Finishing with Urethanes

Finishing with urethanes can be very easy quick and rewarding.   Since Brodak is the dope of choice at this point and time in the Control Line world I will describe the process using this product.  I know it works very well I just did this on my latest ship.

From bare wood I apply 4 coats of clear dope thinned 50:50.  I sand between the third and fourth coat.  Also I sand after the fourth coat.  At this point I apply the covering I am going to use.  I use Poly Span on open bays and carbon fiber mat on the sheeted wood areas.  It has been said that Poly Span does not adhere well with the use of Butyrate dope.  Well with a good tip from Windy the problems were solved.

After the four coats of dope the Poly Span was then applied with 90% thinner 10% dope mixture.  The thinner penetrates well and activates the dope underneath and it sticks great.

After the covering I applied I brush down 2 coats of dope thinned 50:50 over all the areas that are covered with carbon fiber.  Then sand out smooth.  The carbon is used as filler.  It works very well.  I brush down three coats of 50:50 dope over the Poly Span it takes more dope to seal it.  Then sand smooth.

Next comes the filler.  I apply one coat 1 part dope 1 part thinner 1 part Brodak white primer.  I brush this down.  Let dry fully for at least 2 days.  I have found that the longer you wait the easier it sands off.  I waited 1 month on my flaps and I was able to sand it off in about 15 minutes.   Now proceed to sand all of the white primer off.  The surfaces that are covered with carbon will begin to look grey as you sand down through the primer.  Grey is what you are looking for.  I sanded all of the primer off because it is heavy and it does not need to be anywhere but in the low spots, grain, weave, etc.  After that I spray down one coat of the exact same mixture.(1 part dope 1 part thinner 1 part white primer)  Sand again all the way down to the gray.  At this point you should have a smooth clean surface on all parts of the aircraft.  It should have a very dull shine when held up to the light.   Now take a break from all that stinking sanding.  Taking a break or a few days off is important because when you come back you will be fresh and see all the little spots that you missed the first time around.  So you will probably want to sand it again.  I know I know enough with the sanding already.  At least that is how I feel sometimes.

Once your surface is up to your satisfaction the fun starts.  You should probably think of a paint scheme ahead of time.  This helps when applying tape and trim and letters.  So you should head down to your local sign shop and have some stencils cut out of the name and numbers you want use.  All the letters numbers and such have to be painted for the best results.  Be careful the sign shops vinyl is very sticky and can rip covering when pulling it off.  You can also cut your own stencils out of friskit paper or Gerber mask.  I prefer the Gerber because it is very low tack and pulls off with no complications.  I buy it buy the yard and take it to the stencil shop and they cut it how I like it for a very small cost.  You can also cut your own out of it with the trusty old no. 11.  Reese Supply here in Irving Texas carries it.  You can look them up and they will sell you what you want.  They are a supplier for sign shops.  I am sure there is a supplier in your area.  Check with them they might have this product or one similar to it.

Now clean off your table and get ready for a day of painting.  I will use the colors I used on my Bear as an example of a way to get a good light finish.  I picked a base coat that would cover well. Gun Metal gray.  It has metalic in it but there is no hardener or gloss so it is light.  1997 Corvette blue is the main color and 1997 VW Bug yellow is for the highlights.

Prior to painting wash your hands.  Now wipe the plane with a tack cloth.  This will remove any dust that is still laying around on the surface.  I have never used prepsol or material like that.  Wiping the plane with liquids like that scares me.  Between each coat  I wipe with tack cloth.

The paint is sprayed between 30 and 40 psi.  I have found lately that I can spay with as little as 20 psi.   I would recommend using the prescribed amount of pressure.  Also a touch up gun is the gun of choice.  Mine was about 40$ at Home Depot.  The clear is sprayed a 40 psi do not deviate from this setting.

You should also purchase a good painting mask they are about 20$.  You should never spary chemicals of any sort without one.  If you do not use a mask you will end up with an upset stomach, light headed, sick, and some harsh chemicals in your lungs that don’t go away.  Do not take this lightly no model is worth your health.  With a good mask all this is not a factor.

As I suspected the Gun Metal gray covered in one coat.  At this point you can opt to sand the color since you will not be using it as a color that will be seen.  I strongly advise against it.  If you look at your coat and decide it is not smooth enough sand off and paint it again.  When I get to this point I go with what I have.

You need to know that this paint (the paint that will be seen) cannot be color sanded before clear.  The sanding strokes will show and you will not be happy with the end result.

After you have enough gray down for a smooth base coat.  It is time to paint the main color of your paint scheme.  Now if you are planing on one color and just some highlight lines or numbers and letters only go ahead and paint the entire aircraft the color you have chosen.  In my case I was going to paint the entire tail section and the nose yellow.  I taped off the tail and the back half of the fuse and the nose so I would not be painting over an area that does not need the color.  This is back masking. (that is how they keep it really light) So now I have the entire aircraft except for the tail section and the nose 1997 Corvette blue.

Now after about 30 minutes I tape off the front half of the fuse and the nose paint the entire tail section and the nose 1997 VW Bug yellow.  I wait 10 minutes and remove the tape.  At this point I am smiling because I can see it all coming together.  I have been working about three hours since I started painting.

Since I already have yellow mixed up I lay down all of my stencils that will be painted yellow.  In this case it was all the letters and numbers on the wing were going to be yellow.  So I put down the stencils taped all around all the edges to keep over spray off.  Spray the color.  Wait 15 minutes.  Check and see that the yellow is covering the blue all the way.  This may take two or more coats.  This is the case with any light color going over a dark color.  It doesn’t matter what you are painting with this will be the case.  After I am satisfied with the coverage I pull the stencils 15 minutes after the last coat is applied.  Do not leave stencils on for longer than is needed they will end up stuck to the plane.  As soon as the paint flashes and appears dry to the eye it is time to pull the stencils.  This goes for pulling tape also.  Usually when the paint dries it will begin to try to pull the tape up so if you have to go for a second coat be sure to check in the tight corners where you have tape applied or in a curved line.  Just lightly press it back down and paint on as usual.  Red does this more so than the other colors.  If you know to look for this it is really no big deal.  If you should forget you might see some over spray in the tight corners where there were some real tight curves.  Just keep you eyes peeled.

Now I change to the Blue and paint all my stencils on the tail section.  This is a small area so total work time is very small.  It is blue going over yellow so it covers in one coat.  I am done in about 30 minutes.  My total time at this point is approaching 5 hours. 

Now comes the tough part of my paint scheme.  The Moon eyes from Dean Moon racing products.  There is no stencil available so I cut my own and do some pretty wild looking masking around the area in question.  I used white and black for this part. 

These two colors were painted with an airbrush.  The airbrush is not recommended for this paint.  Since we use such small areas it is okay to go for it.  The real reason they don’t want you to use it is even coverage.  I just gave it enough pressure to pull the paint out of the tip and it covered nice and smooth.  I put the white part down first.  It took three coats to cover the blue.  Then I put down the black part.  I took only one coat.  I finished with the black on purpose.

I moved to the nose of the plane.  I was going to put a set of twisted checkerboards on the nose, black over yellow.  I taped the checkers off and one coat later presto a perfect set checkers on the nose.  So it was nice having the black already mixed up in the airbrush.

Now I let the paint sit for about an hour.  I have a total of 6 hours into it so far.

I come back after a sandwich with freshly washed hands and wipe the plane off with the tack cloth twice over the whole airplane.  Once I feel it is clean enough I move onto the clear coat.  I uncover the canopy, I previously sanded it with 1200 grit to get it real smooth.  Yes spray the canopy it will come back very shinny.

Remember there is no sanding prior to clear.  You want to touch the plane as little as possible.  Especially when using metallic paints.  If there is any difference in the paint it will show through the clear.

So when it is clean shoot the first coat of clear.  I recommend going for a dry coat.  I have heard the terms dry coat and wet coat since I got into this Painting airplane stuff.  It was a while before I really knew what they were talking about.  Well on the touchup gun there will be a mechanism (big screw) that will adjust how much product is being sprayed with the given amount of air.  So the more you turn it one way the more air there is and the more you turn it the other way the more product comes out.  You really can’t see it in the air but you can when you apply it to something.  I suggest you test on something and get it how you like it before you go for the plane.  If this is your first attempt at spraying the dry coat will look rough like very fine sandpaper.  It will also dry faster.  So move the gun evenly and smoothly along the air frame staying the same distance away from it all times.   There will be over spray on the plane in some places.  This is hard to avoid with dry coats.   Now I let this dry for at least three hours.  I now have close to ten hours total time after the three hour dry time.  I give it this long so that I can knock off some the over spray before final coat.

Now comes the hardest part of this whole process.  So I recommend if it is late that you go to bed and do it tomorrow when you are completely rested.  If you feel fine after the three hour rest go for it.  It will only take about 20 minutes to put down the final coat.  If it is dry enough to knock off over spray then you can wipe it one more time with the tack cloth.

Now mix it up just like the can says set the pressure at 40 psi.  Do some testing on a board or something smooth.  You want this coat to be wet almost wet enough to run.  Take your time get it right on the smooth board or what ever you have decided to test on.  I usually finish a piece of wood along side of plane for this very step.  Now go for it.  Put down a smooth coat.  Spray the edges first then the flat areas next.  One thing that you will notice is that the wet coat will absorb over spray very nicely.  It will look like over spray then when you come back later it will be gone.  This is called “wetting out.”  If you are getting this result you are right on the wet/dry mixture.  If it won’t absorb most of it then you might be too dry.  Of course if it runs you are too wet or have too much clear on it.  Important; if it does run you cannot wipe the run away like you can with older paints where the clears sits on top of the color.  This clear actually attacks into and activates the color so if you wipe a run you will smear your paint underneath.  Just get away from it and clear elsewhere and sand it out later.  I got big runs on my cowl but I sanded them out later.  Once the coat is smooth and wet stand back a smile at what you have created.  The really cool thing as that once you put it down wet it dries looking wet.  What you see is what you get.

Total time is around eleven hours.  I have spent more time on some paint jobs and less on others.  The real time is spent masking the plane off.

The paint job is done.

At this point if you want you can blow off buffing it out if it is shinny enough.

If you do plan on buffing it out you will need to wait at least six to eight hours for the clear to fully cure.  I would recommend a full twenty-four hours before starting the quest for the ultimate shine.

Buffing urethanes is no secret.  Wet sand the surface down with 1200 grit paper.  Change your paper often for best results.  You can go as rough as 1000 but do not go any rougher then that.  If you do the clear is so hard it will lose shine.  It is called cutting the shine out.  The paint store guys will tell you the same thing.  After the whole plane is sanded evenly with 1200 come back and sand it out with 2000 wet. 

Now you are ready to buff.  Buy 3M Perfect It-II compound and polish until you get a good shine.  I used a machine on my last plane and had the whole thing polished in two hours.  The sanding of course took longer than that.  For the best results an orbital buffer that spins 1500-2500 will bring out that mirror shine like never before.  If you do it by hand it will take longer that is all.  Just keep rubbing until it shines.   If you do buff and sand it out I suggest doing it within one to two days of painting it.  If you wait to long the clear will be so hard it will not buff out.  The compound will not cut it.  If you clean it with Windex or any glass cleaner and the shine wipes off you have not buffed enough.  Just keep rubbing.

I hope this helps you more than it confuses you.  If have any questions just call or write anytime.

I always love to talk airplanes.

Stand back and smile.

Doug Moon