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Old 02-25-2021, 08:42 PM   #21
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That is a good sander. I would start with nothing less than #80 paper. It's not a car body. Let the machine do the work.

Rob
I would not go near 80 grit on the paint job. I would start around 220 and see how it goes. It may come off easily since it is falling off in places. Then you donít have a couple hundred hours working your way back up to 320 which is where you want to be at a minimum in order to paint. From 80 grit you would need to work through 120 and maybe something between 120 and 220. May be able to go from 120 to 220 depending on the paint. But you still need to do 220 and then 320, and maybe 400 depending on the paint and the quality of finish you want.
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Old 02-25-2021, 08:53 PM   #22
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I would not go near 80 grit on the paint job. I would start around 220 and see how it goes. It may come off easily since it is falling off in places. Then you donít have a couple hundred hours working your way back up to 320 which is where you want to be at a minimum in order to paint. From 80 grit you would need to work through 120 and maybe something between 120 and 220. May be able to go from 120 to 220 depending on the paint. But you still need to do 220 and then 320, and maybe 400 depending on the paint and the quality of finish you want.
I think the biggest mistake people make is leaning on the machine. That is what leaves deep whorls and scratches. I got the impression this was wood which is very forgiving if worked with a light hand.

Maybe #80 is too rough but from the description of flaking paint I think the #320 would take an eternity and use a huge amount of paper.

My opinion. YMMV

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Old 02-25-2021, 10:43 PM   #23
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I did not say use 320. I said try 220 and work to 320. Generally you start with one grit and work your way up through the various grits. You need to het to at least 320 to get a good finish. Starting with 80 grit would definitely take it off, probably much more than he wants to take off. But then working all the way up to 320 would take a looong time. Why not try starting with 220 and see how it goes. You can always go to a more aggressive grit but if you start with a really aggressive grit and find out it is too aggressive you are stuck with the results. In painting 3 complete boats I have found that out.
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Old 02-25-2021, 11:21 PM   #24
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OP, you've got an older steel boat. You're going to roll and brush. I'm thinking a work boat finish rather than a glossy yacht finish. If I'm right about the work boat finish based on decades of maintaining steel boats I'd be stopping at 180, maybe 220 grit. Anything finer is for a glossy yacht finish.

Choose a small area, perfect your technique and see if you're happy with the results.

When you buy your sander get one with dust collection and connect it to a good vacuum. You'll cut your daily clean up by a lot.

Painting in the PNW in winter is a challenge. Following the paint manufacturer's specs for surface prep, primer, surface moisture, humidity and temperature. If you don't you risk it peeling off again.
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Old 02-26-2021, 01:48 AM   #25
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It's a steel boat, it doesn't look like it's been faired, so it's lumpy. You're not going to be able to sand the topcoat off the low spots without, at the same time, sanding into the primer, or more likely sanding through the primer on the high spots.
Start around 80 grit, stop around 180-220 grit.
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Old 02-26-2021, 08:44 AM   #26
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If you hook the sander to a vacuum, try to find the mesh sanding disks (looks like drywall screen). They work great for dust collection and they're harder to clog as well. The good ones last quite a while.
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Old 02-26-2021, 09:03 AM   #27
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It all depends on how perfect you want it to look. Feathering ans using a little filler may be as good as a metal boay gets as the underlying fairness of the hull sides will show up at low sun angle no matter what you do..

painters talk of paint jobs in distance terms. A 6" paint job looks like a mirror from 6" A 3' job looks good from that distance but will show imperfections at closer distance.

Regardless they all will show the unfairness of the underlying surface.
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Old 02-26-2021, 10:18 AM   #28
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I have some related concerns about prepping external wooden window/door frames and rub rails where the paint is flaking offóitís also lifted off in places where Iíd used masking tape, which makes me suspicious of the paint/primer compatibility. Or maybe it was too humid when he over-coated? Whatever, there are spots where bare wood is showing and places where just the top coat has peeled off revealing what appears to be sound layers beneath. Iíd like to finish by going over everything with a uniform topcoat.

I have access to a Festool, which will cut down on the dust. Thinking I could remove most of the topcoat and get down to properly sanded primer. I have no idea what the PO used for either primer or top coat.

1) whatís the right way to approach this?

2) other than a two-part epoxy, what kind/brand of paint should I be looking at for longest life and UV resistance.

3) gloss, semi-gloss or other?

4) is the correct order to: sand, prime, caulk and then top-coat? Really want to know where the caulking stage fits in.

Thanks!
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Old 02-26-2021, 10:20 AM   #29
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I have some related concerns about prepping external wooden window/door frames and rub rails where the paint is flaking offóitís also lifted off in places where Iíd used masking tape, which makes me suspicious of the paint/primer compatibility. Or maybe it was too humid when he over-coated? Whatever, there are spots where bare wood is showing and places where just the top coat has peeled off revealing what appears to be sound layers beneath. Iíd like to finish by going over everything with a uniform topcoat.

I have access to a Festool, which will cut down on the dust. Thinking I could remove most of the topcoat and get down to properly sanded primer. I have no idea what the PO used for either primer or top coat.

1) whatís the right way to approach this?

2) other than a two-part epoxy, what kind/brand of paint should I be looking at for longest life and UV resistance.

3) gloss, semi-gloss or other?

4) is the correct order to: sand, prime, caulk and then top-coat? Really want to know where the caulking stage fits in.

Thanks!

3: That's just a matter of preference. Use what you prefer the look of.



4: That seems like a good order to me, provided you use a paintable caulk. It should seal everything up well, yet make the caulk less visible.
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Old 02-26-2021, 02:30 PM   #30
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Just be aware that with narrow pieces like your rails, window and door trim that power sanders are only going to be able to do a fraction of the work and with them you have to be very careful of edges and profile. So be prepared for a lot of hand sanding.
It's likely that the PO just used an enamel so you're stuck with a single part paint. Pick Brightsides or something like that.

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Originally Posted by angus99 View Post
I have some related concerns about prepping external wooden window/door frames and rub rails where the paint is flaking offóitís also lifted off in places where Iíd used masking tape, which makes me suspicious of the paint/primer compatibility. Or maybe it was too humid when he over-coated? Whatever, there are spots where bare wood is showing and places where just the top coat has peeled off revealing what appears to be sound layers beneath. Iíd like to finish by going over everything with a uniform topcoat.

I have access to a Festool, which will cut down on the dust. Thinking I could remove most of the topcoat and get down to properly sanded primer. I have no idea what the PO used for either primer or top coat.

1) whatís the right way to approach this?

2) other than a two-part epoxy, what kind/brand of paint should I be looking at for longest life and UV resistance.

3) gloss, semi-gloss or other?

4) is the correct order to: sand, prime, caulk and then top-coat? Really want to know where the caulking stage fits in.

Thanks!
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Old 02-27-2021, 06:44 AM   #31
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To answer some of you.

1/ the boat is steel
2/ no history on board regarding to the paint
3/ I have already purchased the paint
4/ I am not looking for perfection, only longevity
5/ the black primer you see is very solid and smooth
6/ at this time, Iíll only focus on the large side sections, which I cannot reach easily
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Old 02-27-2021, 07:47 AM   #32
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Any large 9 inch sander will work, you might be able to rent one for a day.

A thick 1 1/2inch or 2 inch foam pad and a very light touch with silicone carbide (Floor sanding paper) # 12 or so glued on with disc adhesive..

This will look like cardboard with small stones glued on , but it seldom gets dull and never gets plugged up.It comes in a roll, snap off a square piece , leave the corners on .

Light touch,Light touch,Light touch,Light touch, maybe an hour a side.
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Old 02-27-2021, 08:49 AM   #33
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You dont want to paint over smooth surface. It needs to be sanded a bit to give tooth for the paint to stick. If you prime everything you might get a smoother look and avoid print through of the black.
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Old 02-27-2021, 10:48 AM   #34
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This may seem controversial, and the boatyard might show concern, however you might explore the containment approach and do a dustless blasting of the entire area to be painted. It'll leave bare metal for which there are excellent primers, and as long as the primer chosen is compatible with the paint you already have, you should be golden. Blasting is fast and the results produce an ideal surface for painting.
Just an alternative approach to consider...
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Old 02-27-2021, 11:03 AM   #35
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This may seem controversial, and the boatyard might show concern, however you might explore the containment approach and do a dustless blasting of the entire area to be painted. It'll leave bare metal for which there are excellent primers, and as long as the primer chosen is compatible with the paint you already have, you should be golden. Blasting is fast and the results produce an ideal surface for painting.
Just an alternative approach to consider...


The yard allows sand blasting, but I donít have time for it now. There are several, more important, issues I need to address, first.
The paint job on the top is mostly for aesthetic purposes. The boat looks really ugly, as it is now.
Plus, the black cover (industrial primer?) is very solid and even. I do not want to disturb it.
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Old 02-27-2021, 11:24 AM   #36
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I think Fred may be joking, but it might work for a heavily painted bottom. Even I would be hesitant to do that though.

Attached is #12 with an #80 disk for contrast.

Rob
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Old 02-27-2021, 11:28 AM   #37
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It's a steel boat, it doesn't look like it's been faired, so it's lumpy. You're not going to be able to sand the topcoat off the low spots without, at the same time, sanding into the primer, or more likely sanding through the primer on the high spots.
Start around 80 grit, stop around 180-220 grit.
N


This is the correct answer. (Just based on my professional opinion painting at a boatyard for five years)
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Old 02-27-2021, 11:53 AM   #38
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I think Fred may be joking, but it might work for a heavily painted bottom. Even I would be hesitant to do that though.

Attached is #12 with an #80 disk for contrast.

Rob

Might as well use #1 grit. LOL
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Old 02-27-2021, 02:08 PM   #39
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What's the paint that you purchased?

Quote:
Originally Posted by LeoKa View Post
To answer some of you.

1/ the boat is steel
2/ no history on board regarding to the paint
3/ I have already purchased the paint
4/ I am not looking for perfection, only longevity
5/ the black primer you see is very solid and smooth
6/ at this time, Iíll only focus on the large side sections, which I cannot reach easily
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Old 03-02-2021, 07:12 AM   #40
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"I think Fred may be joking, but it might work for a heavily painted bottom."


No joke ,fast and sure, just be sure to use a very light touch.
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