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How to get rid of old anti-fouling


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So I got my hands on a old boat from the 80s. It's a 5.25 meter "Still 525" sailing dinghy. She's in great condition but the anti-fouling is horrible. I want to redo it but I have no idea how. The boat is made of fibreglass. I believe the hull is painted but I am not sure what is under the blue paint. It seems the old anti-fouling was painted on the blue paint. I don't know how to proceed. Obviously I need to clean away the old anti-fouling but what's the best way to do that??IMG_20211023_173752.thumb.jpg.d3159b7ebc85d3c802560453b945bdc4.jpgIMG_20211023_173746.thumb.jpg.9d5a2638e36c548ad4264c2bb3b88740.jpg

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If it's thick start with a scraper, otherwise 40 grit, then 80, then as fine as your OCD demands.

If you're going to repaint with AF don't bother going past 80.

Use one of these - available from autobody suppliers.

 

001.JPG

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58 minutes ago, SloopJonB said:

If it's thick start with a scraper, otherwise 40 grit, then 80, then as fine as your OCD demands.

If you're going to repaint with AF don't bother going past 80.

Use one of these - available from autobody suppliers.

 

001.JPG

I'm sorry, where does the cord plug into that thing? Any sanding tool I use better have a cord, the bigger the better.....

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On 12/28/2021 at 6:31 AM, bluefightingcat said:

Thanks everyone for the advice. I'm lazy so will definitely use a oribital sander. 

Orbital is ok, but use one with the little dust bag only take off the dust bag and attach to a good vacuum w/good bag.  That's one ugly assed looking bottom!

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I hook up the sander with a shop VAC and a hepa filter with this inline between the shop vac and the sander

https://www.oneida-air.com/dust-deputy-diy-plus-standalone-anti-static-cyclone-separator?gclid=Cj0KCQiAq7COBhC2ARIsANsPATFi5j0gSZDgmxgZqJHlZQLzmXsEfXefAsL7PqGH-QgSYCHDg1984RwaAvdHEALw_wcB

These cyclonic separators work really really well and are easy to clean.  It will save the shop VAC filter so that you don't have to clean or change it very often.  You still get very good vacuum and the whole thing is super clean.  The suction also speeds sanding up a bit because more material is removed from the disc faster. 

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From the pictures, the worst of that ugly bottom appears to be growth. Wet it down and knock the worst off with a scraper. Where there is paint, the condition doesn't look too bad but if you don't know what is on there you may need to take most if not all of it off before recoating. Decide on what bottom paints work in your area and how you plan to use your boat and read the instructions to see if you can apply it over existing paints. Some can, many can't, or can only go over specific paints. If you pick a paint that can overcoat existing paints, you just need to follow the manufacturer's instructions but mostly get the bottom clean and fair. (how fair is relative to how you plan on using the boat). 

Agree with the suggestions to use an orbital sander with a vacuum attachment and at least a mask. Full bunny suit isn't a bad idea, but is miserable in a lot of places. I usually wear a decent filtration mask, safety glasses or goggles, vinyl or nitrile gloves, and a hat to keep dust out of my hair. For the vacuum, use a decent shop vac with at least a filter catch bag. Dumping out the bin without a bag is a huge mess waiting to happen. The cyclonic separators are great, but a pain to drag around the boat along with the vacuum while sanding, unless you are on concrete and can roll it. 

For sanding, pick a spot to see how easy or hard the paint sands. Start with something like 80 grit just to get a sense of the effort and then move to something more aggressive if needed and go from there. Keep the sander moving up, down, sideways, diagonal. 

Good luck. 

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Connecting the orbital sander to a vac is the best advice ever. Not only does it suck away the dust, it makes the sander more efficient, because it’s not having to re-grind the stuff you already sanded off. 
 

I’m a little surprised no one mentioned hiring a blaster. Or barrier coating…

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The one time I removed antifouling, we spent 2 weekends with orbital sanders (no shopvacs though) and progress was painfully slow.

Then we got some paint stripper (I think Aqua Strip from Westmarine) and paint scrapers and we made more progress in 3 hours than we had in 2 weekends…  We then finished it off with orbital sanders. 

I’d recommend trying multiple methods including chemicals to see which ones works best for your situation. 

 

 

 

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On 12/28/2021 at 12:51 AM, See Level said:

Roll it off the trailer and turn it over, makes it way easier to sand.

How should I do this safely? The boat weights about 250kg and I I will only have a couple of friends to help me. I have old tyres which I can use in the process. I am just wondering that if I flip the boat by first turning it on it's side, will I risk damaging it? Will the side of the boat temporarily carry the weight of the boat whilst it's being tipped over?

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I think you tip it up onto tyres so the edge is protected and position another set of tyres on the other side so it can have a soft landing. The concerning part is controlling the descent after you reach the tipping point. A line around a hefty tree limb might help if one is available. Be careful not to let it land on those pad eyes. 
 

It might not be a bad idea to cover the tyres with blankets so they don't leave black marks on the fiberglass. 

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17 hours ago, random. said:

Had the same experience, only the brand was Citrusstrip or something like it. 

Brushed it on and covered it on cling-wrap to prevent the volatilises from leaving.  Left it for 20 minutes the scraped it off with plastic tools.  Easy as.

This has been brought up in a few threads.  I'll definitely be trying it when the time comes and save the pain for fairing. 

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43 minutes ago, random. said:

I tested the stripper on one side of the rudder.  It was incredible, the AF just wiped off after scraping the bulk off with a plastic tool.

The plastic cling-wrap is the go, it stops the solvents evaporating while it soaks into the paint.  No hurry then.  If you don't cover it I think you could be looking at two applications instead of one.  It's messy, you have to be careful not to get it everywhere.

Agree, when we used paint stripper we wrapped the bottom with cling wrap (bought in a large roll at Home Depot - same as what movers use to wrap furniture). Gives the chemicals time to work without evaporating. Magical stuff.

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