Bottom Blasting

[Celestialsailor]

Originally Posted by minaret

I hate it. It's slow and incredibly messy. Scraping many garbage bags full of toxic goo from overhead is a nightmare. It gets tracked everywhere and stains everything it touches (god forbid you get some on a deck). It was banned from our yard after people kept tracking it everywhere and getting it all over the bathrooms in attempts to wash up. Never again.

...yes...but tell me how you really feel...
Ok...I'm convinced. The few DIY yards here require either a wet sand blast, a wet pneumatic orbital or a vacuum assist Bosch 6". The 6" is close to $200 and a damn nice tool. The shop vac requires a bag for containment. I think you just talked me into that method. I think with a few day workers from Home Depot and myself might crack it out in 2 days. I also use Interlux 2000. Great product. To the OP...After going through all this work, why not spend the $400 extra and do the 2000?..thanx

[minaret]

Originally Posted by Celestialsailor

...yes...but tell me how you really feel...
Ok...I'm convinced. The few DIY yards here require either a wet sand blast, a wet pneumatic orbital or a vacuum assist Bosch 6". The 6" is close to $200 and a damn nice tool. The shop vac requires a bag for containment. I think you just talked me into that method. I think with a few day workers from Home Depot and myself might crack it out in 2 days. I also use Interlux 2000. Great product. To the OP...After going through all this work, why not spend the $400 extra and do the 2000?..thanx

Is this the tool you mean? Amazon.com: Bosch 1250DEVS 6-1/2-Amp 6-Inch Random Orbit Sander with Vacuum Port: Home Improvement

Just to be clear I was in no way advocating the use of a DA for bottom paint removal. They are not even in the same realm as the tool I was suggesting speed wise. The Bosch 6" is a nice tool but it is not torque-y enough to push 36 grit at the speeds needed. It is also by it's nature not flexible enough for the contoured shapes of a boat bottom.
The OP probably has to stick to coal tar epoxy instead of 2000e because he did not remove the existing coal tar from his hull. It doesn't like to be overcoated with anything else.

[Celestialsailor]

This is the one I was talking about...
Bosch 1250DEVS 6-1/2-Amp 6-Inch Random Orbit Sander with Vacuum Port



6.5 amps. is pretty hefty. My friend used one to remove two layers of bottom paint by himself in a few days. I have about 4 coats built up. I'm hoping with three guys taking shifts of 3, 8 hour days. Do you know of another grinder/sander that is up to the task?

[minaret]

Here's what I use-

Amazon.com: Milwaukee 5540 11 Amp 7-Inch Polisher: Home Improvement

But that would be overkill for most non-pro's. Many already own a Makita 7" sander/polisher for buffing their boat. A 7" softpad will chuck right into that and blow away any DA ever made. But of course it is not vacuum extracted. Read the thread I linked to earlier for some idea what I'm talking about.


Edit-Not to be misleading, these are 8" discs on a 7 3/4" pad, we have just always called it a 7" in the yard. It's a habit.

[Celestialsailor]

Yup...I have something similar. A cheaper Craftsman but like you say, there is not a vacuum attachment. You've probably heard the EPA stuff that has California yard owners crapping in their pants. So vacuum or some other type of containment is a must. Years ago I did my Tartan 37 Blackwatch with that craftsman and it worked great. I looked like a smurf (blue dust) and probably chopped 5 years off my life but what the hell.

[lancelot9898]

"The OP probably has to stick to coal tar epoxy instead of 2000e because he did not remove the existing coal tar from his hull. It doesn't like to be overcoated with anything else."

I also have the coal tar epoxy and if all the bottom paint is removed and there are blisters that open up in the epoxy, can any epoxy filler be used to fill and fair those blisters? Another coat of a coal tar epoxy can then be applied, but wonder if the brand of coal tar makes a difference? Jamestown sells it and there is also a primer that can be used. Rustoleum also has coal tar epoxy. Haven't found instructions for application on line yet such as prep for applying bottom paint after coal tar epoxy application.

[minaret]

Originally Posted by lancelot9898

"The OP probably has to stick to coal tar epoxy instead of 2000e because he did not remove the existing coal tar from his hull. It doesn't like to be overcoated with anything else."

I also have the coal tar epoxy and if all the bottom paint is removed and there are blisters that open up in the epoxy, can any epoxy filler be used to fill and fair those blisters? Another coat of a coal tar epoxy can then be applied, but wonder if the brand of coal tar makes a difference? Jamestown sells it and there is also a primer that can be used. Rustoleum also has coal tar epoxy. Haven't found instructions for application on line yet such as prep for applying bottom paint after coal tar epoxy application.

I wouldn't do it. Coal tar epoxy is pretty soft. Personally if it was my boat I would remove it and apply 2000e. I've seen coal tar fail too many times. It sure is a whole lot better than nothing though.

[Celestialsailor]

I used coal tar epoxy on my steel boat in 1976. It was all that was available at the time. It worked well on steel because it was softer and I assume would move a little as the steel expanded and contracted. We're come a long way since then.

[tsl]

first off thanks all for the comments and feedback.

Just got back from the boat. Tested the adhesion of two different spray paints I applied o the black coating yesterday. The Black coating that we think is Coat tar epoxy. Using the tape pull test which is a standard test in the paint industry. Cuts were made to the test area using a razor knife creating a cross hatch pattern with lines about 3/16 inches apart and then at right angles making something like a tick tack toe pattern. You then use the specified 3m tape and place it onto the paint a rip it off. I used a much stronger gorilla tape. The same tape that held up all winter holding my tarp in place on the boat. Both paints stuck very well. That confirms that there is no film on the coating preventing it from being recoated. I'm told the Coat Tar epoxys produce a film when exposed to UV and the elements that has given them the reputation that they can not be re coated. My chemist says that if my spray paint sticks epoxy will stick better. The ruff surface (called profile) the blasting made certainly helped adhesion.

Now on to what to coat it with. I found a old report in paractical sailor intitled "The Blistering Truth 1991" here they say Interprotect 2000/2001 was the best. Later version 2000e is likely much better. I have been talking to the guys at Epoxy products and I like what they say.Great Epoxy Barrier Coat -Rip-Off / Underwater Marine Coatings

Any comments?

[minaret]

Originally Posted by tsl

first off thanks all for the comments and feedback.

Just got back from the boat. Tested the adhesion of two different spray paints I applied o the black coating yesterday. The Black coating that we think is Coat tar epoxy. Using the tape pull test which is a standard test in the paint industry. Cuts were made to the test area using a razor knife creating a cross hatch pattern with lines about 3/16 inches apart and then at right angles making something like a tick tack toe pattern. You then use the specified 3m tape and place it onto the paint a rip it off. I used a much stronger gorilla tape. The same tape that held up all winter holding my tarp in place on the boat. Both paints stuck very well. That confirms that there is no film on the coating preventing it from being recoated. I'm told the Coat Tar epoxys produce a film when exposed to UV and the elements that has given them the reputation that they can not be re coated. My chemist says that if my spray paint sticks epoxy will stick better. The ruff surface (called profile) the blasting made certainly helped adhesion.

Now on to what to coat it with. I found a old report in paractical sailor intitled "The Blistering Truth 1991" here they say Interprotect 2000/2001 was the best. Later version 2000e is likely much better. I have been talking to the guys at Epoxy products and I like what they say.Great Epoxy Barrier Coat -Rip-Off / Underwater Marine Coatings

Any comments?

The problem with applying 2000e to coal tar epoxy is not adhesion, it's that 2000e is not as soft as CTE. It's never a good idea to coat a soft product with a harder one. I certainly wouldn't even remotely consider applying straight epoxy to it. Stick with using more CTE unless you want to remove what's on there and start over with a new product. Pictures?

[lancelot9898]

"The problem with applying 2000e to coal tar epoxy is not adhesion, it's that 2000e is not as soft as CTE. It's never a good idea to coat a soft product with a harder one."

I always thought that the problem was adhesion, but if that's not the case then how is it harmful putting a hard coat over soft?

[tsl]

I'm going to go with a company called Progressive Epoxy Polymers Inc. Their website (while confusing) is extensive and they have very knowledgeable people answering the phone.
I've been in the industrial paint business for most of my working life so I appreciate the time they spend with me. I will reply once more (hopefully tomorrow) with the precise system I will be using and why. I'll look for your feedback then. No time tonight.
Keep in mind that what is on the boat right now has worked for as long as 25+ years. I can't do much harm with what I put on top of it.
P.S, checked harness of the black coating that is now on the boat. It is fairly hard about a 2H (same hardness as a 2H pencil) My guess is that most after market yacht finishes will get as hard once they fully cure. Coat tar epoxies are not soft by definition. They can be formulated to be hard or soft depending upon the application.

[bobconnie]

Used Coal tar Epoxy on my Colvin for over 22 yrs ! never a problem with anything rust or anything else !! worked for me ! Just my 2 cents

[tsl]

Well I'm getting conservative in my old age. I discussed the project with the people at Progressive Epoxies. I'm very impressed with the company and products. Their product is on the bottom of many boats but their market is pipelines and other non-flexible buried stuff. I'm not concerned about their product's ability as a moister barrier. That is relativity easy to do using high quality epoxy and barrier pigments. (google moister barrier pigments and you will see many) It's flexibility and price.
2000e and the West System are intended to be applied on very flexible bottoms and are about the same price.
As for sticking to the black (likely coal tar Expoxy) I see no issue at all. I've tested two paints, one aerosol enamel and brushed-on one latex. Both suck into the black paint's profile like a sponge. Adhesion tests are rock solid.
so.. I see no need to hand grind the black paint off. I feel sure that if there were blisters I would be able to see them since three blisters were very obvious on the rudder. What ever the black paint is everything seams to sick very well to it. It's fairly hard at 2H.
So I'll coat it with several layer of 2000e or the West system later this summer. And file any articles on boat pox along side teenage acne and instructions for my slide rule. I've got plenty more projects before the boat hits the water.

[tsl]

The project is detailed here if you are interested. O'day 39 project boat - SailboatOwners.com