019, 03:38 PM
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Thanks for the information.
Mar 02, 2019, 03:38 PM
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Thanks. I appreciate the tip about the tape.
Mar 02, 2019, 08:09 PM
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kenh3497's Avatar
If using "automotive" (epoxy, urethane, etc) type paints there are flex additives that can be added to the paint to help them flex without cracking. Also it helps to be careful how much paint you add to the surface. The thicker the paint the more apt it is to crack.
Mar 03, 2019, 06:23 AM
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Paul's Avatar
Quote:
Originally Posted by gene6029
Sailorpete, I have used both Butyrate over the nitrate over Koverall, and latex house paint over the Koverall. Never had any issues ............Gene
When you say you used latex house paint over Koverall do you mean the latex went on the bare koverall, or was there something else you sealed the pores with before painting?

I'm half way done building a 1/4 scale Sopwith Pup, and it will be covered in Koverall. It will be electric powered so no fuel proofing issues. I was thinking abut a few coats of water based Minwax polycrylic to seal the pores, then the latex house paint for color, but maybe I'll experiment with just the latex paint by itself.
Last edited by Paul; Mar 03, 2019 at 06:29 AM.
Mar 03, 2019, 11:57 AM
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gene6029's Avatar
No not right on the Koverall. I applied the Koverall with Sig Stixit, then applied Min wax poly crilic waterbase to seal the pores. I then sprayed the model with Napa DC-540 grey rattle can spray paint. Then I sprayed Sherwin Williams latex house paint over the primer.....Gene
Mar 03, 2019, 02:44 PM
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Heres a few pics of the finished model. The areas that represent paint over metal I filled the pores in the koverall solid and sanded it smooth. The areas that represent fabric I sprayed the primer on lightly......Gene
Last edited by gene6029; Mar 03, 2019 at 02:50 PM.
Mar 04, 2019, 09:00 AM
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A quick caution here. If you use anything other than dope over that Nitrate dope you have already applied, you need to let the nitrate gas off before applying any paint. Otherwise, the solvents still in the dope will bubble your paint. I wait about 2 weeks just to be sure. Stick your nose against the fabric and if it still smells like thinner, keep waiting.

You do not need to prime over the nitrate. Straight to paint will work. Primer may tend to crack over open wing bays.

I have used koverall and nitrate dope many times. I have topcoated with Butryate dope, epoxy paint, and water based polyurethane with no cracking or flaking off.

Right now if I were doing a fabric covered plane I would likely go with nitrate dope then topcoat with either butyrate dope or klass kote epoxy. If you go the butyrate route there are a few things to consider. You have to paint your tape edges with clear dope to avoid bleed under. You should also put down an all white coat of dope first even if you are going with another base color. Dope isn't as color fast as epoxies. It also takes several passes with dope to build up the color.

If you use a paint that isn't fuel proof, you will need to top coat with something that is or fly gas.

Good luck and happy painting.

Carl
Mar 04, 2019, 11:34 AM
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Paul's Avatar
Quote:
Originally Posted by gene6029
No not right on the Koverall. I applied the Koverall with Sig Stixit, then applied Min wax poly crilic waterbase to seal the pores.........
Thanks, this is what I plan to do.
Mar 05, 2019, 09:45 AM
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kenh3497's Avatar
I did two test panels several years ago using Koveral and dress lining form the fabric store. Both were adhered to a frame using lacquer ( I think it was Watco brand) from the big box store that is intended as a wood finish. Both were shrunk with a heat gun and then sealed with the same lacquer. Both panels stayed tight and look as good now as they did the day I did them. There was no finish applied as I was only looking at the suitability of using the lacquer as a substitute for dope. Most any paint except dope will go over the lacquer with any issue. While both fabrics worked OK in the test I liked the Koveral a bit better as it seems to shrink better than the dress lining.

Ken
May 15, 2019, 02:00 PM
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Kingbird49's Avatar
Great thread! Subscribed

Quote:
Originally Posted by carlgrover
A quick caution here. If you use anything other than dope over that Nitrate dope you have already applied, you need to let the nitrate gas off before applying any paint. Otherwise, the solvents still in the dope will bubble your paint. I wait about 2 weeks just to be sure. Stick your nose against the fabric and if it still smells like thinner, keep waiting.

You do not need to prime over the nitrate. Straight to paint will work. Primer may tend to crack over open wing bays.
I've been using dope for a long time and didn't know these things. Thanks for mentioning them. Your comments may explain a couple problems I've experienced since switching to using a rattle-can finish over nitrate. In the past I always applied butyrate over nitrate and had no problems with the finishes.

While bubbling paint hasn't been a problem, I've definitely experienced problems with undercoats lifting with the removal of masking tape. Switching to Frog Tape has done little to fix this. This all began when I started using a rattle-can finish over nitrate doped silkspan or polyspan. I've felt that happened because I failed to properly sand or "scuff up" the nitrate doped surface adequately prior to painting and also suspected I should have applied a primer coat. It sounds like I may have two problems to address here: 1) allow the nitrate more time to finish curing and 2) better surface prep.

I'm getting ready to paint another plane now (this one covered with Koverall). I'm trying to decide if I should risk using a rattle-can finish or take the plunge and buy an airbrush kit. Comments in this thread are helping me decide how I'll finish my planes in the future. I really appreciate everyone's ideas, experiences and suggestions!

Cheers!
May 15, 2019, 04:48 PM
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gene6029's Avatar
Kingbird, All my models that I spray have been with the very in expensive spray guns that Harbor Freight sells. I have done smaller models with a Badger also. So there is no need to spend a lot of money on spray guns etc. Hopefully you have an air compressor. If not, I got by for years using a small compressor with a pancake style tank until I splurged for a larger compressor....Gene
May 15, 2019, 05:59 PM
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Kingbird49's Avatar
Quote:
Originally Posted by gene6029
Kingbird, All my models that I spray have been with the very in expensive spray guns that Harbor Freight sells. I have done smaller models with a Badger also. So there is no need to spend a lot of money on spray guns etc. Hopefully you have an air compressor. If not, I got by for years using a small compressor with a pancake style tank until I splurged for a larger compressor....Gene
Thanks Gene -

I do have a compressor but it's a real horse! Big shop-style standup unit that will run an air ratchet all day. But I've got no experience with airbrushes. Do I just hook up to my monster compressor and turn the pressure way down?

Doug


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