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  #16 (permalink)  
Old 03-27-2012, 09:20 AM
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Hi dr.strangelove.
Sorry you are having trouble. Can I ask a few questions?
What kind of high build primer are you using?
Are you mixing it according to directions?
What temperature are you spraying at?
Is it spraying too dry?
What gun and tip do you have?
Are you waiting between coats?
It is not a good idea to add more reducer to get it to flow. This can lead to a too thick build and solvent popping.

Generally speaking, high build primer should sand easily and level quickly. Assuming your body work is ready for primer, and you are not trying to level deep dents that should have been already been hammered and dollied, or filled.
Epoxy is not meant to be used as a surfacer, so would be an expensive waste.
You should only need to block with 180 once using a guide coat to level.
Prime again with only a coat or two as needed to cover breakthroughs.
Sand with 320 and a guide coat to ensure the surface is flat.
You can spot prime if some areas need more leveling.
When you are satisfied that the body is where you want it, then what I do is tint the primer with the color the car will be and spray another coat over the whole car. This will leave a semi gloss surface that will show any flaws, high, low etc.
If it looks good, (which it should at this point), then just wet sand with 600 and DO NOT break through. if you break through, you need to apply primer in that area. When finished sanding you will have a smooth surface all one color ready for paint.
I do not use sealer nor do I recommend it, if you have a smooth unbroken surface, your top-coat will cover fine, and since its tinted it will cover quick.

I forgot to mention, you should clean the surface with wax and grease remover before each application of primer, and hopefully before you started the bodywork or applied anything! Follow the directions, don't just put it on and let it dry. Spray it on or use a clean white paper towel (bounty) to apply, then use another paper towel to wipe it off, then throw it away.
The idea being the contaminants float to the surface in the solvent then are wiped off with the paper towel. One sheet for each small section. I will go through a whole roll on a big car. Much cheaper to spend a dollar on a roll of paper towels, than to re-prime and sand!

Sorry for the long winded reply

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  #17 (permalink)  
Old 03-27-2012, 10:51 AM
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Thank you for the writeup, I'll try to answer your questions the best I can...

What kind of high build primer are you using?
ProForm 2K Urethane Primer Surfacer PF 656C

Are you mixing it according to directions?
The first application I used it as high build, the second time I added reducer as per the manufacturers instructions to use as a sealer

What temperature are you spraying at?
-When I sprayed it was about 20 C / 68 F

Is it spraying too dry?
-Yes, even when I used reducer with it.

What gun and tip do you have?
-1.7mm

Are you waiting between coats?
-It went on so thick I only laid one coat.

It is not a good idea to add more reducer to get it to flow. This can lead to a too thick build and solvent popping.
-I'm not sure that I added too much. the first time I sprayed I didn't add any and the surface was not smooth after spraying. Also, it takes a lot to sand down to a surface that is flat (not pitted).
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Old 03-27-2012, 11:00 AM
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I also wanted to add that there are a few spots that are down to bare metal now. I most likely did not fix some dents sufficiently before applying coatings. I was planning on respraying epoxy to seal in the primer, any spots that may require more putty, and protect any bare metal.

One more thing...

I've sanded most of the car with a block and sandpaper, but there are a lot of curves that make this very difficult and I was going through a ton of sandpaper without taking of much material. I switched to a smaller block with some red scotch brite and I went MUCH better. After using the scuff pads I went back to the large block and continued to level the panels with finer sandpaper--much easier than before. Has anyone else done this or is it bad practice?
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Old 03-27-2012, 01:14 PM
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Well, sounds like what you are doing is fine, I don't know why it should spray so thick or dry. Are you setting air pressure at the gun?

Mix 4:1:1 - medium build
Normal shop temp is 77 degrees
Siphon Feed 1.6-2.0mm 40-50 psi
Gravity Feed 1.6-1.8mm 35-45 psi
HVLP 1.6-1.8mm 10 psi

For curved areas you need a curved or rubber block. Basically anything to wrap the paper around.
I don't quite understand how the scotchbrite pads are helping?

Keep at it, you are learning a lot as you go!



Quote:
Originally Posted by dr.strangelove
Thank you for the writeup, I'll try to answer your questions the best I can...

What kind of high build primer are you using?
ProForm 2K Urethane Primer Surfacer PF 656C

Are you mixing it according to directions?
The first application I used it as high build, the second time I added reducer as per the manufacturers instructions to use as a sealer

What temperature are you spraying at?
-When I sprayed it was about 20 C / 68 F

Is it spraying too dry?
-Yes, even when I used reducer with it.

What gun and tip do you have?
-1.7mm

Are you waiting between coats?
-It went on so thick I only laid one coat.

It is not a good idea to add more reducer to get it to flow. This can lead to a too thick build and solvent popping.
-I'm not sure that I added too much. the first time I sprayed I didn't add any and the surface was not smooth after spraying. Also, it takes a lot to sand down to a surface that is flat (not pitted).
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  #20 (permalink)  
Old 03-27-2012, 03:32 PM
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the scotchbrite doesn't seem to clog nealy as much as the sandpaper and I wasn't sure if I should wetsand. As I mentioned there are a few spots of bare metal and I don't know if the primer will like getting wet. I read the data sheet for the primer I listed above (high-build), but it doesn't say anything about wetsanding. I've made every mistake in the book, except for that one so far ...and then again I could be making a mistake by not wetsanding too!

My next purchase is going to be a set of flexible durablocks. I find with the longboard it's easy to apply too much pressure to the centre of curves. In the case of my good, which has a slight radius, everytime I go over the centre it is pushed down slightly.
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  #21 (permalink)  
Old 03-28-2012, 01:55 PM
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I generally wet sand with anything finer than 180 paper. Otherwise it clogs too much. You should have no trouble water sanding that primer.
Sanding is a pain, but has to be done. Its the only way to get a flat smooth surface. Let the paper do the work, using a quality paper helps too.
Just a note, you can use a direct to metal surfacer which will save an epoxy step over bare metal.


Quote:
Originally Posted by dr.strangelove
the scotchbrite doesn't seem to clog nealy as much as the sandpaper and I wasn't sure if I should wetsand. As I mentioned there are a few spots of bare metal and I don't know if the primer will like getting wet. I read the data sheet for the primer I listed above (high-build), but it doesn't say anything about wetsanding. I've made every mistake in the book, except for that one so far ...and then again I could be making a mistake by not wetsanding too!

My next purchase is going to be a set of flexible durablocks. I find with the longboard it's easy to apply too much pressure to the centre of curves. In the case of my good, which has a slight radius, everytime I go over the centre it is pushed down slightly.
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  #22 (permalink)  
Old 03-28-2012, 02:40 PM
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Generally you don't wet sand with anything coarser than 400 grit
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  #23 (permalink)  
Old 03-29-2012, 05:55 AM
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Yes, that's true.
I seem to have fallen into a routine of 180 dry, 320 wet or dry, 600 wet. Just what seems to work for me.

Thanks

Quote:
Originally Posted by mitmaks
Generally you don't wet sand with anything coarser than 400 grit
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Old 03-29-2012, 01:00 PM
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I was thinking about one of the earlier comments regarding line size and decided to look at what I was using at the time. I have 1/2 to the main regulator and to the water/oil separator, then some type of connector that has a 1/2 NPT to a 3/8" air hose, to the regulator at the gun that is 1/4". I measured the ID of the male 3/8 and 1/4 connectors and they were basically the same (i.e. ~.191").

What gives?

What size/type fittings are you guys using?

Sorry for all the dumb questions and thanks for the help.

Mike
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Old 03-29-2012, 01:11 PM
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I should have looked around a bit more. This topic has been discussed here already:

air couplers / fittings - whats it all mean?
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Old 05-04-2012, 12:46 PM
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Just wanted to post some updates.

These pics are somewhat new; however, there have been recent developments. I've gotten through the pinholes and sanded out the cracks. Now I'm trying to flatten out the panels and make sure everything matches up. My friend right now is Metal Glaze by evercoat (i think). It's really smooth but I find it dries too quickly for spreading out on large surfaces.

What's the deal with re-applying additional coats of glaze? sand first or just re-apply within a certain window?
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  #27 (permalink)  
Old 05-04-2012, 02:51 PM
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Quote:
Originally Posted by hemiguy
Yes, that's true.
I seem to have fallen into a routine of 180 dry, 320 wet or dry, 600 wet. Just what seems to work for me.

Thanks
It's too much gap there between 320 and 600. What works best for me is 320 dry and then (after couple more coats of primer) 400-600.
Of course you would 320 wet and give it a coat or two more and then finish off with 600.
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Old 08-03-2012, 02:12 PM
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Dr.Strangelove's Running Nightmare - Body Lines and Wheel Arches

Happy Friday Ladies and Gents,

With the impending clear skies this weekend, I INTEND to paint my car.

I must be doing something wrong, because I am constantly sanding through my primer and find myself repeating this process to the detrement of my bank account. As such, I'm going to put in another 10 hours of sanding to leave the car in 220 scratches, before spraying a couple of coats of epoxy on everything and topcoating.

There have been a number of factors that have contributed to the delays over the course of this project, but the one I am facing now is dull body lines, especially those that appear around the fender arches.

Does anyone have any advice for a poor SOB who wants to give one last shot at cutting some nice lines into this car before I completely botch it?

I've attached two photos, one of a car with proper lines (notice the definition between the fender/quarter panel flat and wheel arch (you know those warning/waxing moon crescent shapes), and the second two of my car with its rough, poorly defined, body.
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  #29 (permalink)  
Old 08-03-2012, 02:37 PM
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your bodywork looks good, however I'd recommend putting 2-3 coats of high build 2k primer over it and wet sanding whole thing with 400 and then seal it and paint it.
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Old 08-03-2012, 11:42 PM
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I was in the same hole but all that sanding and re-sanding just means that your panels are not blocked. It will all pay off in the end. What I was runing across this I would start with 220 finish with 400 before adding another coat if the bottom coat was showing again. after a few times I shot a heavy coat of G5 feather fill that fills more than Urethane primer. that made it the final coat of primer I had to block. I then applied a coat of Urethane and wetsanded to use as the sealer.
My first car Im very very happy with how straight my panels came out
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