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Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

What constitutes a "scuff coat" sanding?

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Initially Posted - 04/23/2011 : 11:32:15

So, I'm working on SL today to try to finally get her back in the water. Since we weren't able to do so after we painted last fall, I need to do a "scuff coat" according to the manufacturer (Pettit), and put on a single coat of paint to reactivate the paint underneath. OK, so what does a "scuff coat" entail? I've started sanding and it's stunning how fast you can sand through all three of the previous layers with a random orbit sander. Fortunately that learning curve was short & sweet & I only have one spot on the starboard keel to deal with. I would be using my 1/4 sheet sander, but I think a friend may have borrowed it, and I can't find it. So it's the random orbit sander, or a hand sander (which my shoulder isn't likely to deal kindly with).

Right now, I'm using 100 grit paper which has shown itself to more than aggressive enough if I want to cut through all the paint right down to the fiberglass. Pettit recommended 80 grit but I figure 100 is close enough. I'll continue with the 100 grit, but wanted to see if any of you guys have suggestions.

I'll follow up with an acetone wipe down to get all the paint dust off, and then do the coat of paint after taping off the boot stripe, and around the pads.

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

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John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 04/23/2011 : 11:56:37

I'm guessing that 100 grit would be enough but without power tools. You just want to give the surface a little "tooth" to hold the new coat of paint. Just like before the last coat of finish on your beautiful Treen.

Sorry 'bout your shoulder.

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 04/23/2011 : 14:04:20

Thanks John.

I'm mostly done sanding now, on to the acetone wipe down. My shoulder's grumpy, but not too bad. A soak in the Jacuzzi will help with that.

Here's the face of joy:

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dmpilc
Master Marine Consultant

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USA
4593 Posts

Response Posted - 04/24/2011 : 04:31:23

I like to use a drywall sanding tool. It's a long handle device with a swivel head. gives me some distance from the dust.

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Tradewind
Admiral

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USA
531 Posts

Response Posted - 04/24/2011 : 14:53:16

I put on 2 coats of ablative paint a year ago, boat's been out of the water since then. I called the paint manufacturer, SeaHawk, to see if I needed to repaint and they recommended a low pressure wash to activate the paint before putting it in the water.

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 04/24/2011 : 15:09:11

Steve,
Yeah, this is a hard paint (Pettit's Trinidad SR), so a pressure wash won't touch it. It's loaded with copper and other stuff, so the paint has to be only mostly dry when it's put in the water, so the copper begins to react with the water to form it's biocide, or at least I think that's what I understand. So the scuff coat's necessary to give the next coat of paint something to bond to.

I did find that the acetone wipedown seems pretty effective at dissolving the outer layer of paint, I wonder if I could have skipped the sanding (my shoulder certainly wished I had). I only got about half or so of that done before I called it quits for the day. I was sunburnt (first nice day of the year here in Seattle, and it's raining again today, go figure), headache from the acetone, blue paint dust all over the place, etc. I still have marks by my nose where the dust snuck through my filters, and I'm still working on getting all the blue out of my fingernails, and it's stunning how much made it past my respirator into my nose, but I'll spare you the details. When I took another shower this morning, I discovered lots of blue spots on the walls of the shower from yesterday afternoon's shower. What a mess.

Next time I decide to soda blast & paint my hull, I'm just going to pay someone else to do it.

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Tradewind
Admiral

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USA
531 Posts

Response Posted - 04/24/2011 : 18:13:06

Dave, I understand. I really don't like doing bottom jobs, though it's much easier now with a 25'. My 36' was a real bear, but I was much younger then.

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pastmember
Master Marine Consultant

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2402 Posts

Response Posted - 04/24/2011 : 18:49:05

My son sanded the ablative Hydrocoat off this weekend on my new boat and I ordered my VC 17, now for the rest of the time I own the boat painting in the spring will be no more trouble than rolling on paint for thirty minutes and launching within minutes. I am so glad I can use VC 17.

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 04/24/2011 : 19:05:37

Frank,
That's exactly what we used to do (minus the teenager part) until we left the boat in the water too long. I wish I could have stayed with VC-17, I even have three extra quarts I picked up at WM on clearance.

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TakeFive
Master Marine Consultant

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2272 Posts

Response Posted - 04/24/2011 : 19:21:57

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by delliottg
 Thanks John.

I'm mostly done sanding now, on to the acetone wipe down. My shoulder's grumpy, but not too bad. A soak in the Jacuzzi will help with that.

Here's the face of joy:

<hr height="1" noshade id="quote"></blockquote id="quote">
Regarding your PPE for sanding, this $11 sander interfaced perfectly with my Shop Vac:

<center>

</center>

I also added a 4' flex hose that I bought at a pool store so I had a flex hose all the way to the sander, instead of the 1'+ hard tube that terminates the Shop Vac hose. With this combination, I sanded all day without getting a trace of blue dust on my dust mask.

Note that I had hard paint, so a sander was absolutely necessary to cut into it at all.

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JohnP
Master Marine Consultant

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1520 Posts

Response Posted - 04/25/2011 : 12:20:18

When I applied new coats of Pettit SR bottom paint last summer, the marina had first removed the barnacles with a power washer. I scraped lightly with an angle-scraper to smooth any remaining barnacle adhesive, and then sanded lightly by hand to prepare for the new paint. Washed with a hose and then wiped with acetone.

On the safety side, I set up a house fan pointed along the side of the boat where I worked, to blow dust away from the work area. I used a respirator and a pair of goggles over my glasses, with a hood covering my head, blue plastic gloves, and long sleeves taped to the gloves. No skin exposed.

I don't like to get any of that dust on or in me.

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