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Old 13-06-2018, 10:53   #31
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Re: Crushed glass for taking bottom to gelcoat

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So the contractor I agreed to use texts me this morning indicating he wants to start the blast work tomorrow, all good I think. Then get text asking me if boat is gel or paint, sets of my alarm bells after all we're supposed to be peeling bottom? I indicated that the hull side are paint and needs to be protected from blast media, his response is tarps are hung from toerail, "Vessel has no toerail" and no tape will be used and blast media will be escaping from top of tarp and I need to make sure all hatches are closed. I ask him why boat can't be tented below water line and material kept off the finished parts of the boat, my neighbors boats and out of the Hudson River.
His response is that my request is unreasonable and that you have to break a few eggs to make an omlette.
Have you discussed with the yard? some wont even allow blasting. This sounds like trouble to me.
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Old 13-06-2018, 11:41   #32
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Re: Crushed glass for taking bottom to gelcoat

Tenting [read: masking and containment] ain't rocket science. A layer of masking tape on the waterline, a layer of polythene going up from there (and over the deck if needed), sure it adds TIME as well as some material cost and more in the dumpster when the job is done, but it ain't rocket science.

In the general issue of tenting the boat? I'd expect that with NYS's environmental reputation, and the issues of the Hudson in particular, that the state DEP might have some serious concerns about *any* residual media, contaminated with bottom paints, being able to get into the water. And the yard might say "HELL NO!" because any bottom paint that drifts onto their soil, can make the state write off their entire property as hazmat. I know a yard that had to close for a whole season, while heavy equipment removed a thick layer of the yard for hazmat burial elsewhere. They were somewhat allergic to the words "bottom paint" after that. Licensed contractors and ground tarps only.

Not that this makes the contractor a bad or uncompetent blaster, just that it sounds like he's not quite up with the times. I'd want to have written permission from the yard, and know that if the neighbors wind up with complaints about the blue [sic] dust on their boats, the contractor is insured and going to make good for them.

Looking at potential problems like those...I'd rather DIY. I've been formally trained, many years of hard study and apprenticeship, so I KNOW how to select, apply, use, and remove masking tape of all kinds and colors. Even for plasma sprays.

CB, you want that man to prove he's had equal training. Doesn't sound like a Guild member to me.
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Old 13-06-2018, 11:50   #33
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Re: Crushed glass for taking bottom to gelcoat

Also, many yards want the ground tarped so the bottom paint that comes off from grinding or blasting can be disposed of properly.
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Old 14-06-2018, 02:57   #34
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Re: Crushed glass for taking bottom to gelcoat

Will attempt to find a company willing to do work to required environmental standard
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Old 14-06-2018, 14:16   #35
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Re: Crushed glass for taking bottom to gelcoat

Have come to the realization will blast myself, powerwasher with wetblast attachment, have to figure out what material to shoot.
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Old 14-06-2018, 14:31   #36
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Re: Crushed glass for taking bottom to gelcoat

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Have come to the realization will blast myself, powerwasher with wetblast attachment, have to figure out what material to shoot.
Looking at your OP that doesn't sound right. Shoot from what?
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Old 15-06-2018, 03:36   #37
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Re: Crushed glass for taking bottom to gelcoat

Wet sand blast attachments are available for standard pressure washers
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Old 15-06-2018, 03:57   #38
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Re: Crushed glass for taking bottom to gelcoat

Now this I am quite interested in as I am considering the same thing. Having watched the YT video I posted earlier I wonder just how effective it is. Seems in the video his started with the chemical strippers and failed but softened the bottom paint and then finished with the wet sand blasting. So be interested to here how you get on with multiple coats of bottom paint.


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Old 15-06-2018, 09:59   #39
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Re: Crushed glass for taking bottom to gelcoat

I just recently had my boat blasted with crushed glass. The finish that is left is fairly rough after. I then sanded with a random orbital sander and 80 grit to smooth everything out before painting the barrier coats. This is the first time having something blasted so I don t have a comparison to how smooth the finish might have been with soda or another medium.

The previous owner had about 25 years of hard epoxy bottom paint and he only ever spot painted it so the bottom was very rough and very thick.

Here is what it looked like when I started


And here is what it looked like after the blasting with crushed glass
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Old 15-06-2018, 10:03   #40
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Re: Crushed glass for taking bottom to gelcoat

I'd check on yard and governmental regulations for containment and disposal unless you're in a third world country. I'd also guess that pressure washer sand blaster won't do the job or you can let us know in two years that it is complete.
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Old 15-06-2018, 10:04   #41
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Re: Crushed glass for taking bottom to gelcoat

This picture might better show the close up texture after the blasting with crushed glass.

The blue square is after the crushed glass blasting, and the surrounding white is the area I sanded with 80 grit.
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Old 15-06-2018, 14:47   #42
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Re: Crushed glass for taking bottom to gelcoat

I have had some experience of soda blasting on my boat. Never heard of adding crushed glass. The soda is meant so seek any soft spots and can easily strip the gelcoat off. In my opinion it is superior to planing or wet power sanding the layers off. Be sure to clean the boat well with clean fresh water before putting on any filler or resin. Good luck Doug.
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Old 15-06-2018, 19:11   #43
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Re: Crushed glass for taking bottom to gelcoat

See for yourself:
Pour some baking soda on a crusty oven pan at home. Scrub till you are bored.
Now, pour some crushed glass (beach sand will do) on the same pan. Scrub some more.

I think you'll find the ground glass is FAR more abrasive than baking soda. Baking soda is a gentle abrasive, even in an air gun. Crushed corn media. slightly more abrasive. Crushed walnut shells, put a nice texture on metals. Hasselblad used to polish their camera bodies with walnut blasting. Crushed glass or sand--now that's abrasive and used to chew through things.

The only news in "blasting" is maybe ten years old. There are guys who used crushed DRY ICE for the blasting media. It is almost as abrasive as sand, but has the advantage of evaporating and leaving zero cleanup, except of course whatever you blasted off the hull. Makes for real easy cleanup. No used media to dispose of.
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