Blasting of bottom paint

[Mike.Gritten]

Okay, we have our haul out coming in a few weeks and I want to remove all the old bottom paint and apply a new epoxy barrier coat before repainting again with bottom paint. We tried sanding/grinding/etc. last time and were not up to the task ourselves, so we have been thinking about having it blasted off by a sand blasting contractor. They have some wonderful stuff these days that they claim will remove all the icky bottom paint and everything else right down to the gelcoat, but without harming the gelcoat. I have heard talk of walnut shells, corn husks, biodegradable staurolite sand, and other witches' brews to load into the blasting machines. The contractors vary in service supplied (some will come and "wrap and secure the boat so we have total containment" in addition to the actual blasting and cleaning process. Others want me to isolate the boat from the rest of the yard myself. Prices range from $2000 (I do all the wrapping and cleanup), to over $10000 to put it inside a yard paint shop and have them do it all.
Has anyone had experience with this process? I am interested in knowing if the value is really there. The photos I've seen of boats that have had this done are amazing! The prices I'm getting seem steep (but OTOH I would hate to do it all myself). Removing ALL the old stuff has not been done by us before and it would be nice to get a good job of it. We're wrestling with the multiple boat bucks cost. (We could get a new main sail and a bunch of other stuff done for the same money!) Any help or opinions would be appreciated.

 

[NateHanson]

I did this project myself. Rented a big compressor and pressure pot blaster for $100 for a weekend, mail-ordered a few hundred pounds of walnut husks for less than $200 (actually got way more than I needed), and blasted away decades of hard paint! It was kinda fun, quite messy, and not at all difficult.

If your yard will allow it, then I'd say do it yourself! It'll take you half a day.

 

[treilley]

I followed Nate's advice and did the same thing. You will need to wrap the boat because it generates a lot of dust. I simply covered the ground with some cheap plastic I bought at a box store and then hung the same stuff from the rubrail down to the ground in order to contain the material and reuse the shells. It is a two man/woman job and it will go very quickly. Of all the blasting methods I have heard of, the walnut shell seems to be the one that requires the least amount of experience.

 

[jkm]

Mike

Both Nate and Tim are Mainers. I was born and bred there so I guess I'm a Mainer also. Contrary to their advice I wouldn't go that route at all.

They both are meticulous operators. If you follow their threads and comments you'll see that. If you could put one of them up for a few days to supervise the project go for it. That said you have no idea what can go wrong. Sandblasting and gel coats don't belong in the same sentence, in my humble opinion.

You'd be a lot better off and substantially richer to sand it off or hire some laborers to do it with your supervision.

I've had thousand of dollars damage done to homes with professional sandblasters at work-it just happens. No one is at fault it just happens. Most cases with walnut shells, though some times with sand. I mean thousands of dollars and weeks of delay to repair the damage.

I guess because I was born in Maine I just don't like new fancy ways of doing things. I build my houses the old fashion way and I'm very suspicious of new 'easy' ways to get the hard work done.

I don't use plastic electric boxes and romex, don't allow nail guns, don't use PVC piping or ABS and now I get lumber sandblasted at their yards before installation-no more OTJ.

FWIW

With the current state of the economy $.05 (canadian) please.

John

 

[treilley]

John, I hope you don't use nails and you hew that lumber by hand

You obviously build based on quality and I would love to see one of your finished products but you also realise some methods, even though they are newer, can be better.

Sandblasting and boats do not go together unless you own a steel trawler. The great thing about walnut shells is that you start off at a safe distance and then move a little closer until you find the sweet spot that allows you to remove the right amount of paint without damaging the gelcoat. The key is to keep moving. The shells break down much easier than sand so you really have to stay in one spot at a close distance for a few seconds before any damage is done.

Just out of curiosity, why not plastic junction boxes? Plastic does not conduct electricity and I would think much safer in such an application.

 

[jkm]

Tim

I've got friends out of Bar Harbor and on Nantucket that actually do that.

I won't use romex. In my first home I lost a circuit to a nail and because I haven't the time to test all circuits after lath or drywall is hung (I'm usually sailing) I just stay away from it. (Actually sold the place to some displaced Mainers from Camden-they still give me grief about it)

Once I had to replace a 20 by 8 double glazed slider because the nozzle operator coughed. I've replaced windows, inlaid wood, on and on because of inadvertent errors with walnuts and sand.

Hey I was just trying to get you or Nate a gig in British Columbia. Thought the early winter might be getting you guys down. My sister tells me the winter drinking is starting early!!!

John

PS If anyone wants to see what a Malibu fire looks like click on this link. This is the second house I ever built before and after a fire.

http://gallery.mac.com/adscience#100257&bgcolor=black

 

[Shamwari]

Mike - where are you taking your boat out?

Mike
I'm just about to take my 39 out for the winter repairs and was wondering where you have found that lets you work on the boat near Vancouver.

John Gleadle

 

[Mike.Gritten]

John,

I have had the boat out at several marinas over the years we have owned her. Granville Island, Lynnwood Marina, and this year at Mosquito Creek marina in North Vancouver. All these places will let you do most of your boat maintenance chores while the boat is on the hard in their yards. Check with the yard manager in each case to find out if what YOU want to do is okay. Usually these guys are a bit gruff, but are reasonable for the most part if you are reasonable with your requests. Good luck in your search.

 

[Mike.Gritten]

Hull Blasting

We have decided against having the hull blasted. Too rich for our blood. We are going to invest the money in better tools to enable us to do the job ourselves more efficiently.
I can already feel my arms aching in anticipation of sanding the old paint off! Maybe we'll look at some sort of chemical stripper....Stay tuned!

 

[treilley]

MIke, your best bet to do this manually is scraping. I did this on 2 previous boats. I used a 2 1/2 inch carbide scraper and a stiff putty knife that I rounded the corners on and sharpened. Sanding works but is very messy and toxic. Scraping is less so. Chemical strippers needs heat to work. 80 degrees for prolonged periods. If you do use chemical strippers, the key is to lay the material on in one thick forward stroke and not brush back and forth. Also, seal out the air with plastic wrap.

 

[NateHanson]

At risk of sounding pushy (I swear, I'll shut up after this ) the best way to keep those arms from hurting, is to find a rental place with a big pressure pot blaster, and order yourself 200 pounds of walnut husks. It's quite easy, and while I agree it abrades the gelcoat a very little bit, I think this is not an issue if you're applying a barrier coat after stripping (as most are).

Ok. I'm done.

 

[rwthomas1]

I use a Fein vacuum that turns on automatically when I trigger the 6" Metabo sander. For heavy paint buildup I like 40 grit but I only use 40 until I start to see the slightest hint of white scratches indicating I'm down to gelcoat. Then I change to 80 grit and finish. The vacuum setup plugs into the back of the sander and gets 99% of the debris. My hands barely have any dust on them and (I hate to admit it) I don't bother with a mask. It works that well. Scraping and stripping make a much bigger mess. Vac/sander should set you back @$450.00 and is great for many other projects. RT

 

[Rob Hessenius]

Bottom Paint Removal

Mike- Last spring I took off I think 34 years of build up. I was looking for what I thought would be an easier way than scraping. I tried various strippers that were messy. I tried sanding and found that to be tedious and messy too. I was going to try walnut shells, but was racing a clock and I could not put it together in the time frame.

I realized that I was going to have to do it the hard way, scraping. I bought two scrapers from the hardware store. I had four days to scrape, barrier coat and apply VC-17. I got up the next morning at 6 A.M and started. Thinking that this was going to be a couple of day job I started at 7. I started and to my surprise it was coming off easy, really easy. Christ I had the boat down to the glass in about five hours. Granted it was only a 25' boat versus 35', but it was easy!! I was freaking out on the thought that scraping was the last way to go, but I would never do it any other way. I would think about having it blasted if the price was right.

My arms did not ache and I wore gloves to prevent blisters and a dust mask. Get a couple of your buddies together and you will have her knocked out by noon. You will find out who youre friends are. Best of luck!

Regards,
Rob Hessenius

 

[jmcpeak]

Rented a big compressor and pressure pot blaster... mail-ordered a few hundred pounds of walnut husks...

Two questions:

1. Does it need to be a "pressure pot blaster"?
2. Where did you order the walnut shells from and what "grit" shells did you use?

Thinking about doing this and splitting the cost and work between two boats if the boat yard lets us. I think they will if we drape with plastic, keep dust down to minimum and clean up well.

Thanks in advance,

Jason

 

[NateHanson]

Two questions:

1. Does it need to be a "pressure pot blaster"?
2. Where did you order the walnut shells from and what "grit" shells did you use?

Thinking about doing this and splitting the cost and work between two boats if the boat yard lets us. I think they will if we drape with plastic, keep dust down to minimum and clean up well.

Thanks in advance,

Jason

Splitting the work/materials/equipment with a friend is a great idea. I split it with two friends with smaller boats. They trailered their boats to my driveway, and we did all three in a day.

I don't know much about sandblasters. You need a blaster that can hold a lot of material (or else you'll be refilling it every few minutes). The one I got was a 300# pressure pot blaster. (that's 300# capacity for sand-type blasting media - it held about 100 pounds of walnuts). The compressor was a diesel tow-behind compressor, like you see road crews using to run a couple jackhammers. I could tow it with my S-10.

I found people selling the walnut husks online. The place I used was out of michigan, and they were called "Consolidated" something. Maybe consolodated stripping? The guy there was really helpful with recommending what sort of blaster to use, which grit of media to order, and how much. It was a few years ago, so I don't think I've got the contact info anymore.

 

[NateHanson]

found it: www.consolidatedstripping.com

I used the 20-30 grit walnut husks. I also ordered some black magnum media for blasting my iron keel. Made that thing shine!

 

[jmcpeak]

found it: www.consolidatedstripping.com

I used the 20-30 grit walnut husks. I also ordered some black magnum media for blasting my iron keel. Made that thing shine!

Thanks for all the info Nate!

I'll see if I can't get more boats/people interested.

Did you have a local rental place that had such heavy-duty equipment?

I plan on doing a little racing in the coming years and would love to get the years of build up of West Marine CPP Plus paint off and get some VC17 on. $$ *sigh*

Jason

 

[NateHanson]

Thanks for all the info Nate!

I'll see if I can't get more boats/people interested.

Did you have a local rental place that had such heavy-duty equipment?

I plan on doing a little racing in the coming years and would love to get the years of build up of West Marine CPP Plus paint off and get some VC17 on. $$ *sigh*

Jason

I got mine from a local Taylor Rental. They're a chain of tool rental places that caters to both homeowners and construction companies, so they've got everything from hand drills to excavators. I did a little calling around and found the best (ridiculously cheap, I think) deal at a location in Manchester, NH, which was about 30 minutes from where I lived at the time.

Look up equipment rental in your yellow pages, and I'd think you'll find a few leads.

 

[Captainpeter]

Alternative to blasting of bottom paint

In 2003 I decided it was time to remove 19 years of accumulated bottom paint on my E38. After investigating and comparing various methods I had a local yard (Anchors Way Marine, Ventura CA) sand the hull bottom to gel coat. They completely surrounded the boat with canvas curtains (including drop cloths on the ground), sanded the boat, and cleaned up all the residue. The bottom turned out remarkably smooth, especially considering the coarse sand paper the yard used - the yard person doing the sanding was an experienced pro. I did the painting, including three coats of an Interlux epoxy primer and two coats of bottom paint. I also had supplied all the primer and paint myself. The yard also replaced the cutlass bearing which required removing the shaft - this proved very difficult and required 4 hours of labor, not including my labor helping the yard worker. The bill for all this, including the 2 way hauling and fixing that anoying crack between the keel and the hull came to $2000, not including the cost of the primer and paint. The labor cost for the sanding was only $650. I realize that today, 5 years later, things are more expensive, but my advice is still to shop around until you find a yard that really wants your business and is staffed with experienced professionals.
Peter

 

[Mike.Gritten]

This is a final post to let you know what we actually ended up doing!

First off, the media blasting provided by a commercial firm was going to cost somewhere around $4,000 - not going to happen when I could use that money for a new main!
I took a week's vacation from the office and did it the old fashioned way. Of course, the weather was not at all what I would consider cooperative. We had temps as low as minus 3 Celsius (approx 28 Fahrenheit), snow, lots of rain, winds up to gale force, etc. Not my idea of a good time! The yard had blocked the boat up about 2 feet off the ground, which put the deck roughly 12 feet in the air. It was great to get at the keel but sucked for stuff up by the waterline - I'm only 5'7" on a good day. I tried all the tools and methods suggested by those on this list and ended up manually scraping it all off. The old paint was many layers deep with the oldest stuff being what I was told was VC Offshore, a VERY hard paint marketed to the racing crowd out here. The scraper took off the stuff remarkably well as long as it was sharp. We went through 8 double sided scraper blades over the duration of the project. It took me, working alone for perhaps 5 or 6 hours a day, 4 days to get to the point where I could use a random orbit sander with 80 grit to get rid of the last remnants of paint and primer! BTW, my arms did ache! You guys must be much younger than I am, or just have shorter memories! I had a few small blisters to fix which I ground out with a dremel tool, let them drain for over a week, and then filled and faired with thickened epoxy. I then put 4 coats of Interprotect 2000E on the bottom and finally 2 coats of blue Interprotect ACT anti-fouling. I am no racer, but the result was remarkable - the bottom was very smooth and looked great.
Overall, I am very happy with what we did, but do not relish doing it again anytime soon. Next season should be MUCH easier!

BTW, total bill for haul in and out and 14 days on the hard - $487 CDN.