Sand Blasting Tips

Both boats were sandblasted earlier this month. Getting this done saved us weeks of sanding, but there are a few things to consider if you’re thinking about going this route.

Why sandblast? If you want to take your bottom down to barrier coat or gelcoat, this is the reason to sandblast. Why would you want to do that? (Note: all three of these were in our list of reasons to sandblast.)

Bottom paint builds up over time, even if you go the ablative paint route. Even if each coat was properly applied under good conditions, at some point the oldest paint may well give up the tenacious hold it’s got on your bottom and then . . . the foundation has been removed. Gotta get back to the basics to start building back up, right? (A friend just realized he’d need to sandblast his bottom when a quick haul and pressure wash had chunks of paint coming off. No issue with application, but definitely an issue with age of layers.)
Maybe you want to shift from ablative bottom paint to hard paint. Or you want to do Coppercoat. (Our friends on Totem have been very pleased with their Coppercoat bottom!)
There’s some kind of catastrophic failure somewhere in the system and (cough) you can peel chunks of epoxy off the bottom. With a flexible paint scraper. (We’re still in the dark about what was on Mischief’s bottom. Suffice to say it needed to all come off.)

Close all of your thru hulls. In addition to closing them from the inside, plug them from the outside with something, even if it’s just paper towels.

Dustless does not mean dust free. The current standard seems to be “dustless” blasting, which is a fancy way of saying they mix water and sand together to spray onto your boat to remove the coatings. Not as much dust flying into the air - but definitely still a lot. And the fabric under the boat, there to contain any drips from boatwork, now looks like a beach.

Any overspray is not dangerous to your paint job but it is messy and dirty. The nozzles concentrate the blast zone pretty effectively. There is, however, a kick-up kind of effect that means the residue is deposited. All. Over. The. Place. If, though, your gelcoat is porous and chalky, the dust from old bottom paint may well wind up staining the hull if not removed quickly. We were very glad we were on the scene and could follow the blaster with a hose and soft deck brush.

Ask the blaster what their protocol is for protecting your boat AND THE BOATS AROUND YOURS. Some blasters do nothing (so that is on you); others will tent the part of your boat they’re blasting so everything is contained. As referenced above, the protection is more for the mess than any worry about destruction.

The dust is messy. If you’re going this route, it’s probably because you have years of bottom paint on that you want removed. When the bottom is blasted, bottom paint filled spray will spray up onto your topsides (and deck). Clean up is far easier before the residue has had time to dry, but even still will require more elbow grease than just running water. If your gelcoat is chalky, the stain potential is high.

Be a good neighbor. If the blaster is doing nothing to protect the boats around you, you might want to be a proactive helpful neighbor and drape plastic/tarps or something to minimize the dust. Otherwise, plan on spending some time cleaning your neighboring boats. With permission, please, if you need to get on board.

You haven’t dodged the sanding requirement completely. The blasting will remove a lot of the paint but not everything, and there will be parts along the waterline that are untouched.

Blasting the bottom is not an every year proposition. It’s not especially cheap, takes off a lot of material, and is more work than you’d think. That said, when the other option means spending weeks in the yard with my arms over my head holding a sander to get rid of years of bottom paint . . . yeah, I’ll choose blasting again.

Just know what you’re in for!