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Building Tips and technical articles. => Paint and finishing => Topic started by: Tim Wescott on April 15, 2011, 09:03:33 PM
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A long time ago, when I was finishing the Waiex, I mentioned that I was going to try mixing talc with Minwax Polycrylic. It makes the Polycrylic sand very easily -- without talc, the stuff wants to ball up in the sand paper something fierce.
What I didn't know was how the talc affected the long-term adhesion and stability of the stuff. So, after crashing the plane and being reminded of the finishing process, I'm reporting in: it works fine. While it isn't proof from getting ground off of a plane by sliding it on asphalt, it hasn't shown any signs of chipping or cracking or any other misbehavior. And it sands nice.
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I'm new to finishing with anything other than 'cote. How much talc do you use? How many coats does it typically take to get to the paint stage?
Steve
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I'm new to the Minwax/Rustoleum process, but here's what I know (I wonder if there's a web page out there?):
This is a process that seems to really only work for solid sheeted surfaces. So it really should be called the Minwax/Rustoleum/'coat process. On planes that have open bays on the wings and a solid surface on the fuse, the idea is to paint the fuse, and cover the wings. You can either cover the wings (and tail) first, glue things together, then paint the fuse and overlap onto the 'coat. Or you can paint the fuse and go out a bit on the sheeted part of the wing, and 'coat when you're done. So far I've just done the latter -- but I'll be trying the former soon.
Don't expect to find a perfect match between paint and 'coat. If you do -- woo hoo! Celebrate and enjoy.
Maximal enjoyment of any finish job can be attained by first deciding how good of a finish you want. I measure this in feet -- if it looks good from 50 feet, but not from 20, then it's a 50 foot job. If it looks good from 5 feet but not from 2, it's a 5-foot job. If you try to assess a really good finish then you'll get in trouble with the owner, because you'll leave nose-grease on the plane -- just call those ones "really good", and keep your hands behind your back when you look at them.
I figure this process to be good for a 5 to 2 foot finish -- any closer than that, and you have to start working hard enough at overcoming the deficiencies of the materials that you may as well start using real paint, like automotive finishes or dope. You may think differently -- I've only seen his finishes in pictures, but Fay Stiley (spelling?) does Monocoat finishes that win prizes, and I get the impression that he's doing finishes measured in inches. I'm sure that if you were really motivated you could do a 5 inch finish with these materials -- but for that good of a finish, you may do less work overall and spend less money by doing it in real paint.
Materials are Minwax Polycrylic (the water-based stuff), silkspan (optional, but it really seems to help), and Rustoleum Gloss Protective Enamel. I also use Rustoleum metal primer, but some leave out this step -- I haven't tried it without, so I can't comment on how it looks. There are other Rustoleum products, but the gloss protective enamel has a rep for being the most fuel proof. Note that I'm talking about rattle-can Rustoleum. I doubt you could get a decent finish with the stuff without spraying it. If you have spray equipment and you don't want to spend a few extra pennies on dope, I'd be interested in hearing of your results using the Rustoleum that's sold in cans.
Before you start, get a jelly jar or some other container that holds about a cup of liquid and can be sealed tightly. Put in about 3/4 of an inch of Polycrylic, then dump about 1/4-1/2 inches of talcum powder (baby powder works fine, and smells nice, too). Mix well. This is your sanding sealer*.
- Prep the wood as you would for paint -- i.e., build it well from the get-go, don't leave any big gaps in the structure, and sand until it's as smooth as a baby's butt.
- Brush on a coat of Minwax, let dry.
- Brush on a coat of sanding sealer, let dry.
- Sand just enough that things are smooth. Don't sand through to bare wood!
- Apply silkspan to the Minwax'd surface, and hold it down with a generous coat of Minwax. I haven't entirely figured out how to do this and get all the teeny wrinkles out, but applying it wet seems to help. Let dry
- Sand lightly, to knock down the really high spots. Note how the stuff balls up in your sandpaper -- this is what you're avoiding with the sanding sealer
- Brush on a coat of sanding sealer, and let dry overnight. Maybe two. Let dry overnight.
- Sand. Ideally, you'll sand down until you're just kissing the paper on the high spots, but not cutting into it. Leave too much material and your plane will be heavier. Sand through the paper and you'll compromise it's ability to fill the wood grain.
- Repeat the application of sealer and sanding until you've either achieved a perfect finish or you're bored. Remember that the wood grain is going to show up a lot worse in the finished part than it does now
- Let everything dry for a few days
- Mask of the parts of the model that you aren't going to spray, and paint. I apply a coat or two of primer, as lightly as I can, then I apply two coats of color, again trying to spray lightly. Getting a finish that has neither orange peel nor sags and runs is my personal bugaboo -- going for two light coats helps with this. If you apply paint per the directions, this'll be a four-day task, and more if you go for two colors of paint.
- Let everything dry for two weeks before you even think about flying. This stuff becomes fuel proof, but it needs a lot of curing time to do it. I've heard that the darker colors need more time, and I know for a fact that the flat black needs a lot more time -- four weeks seemed to be enough for mine.
- Go fly
Note that I didn't wax the plane -- since finishing it, I've heard that wax has some fuel proofing properties, so I may try this after I get my current crash repair completed.
* This is not some new and astonishing idea -- dope-based sanding sealer is just dope and talc mixed.
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I just like the fact I can do this in the basement without a major ventilation project. Of course sanding will still be done in the garage.
In your directions you mention Minwax, thats full strength and the sanding sealer has the talc?
Thanks
Steve
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I just like the fact I can do this in the basement without a major ventilation project. Of course sanding will still be done in the garage.
Spray the Rustoleum outside, though! Once you're done spraying you can bring it in.
In your directions you mention Minwax, thats full strength and the sanding sealer has the talc?
Yes. Note that when you get to the hardware store you don't want to get the first can that says "Minwax" on it -- you specifically want Minwax Polycrylic. There are oil-based Minwax varnishes, but the word is that they yellow with age (although I have some, and it makes a really nice finish on a handle).
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Minwax polycrilic is in the garage already, just haven't used it with talc.
Thanks Steve
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I can't comment on the chemical make up of the polyacrylic. I do know that Jerry Nelson of Nelson Hobby paints provided water based polyurethane. His product could virtually go over all latex products and even enamels then his clear could be used for fuel proofer. I know a few guys who would paint their pilots and cockpits (open style) using the Nelson clear which was a flat clear. Jerry would just add talc to his gloss to make the clear flat. He just suggested adding more if I didn't like the sheen it left to dull it out. Ken
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More news. And why no one mentioned it, I don't know. Or maybe they did, and I was too dim to notice.
Anyway, I'm finishing yet another plane with the "Polycrylic and Rustoleum" method, and I'm getting very frustrated with the whole problem of the Polycrylic and talc mixture being clear. Clear meaning, in this case, that you simply cannot tell when you're about to punch through your primer coat into bare wood. You just know when it happens -- and then it's too late.
Now, I'm all too prone to sanding down to bare metal (or whatever) as it is. I'm a menace in the paint shop, because after the primer goes from gray to undercoat color, I tell myself "I can sand this down just a bit more" -- and then it goes from undercoat to silver. Oops. So I need any help I can get.
So, being me and totally unable to do anything directly, I start by saying "how can I doctor up this Polycrylic stuff even more to make it like primer?". So I go out and look around for pigment powder. And I find it! I find it on a soapmaking website, I find it on a home paint-making web site, I find it on a home-cosmetics website, etc. (paint! note that the light has not dawned). Then I tell myself "no, I am not going to worry about this any more, I am not going to flog the finish on this Flight Streak any more, I've given Mark Scarborough too much ammunition to convince Randy Powell that I'm demented as it is. I'm just going to stop this nonsense, squirt Rustoleum primer (primer!! -- note that the light has not dawned) on this thing and accept the rough spots where it's over bare wood.
Then, as I'm drifting off to sleep, I think . . . PRIMER!!! By gum, if you can get all the stuff to make acrylic primer for things other than fine art, surely someone makes it. Finally, the light dawns.
(http://www.donmartinshrine.com/images/tn_g1_think.jpg)
I have to get up and do a web search before I can go sleep, but from there it's just a hop, skip, and a jump to the Miller Paints web site, where I find that I can get a quart of acrylic primer already made up and tinted and everything. Dang but I'm stupid.
Anyhoo, I've got the Fright Streak painted up with white primer (calm down, Mark: I'm not trying to make the plane better, I'm experimenting with a cheap paint job with a plane where it won't matter if I go for my first official flight of the Spring Tuneup and have the entire paint job on the fuselage go "floop!", peel off as one piece, and flutter onto the judges score sheets -- because it's just a Flight Streak, anyway). It'll get two coats today, and then sometime tomorrow I can see how well it'll sand (and Mark: it's not a good thing because the plane may look better (assuming I have enough self control to not sand through the bare spots), it'll be a good thing because I will be advancing knowledge).
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The only thing I've noticed with the stuff is that painting it on bare wood can cause some warping. Not so bad with reinforced sections, but sheeting can get twisted. Probably due to Polycrylic being water based. Just something to be aware of.
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The only thing I've noticed with the stuff is that painting it on bare wood can cause some warping. Not so bad with reinforced sections, but sheeting can get twisted. Probably due to Polycrylic being water based. Just something to be aware of.
That makes oodles of sense. To date I've only felt motivated to use it on profiles out to the edge of the center section sheeting. So everything's pretty well supported. And, indeed, I haven't seen anything warp.
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Oh frabjous day! The stuff sands like a dream, easily and accurately, and I can see when I'm sanding it off (which is a big help given how quickly it sands).
I think I'm in love.
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Hi guys, i'm new here, but been building for 45 years. I have used the Minwax Polycrylic myself & to minimize any tendancy for the wood to absorb moisture from the polycrylic i apply a coat of Deft lacquer sanding sealer. It really has a strong smell to it so take that into consideration. I'm just now getting back to C/L flying, since my grandson has taken an interest in building & flying. This is my first post after reading posts for the last week!....Gene
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If you try to assess a really good finish then you'll get in trouble with the owner, because you'll leave nose-grease on the plane -- just call those ones "really good", and keep your hands behind your back when you look at them.
Tim,, one other pointer when getting nose grease close to one of these, MAKE SURE YOU DONT HAVE A PEN IN YOUR POCKET WHEN YOU LEAN OVER TO LOOK AT IT,, or you may not have a chance to straighten up and run away if the pen falls out,, this includes, glo ignitors, tachs, screwdrivers and any other object in your shirt pocket,, just sayin,,
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and note, no comments regarding the flight streak,, rebuilding, refinishing, or trying to get a multiple point finish on the "donor fly it like you stole it cause it was free" flight streak,,
sigh,,, HB~>
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Tim,, one other pointer when getting nose grease close to one of these, MAKE SURE YOU DONT HAVE A PEN IN YOUR POCKET WHEN YOU LEAN OVER TO LOOK AT IT,, or you may not have a chance to straighten up and run away if the pen falls out,, this includes, glo ignitors, tachs, screwdrivers and any other object in your shirt pocket,, just sayin,,
Oh, man, I'm cringing just thinking about that.
My dad built show cars, and all of us kids grew up being told DON'T TOUCH THAT PAINT!!!. I cringe when acquaintances want to pet the pretty cars -- so imagine what the thought of dropping a screwdriver through a wing does to me...
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Oh frabjous day! The stuff sands like a dream, easily and accurately, and I can see when I'm sanding it off (which is a big help given how quickly it sands).
I think I'm in love.
Note that it's having adhesion problems to the Minwax -- I'll be trying it from bare wood out, soon. Rustoleum sticks quite well to it, though, so that's not a problem.
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"donor fly it like you stole it cause it was free" flight streak,,
Well, given that my "buy cheap stuff from the hardware store and paint" plan seems to be leading to at least one area where the primer is chipping off of the bottom coat (taking the top coat with it), at least I'm painting it like I stole it!
Don't worry. I'll crash it. That's inevitable.