Sandblasting Bottom Paint from Gel Coat

[Spliced]

I have a reputable boat yard in the upper Chesapeake that has proposed to blast my boat's bottom for a very attractive price. It was a while into the discussion before I learned it was to be sand blasting, not soda blasting.

They assured me that they had been doing sand blasting to remove bottom paint for years, having abandoned soda blasting because of the cost. They showed me a recently blasted hull, prior to any over coating, and the surface looked acceptable.

The Conventional Wisdom seems to be all against sand blasting... but all the negativity seems to be apocryphal. Can anyone tell me of their first hand experience, possitive or negative, with sand blasting, noting age and condition of the boat's gel coat (and bottom paint), the experience of the operator, and the grit size used?

[Chief Engineer]

As long as you have someone who knows what they are doing.

Why should they worry about the cost of soda blasting? You are paying for it.

[osirissail]

The yard I use in Florida that also quit soda blasting for the same high cost problem and went back to sand blasting. I am always standing right there watching while the yard worker starts the sand blasting. I brief the worker on what I want done and then slip him a nice large tip with the admonition to "do it right" and - carefully - to take off the bottom paint and not the gelcoat. That has always worked for me with a now inspired worker who is willing to put forth the extra effort to please me.

[Sandero]

Blasting too much and focusing on a single area will dimple and even go through the gelcoat... with soda blasting. You need a light touch I suppose. In fact it's better to leave a bit of paint rather than try to get it squeaky clean and end up breaching the gelcoat. Then you have to epoxy fair and long board.

I would not recommend this unless you say work... ie directly AFTER the blasting was done to make sure that they know what they are doing. Filling and fairling can be a huge job if they get carried away. If you have no blisters a peel can get you back to gelcoat and ready for paint. But otherwise your looking at lots of fairing and then interprotect epoxy barrier coat and you are looking at a major amount of work and cost AFTER the blasting.

[Windgeist]

The link may be helpful to you?

SailNet Community - View Single Post - Bottom Repairs

Bob Hassellbeck a.k.a. "The Sandman". 410-905-3587

He regularly strips boats in the area (Baltimore/Annapolis), he's very good, in fact he is at the marina yesterday doing a boat. I was very pleased with his work, he is an artist with that thing, really. If I recall correctly I paid somewhere around $600 for him to do my 37' hull, (five years ago).

[Redcoat]

I used Jabesco Premium Gold on mine. 5 Five gallon buckets worth of bottom paint.Like new now

[rob2hook]

I sandblasted my Weston 8500 with an attachment on a Kaarcher pressure washer. It took a week! As there was an epoxy anti-osmosis coating under the antifouling and I was preparing to use a copper coating, I took every scrap of paint off and allowed the blasting to open the surface a little to key the new coating. It may have taken less time, but trying to keep kiln-dried sand dry in UK rain can be a problem!

Plus point, despite overalls, gloves and goggles, my face was beautifully exfoliated - soft and smooth.

If you specify exactly what finish you want to achieve, it shouldn't be difficult to get it exactly right. A professional will also know that you need to collect up all the sand - I'm still finding it trodden into the boat two years later.

Rob.

[Redcoat]

The way the EPA is in the USA I surprised that you can still use a blaster to remove anything.

[osirissail]

Sandblasting is still legal - if - done in a containment enclosure with a capture and reprocessing system to separate out the sand from the paint chips. A lot of boat yards have installed the systems and are continuing to offer sandblasting at a slightly higher price than what they did when they could let everything wash back down into the water/bay/river/creek.