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Author Topic: A Few Thoughts on Finishing  (Read 19570 times)

Offline Randy Ryan

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A Few Thoughts on Finishing
« on: September 15, 2007, 09:14:01 AM »
One of the things we often hear about is the weight the final finish adds. Now I haven't used many products other then dope and some rattle can paints for my models, so I can speak with some authority on Lacquer based finishes. Regardless, the preparation for the finish is probably of the greatest importance.

This post was sort of triggered by Ty's mention that Brasso is a rubbing compound. That is basically true, but the quality it has over and above compounds made for paint polishing I think is in its grit size and lubricity. That said, what follows are the suggestions I make and I have proven them on myown models.

1. No matter what you cover with, the finish begins before it gets anywhere close to the model. Attention to fits and level joints is paramount. Sure, there are good fillers out there, but here lies the first batch of calories. Balsa is lighter that any filler I've ever used, and I have yet to find a filler that sands the "same" as balsa. Because of that, it will always read through the covering and the only remedy is what else, more filler. So, here is where you can start you weight watchers program, right down to paying close attention to wood thickenss because 1/16 balsa for example will vary from .01 under to .01 over. If for instance you do your sheeting with some that's thick, and cap strips with some that's thin, it will require that you sand a bunch to level the joints. This in turn will cause bumps in the sheeting over all the ribs because the sheeting is not supported between them. Careful selection of not just quality, but thickness will save allot of time and uglyness.

2. OK, you've built the perfectly fitted and joined airframe and sanded it well, now what. Give it a "bath", wipe it down with a wet cloth and leave it to dry. This will raise out small dents and areas that were compressed rather then sanded smooth. In 4-6 lb stock, its very easy to simply compress and burnish the wood, but if that's what you've done, it'll come back and bite you down the line. When its all dry, carefully and LIGHTLY go over it with nothing rougher then 400 grit. Cut the sand paper into ovals about 1 1/2 wide by 2 1/2 long, curl it over the edge of the bench grit side up. This will make the edges tend to pull away from the surface rather then dig in. Still you'll have to be careful. Remember this from now on, you'll want to use it the rest of the way through. If you're using iron on, you're ready to cover, if silkspan, silk or tissue, you're ready to dope. Now the tricks get more subtle. I use all of these materials, but I will concentrate on span although these tips will work on any doped on covering except synthetics. The main areas to watch are the wing, stab, and rudder tips and other compound curved area where you use slits to make the covering comform. When you do that, you double the thickness in areas and that's not necessary. Get a couple coats of dope on the whole thing then start sanding with your little ovals. From this point on, nothing rougher then 400 should be used. concentrate on the lapped joints and even use a couple extra coats to seal them sanding in between to feather them out eliminating the need to apply filler later on. This can be done on the LE, TE and fuselage seams too, but be careful not to sand through. From about 3 coats on, sand lightly knocking off nibs and raised fibers, but be WAY careful if you're using silk. I normally use about 6 coats of full strength dope before I prime. What you want to do is make the surface as perfect as you can BEFORE you prime.

4. Priming. Here is where some will part company with me, but that's OK, I've proven my point to those that have seen my models, so I won't argue. I am a big fan of Duplicolor rattle can primers. They make a filling primer and a basic sandable primer. No matter what you use, the principal will remain the same. The prime should not be seen as the opportunity to fill small imperfections, you should have already taken care of that. From the first coat of primer never use anything rougher then 400. You need to some roughness here refered to as "tooth" to give the color something to latch onto. I can't stress enough how important this phase of the finish preparation is. Sanding can be tedious, but it is necessary, you do not want to be filling imperfections with clear at the end. Remember the paper ovals. Sand fillets with rolled up paper, and oh yes, this is one place you may want to go just a bit rougher, I use 320 grit on the fillets. DO NOT use progressively fine grits to get to 400!!! Start and finish with it. Progressively sanding with finer grits really just takes longer, and the fact is, you will only be trying to sand away the scratches from larger grits and in fact will miss allot of them. If you have done the building and covering well, you will notice that the primer sanding goes quickly and levels instantly. By holding up to the light and looking down the surface you should see one unbroken continuous surface. If you see irregularities and the primer is intact, sand a bit more. If the primer is gone, SPOT prime, not need to add where its not needed. You're looking for that all over sheen when you look across the surfaces.


5. Color; use only as much as you need and NO MORE! If you use silver, then give it a coat of clear before you go on to trim, this will seal and bind the pigment and keep the silver pristine. Trim edges, here's another place to cut some serious calories. Don't be afraid to lightly feather the masked edges of opaque colors, even translucents can be feathered because they are generally heavier at the masked edge and therefore darker, but be CAREFUL. Use 2000 grit for this, and do it wet. I'm not talking about massive sanding here, mostly just a rub down, You will not get a total feathering at this point, but you WILL knock off the raised edge that takes some much clear to fill later. OK, now you have all your trim done and lightly feathered. Ready for clear coats right??!!! WRONG!!!. Now get your air brush good and squeeky clean and carefully put 2 or 3 thin coats of clear on all the tirm edges, 2000 grit between coats. You will be amazed at how fast the edges disappear and the surface levels. Carefully and LIGHTLY go over the entire model with 2000. Once again holding up to the light and looking down the surface you should now see one unbroken continuous surface. No little shiney spots, stippling, no little hollows.

6. Clear at last. Here is where we tend to get carried away. We use clear coats the try to fill all those ewglies that read through. If you look at my Sabre Stunt thread you'll see the finished product. This model has only 2 coats of thinned clear on it. A tad bit of retarder to let it flow a bit. After the first coat, it was merely "rubbed down" with 2000 grit. After the second coat it was thoroughly sanded with 2000 grit wet and polished with Brasso. This model tips the scales at 38 0z using an OS .40FP, so you can see that the finish weight is down.

So you see, the "trick" of the good finish is really many little ones along the way. We are always anxious to see and fly the finished product, but don't let that make you skimp along the way and cost you allot of work and flab in the end.

Edited for MANY typos, AGAIN.
« Last Edit: May 30, 2009, 09:37:07 AM by Randy Ryan »
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Offline Randy Powell

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Re: A Few Thoughts on Finishing
« Reply #1 on: September 16, 2007, 12:12:35 AM »
Randy,

I vary from you only slightly. I use finishing compound at the end and hand glaze. I hadn't thought about wetting the airframe before, but then, I live in a high humidity place. <grin>

I've used rattle can lacquer primer before and it works well. Unfortunately, I live in communist Washington and it's not available anymore. So I'm sort of stuck with other alternatives. I've used K-36 and that works pretty well, but you have to be aggressive with the sandpaper. The stuff is heavy, though you can have dope both over and under it without problems. More recently, I've take to just making my own (clear, filler material, a bit of toner to make it gray. Again, works OK, but I wish I could still get lacquer primer.
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Offline Bill Little

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Re: A Few Thoughts on Finishing
« Reply #2 on: September 16, 2007, 12:07:42 PM »
Randy R.:  Great theme, and totally true.  As Sparky says, the finish begins with the first piece of wood cut.  I recently did a model using nothing but tinted Nitrate as the filler.  Lightestr finish I have ever put on!  Would have been outsyanding (my best ever) but I got in a hurry and used too much retarder (WAY TOO MUCH!) in the color and pulled off paint all over the place. (See the "Paint Job from Hades" thread).  But i had the framework totally smooth and flat before I started putting on color.  No grain or imperfections anywhere to be found, and only *filler* was the fillets.

Randy P:  Duplicolor has a new line of totally VOC compliant lacquers available now in their "Body Shop" series.  We are in the process of painting Aaron's T-Bird I using this *lacquer*.  So far it has been OUTFREAKINGSTANDING!  It comes in prethinned quarts (still need to add thinner ansd a touch of flex additive) and dries quicker than the old lacquer.  No compatibilty issues with Sig dope or Dupont A/L.  I think I am going to love this stuff.  I can buy it about a 1/2 mile from my house, and it thins with Dupont 3608S.  Flows great.  Going to do a test shot with Sig Lite Coat as a clear finish.  So far there have been no problems, and it is around $15 a quart.  Have well over 1/2 the can left with the plane completely covered in *White*.  This was over a "speckled" Duplicolor primer finish.  They also have a clear and primer in this "System".  Don't have a clue as to how *Fuel Proof* the Clear is but I will find out on an old beater! ;D
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Offline Clint Ormosen

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Re: A Few Thoughts on Finishing
« Reply #3 on: September 29, 2007, 03:44:48 PM »
Randy, Im trying to follow your posted method for finishing. You listed Duplicolor as the primer you use, but I want to use Sig dope for color and clearcoat. Are the two products compatible?
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Offline Greg L Bahrman

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Re: A Few Thoughts on Finishing
« Reply #4 on: September 29, 2007, 04:36:37 PM »
Randy Ryan,
Thanks for taking the time to type it out and post it for us. I really appreciate it. Your planes always appear top notch. Thanks again.....
Greg Bahrman, AMA 312522
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Offline Bill Little

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Re: A Few Thoughts on Finishing
« Reply #5 on: September 30, 2007, 12:30:24 PM »
Randy, Im trying to follow your posted method for finishing. You listed Duplicolor as the primer you use, but I want to use Sig dope for color and clearcoat. Are the two products compatible?

In a word, yes! ;D
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Offline Randy Ryan

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Re: A Few Thoughts on Finishing
« Reply #6 on: October 01, 2007, 07:02:11 PM »
Randy, Im trying to follow your posted method for finishing. You listed Duplicolor as the primer you use, but I want to use Sig dope for color and clearcoat. Are the two products compatible?



Clint,

I have no experience using SIG over Duplicolor, but see no reason it shouldn't be compatible. I have used Brodak color and clear over it with great results. Easiest way to find out is to do a test piece, just a little square of balsa covered and finished the way you intend to do it.
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Offline Clint Ormosen

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Re: A Few Thoughts on Finishing
« Reply #7 on: October 01, 2007, 10:48:46 PM »
Well, since I haven't bought the color dope yet, I can use Brodak. It's just that I don't have any experience with anything other that Sig. It's a comfort zone sorta thing.
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Offline Randy Powell

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Re: A Few Thoughts on Finishing
« Reply #8 on: October 02, 2007, 02:06:05 PM »
>>Duplicolor has a new line of totally VOC compliant lacquers available now in their "Body Shop" series. <<

Turns out it's still not available here in the wonderful nanny state. At least my auto paint guy says so. However, he does say that DuPont makes an acrylic lacquer primer that may work and is available special order. Of course there's an outrageous EPA surcharge. It's not that we don't want you to use it, just that we want to make a bunch of money from you using it. They'd probably have a cow if they knew I was getting actual lacquer mail order.

Hey, there's an idea! 

---------------------------------------

OK, update. I found out that I can order the stuff online from a number of sources. I take it that the Duplicolor filling primer is a lacquer. It seems to be based on the description and it's listed under lacquers.
« Last Edit: October 02, 2007, 04:23:24 PM by Randy Powell »
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Offline Mark Scarborough

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Re: A Few Thoughts on Finishing
« Reply #9 on: October 02, 2007, 04:36:57 PM »
Randy,
shhhhhhhhh dont say that out loud you live WAY to close to Olympia they will hear you!
I can get Kondar Acrylic laquer primer, its the same price as K-36! guess which one I want to use?
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Offline Bill Little

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Re: A Few Thoughts on Finishing
« Reply #10 on: October 02, 2007, 06:58:17 PM »
Well, since I haven't bought the color dope yet, I can use Brodak. It's just that I don't have any experience with anything other that Sig. It's a comfort zone sorta thing.

Hi Clint,

In case you didn't see mt previous post, Sig will go over the Duplicolor filler/primer with out any problems.  I use Sig colors all the time over it, both of the Sig clears, too (Lite Coat, Supercoat.).
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Offline Clint Ormosen

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Re: A Few Thoughts on Finishing
« Reply #11 on: October 03, 2007, 12:49:34 PM »
Thanks for the input on the Sig dope, Bill.

I shot the model with Duplicolor primer and am sanding it down again. Seems like good stuff.

Randy, what thinner are you using with the dope. (note: Dupont V-3608S and 3608S thinner is not available here in northern CA)
« Last Edit: October 03, 2007, 01:44:37 PM by Clint Ormosen »
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Offline Bill Little

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Re: A Few Thoughts on Finishing
« Reply #12 on: October 03, 2007, 03:27:47 PM »
Clint,

Randolph's Butyrate thinner will work fine in Sig dope.  It *should* be cheaper by the gallon than Sig or Brodak's.  A local airport that does repairs is where I used to get mine.

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Offline Randy Ryan

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Re: A Few Thoughts on Finishing
« Reply #13 on: October 03, 2007, 07:11:55 PM »
OK, you guys will laugh at this, but I do it and it works. Not sure about SIG but I use plain ol' lacquer thinner from Miejer's with Brodak dope. I used to keep it on hand for cleaning brushes and spray guns and noticed that it never clotted up in the container. So, I mixed some clear and gave it a try. That's what's on the Sabre, both color and clear are thinned with cheap lacquer thinner.
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Offline Randy Powell

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Re: A Few Thoughts on Finishing
« Reply #14 on: October 04, 2007, 09:45:52 AM »
Randy,

I believe it. I've used stuff that just says "Paint Thinner" on the can (lacquer in fine print) from Home Depot before. It seemed to work fine, though it wasn't much cheaper than what I pay for a gallon of Certified Thinner. I've always maintained that as long as it's compatible, use whatevers to hand, just make sure you have enough to thin paint from wood to topcoat. Most of the finishing problems I've had with dope have been from changing thinners in mid finish. I once switched from using 3608S to Sig thinner in the middle of shooting trim color and developed horrible problems with adhesion (pulling up sheets of colored dope when I pulled the tape off). Cured me of that.

On another note, Phil Granderson's suggestion in his MA ariticle that after shooting and sanding primer, shoot a thin coat of heavily reduced clear is a really good idea. Last plane I finished, after sanding the primer, I shot a coat of clear mixed 80% thinner/20% clear on the primer. It sort of locked the primer down and I had enormously less problems with tape pulling up paint. I'd always just gone from primer to a blocking coat of color without the mostly thinner clearcoat in between. Man, don't miss this step. It will solve a multitude of problems later on.
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Offline Mark Scarborough

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Re: A Few Thoughts on Finishing
« Reply #15 on: October 04, 2007, 10:05:55 AM »
Randy,,,
arghhhhhhhhh I know it works for you BUT,,,,,,,
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Offline Randy Powell

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Re: A Few Thoughts on Finishing
« Reply #16 on: October 04, 2007, 10:52:32 AM »
Mark,

Clearly the safe way is to use thinner matched to the dope you're using. If you use Randophs dope, use Randolphs thinner. You will be enormously less likely to run into problems. But as Randy R notes, if your into experimenting, you can find stuff that is compatible. And it's true that it might not work every time. Something to think about. Could be that it worked for Randy R (and me) because we happened to use it in the right conditions (heat, humidity, whatever). I wouldn't do it as a matter of course. Randy R on the other hand may have enough experience with the specific brand he gets to trust it. The reason I switched for 3608 to Sig in the middle of a job was that I was foolish. I ran out of the 3608 and was almost done. I had some Sig laying around ...
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Offline Randy Ryan

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Re: A Few Thoughts on Finishing
« Reply #17 on: October 04, 2007, 05:03:03 PM »
Randy,

You're correct about changing thinner mid project, seem the thinner is actually more of a critical substance then the finishing material.

The thinner I buy from Miejer's is labled Lacquer Thinner, nothing more, and I buy a gallon of it for the price of a quart of Brodak's, and I understand Brodak's and SIG's dope prices just went up to the tune of 50%. It does by the way smell exactly the same as Brodak's thinner.

In reference to Phil Ganderson's clear over primer, I have never tried that, but I have put it over silver and gold basecoats to bind them, it works well, but I'll try the other method. I use heat when I remove masking, its always worked well so I never explored improving color adhesion.

Mark,

Experimentation will yield rewards, usually in the form of $$$ savings and sometimes time and frustration. Sticking to a single finishing system will yield rewards in the form of the same finish without the need to experiment, but will cost you more $$$. Over the years I have tried allot of different things, not just on model airplanes, but cars and motorcycles as well. I've found allot of things that will work together, but its taken time. My suggestion is just as I said earlier, do small samples if you want to try some thing out, you don't need to put a total project in jeopardy to find out is Y thinner works with X dope.
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Offline Randy Powell

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Re: A Few Thoughts on Finishing
« Reply #18 on: October 04, 2007, 10:38:26 PM »
Randy,

So you've found stuff that works for you consistently. That's the goal. I use Certified thinner. At just under $20 a gallon, it's not too bad on cost. Certainly cheaper than buying some others I could name.
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Offline Bill Little

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Re: A Few Thoughts on Finishing
« Reply #19 on: October 05, 2007, 05:46:38 PM »
I TOTALLY UNDERSTAND what Mark is saying about compatible materials.  I would not argue with him on his theory.

Problem is, i am not sure if he grew up as poor as I did! LL~ LL~  We actually MADE stuff when we could not buy it.

I have had ONE problem with paint on a model since I started building in C/L planes in 1963.  I tried to mix Testors Dope with Aero Gloss dope.  Needless to say, that did not work! LL~ LL~

I have used several different brands of automotive acrylic lacquer with both Randolph and Sig dope with no problems.  I have used Sig, Randolph and Brodak's onthe same plane with no problems.  I have used Dupont 3608S in all of them with no problem.  Ditto Randolph's thinner.  I didn't like one grade of PPG lacquer thinner, it was TOO HOT!  It ate into the finsh (didn't craze it), but I put the clear on too heavy, and it sorta faded the color.  That wasn't the product's fault, it was MY fault for spraying it too heavy.

Many more problems are caused by insufficient drying times, too much retarder, etc., etc..  There ARE paints that will not go over another paint without causing it to look like lizard skin, but they are not usually a dope or lacquer product over like product.  Like "Don't spray Sig Lite Coat over Chromabase color".  And don't brush nitrate over butyrate.  Ditto putting a real lacquer over an enamel.

Over the years I have found that what ever thinner you use, if it thins the paint (doesn't congeal or clump up), it works.  Just keep the same thinner going through out.  And avoid retarder at all costs, unless it is TOTALLY necessary! LL~   

I'm not argueing wqith anyone, so don't take it that way, please! ;D  But I haven't been ashamed to put down one of my planes anywhere (if it's one I actually took my time on).  I have an Argus posted on here.  It has a Sig Nitrate substrate, Dupont fill'n'sand filler/primer, white PPG mixing base acrylic lacquer blocking coat, Chromabase colors and Chromaclear top coat.  it is still perfect (except I tore the outboard wing off! LOL!!) about 8 years later.

Of course, "I AM the BLIND hog"...............
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Offline Clint Ormosen

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Re: A Few Thoughts on Finishing
« Reply #20 on: October 05, 2007, 11:24:14 PM »
Well, after my chat with Randy P., I've decided to go with Randolphs clear dope and thinner. And since Brodak dope is the same stuff, I ordered some color dope from them. Of course all this will go over the top of Sig nitrate and Grow automotive lacquer thinner, so this will certainly be a compatability test.
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Offline Jim Treace

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Re: A Few Thoughts on Finishing
« Reply #21 on: October 06, 2007, 01:42:58 PM »
Slightly off the topic points of this thread, but....what do you guys use and method to remove the over spray of color trim over the base color. Sometimes I just miss a little on my tape job and a little color shows up where it shouldn't. Talking about dope finishes here.
Jim
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Offline Randy Ryan

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Re: A Few Thoughts on Finishing
« Reply #22 on: October 06, 2007, 03:01:48 PM »
Jim,

I just mask so that can't happen. Aluminum foil is the best for masking and insuring no weepage or sticking ocur. The areas where the insignia and stars are going was done with frisket paper. The lettering is decals doped under and feathered.



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Re: A Few Thoughts on Finishing
« Reply #23 on: October 06, 2007, 05:06:36 PM »
OK, so it's my masking. I know, but since I have some slight "misting" of the trim color. What is the best way to remove it. I am not talking about heavy blobs of paint, just very lite whispers of it.
Next one will be masked properly.
Jim
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Offline Clint Ormosen

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Re: A Few Thoughts on Finishing
« Reply #24 on: October 06, 2007, 06:55:51 PM »
I'm guessing that you haven't clear coated anything yet? If you already tried heavy wiping with a cleaner or something, try to remove the misted color with 2000 grit paper. Very carefully. I would not use thinner to remove it.
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Offline Randy Ryan

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Re: A Few Thoughts on Finishing
« Reply #25 on: October 06, 2007, 07:36:55 PM »
I'm guessing that you haven't clear coated anything yet? If you already tried heavy wiping with a cleaner or something, try to remove the misted color with 2000 grit paper. Very carefully. I would not use thinner to remove it.



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Offline Patrick Rowan

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Re: A Few Thoughts on Finishing
« Reply #26 on: October 06, 2007, 09:44:40 PM »
A clean rag with 91% Rubbing alcohol will remove overspray if not to old.
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Offline Greg L Bahrman

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Re: A Few Thoughts on Finishing
« Reply #27 on: October 06, 2007, 11:21:43 PM »
On what you've described I have used fine rubbing compound successfully. y1
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Offline minnesotamodeler

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Re: A Few Thoughts on Finishing
« Reply #28 on: October 07, 2007, 06:27:31 AM »
Jim, try a white plastic eraser. Called "hi-polymer", made by Pentel, lots of other brands, get it at any arts-n-crafts type store.  Removes overspray quite well.

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Offline Jim Treace

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Re: A Few Thoughts on Finishing
« Reply #29 on: October 07, 2007, 08:44:56 AM »
No clear coat, yet. Just working on the slight over spray mist marks. I had tried the 2000 grit paper. Probably rubbed a bit too much. Took off a little of the base color, so I am now paper shy. So, I will try the other metods described.
Jim   
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Offline Chris McMillin

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Re: A Few Thoughts on Finishing
« Reply #30 on: October 07, 2007, 09:18:00 PM »
OK, so it's my masking. I know, but since I have some slight "misting" of the trim color. What is the best way to remove it. I am not talking about heavy blobs of paint, just very lite whispers of it.
Next one will be masked properly.
Jim


I scrape it off very lightly with a brand new razor. Sometimes a little bit more than lightly.
My using thinner or alcohol just makes a mess, usually!
The eraser sounds like an idea, I need to try that.
Chris...

Offline RC Storick

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Re: A Few Thoughts on Finishing
« Reply #31 on: October 08, 2007, 07:00:34 AM »
Very good thread. I use NAPA primer part #DC540. The trick to a good finish is not how much you put on but how much you take off. The razor technique also works for ink lines that cross over.
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Offline Jim Treace

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Re: A Few Thoughts on Finishing
« Reply #32 on: October 08, 2007, 10:03:43 AM »

I scrape it off very lightly with a brand new razor. Sometimes a little bit more than lightly.
My using thinner or alcohol just makes a mess, usually!
The eraser sounds like an idea, I need to try that.
Chris...

OK, I used the manual razor blade before I tried the liquid stuff. The blade worked pretty good. It is a technique thing, though. Much like the sandpaper. Need to get the eraser and try it too. I will try some of the NAPA and alcohol, but test it out on test wood first. Here is a picture of my Cardinal. I tend to get a bit anxious and want it done. I hope to fly it end of this month at a little gathering that RootBeard is putting together. For me, the color red seems to be the most difficult to work with.
Jim
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Offline ptg

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Re: A Few Thoughts on Finishing
« Reply #33 on: October 11, 2007, 12:40:24 PM »
OVER SPRAY .........

So far I've gotten it on every plane ever painted.  Used all methods here with varying levels of success. 
Three years ago found "Mr. Clean Magic Eraser" and since then over spray is no big deal.  Wrote about it several times.  This product was never intended for use in model painting but is quite possibly the most useful thing I have found in painting.  You can find it at any super market, drug store or variety store and even some hardware stores.  Just use as directed and you will be amazed at the results.  I've even removed black over spray from a white base coat with no damage to the base! 

Try it......you'll like it!  Also useful for cleaning up masking lines where there is slight seepage under the tape. 
PT Granderson

Offline Clint Ormosen

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Re: A Few Thoughts on Finishing
« Reply #34 on: October 11, 2007, 01:08:27 PM »
'Hafta agree about the Magic Eraser. I use them all the time for stuff around the house and car. Never thought about trying them on a model.

Good idea. H^^
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Offline Randy Powell

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Re: A Few Thoughts on Finishing
« Reply #35 on: October 12, 2007, 11:11:24 AM »
On the subject of fillers, primers and thinner.

I managed to scare up a quart of Duplicolor filler/primer. I did a test last night by mixing the primer with Certified thinner. Seems to mix really well and has a very silky texture. I'm going to let it sit for a bit in the jar and see if it continues to re-mix well. As Bill Little noted, if it mixes well, it's probably compatible.

I've tried about everything under the sun for filler coat. Catalyzed products like K-36, various urethane based auto primers, your standard dope and talc or zinc sterate or even cornstarch in endless variation, various lacquer primers and a few things I don't even want to admit to. All systems, like anything else, have advantages and drawbacks. The one thing I've learned is, find something that works and you understand and know how to run and stick with it. I'm trying the Duplicolor primarily because Randy Ryan and Sparky have had success with it and it seemed easier using a standard product than brewing up the stuff I normally use (an alchemic talc/dope mixture with about 6 ingredients - don't laugh, it worked).

Bill also noted that he had used disparate materials (Sig, Randolph's, DuPont) on the same plane and he's right. This will usually work, given the same basic lacquer base in the materials. But again, the key to this is using the same thinner throughout. Of course, you are taking a chance with this. I suspect that, using such materials on the same project, that humidity, temperature and such will be more critical. As an example, thinners like 3608 are temperature rated. Some are designed to work in 70-90 degree temps, others are designed to work in 50-70 degree temps. Same with various paints. If you mix them and get outside the design temp range, it might work fine or it might have problems.

Typical problems include adhesion issues, lifting, crazing and evaporation issues. Often, if you shoot a product that takes some drying time and you are doing it in relatively cold temps or in higher humidity, the drying time will be substantially extended. Perhaps measured in days. If you turn around and shoot a product over it that flashes more quickly, say a clear with a hot thinner, so that the stuff skins over rapidly, you will probably have problems. As the undercoat continues to gas off (sometimes long after you think it's done), it can lift the topcoat and cause fillets to pull, bubbles to appear or just poor adhesion issues that always show up when you pull tape.

These are just a couple of the problems. It seems that when I start experimenting with finishing products, it's an invitation to invent new problems. I've had some pretty weird stuff happen when I used disparate products. Then it's back track and hope you don't have to strip it back to down to the paper...
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Offline Mark Scarborough

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Re: A Few Thoughts on Finishing
« Reply #36 on: October 12, 2007, 05:09:54 PM »
need I say more Randy,, lol,,  ;D yeah I know I draw a hard line on this. but I have tried, and been burned by all kinds of stuff, and normally on things bigger than an airplane, try a whole full sized pickup that went gunnybags and I had to start over with it! yeah you only have to pay the price one time to learn that lesson. reality, as long as you understand the risk you are taking, and dont portray your mixed morphedite system as "the answer" experiment away. But if ya ever ask me for advice, if it doesnt have the samen name on the label , I will thnk long and hard about using it over something else with a different label.
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Offline Randy Powell

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Re: A Few Thoughts on Finishing
« Reply #37 on: October 13, 2007, 12:27:07 AM »
Hey, I agree with you, Mark. I've gotten away with mixing some stuff and I've developed a good enough feel, over the years, usually get away with it. But the truth is, you're better off doing just as you say; use paint systems that are desgined to go together. As it turns out, lacquer thinner isn't all the same. The base chemical concept might be the same, but what each manufacturer comes up with might or might not be compatible. Ask anyone that used Aerogloss with Testors dope together. Talk about a crap shoot.
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Offline Randy Ryan

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Re: A Few Thoughts on Finishing
« Reply #38 on: October 13, 2007, 09:42:10 AM »
Just to bring this back into perspective. My intent was not to advocate experimentation with different finishing products, though I don't shrink away from that. The intent of this post was to highlight finishing tips and techniques which are valid no matter what finish you chose.
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Offline Bill Little

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Re: A Few Thoughts on Finishing
« Reply #39 on: October 13, 2007, 09:46:55 AM »
HI Guys,

Since I seem to be the "Blind Hog", I want to add the usual disclaimer, your milage may vary! LL~

Mark,  if I am painting a car, I use all the same line of products all the way through.  A project like that is something I don't want to do over!

Randy P., the Duplicolor Paint Shop quarts work great.  We have a T-Bird Mk-I we are using the colors on now.  It is simply a VOC compliant lacquer.

I do not have a local supply for ANY "dope products".  The local airport no longer sells, and the nearest Hobby Shop is over an hour away (but a GREAT one it is!).  Over the years I have had to use what I could.  When auto lacquers were widely available, I had no problems.  Since then I have had to find just what does work that I can buy around town.  I have found out several things that will work, and work well.   I can't tell you what doesn't work, because I don't use it again, and can't remember!

So, I have a couple systems that DO work, and that's what I use.  ;D

Brother Randy R., thanks for the tips! 
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Offline Randy Powell

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Re: A Few Thoughts on Finishing
« Reply #40 on: October 14, 2007, 12:02:18 AM »
Randy R.,

Ok, at tip.

Friend of mine is doing his first dope finish in about 30 years. He has had no end of problems with it. One thing he did that I didn't catch in talking to him until pretty late in the prep process was that he was using full shink dope from the wood up. He had a lot of problems with fillets (no paper over them) bubbling up and some odd adhesion problems. After he had sanded the fillets and bad spots back down to the paper (or fillets as the case may be), I told him to switch to non-taunting dope. Problems went away.
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Offline Matt Colan

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Re: A Few Thoughts on Finishing
« Reply #41 on: July 25, 2009, 10:25:56 AM »
Great thread guys, I learned a couple of things I may try on my new stunter that I plan to do a full blown finish on it.

Matt Colan

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Re: A Few Thoughts on Finishing
« Reply #42 on: August 18, 2009, 10:14:21 AM »
I came back to this one, since it has been pulled back up. ;D

Like I always say, I am the *Blind Hog*......  Since I started this hobby for earnest back in 1963, I have always been on a budget.  Champagne Taste on a Beer budget, so to speak.  I also had to repair and paint my cars for many years, including my first road car which didn't run when I bought it at 15 1/2 years old, and had a torn up rear 1/4 panel.  So my *experience* is tainted.

I can totally understand Mark's stance on only using one product, the best guns, etc., and have no argument with him at all! ;D  But, I also know that there are other ways to skin a cat and end up with a great looking skinned cat. y1  Lots of airplanes, cars, etc., have shown me that.  And the wonderful thing about this hobby is that you can do things the way you want.   

So, I would suggest that you use stuff that is from the same line! (unless you are like me and cannot get it! ;D )

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Offline Bryan Higgins

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Re: A Few Thoughts on Finishing
« Reply #43 on: October 01, 2009, 10:44:08 AM »
Anyone who is looking for information on "How to Paint" a control line plane.

Look Here

Thanks guy's what a helpful thread.


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Offline john e. holliday

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Re: A Few Thoughts on Finishing
« Reply #44 on: July 26, 2011, 03:16:14 PM »
None of the hi-lighted stuff come up. ??? ???
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Finish sand a piece of wood before assembling it onto the model
« Reply #45 on: December 14, 2012, 08:27:33 PM »
One trick I learned is to 100% finish sand a piece of wood before assembling it onto the model.  Especially sheeting over open bay type structures.  That way you reduce the risk of damaging the wood after it is on the model or causing the high and low spots from where the wood is supported and not supported.

-Scott


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Re: Finish sand a piece of wood before assembling it onto the model
« Reply #46 on: December 15, 2012, 12:24:15 PM »
One trick I learned is to 100% finish sand a piece of wood before assembling it onto the model.  Especially sheeting over open bay type structures.  That way you reduce the risk of damaging the wood after it is on the model or causing the high and low spots from where the wood is supported and not supported.

-Scott

Hi Scott,

That is really a great tip and practice for building.  One of the worst things is a "starved horse" look on the LE of a wing where heavy sanding takes wood off the areas where the skin is held by the ribs while the areas between sink down a bit.

BIG Bear
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Offline Chris Fretz

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Re: A Few Thoughts on Finishing
« Reply #47 on: January 01, 2017, 06:26:43 PM »
What do you do when you wipe a wet cloth on a stab to raise the wood and it causes a warp?
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Offline john e. holliday

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Re: A Few Thoughts on Finishing
« Reply #48 on: January 01, 2017, 09:01:22 PM »
The rag is too wet.   You can rewet it and warp the other direction until it is dry.  In fact if you only wetted one surface it may come back straight once it dries. H^^
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Offline Chris Fretz

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Re: A Few Thoughts on Finishing
« Reply #49 on: January 01, 2017, 09:50:56 PM »
The rag is too wet.   You can rewet it and warp the other direction until it is dry.  In fact if you only wetted one surface it may come back straight once it dries. H^^
I rewet it an put some heavy objects on it an that seemed to work,  the flaps were a little more difficult but I think I got it.
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Offline Clint Ormosen

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Re: A Few Thoughts on Finishing
« Reply #50 on: March 21, 2019, 04:05:30 AM »
I just wanted to mention that the OP here from Randy Ryan, even 12 years later, is still one of the best ways to do a traditional dope finish that can be found on this or any other modeling forum. I follow it pretty closely on all my models and it hasn't let me down. It's printed out and hangs on my shop wall.
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Offline Shorts,David

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Re: A Few Thoughts on Finishing
« Reply #51 on: November 24, 2019, 04:12:54 PM »
Question for Clint, Randy, or anyone else. Why do we wet sand? Is it just to keep dust out of our lungs, because that's a pretty good reason...

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Re: A Few Thoughts on Finishing
« Reply #52 on: August 30, 2020, 12:47:43 PM »
Straightening warped balsa is quite easy in must cases. First soak well with clear water, hot water speeds the soaking process. Remove from water and straighten the piece by flexing it opposite the warp. When it is straight suspend vertically and let dry thoroughly. I have done this many many times and never had it fail.
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Online MikeyPratt

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Re: A Few Thoughts on Finishing
« Reply #53 on: October 31, 2021, 09:35:44 AM »
Hi Guyís,
Iíve been following this post closely about the different types of paint used for models.  Personally, this makes me very nervous to read some of the posts.  After more than 50 years building and flying them I myself have tried many different systems looking for something easier and faster.  I still havenít found anything as easy and fool proof as dope, period!  After putting in months of work carefully building your new model, why risk your new world beater on a sub par finish.  To do a just a fare finish it takes as long as it took to build your new Stunt model in the first place.  I think it takes way longer to apply a good finish that it took to build it thatís why it takes a year.

OK just my opinion, why do all the work building you new model and screw it up with the paint job!  Some of you know my finishes pretty darn good and Iíve had many 18 to 19 point models at the Natís, so they arenít too shabby.  They were all done with Sig Dope, later versions were cleared with epoxy or urethane finishes but they all used dope under that.  Now I understand if your donít want the smell dope in the house, but itís not any different than using the Duplacolor system, it stinks as well.  Iíve tried the the primer that Bob S recommend and that did fine as a primer under Sig Dope and colors.

One of my jobs at Sig was to handle complaints from modelers about our products, that includes dope products, and epoxyís (including Epoxy-lite) and a few more.  I would have them send the product back to me so I could inspect and verify it was our product and I then used it on a test model.  Guess what, they always worked every time with the exception of a few cans of dope that were rusted on the inside (they were really old cans of product) but they were replaced anyway.  One guy even told me he was getting a reaction to some thing on his model and the dope wouldnít dry, not even on the second coat.  I asked what he was doing before hand while he was painting it, ďhe said eating buttered popcornĒ, go figure that one lol.

Lately, Iíve been trying model R/C car paints (water base) with some really good results so far, weight seems ok and itís holding up pretty good for now after a clear coat of automotive clear.  Iíll let you know about that later if is good or not.

Later,
Mike Pratt 


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