Best grit no for orbital sanding off old antifoul?

[fredrussell]

I’ve got to remove a fair few years of antifoul. Can anyone suggest which grit number discs to go for for the bulk removal bit please? Ta.

 

[crewman]

I use 80 grit mesh on a pad used wet. Dry sanding antifoul will release a lot of toxic dust unless you have very good extraction.

 

[Tranona]

Not a good idea to sand other than a quick going over before recoating. Toxic waste collection and disposal problems plus protective gear required. If removing "several years" then blasting is best, manual scraping or chemical stripping cheaper but hard going.

 

[Shaddickp]

Agree with crewman, I always use 80 grit on velcro foam sanding block with permanently running hose in left hand so no dust is created. Takes around 12 hours to do the hull of a 36 foot boat. Wear waterproof protective coverall, long rubber gloves fastened with duct tape around arms, hood, hat and protective glasses, and rubber boots. Tedious but not particularly hard providing the boat isn't sitting on her keel. It's easier if raised at least 6 inches so much less limbo sanding.
I tried using a brahco scapper once and whilst it took more old antifoul off it was harder work and took longer.
Alternatively pay some poor b to do it for you.

 

[ChromeDome]

Sanding mesh if you must. Coarse to start with - like 40-80.

Personally stopped that after a "never, ever, again" experience. Had it dry ice blasted years ago in prep of changing AF regime (to thin film). Happy ever since.

 

[fredrussell]

Cheers for replies - money won’t stretch to blasting. This is pre coppercoat so I’m already at the limit financially. Funds tight, to say the least.

 

[Momac]

Try wet sanding with mesh. I used a sanding plate on a pole but by hand for the fiddly areas. But must admit I did not attempt to get back to bare GRP.

 

[Tranona]

Cheers for replies - money won’t stretch to blasting. This is pre coppercoat so I’m already at the limit financially. Funds tight, to say the least.

If it is pre Coppercoat then blasting even more valuable as it will get you to a sound surface ready for immediate application except for any local filling. Really hard work to get the surface good enough by hand. Most people who try it regret not blasting!

Coppercoat is a 10 year investment.

 

[LittleSister]

Pro tip - The more (and lumpier) layers of old antifouling you have the slower the boat goes, hence more time is spent sailing. What's not to like?

 

[Poignard]

I employed a young man to scrape off my antifouling. He was saving up to get married oand wanted some extra cash.

I supplied the scrapers, and paid him by the hour at slightly over whatever was the mimium wage at that time.

He only worked on it on Saturday afternoons and it took him a few weeks.

I can't remember what it cost but it was a lot cheaper than a sandblasting contractor would have charged'

 

[thinwater]

Vacuum sand (HEPA filter) with mesh or paper, 40-60 grit to start. 80 is WAY to fine for bulk removal; that is what you use for a light sand on otherwise tight paint. With a good setup there is very little dust. He's using a Bosch dual-action 6-inch sander. Stripped a 40' boat in a long day. He's near the end and no much dust on him. I was 2 bays away extending and fairing a keel.

 

[thalassa]

I've scraped off 20 years of antifoul with the yellow Pro Vacuum scraper 'made in Scotland'. It took two blades and 5 days of the life of a 77 year old. No dust, clean hull.

 

[thinwater]

Checkout this sign, common in US marinas. The reasons are heath, environment, and mess. Scraping is allowed ... but it sucks and is VERY unusual. Many marinas will rent good vacuum sanding rigs, and they will stop open air sanding without vacuum in a heart beat.

Power washing is permitted, but it is by marina staff, on dedicated bays with water capture and treatment. The fee seems reasonable to me, and is usually done at the time of haul-out (power washing is best done while the hull is still wet). But most DIYs have their own rig.