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Clearcoat - Yes or No
- Thread starter Webb
- Start date
I wouldn't
I bought an RV-6A that had been painted with clear coat. It sat outdoors in the sun for about 5 years, and the clear coat is ruined on all the top surfaces. Ever see a 10 year old car that has been out in the sun the entire time?
PS: Is there any way to remove JUST the clear coat and leave the color coat?
I bought an RV-6A that had been painted with clear coat. It sat outdoors in the sun for about 5 years, and the clear coat is ruined on all the top surfaces. Ever see a 10 year old car that has been out in the sun the entire time?PS: Is there any way to remove JUST the clear coat and leave the color coat?
Norman CYYJ
Well Known Member
You m to remove the clear coat but the paint colour will look terrible. The base coats are dull and will show as a different shade.
There is no value in the color coat. It is so thin that you can't rub it out to make it look like anything. SAND IT ALL DOWN and re paint.
You might try to spray clear coat after you sand off all of the bad clear coat. Expect the base (color) coat to have the gloss of an old sidewalk without the clear coat.
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Nothing is going to look real good after years in the sun, single stage or two-stage. Assuming quality paint applied per the tech sheet, I doubt there is much difference. Cheap clear over a different brand of base may be another story.
Solid colors look good in single stage. Metallics and pearls are better in base/clear. Either way there is no difference in gloss. The difference is depth and refraction.
Base/clear costs more and adds (for me) at least an additional hour to every paint session. However, the scheme and color choices on this project would look awful in single stage, so.....it just depends on what you want.
Solid colors look good in single stage. Metallics and pearls are better in base/clear. Either way there is no difference in gloss. The difference is depth and refraction.
Base/clear costs more and adds (for me) at least an additional hour to every paint session. However, the scheme and color choices on this project would look awful in single stage, so.....it just depends on what you want.
f1rocket
Well Known Member
I've had both a single stage Poly and a base coat/clear coat. I would go base/clear any day. I actually think touch ups are easier. Sand, spray, clear, buff and you can't see it. Ever try that with a polyurethane? I have and it takes some skill that I don't have.
BTW, I didn't think our airplanes ever sat outside for long periods of time!
BTW, I didn't think our airplanes ever sat outside for long periods of time!
I realized that I haven't been clear with my question. What I'd like to do is to remove the clear coat in the damaged areas, then spray a new clear coat over the old base color coat. Every time I try to sand off the clear only, I go through the color coat as well. I was hoping for a chemical that would remove only the clear, but I guess no such thing exists.
And the plane sat outdoors, unflown, for the 5 years just before I bought it. Hangared now!
Thanks for the input.
Doug
Well Known Member
Randy,
Is the base/clear acrylic rather than poly.?
As far as I understand acrylic can be retouched and blended in either single or two stage systems, whereas polyeurethane is much more difficult and as you say beyond my skill level as well.
I am considering acrylic for this reason as well as cost, still debating clear over base tho...
Doug Gray
f1rocket
Well Known Member
Yes. The Polyurethane was DuPont Imron single stage. The Base coat/Clear coat was acrylic. (I forgot the manufacturer!)
Paint weight/Clearcoat repairs (long-sorry)
Paint weight
According to the PPG website, dry film paint weight generally ranges from .006 - .008 lbs. per sq. ft. per 1 mil of thickness From drawings, I estimated that there is about 450 sq. ft. of surface area to cover on an RV-7 I welcome more accurate input from builders closer to completion than I am.
PPG recommends basecoats be sprayed very thin - the criteria is just hiding. Their data shows recommended basecoat dry film thickness of 0.8 mil! (Deltron 2000 DBC)
Primer coats can be tinted to minimize the basecoat coverage amount.
450 x .008 x 0.8 = 2.88Lbs. That really isn't adding a lot of weight in return for appearance and durability.
Polyurethane clears are remarkably tough and durable. The disadvantage is that they require skill to apply, they need to be applied within hours of shooting the basecoat, and if you want that custom deep gloss finish, you will have to color sand within 24 - 48 hours of painting, then compound. You also should practice a lot before you paint your plane. A basecoat clearcoat job for an RV-7 is going to cost $1500 - 2000 for quality materials (depends on color - red will really cost you) PPG specifically cautions against sanding after 72 hours. Does that perhaps suggest how tough the stuff is? Think how miserable you'd be if you didn't practice, screwed up your paint job and wasted that amount of money + having to remove it and start over.
Paint repairs
I have a 73 Cherokee 180 that was painted with basecoat clearcoat in 1989. When I purchased the aircraft in 1998 I could see that the clearcoat on the portions most exposed to UV, the upper wing skins and the fuselage from the trim stripes up over the top, was on its last legs. Because I am somewhat frugal (some might call me cheap!) I endeavored to repair the paint job by sanding and reshooting the Durethane clearcoat (PPG DU 1000). There were also areas that I had to spot repair, for which I used an airbrush). No commercial aircraft painters would talk to me about recoating the upper wing surfaces and top half of the fuselage, so I was forced to figure it out for myself. As you know, the Cherokees are built with dome-head style rivets. To scuff up the rivet heads and transition paint filet I had to use sanding paste and a tooth brush.
To finally shorten a long story, if you consider a 5 - 10' paint job a successful outcome, then I had a successful outcome. Using a LOT of elbow grease, I saved the paint job of my Cherokee for $750 worth of materials. My spray booth was the apron in front of my private hangar very early in the morning in still air. To this day I continue to get unsolicited remarks from other pilots about how nice the paint is. I thank them and don't point out all the spot repairs. White is a very forgiving color from 5+ feet away! The gloss is NOT in the basecoat, the gloss is in the properly applied clear. In fact freshly sprayed basecoat will be absolutely flat.
Paint weight
According to the PPG website, dry film paint weight generally ranges from .006 - .008 lbs. per sq. ft. per 1 mil of thickness From drawings, I estimated that there is about 450 sq. ft. of surface area to cover on an RV-7 I welcome more accurate input from builders closer to completion than I am.
PPG recommends basecoats be sprayed very thin - the criteria is just hiding. Their data shows recommended basecoat dry film thickness of 0.8 mil! (Deltron 2000 DBC)
Primer coats can be tinted to minimize the basecoat coverage amount.
450 x .008 x 0.8 = 2.88Lbs. That really isn't adding a lot of weight in return for appearance and durability.
Polyurethane clears are remarkably tough and durable. The disadvantage is that they require skill to apply, they need to be applied within hours of shooting the basecoat, and if you want that custom deep gloss finish, you will have to color sand within 24 - 48 hours of painting, then compound. You also should practice a lot before you paint your plane. A basecoat clearcoat job for an RV-7 is going to cost $1500 - 2000 for quality materials (depends on color - red will really cost you) PPG specifically cautions against sanding after 72 hours. Does that perhaps suggest how tough the stuff is? Think how miserable you'd be if you didn't practice, screwed up your paint job and wasted that amount of money + having to remove it and start over.
Paint repairs
I have a 73 Cherokee 180 that was painted with basecoat clearcoat in 1989. When I purchased the aircraft in 1998 I could see that the clearcoat on the portions most exposed to UV, the upper wing skins and the fuselage from the trim stripes up over the top, was on its last legs. Because I am somewhat frugal (some might call me cheap!) I endeavored to repair the paint job by sanding and reshooting the Durethane clearcoat (PPG DU 1000). There were also areas that I had to spot repair, for which I used an airbrush). No commercial aircraft painters would talk to me about recoating the upper wing surfaces and top half of the fuselage, so I was forced to figure it out for myself. As you know, the Cherokees are built with dome-head style rivets. To scuff up the rivet heads and transition paint filet I had to use sanding paste and a tooth brush.
To finally shorten a long story, if you consider a 5 - 10' paint job a successful outcome, then I had a successful outcome. Using a LOT of elbow grease, I saved the paint job of my Cherokee for $750 worth of materials. My spray booth was the apron in front of my private hangar very early in the morning in still air. To this day I continue to get unsolicited remarks from other pilots about how nice the paint is. I thank them and don't point out all the spot repairs. White is a very forgiving color from 5+ feet away! The gloss is NOT in the basecoat, the gloss is in the properly applied clear. In fact freshly sprayed basecoat will be absolutely flat.
Good post Larry.
<<450 x .008 x 0.8 = 2.88Lbs.>>
Of course that would be the weight of the DBC base only. I use a handheld electronic paint meter when I'm out buying cars in the wholesale market. 3.5 to 5 mils is the range for most OEM base/clear finishes. My old meter only measures film thickness on a steel panel, so I can't measure the finished thickness of my own work sprayed on aluminum. Assume 6 mils (I'm spraying a little extra clear so I have some to cut and buff), and the total is 450 x .008 x 6 = 21.6 lbs for a deep base/clear finish. Assume 3 mils for a thin single stage and the difference would be about 10 lbs. Those numbers sound realistic?
<<450 x .008 x 0.8 = 2.88Lbs.>>
Of course that would be the weight of the DBC base only. I use a handheld electronic paint meter when I'm out buying cars in the wholesale market. 3.5 to 5 mils is the range for most OEM base/clear finishes. My old meter only measures film thickness on a steel panel, so I can't measure the finished thickness of my own work sprayed on aluminum. Assume 6 mils (I'm spraying a little extra clear so I have some to cut and buff), and the total is 450 x .008 x 6 = 21.6 lbs for a deep base/clear finish. Assume 3 mils for a thin single stage and the difference would be about 10 lbs. Those numbers sound realistic?
Total paint thickness
PPG recommends clear coat dry film thickeness of 2 - 2.5 mils. Beneath the basecoat are typically primer/primer-surfacer/primer sealer. A new OEM basecoat clear coat finish is typically 5 mils - 6 mils, with the thicker jobs being the tri-coat pearls like Cadillac and Lexus. Single stage polyurethanes have dry film thickness in the same 2 -2.5 mil range.
SO, the point I was trying to make was that the difference in weight between a single stage polyurethane and a two-stage basecoat/clearcoat is about 3 lbs. on an RV-7.
The durability of a clear coat job is about 2x single stage job. It is grueling work to paint a plane and even more grueling to repaint one. If you could pick a paint system so you never had to do it again, why wouldn't you? For me, that is worth giving away three pounds. It is difficult for me to imagine that someone would go to all the effort to build an RV and NOT hangar it. My Cherokee is hangared and the refurbished clear coat still looks as good (at 5-10 ft. as earlier stated) as the day I rubbed it out 9 years ago. I expect the basecoat/clearcoat job on my RV-7 to last a long, long time. Tieing down outside is a pay-me-now or pay-me-later proposition.
PPG recommends clear coat dry film thickeness of 2 - 2.5 mils. Beneath the basecoat are typically primer/primer-surfacer/primer sealer. A new OEM basecoat clear coat finish is typically 5 mils - 6 mils, with the thicker jobs being the tri-coat pearls like Cadillac and Lexus. Single stage polyurethanes have dry film thickness in the same 2 -2.5 mil range.
SO, the point I was trying to make was that the difference in weight between a single stage polyurethane and a two-stage basecoat/clearcoat is about 3 lbs. on an RV-7.
The durability of a clear coat job is about 2x single stage job. It is grueling work to paint a plane and even more grueling to repaint one. If you could pick a paint system so you never had to do it again, why wouldn't you? For me, that is worth giving away three pounds. It is difficult for me to imagine that someone would go to all the effort to build an RV and NOT hangar it. My Cherokee is hangared and the refurbished clear coat still looks as good (at 5-10 ft. as earlier stated) as the day I rubbed it out 9 years ago. I expect the basecoat/clearcoat job on my RV-7 to last a long, long time. Tieing down outside is a pay-me-now or pay-me-later proposition.
Left out of previous reply
OEM automotive paint is a thermoset process that is baked at 350F. Body shops typically bake at 150F to kick off paint, the primary objective being increased production. The paint chemistry for OEM and auto refinish markets (which is what RV painters are) are NOT the same.
OEM automotive paint is a thermoset process that is baked at 350F. Body shops typically bake at 150F to kick off paint, the primary objective being increased production. The paint chemistry for OEM and auto refinish markets (which is what RV painters are) are NOT the same.
RV7Guy
Well Known Member
Clear
I used PPG base/clear on my plane for the finish. My friend, body shop owner and custom painter said that done properly a base/clear will be lighter than a single stage.
He explained the single stage is very heavily pigmented to provide the finish, the paint itself is heavier than an equal quantity of base/clear and finally, there is usually no post painting work. He said the heaviest single stage is red followed by any metallic.
The base coat is extremely light in weight and is applied very thin. The clear is lighter for an equal quantity of single stage and the clear is usually color sanded and buffed which removes material, i.e. weight.
Bottom line, everyone believes that single stage is lighter, when in fact, that may not necessarily be accurate. Prep, type and brand of paint and technique!!!!
I used PPG base/clear on my plane for the finish. My friend, body shop owner and custom painter said that done properly a base/clear will be lighter than a single stage.
He explained the single stage is very heavily pigmented to provide the finish, the paint itself is heavier than an equal quantity of base/clear and finally, there is usually no post painting work. He said the heaviest single stage is red followed by any metallic.
The base coat is extremely light in weight and is applied very thin. The clear is lighter for an equal quantity of single stage and the clear is usually color sanded and buffed which removes material, i.e. weight.
Bottom line, everyone believes that single stage is lighter, when in fact, that may not necessarily be accurate. Prep, type and brand of paint and technique!!!!
I realized that I haven't been clear with my question. What I'd like to do is to remove the clear coat in the damaged areas, then spray a new clear coat over the old base color coat. Every time I try to sand off the clear only, I go through the color coat as well. I was hoping for a chemical that would remove only the clear, but I guess no such thing exists.
And the plane sat outdoors, unflown, for the 5 years just before I bought it. Hangared now!
Thanks for the input.
If there is as much damage to the clear coat as you say, there is probably significant damage to the base coat also. I doubt that you would be able to strip the clear coat and respray with good results.
Is the clear coat just milky or is it lifting an peeling off? A better description of the damage, or better, photos may help.
Good luck,
Karl
Now in Sandpoint, ID.
