REFLECTOR: Striping tape; painting

Sat Nov 12 09:34:25 CST 2005

Hi Al,

I have found that clear coat will not work well over plastics.  Adhesion is usually good, but the clear does not wet out well on plastics.  PPG calls for using plastic primer under topcoat and only recommends using the clear over a topcoat.  If you want to use the scotchcal, I would suggest application after the paint is finished or paint all lines.  Painting all the lines gives a nice smooth finish.

I have been having better results with my conventional gun with a 1.8 fluid tip.  My HVLP has a 1.5.  I have found more reducer (see below) has resulted in a much smoother finish.  Due to EPA restrictions on VOC emissions, I think the mfg tends to recommend less reducer than the ideal (IMO).  One reason I like a base/clear system is the finishing options - 3M finishing film disks can make my mediocre painting look great.  After painting and drying (16 hrs)  I finish out the paint job in the following order:

3M finishing film disks (P1200 or P1500) in my DA to smooth any orange peel, dust nibs and runs.          

  a.. 3M Perfect It III extra cut rubbing compound with a wool bonnet.
  b.. 3M Perfect It II Rubbing Compound wit a wool bonnet.
  c.. 3M Swirl Mark Remover with a foam pad.
  d.. Apply 2 coats of your favorite wax.
  e.. This yields a very flat painted surface with a high enough gloss to show every little wave under             the paint, but a reflection deep enough to shave in.
I too am using DBC and a DCU clear.  I tend to like the DCU2002 better, it is the same as the DCU2021, but it is high solids.  Generally I like to go 1 step slower on the reducer (if temp calls for 870 then I use 885.)  I have also found much better results by increasing the reducer ratio.  Both DCU2002 and 2021 call for 4:1:1 (clear/reducer/hardener.)  I am currently using 4:2:1 and have found much better results (still have a small level of orange peel, similar to factory new car finishes, but that is taken care of with the finishing steps I have mentioned.)

I agree with a thin coat (60% to 70% coverage) for the topcoat followed by a heavier subsequent coat(s).  I definitely agree with the rep on the application of wet coats on the clear, there has to be enough material for the clear to flow out and flatten, and too thin a thin coat will not.  I try to regulate material flow to the size of the area I am painting and best atomization,  I then regulate the coat weight by using several passes and speed of gun movement.  Also use plenty of light.

Hope this helps.  If you decide to use the finishing film disks, let me know and I can offer a few tricks I have learned.

Joe 

  ----- Original Message ----- 
  From: Al Gietzen 
  To: 'Velocity Aircraft Owners and Builders list' 
  Sent: Thursday, November 10, 2005 6:22 PM
  Subject: REFLECTOR: Striping tape; painting

  Subject: Re: REFLECTOR: Striping tape

  Al,

    I have not used Scotchcal, I paint my stripes in before clear coating.  If you are looking for a tape to mask off painted trim/stripes, I would suggest 3M Fine Line Tape.  It has very good bond for masking painted lines, but also has good release from freshly coated under color.  3M 233 is also the best all around masking tape for automotive finish painting.

    Joe;

    Yes; I've been using the 3M Fine Line for masking around the edge of windows for primer, and now for topcoat, as well as for trim striping.  I'm planning on using ¼" Scotchcal as a border on a painted trim stripe. It will go on where I pull off a ¼" Fine Line between colors. I expect to then clearcoat over both, but I haven't yet verified adherence of the clearcoat to the Scotchcal.

    I've completed all the prep, ready to spray some real paint.  I'm transitioning from conventional sprayer to HVLP.  First tests of shooting topcoat and clearcoat are not satisfactory, and I'm still trying to figure out "why?".  The paint is not "flattening" out well, and going back over and adding more material results in orange peel or unevenness.  I'm going to have to sand my test panel and do again.  

    I'm using the DBC base and DCU2021 clear, and the DT870 reducer. What size fluid tip did you use?  The Guys at Finishmaster are guessing that a 1 mm tip is too small, which surprises me a bit since the viscosity of this stuff is like a lacquer; 12-15 seconds on the #2 Zahn cup.  Next available size up for my Apollo gun is 1.5 mm, and it's $50 for a tip and needle; almost as shocking as the price of the paint.

    The PPG expert is suggesting larger tip and higher pressure; the Apollo expert is suggesting lower pressure with the 1 mm tip.  Go figure.  I think I need to try increasing the material flow, and getting a thicker first pass.  I'm used to paints (like the epoxy primer) where you first get a thin tack coat, and then come back with more.  The PPG rep says for this stuff you want a full wet coat first pass.

    I'm interested in any helpful hints.

    Al (Waiting a couple of days for better weather)

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