Help Requested: Bottom Paint Sanding?

[Leela Ray]

Hey y’all,

Before I launch Alii Kai this year I’m going to sand and replace her ablative bottom paint with hard copper paint the weekend of June 20-22nd. The plan is sand on Friday afternoon/Saturday and paint/wax Sunday. My sister will be there to help me so I’m not sure I need extra hands as much as guidance with how to approach sanding as it’s my first time attempting something like this.

I have a spot in the Port of Everett boatyard for the weekend and a friend’s vacuum sander. Dave Atwater recommended 80 grit sandpaper to remove the old paint.

In addition to the sander, I’m assuming I need a coveralls suit and respirator, as well as drop cloths for any mess. The boatyard says they have boat stands, but I might be more comfortable borrowing the club stands, since the boat will need to come off the trailer.

Should I also bring sandpaper blocks to hand-sand hard to reach areas? Am I missing anything else?

Also - if possible I’d like to launch her during the week with the possibility of sailing her to Port T for the meet-up. I’m free Tuesday or Thursday for the whole day if people are around to lend a hand.

Best,
Leela

[Scott Bushnell]

Two large stands are currently under the former "Starry Nights"  now "Red Dwarf" in Anacortes, I'll free them up if possible for you to use in Everett.

Scott Bushnell 

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[Jeff Oaklief]

The other two stands are at my house and are free for use.

Jeff Oaklief

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[Vincent DePillis]

I'd use a sander with a random orbit function and vacuum extraction.  MUCH less mess.  I have a 5inch festool with both random orbit and grinder modes, that can be hooked up to vacuum.  Hook and loop pad.  you need to buy a box of 80 grit velcro backed  disks with matching holes-- or Mirka mesh disks (more expensive, but don't need to change as often). 

6" sander is better, but heavier.  get the tyvek coveralls with a hood, and gloves.  respirator with integrated face shield, or separate safety goggles. Better respirators come in sizes-- you might want the smallest you can get.

Happy to lend u the sander and vacuum.

V

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[Ginnie Jo Blue]

Hi Leela, 

I'm excited to see you in PT. I've never sanded the bottom of my boat (although it desperately needs love). Just a couple considerations: 

1) Have you double checked with the boatyard regarding your plan to sand ablative paint and the tools you'll use? I assume you have. I've heard boatyards can be very picky about sanding paint and there are a number of rules around it. 

2) Protective gear: Yes, plan to wear a full bunny suit, not just coveralls. Where a full face respirator vs. goggles and a nose/mouth respirator. The full face respirator does a much better job of managing foggy face. Keep your filters in a sealed plastic bag and remove them only when you're using them (don't let them sit on your mask overnight, for example, to save the filtration). Make sure you have ear protection. Yes on the drop cloths. Sanding the bottom of your boat will be the most toxic thing you do, so protect yourself. 

3) Use a multitool for the hard to reach places and avoid any hand sanding, which would quickly suck. 

You're going to have such a pretty bottom!

Ginnie Jo

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[Ginnie Jo Blue]

Ha! Yes to everything Vince said. Which reminds me, add a filtration bag between your shop vac and hose. It will help save the internal filter on your shop vac. 

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[Andrew Miller]

For sanding you shouldn’t need an organic vapor cartridge as the solvents have long since left the paint, the P100 filters (they come as pink circles for 3M respirators) are cheaper and better (lighter, less airflow resistance) and will save the activated carbon lifetime like Ginnie says. They won’t filter anything but particulates though so switch back to the organic vapor cartridges for applying the new paint. I like to use a full face shield on big sanding jobs as a first layer of protection to keep as much crud off me as possible, especially sanding upside down spots.

If you have a Fein or Festool vacuum you can get disposable paper filter bags that are meant to fit up against the hose input like old school vacuum cleaner bags, but some duct/masking tape could probably make a wrong sized bag work pretty easily.

Andy

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[Bill Gibson]

I haven't done this task. But here's a couple of thoughts. 

The boat will most likely have an epoxy coating over the fiberglass, under the bottom paint, which protects the boat from water intrusion (fiberglass can wick water into itself (osmosis) and develop blisters over the long term).  When you sand the old bottom paint off you will need to make sure you don't remove the epoxy layer (which will only be a few microns thick!).  Others may have some advice on how you know when to stop sanding...  For example, don't go beyond removing the colored paint...  Removing ablative paint, which is by its nature soft, might require extra care.

Also, ablative paint, which is soft, will most likely clog the sandpaper more quickly than a hard paint, so you may want to make sure you have plenty of sheets available.  Again, others, please chime in on how this is likely to go.

Bill

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From: northwest-multi...@googlegroups.com <northwest-multi...@googlegroups.com> on behalf of Andrew Miller <andym...@gmail.com>
Sent: Wednesday, June 11, 2025 10:05 AM
To: northwest-multi...@googlegroups.com <northwest-multi...@googlegroups.com>
Subject: Re: [NWMA] Help Requested: Bottom Paint Sanding?

 

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[Leela Ray Barlow]

Woah I just realised I never finished my email before it sent. Thank you everyone for all this advice - I’m feeling pretty confident I can get this done right. 🫶

Cheers,

Leela

On Jun 11, 2025, at 19:20, Bill Gibson <bill....@outlook.com> wrote:



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