Question for painters-priming?

[dannyual767]

Guys, I'm a newb to painting and I've got some priming questions. Here are some details to start:

I'm using PPG Omni paints including MP282 high build, 2K urethane primer and, on Tuesday, I shot it on 4 boats that I'm currently working on.

a.) Aeromarine Avenger-a rebuild with some polyester resin/cloth repair work

b.) Dumas SK Daddle original build

c.) Dumas Lil Rascal original build

d.) Dumas DV20 rebuild with a very rough hull

I didn't know how much primer to apply so I shot a ton of it with my HVLP detail gun . When I started sanding on Wednesday, I couldn't believe how much primer was on the SK and DV20! I know the Avenger and Lil Rascal have less.

Anyway, I dry sanded and sanded with a used piece of 220 grit wet or dry paper. I then used 400 grit and got it smooth as glass. Lots of primer came off and I got the SK and DV20 nice and smooth and evenly blocked but there are some areas where I sanded back down to the epoxy sealed wood. 95% of the hull is still covered in grey primer. I'm planning on shooting one more thin coat of primer to recover everything h34r: .

How much primer should I be sanding off? Weight is always an issue! As far as my final coat of primer goes, what if I sand through some areas again? Will I have to reshoot a third time to make sure everything is covered in primer before I spray color?

Thanks for any suggestions and info!

Danny

 

[Marty Davis]

Guys, I'm a newb to painting and I've got some priming questions. Here are some details to start:
I'm using PPG Omni paints including MP282 high build, 2K urethane primer and, on Tuesday, I shot it on 4 boats that I'm currently working on.

a.) Aeromarine Avenger-a rebuild with some polyester resin/cloth repair work

b.) Dumas SK Daddle original build

c.) Dumas Lil Rascal original build

d.) Dumas DV20 rebuild with a very rough hull

I didn't know how much primer to apply so I shot a ton of it with my HVLP detail gun . When I started sanding on Wednesday, I couldn't believe how much primer was on the SK and DV20! I know the Avenger and Lil Rascal have less.

Anyway, I dry sanded and sanded with a used piece of 220 grit wet or dry paper. I then used 400 grit and got it smooth as glass. Lots of primer came off and I got the SK and DV20 nice and smooth and evenly blocked but there are some areas where I sanded back down to the epoxy sealed wood. 95% of the hull is still covered in grey primer. I'm planning on shooting one more thin coat of primer to recover everything h34r: .

How much primer should I be sanding off? Weight is always an issue! As far as my final coat of primer goes, what if I sand through some areas again? Will I have to reshoot a third time to make sure everything is covered in primer before I spray color?

Thanks for any suggestions and info!

Danny

Danny:

Sand off as much as possible to get the weight of the primer off.

One additional thing, DON'T make it too smooth. If it is too smooth without enough sandpaper grooves, the paint won't stick and will peel off. You need something for the paint to stick to. 320 is fine enough that the paint will fill the sand marks.

Marty Davis

 

[Topfuel666]

Guys, I'm a newb to painting and I've got some priming questions. Here are some details to start:
I'm using PPG Omni paints including MP282 high build, 2K urethane primer and, on Tuesday, I shot it on 4 boats that I'm currently working on.

a.) Aeromarine Avenger-a rebuild with some polyester resin/cloth repair work

b.) Dumas SK Daddle original build

c.) Dumas Lil Rascal original build

d.) Dumas DV20 rebuild with a very rough hull

I didn't know how much primer to apply so I shot a ton of it with my HVLP detail gun . When I started sanding on Wednesday, I couldn't believe how much primer was on the SK and DV20! I know the Avenger and Lil Rascal have less.

Anyway, I dry sanded and sanded with a used piece of 220 grit wet or dry paper. I then used 400 grit and got it smooth as glass. Lots of primer came off and I got the SK and DV20 nice and smooth and evenly blocked but there are some areas where I sanded back down to the epoxy sealed wood. 95% of the hull is still covered in grey primer. I'm planning on shooting one more thin coat of primer to recover everything h34r: .

How much primer should I be sanding off? Weight is always an issue! As far as my final coat of primer goes, what if I sand through some areas again? Will I have to reshoot a third time to make sure everything is covered in primer before I spray color?

Thanks for any suggestions and info!

Danny

Danny,

I usually shoot three medium coats of high build primers using a 15 or 17 tip on HVLP, then I block wet sand with 320 or 400 until there are no high or low spots. I only add additional coats if I need to build up. I use House Of Kolor epoxy primers. I believe most paint facts sheets indicate you should have no bare substrate before applying paint. The PPG single stage Omni's work fine but check to make sure a sealer is not required before the basecoat. HOK requires it.

Bill

 

[dannyual767]

One additional thing, DON'T make it too smooth. If it is too smooth without enough sandpaper grooves, the paint won't stick and will peel off. You need something for the paint to stick to. 320 is fine enough that the paint will fill the sand marks.

Marty, I called my PPG dealer 2 days ago and he said to use a fine grit.....as fine as 600 grit just before laying down color ! Seemed too fine to me but that is what he said.
posted by Bill,

I usually shoot three medium coats of high build primers using a 15 or 17 tip on HVLP, then I block wet sand with 320 or 400 until there are no high or low spots. I only add additional coats if I need to build up.

As I'm block sanding, I'm getting the high spots down which are usually the edges of the panels. Using a hard rubber sanding block makes matters worse so I've tried some substitute blocks such as styrofoam (sp?) which conforms to the curves of the boat's sides. Works great!

I believe most paint facts sheets indicate you should have no bare substrate before applying paint. The PPG single stage Omni's work fine but check to make sure a sealer is not required before the basecoat. HOK requires it.

Yeah, this is what I was thinking as well. No substrate showing. I'll call PPG again today and see if I need the sealer.

 

[Don Ferrette]

One of these days I'm gonna archive my paint question replies.

Ok you want to use your high build primer/surfacer as an imperfection filler, pinholes, scratches, etc. I use PPG DZ-3 & typically shoot 2 or 3 times sanding off about 90% each time until I'm satisfied with the surface quality. I like the DZ-3 because it dries super fast & sands off like baby powder. One real good trick when you're done (or think you're done) is to spray the hull with water until it's completely wet on surfaces to be painted. Water is a great magnifying glass to show small imperfections that may not be readily visible but will show in the paint. Because it is in fact heavy you want to wind up sanding as much of the primer/surfacer off as possible until you have the surfaces where you want them then shoot a regular primer intended for whatever paint you choose. You want the hull to look like it's ready for a coat of paint even before the primer goes on. Regular primer is just that, something that gives your top coat something to bite into, not for fixing blemishes. In my instance I shoot PPG DP48LF epoxy primer. Absolutely tough as nails & my top choice for the base for my paints. I use the PPG Concept acrylic urethanes which requires no clearcoat (i.e. it is not a basecoat/clearcoat system). As far as sanding what the PPG guy told you is correct, current paints designed for HVLP typically go on thinner & will show sanding scratches easier so the 400 grit done wet is good advise. One thing I will tell is get the spec papers (the sxxt sheets as we call them) for all paints & primers you are using & follow them to the letter as far as mixing, drying times & compatability. And get yourself a real good prep solvent like PPG 303 Acryli-clean & wipe down thoroughly before each level of painting to remove fingerprint oils & other potential surface contaminants. Let dry completely, about 10-15 minutes, before you start spraying. You do not need to do this between color coats unless you do any sanding, then clean it.

Oh yeah while I'm thinking about it ........

Sometimes doing a subject search here on I/W will yield the answers you seek. I can't think of how many times I've posted on painting .

 

[Topfuel666]

Just a tip on sanding. I use rubber body filler squeegees (sp?) as they have some body but are easier when following contours. I wrap the wet/dry paper strip around it and soak it (about 30 minutes) in a bucket of water with a few drops of Dawn (wetting agent) in it. As the paper wears, you just tear off one side and you're back in business. Some folks may disagree on this but this works for me.

Bill

 

[Don Ferrette]

Just a tip on sanding. I use rubber body filler squeegees (sp?) as they have some body but are easier when following contours. I wrap the wet/dry paper strip around it and soak it (about 30 minutes) in a bucket of water with a few drops of Dawn (wetting agent) in it. As the paper wears, you just tear off one side and you're back in business. Some folks may disagree on this but this works for me.
Bill

30 minutes??? :blink:

A bucket of water is all I ever use. Dip the paper in until it's wet, sand, rinse paper & repeat. No soaps, no additives.

As for sanding blocks the only time I will use anything other than my hands is blocking up & truing running surfaces. Beyond that it's always by hand as you simply cannot match the "hands on" feel for the surface you're sanding on. I also try to steer beginners away from using sanding blocks for two reasons- first, sanding by hand helps one quickly develop a good touch or feel for what you're doing & second is exactly the opposite. Using sanding blocks does not allow for the "feel" & all too often a beginner's "heavy hands" will blow right through primers & paints as they sand with blocks so quickly they don't even realize it until it's too late especially on curves and/or uneven surfaces.

Everyone has there own ways but I got mine from one of the best painters I have ever seen. He told me the two most important tools for paint prep work needed is something everyone has ..... he then held up his two hands & smiled. B)

 

[Josh Stollfuss]

Soaps helps keep the sand paper from clogging up when sanding primers. It works!

Josh-

 

[Topfuel666]

Just a tip on sanding. I use rubber body filler squeegees (sp?) as they have some body but are easier when following contours. I wrap the wet/dry paper strip around it and soak it (about 30 minutes) in a bucket of water with a few drops of Dawn (wetting agent) in it. As the paper wears, you just tear off one side and you're back in business. Some folks may disagree on this but this works for me.
Bill

30 minutes??? :blink:

A bucket of water is all I ever use. Dip the paper in until it's wet, sand, rinse paper & repeat. No soaps, no additives.

As for sanding blocks the only time I will use anything other than my hands is blocking up & truing running surfaces. Beyond that it's always by hand as you simply cannot match the "hands on" feel for the surface you're sanding on. I also try to steer beginners away from using sanding blocks for two reasons- first, sanding by hand helps one quickly develop a good touch or feel for what you're doing & second is exactly the opposite. Using sanding blocks does not allow for the "feel" & all too often a beginner's "heavy hands" will blow right through primers & paints as they sand with blocks so quickly they don't even realize it until it's too late especially on curves and/or uneven surfaces.

Everyone has there own ways but I got mine from one of the best painters I have ever seen. He told me the two most important tools for paint prep work needed is something everyone has ..... he then held up his two hands & smiled. B)

Don,

Sorry, not trying to make this complex or misleading. You are definitely correct on the feel. I blew through the clear coat a few times and it is really frustrating when I saw the candy apple layer bleed on the paper. "heavy hands" is a good way to put it.

I think I got the tip of adding a drop or two of Dawn was from the House Of Color spec sheets. I really only soak the paper when I am wet sanding the clear coat to make the paper is butter soft.

Bill

 

[Don Ferrette]

Hey Bill it's all good, if we all didn't share we all wouldn't learn.

 

[Topfuel666]

Don,

Thanks!! The learning process is ongoing on everything. Isn't it amazing how some TV shows (mostly the bike builds) make painting look easy. They don't show you the sags, runs, etc.. They still manage to paint a bike and cure it in 15 minutes - amazing LOL.

This is a great site for sharing info AND learning.....

Bill

 

[Joe_Knesek]

My uncle has always painted my boats but he just gave me a nice HVLP gun. I think he's tired of painting them but at least I have access to his paint booth! I'm wondering if I have to prime a gell coated hull or can I just scotch brite it and shoot the color. I do not want to paint the running surface.

 

[Don Ferrette]

My uncle has always painted my boats but he just gave me a nice HVLP gun. I think he's tired of painting them but at least I have access to his paint booth! I'm wondering if I have to prime a gell coated hull or can I just scotch brite it and shoot the color. I do not want to paint the running surface.

I have had success with just shooting over wet sanded white gelcoat but laying down a coat of primer is optimum choice. On the just paint over gelcoat started with 320 wet then 400 wet and a very thorough cleaning. As typical with me that was using PPG Concept acrylic urethane (non basecoat).

 

[Joe_Knesek]

My uncle has always painted my boats but he just gave me a nice HVLP gun. I think he's tired of painting them but at least I have access to his paint booth! I'm wondering if I have to prime a gell coated hull or can I just scotch brite it and shoot the color. I do not want to paint the running surface.

I have had success with just shooting over wet sanded white gelcoat but laying down a coat of primer is optimum choice. On the just paint over gelcoat started with 320 wet then 400 wet and a very thorough cleaning. As typical with me that was using PPG Concept acrylic urethane (non basecoat).

Thanks Don. I've been using the single stage PPG Concept acrylic urethane since that's what my Uncle's shop uses. His mixing system is all computerized so you just plug in the paint code and quantity and it mixes it for you. It's nice being able to mix only what I need and not having to commit to a quart at a time. The clear stinks to high heaven! I painted the inside of my 60 mono to seal the glass and I can't hardly stand to work on it because of the smell. :blink:

Here's a shot of my daughter's Sport 20.

 

[Wesleys Custom RC]

I would like to know how you guys are wet sanding into the wood grain. I have had serious problems with this in the past. The grain swells from the water and there is an over all swelling and adhesion problem unless you let the wood dry for a fiew days. I sanded thru the filler primer once on a guitar once and had issues with the grain. After several primer coats I did my artsy fartsy crap and cleared it. 2 weeks later the wood cracked or "checked". The wood was birch, same as a boat hull. From then on I always dry sand unless I know I'm not going to go through the primer. Maby Don's single stage lets the wood ex hale this moisture, I don't know.

 

[Don Ferrette]

I would like to know how you guys are wet sanding into the wood grain. I have had serious problems with this in the past. The grain swells from the water and there is an over all swelling and adhesion problem unless you let the wood dry for a fiew days. I sanded thru the filler primer once on a guitar once and had issues with the grain. After several primer coats I did my artsy fartsy crap and cleared it. 2 weeks later the wood cracked or "checked". The wood was birch, same as a boat hull. From then on I always dry sand unless I know I'm not going to go through the primer. Maby Don's single stage lets the wood ex hale this moisture, I don't know.

In all fairness I do not wet sand epoxy sealed wood, dry sand only. But then again the only wood stuff I'm doing lately is riggers, all the scale hulls are 'glass.

 

[Bob Finn]

We've had outstanding results dry sanding the epoxy that we use to seal the wood boats. Generally cut it back with 120-180, and then use DP48LF epoxy primer sealer. If you lay down a nice smooth coat, you can follow it within 30 minutes with base coat or epoxy top coats. If you want it really slick, guide coat and wet sand the sealer after it cures about 24 hours. Trying not to break through the white sealer. Then prep it and go with Urethane or epoxy. We use the dp48LF on gelcoat also. It bonds really well.

 

[dannyual767]

posted by Don,

Ok you want to use your high build primer/surfacer as an imperfection filler, pinholes, scratches, etc. I use PPG DZ-3 & typically shoot 2 or 3 times sanding off about 90% each time until I'm satisfied with the surface quality. I like the DZ-3 because it dries super fast & sands off like baby powder.... Because it is in fact heavy you want to wind up sanding as much of the primer/surfacer off as possible until you have the surfaces where you want them then shoot a regular primer intended for whatever paint you choose. You want the hull to look like it's ready for a coat of paint even before the primer goes on.

Don, I'm assuming that you sand 90% of the primer off of your glass hulls :unsure: . My epoxy resin sealed wood hulls would be sanded all the way down to bare wood in way too many spots if I tried to get that much primer/surfacer off. I'll probably be able to get that much off of my glass Aeromarine Avenger, though. I think that you said on another post that painting over gelcoat is okay.

The two boats that I've already sanded, SK (original build) and DV20 (rebuild) have a lot of primer left on them but the surfaces are very, very smooth. I'm sure that I could keep sanding to remove more weight but I'm scared that I'm going to end up with a lot of bare wood spots. Maybe for my next wood hull build, I'll sand the bare wood hull a lot more before I start applying my epoxy sealing resin.

I spoke with the PPG dealer again. I was told that a sealer isn't necessary in my case but that I should shoot another thin coat of primer/surfacer because I shouldn't have any bare substrate showing. I think that I'm going to end up with a real nice surface for my color coats but next time I'll save on the extra primer/surfacer weight !

 

[dannyual767]

posted by Wesley's'

I would like to know how you guys are wet sanding into the wood grain. I have had serious problems with this in the past. The grain swells from the water and there is an over all swelling and adhesion problem unless you let the wood dry for a fiew days.

I learned many years ago not to wetsand wood . Much as I'd like to do that to my epoxy sealed wood hulls, I probably won't for fear of sanding through to bare wood! I'm sure I'll wetsand my AM Avenger, though.

 

[Don Ferrette]

Don, I'm assuming that you sand 90% of the primer off of your glass hulls :unsure: . My epoxy resin sealed wood hulls would be sanded all the way down to bare wood in way too many spots if I tried to get that much primer/surfacer off........

That's where that term "heavy hands" comes in, it's all developing a touch or feel for sanding. Less pressure & more time is always better than less time & too much pressure where you wind up having to re-seal something.