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How to finish a model Empty How to finish a model

Post  RK Flyer Wed Oct 09, 2013 11:02 am

I've been trying to locate a tutorial or tips on How to finish a model with
both Painting & something like Mono Coat. I am not trying for a show quality finish just something that I can fly that looks good.

Thanks, RK Flyer cheers 
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Post  pkrankow Wed Oct 09, 2013 1:08 pm

Dope the painted surfaces first. It is lighter than enamels and very fuel resistant. If you can only get clear locally, use that. You can build a cheap filler/primer by adding cornstarch to dope with thinner. Putt he corn starch in the thinner, mix well, then add the dope. The tolerated proportions vary wildly, but...

by volume
1-3 parts cornstarch
1 part thinner
1-2 part clear dope

It sets up in about an hour for sanding, but overnight is better (sands much easier). Only mix what you are going to use in that sitting. I don't clean my dope brushes since a splash of thinner softens them right up even after years, so one brush per color/recipe. (yes, I use different corn-starch recipes with the same brush.

Sand the dope + cornstarch all the way off. Use 400 grit start to finish, lower grit leaves lines that you need to remove. For competition finishes 400 grit is too coarse, so start and finish with 800 or 1000. Re-apply and sand off at least 2x to get a good sealed base.

For color use dope. (har har, I can't get dope either locally)

Use enamel! Rustoleum "Stop Rust", "Painter's Touch", "professional", or "automotive" all work acceptably well, if heavy. ***DO NOT USE metallic or clear as they are not fuel/exhaust proof!*** (unless electric power)

The trick to rattle can enamel is 1 coat primer, sand it most of the way off, 1 coat color, touch-up only. 2 week cure before fuel proof, so don't even put the engine on it till then.

Yes, I recommend paint before Monokote. Wait at least 48 hours before putting Monokote over enamel. Longer is better.

Monokote has good instructions.

http://www.monokote.com/monoinst1.html

Start at the hard spots, work to the accessible spots. Typically this is fuselage (or about 1/2 inch from the fuselage), LE, TE, wingtip, flip and trim, fuse, LE, TE, wingtip. Cover control surfaces before hanging them. If it is a repair and there are wires/connectors that cannot come out you can cut the hinges out and cover in place carefully, then re-hinge.

I haven't covered fuselages before so not much help there. The recommendations are bottom, sides, top for cosmetic reasons.

For push rod holes make a "stamp" or patch larger than the opening and seal it down then cover the whole area. This prevents the opening from tearing out later.

Trim is easy. Mark out the desired pattern using marker, crayon, or tape. Trim out the contrasting color shapes. Seal one edge down carefully and work to the other edge. Corners need care and practice to not stretch under heat and distort.

Most films change color at the glue activation temperature. The shrink temperature is slightly higher. Monokote has very little separation between these temperatures.

Best of luck.

Phil
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Post  RknRusty Wed Oct 09, 2013 2:53 pm

All good info from Phil. Regarding heat shrink covering, I think Ultracote is easier for first timers. I can lay Monokote down neater at the very edges of the wingtips, but for me, it's harder over the larger compound curves without wrinkling. And like Phil said, Ultracote's difference between adhesion and shrink temperature of is very much separate, where the temps overlap with Mono.

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Post  ian1954 Wed Oct 09, 2013 7:20 pm

I have been using Ligh tex - it goes on well and I bought it on the advice that it is exceptionally fuel proof (glow and diesel).

That I have still to test!

Never used these iron on materials before and I can't say that I have found it easy - Particularly on the fuselage of the Radian I am building. Wings were easy but stretching it around the fuselage wasn't.

http://www.theworldmodels.com/para/products/covering/LighTexInstructions.jpg

The Radian looks OK from a distance but close up is not neat, tired and wrinkly (a bit like me I suppose). Nothing to do with the material but my impatience in applying it.

I miss the traditional tissue/nylon, humbrol coloured dope and humbrol fuel proofer.

I tried butyrate dope over acrylic paint with the all balsa NightHawk - it was not fuel proof! (Or fool proof!).

I expect that practise makes perfect and the advice from the modellers on this site is excellent. I look at some of the buid and finishing skills displayed and wish I had that patience. I build and engineer well but rush the finish and covering!



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Post  RknRusty Wed Oct 09, 2013 8:00 pm

I get impatient with the finish too.
I didn't mention above that I've mostly only covered built up wings, and they turn out well, even on my first try. Small solid surfaces like the stab and elevator are easy, but large flat surfaces are hard to get right. Especially with Monokote because the heat caused gas bubbles to form as you iron it down. Some people use a "Woodpecker" roller to perforate the surface of sheeted areas before covering, allowing an escape for the hot gasses. But I would hate to do that to my beautiful wood work. I just paint the balsa fuse and plank wings. Where I do cover small sheeted areas, I prick the few bubbles with an exacto blade and iron them back down. It usually looks pretty good.

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Post  RK Flyer Wed Oct 09, 2013 8:03 pm

Thanks to everyone for the help!

Ian , where can I buy the Lightex?
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Post  Cribbs74 Wed Oct 09, 2013 8:51 pm

Probably in GB is my guess...

If you really wanted to go that route you could maybe order it online.

Ron
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Post  JPvelo Wed Oct 09, 2013 11:42 pm

I've found that ultracote is the easiest iron on film for me to use. I don't like to use iron on for my (profile) fuselages. My last two builds I have really tried to step it up on the fuselage finish, here's what's working for me:
After sanding smooth with 320 I apply two coats of full strength clear dope. I then apply light silkspan/tissue using full strength dope. After that on goes the cornstarch/dope/thinner. I like about a 60/40 thinner/dope ratio. Do five or six coats sanding with 400 between coats. You are essentially filling the "weave" in the tissue and creating a smooth surface to paint on. I let it dry 24 hours after the last coat before painting but I live in the desert, a humid climate might need more dry time.  After that I spray rustoleum, one light coat and then one wet coat immediately after.  If it's summer time I can bake that in a parked car and fly 24 hours after painting. If it's cool out I have to wait two weeks like everybody else.

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Post  RknRusty Thu Oct 10, 2013 2:20 am

Is that tissue that comes in kits what's called silkspan? I have some I've never used. Some of it has yellowed but I think the stuff from my BFS is still white. I'd like to try this. Is there a brand of dope and thinner you recommend? I've never used it before, I usually just use gray Rustoleum primer, but it doesn't cover all the grain. Maybe because I don't sand and re-apply enough times.

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Post  JPvelo Thu Oct 10, 2013 6:29 am

RknRusty wrote:Is that tissue that comes in kits what's called silkspan? I have some I've never used. Some of it has yellowed but I think the stuff from my BFS is still white. I'd like to try this. Is there a brand of dope and thinner you recommend? I've never used it before, I usually just use gray Rustoleum primer, but it doesn't cover all the grain. Maybe because I don't sand and re-apply enough times.
Yep, that's the stuff. For dope I use Midwest Products Aero Gloss Clear.
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I use regular acetone for thinner.

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Post  ian1954 Thu Oct 10, 2013 10:35 am

I think this is the stuff in the USA. We get it in rolls in the UK - not packets like this.

http://www.theworldmodels.us/shoppingOnline/index.php?type=covering&category=Lightex
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Post  RK Flyer Fri Oct 11, 2013 10:42 am

Thanks Ian,

I will order some soon!

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