Bottom paint

[62cruiserinc]

A quick question.

I am adding new bottom paint. There are a few bare spots after pressure washing, but most paint is good.

What grit of sandpaper did you use to rough-up the existing paint?

I have a bunch of 120 grit, but it gums up quickly.

Should I try 80 grit? Hand sand or use a pad sander?

Thanks
Steve

 

[alldodge]

Yes 80 grit, and random orbital
Hand or other sanding is ok, but the hand is hand on the shoulders

 

[62cruiserinc]

Thanks, alldodge.

I have a full-face respirator and a Tyvek suit to wear while doing it.

Yesterday I hand-sanded a small area to try it and my hand and arm were instantly covered in black dust, so this is going to be a messy situation.

I was thinking of buying a cheapo HF random orbit sander so I don't mess up my good Porter-Cable sander I use for woodworking. They have a 5" random orbit sander for $35 with a port that I can hook up to a shop vac to pull at least some dust away.

Steve

 

[Scott Danforth]

when I removed my old bottom paint, I used 40 grit until it got thin, then went 80 grit.

 

[Chris1956]

If the paint is in good shape, it does not require sanding. if the hull was properly primed, it also does not require sanding.

However, if the hull was not primed, it must be sanded to remove mold release wax and allow the paint to stick.

Generally, there will e spots where the paint peeled off, if the hull was not prepared properly.

 

[alldodge]

If the paint is in good shape, it does not require sanding. if the hull was properly primed, it also does not require sanding.

Which paint manufacture agrees with this prior to new paint?

 

[62cruiserinc]

I'm not removing all the bottom paint. I'm just painting over the old stuff (ablative).

There are some spots where the pressure washer knocked off some previous bottom paint down to the hull (not as much on the bottom, but more along the top edge of the paint at the waterline).

The new bottom paint says to sand the old paint for better adhesion. It also says to use their dewaxer on any bare spots down to the hull. I looked at the ingredients of their dewaxer and it is xylene and isopropanol. I have both chemicals here at home, so I could just clean the bare spots with them (after sanding everything).

Steve

 

[alldodge]

Bare spots that are under the water need barrier coat before bottom. Many boats have been painted without barrier coat and there fore the hull isn't protected

 

[62cruiserinc]

What does the barrier coat do?

Steve

 

[alldodge]

Water will penetrate thru Gelcoat and bottom paint. Barrier coat is design to stop moisture from penetrating thru it to the Gel. Nothing is 100% and is also the reason the manufacture of the coating says 3 coats is best, its epoxy paint.

Bottom paint is designed to be replaced every so often, ablative or hard, they all need replacing, but not the barrier coating unless its been compromised

If any blisters are found, they need to be dug out, cleaned and dried. Then filled, patched as needed, barrier coat and bottom paint

I got tired of painting mine so I bought a lift

 

[CruisingJacksonRose]

Hey, can I add to this question? I'm a rookie here and recently bought a freshwater cruiser. Do freshwater cruisers need bottom paint as well or just salt water boats? There doesnt appear to be any bottom paint on this boat and I thought that was odd.

Thanks

 

[alldodge]

Fresh or salt a boat which sits in the water for any length of time should be bottom painted. The difference is which type of bottom is used depends on type water and hull material

 

[CruisingJacksonRose]

Ok thanks. Plan on trailering mine around a fair bit so I should be good then. I hope.

 

[62cruiserinc]

I finished sanding the bottom paint. I bought a HF 5" random orbit sander ($25 with coupon) with a dust collection port that I hooked up to my shop vac. The sander worked great and I didn't get the dust all over my good woodworking sander. Now I have to wash out the vacuum to get the dust out of it. I threw out the filter and will put a new one on. There was actually very little dust with this setup. I had a full-face respirator with a complete Tyvek suit on. I looked like a Hazmat cleanup guy. Only problem was it got too hot after 30 minutes and I had to rest and rehydrate myself.

Now I need to clean the dust off the sanded bottom paint. What should I use? Since I have a 26' boat, it will take a lot of whatever I use. I would like to avoid any expensive solvents, especially since the boat is sitting on stands on blacktop, which is easily damaged by solvents. I plan to buy a cheap sponge mop and use that to clean it off. Can I use water if I let it dry well before painting? Water with something added to it?

Thanks
Steve

 

[alldodge]

Soap and water, let dry then wipe down with acetone just prior to painting

 

[62cruiserinc]

Thanks, alldodge.

I washed the boat off with soap and water.

There will be rain later so I can't paint today. maybe tomorrow.

What a mess the sanding creates. Next time I will be tempted to have someone do it. I think next time it will have to be stripped down to the hull and then bottom paint.

I have a question for anyone who sanded the old bottom paint: how far did you go to clean everything you used? The dust gets into the vac hose and the vacuum that you use for the sander dust extraction. I actually took apart the shop vac and washed everything except the motor assembly. It's not possible to get every bit of the dust off of everything. There is some in the motor impeller assembly. Also, what did you do with the sander? Blow it out with air?

If this stuff is so toxic, I want to make sure I won't be blowing it around later.

Steve

 

[alldodge]

I had mine sanded, then I painted it. You need an industrial dust filter, the home type as your can see gets clogged up to easy. I also took my drive off and covered it.

Yes its toxic, how toxic depends on what is used
Search "is boat bottom paint toxic"

 

[62cruiserinc]

Did you repaint yours with a copper-type antifouling or one of the new environmentally-friendly non-copper based ones?

The old paint was a copper-based paint.

Everything is pretty well cleaned up now. Everything got washed down. I just need to de-dust the vacuum motor.

Steve