Equipment for Bottom Paint

[George ( Triton #236 )]

Hi Guys,

My yard is telling me that the sandblasting equipment they have is probably too harsh for doing the mast and might even be a little hard on the bottom of the boat since it has such a nice smooth and faired surface. In any event they feel it will have to be hand sanded once the sand blasting is done.

So...

It looks like it might be time for the ol random orbit sander or perhaps another tool to strip the old bottom paint off.

My question is: What is the best and fastest tool for stripping bottom paint off a big hull like a C&C 40 and keeping the nice fairing intact. Would it be a bigger random orbit sander ( I currently have the same Porter Cable sander that Tim has )? Would it be a type of auto body sander? Would it be a weed eater type machine with a big abrasive pad on it? Is chemical stripping the way to go?

Those of us about to be covered in black paint want to know!

Sandblasting is going to run around $1,350 and I'll still have to sand it smooth afterwards. so even spending $1,000 on a tool and supplies will be a good deal for me.


Thanks,

George

[David]

I would be careful and think twice about sandblasting: It will ruin your gelcoat, pock it with minute holes or take it down to glass depending on the thickness and hardness. If the bottom is exhibiting blistering, this is a good way to exacerbate the problem.

If the operator is not really an expert, local damage from staying too long with the gun in one area can happen very quickly. IMO if the yard is telling you it's a no-brainer way to get off the bottom paint, they are just selling the work and don't know or don't care.

Just curious as to why you want to remove the existing bottom paint? Are you changing from an ablative to an epoxy?

David

[Tim]

I echo the thoughts about sandblasting. I've never been a fan, though it remains a common practice. Throwing rocks (or whatever) at a boat at high speeds just never seemed like a good thing to me.

With care, you can sand the bottom paint off with your random orbit, leaving a very small amount that you could then sand with a long board if you want to maintain fairness. If you can get access to an excellent compresser, the autobody-type DAs are far superior to the electric version (not to mention lighter). But you need a large CFM capacity to run them, meaning that most small contractor-type compressors fall short. If you're looking to make a tool investment, this would be an excellent way to go, in my opinion. I keep looking for an acceptable excuse to buy a good compressor and air tools, but haven't quite gotten there yet.

Either way, you're about to find out exactly how big that boat is! And black might even be worse than red, in terms of the grossness factor of the dust that will invade everything. I don't envy you!

There's also the chemical stripper option. Sometimes they actually work well; other times, you might as well just sand. If you were going to pay the yard for the sandblasting, you could consider seeing if they offer a price for chemical stripping. Lousy work, to be sure.

You can probably use a good stripper like methylene chloride on your mast (not on the hull, of course). I don't know if this reacts at all with aluminum, but I wouldn't think so. This stuff really works, unlike all the "safe" strippers.

Good luck, George.

[George ( Triton #236 )]

Hi David,


The boat has spent the last 25 years in Lake Erie and has had strictly fresh water racing bottom paint. Also the boat is only sailed four months a year and spends the rest of the time out of the water.

Before it started to spend 12 - 18 months at a time in salt water I thought this would be a good opportunity to strip it down, get it really dry over the winter and then layer it with three or four coats of West System with their aluminum barrier coat additive ( 422 I think ). I could then add a good salt water bottom paint suitable for racing.

This time in the yard would also give me the opportunity to do some minor repair to areas of the core with high moisture and rewire the mast and light fixtures for offshore use.


George

Triton #236
C&C 40 # 21 -- someone in the yard told me that this makes me an Admiral ;-)

[David]

That's a tall order George. I've done that myself to the Bristol and it was pergatory for a long time to get it done right. Good luck with it....

David

[George ( Triton #236 )]

Hi David,


Yeah it's going to be a pain, but it's nothing I haven't done before. Apart from getting the bottom paint off, I actualy enjoy the epoxy work, wiring, finish sanding, and painting.

Also, I'm going to look at the chemical strippers that Tim mentioned. Although for the mast, it might just be easier to go with a light sanding and re-paint with a hard chip resistant enamel like is on there now.


Take Care,

George

[David]

I repainted my spars as well, using Interthane Plus. It has lasted well (I think it is harder than Awlgrip) for the past 8 years. I used a zinc chromate primer but did not sand the aluminum. I am not sure personnally that you want to do much sanding to it, as you will remove the annodizing if you are careful. My feeling anyway...


David

[JetStream]

All good comments about stripping. I've learned there are few shortcuts and there is a lot of bottom to clean. I would just like to add two comments:

First - If you are set on blasting, sand will certainly do a job on the gelcoat. However, there are folks that will blast with plastic media or walnut shells that carry claims of no damage to the gelcoat. They apparently use walnut shells to blast Corvettes for painting and body work.

Second - If you are sanding, please take the time and invest the money in a GOOD respirator. I prefer the full face shield with either organic cartridges or remote supplied air. Remember that bottom paints are designed to kill living things. Make sure it doesn't include you.

You can read about my method of removal and difficulties at www.javelin38.com

[Dave, 397]

I'm all down with the DA sander...if you can afford it, get the big 8" model. Fast work of it!

Another tool which is really great, if you can find one, is a "vertical air polisher". There are also grinders so configured, but you don't want that! The polisher version turns less than 3000 RPM and makes an excellent bottom sanding tool. I have recently seen some Taiwan ones in the Harbor Freight circular...while my impression of the Taiwan air tools is not too good in general, you can at least see what you'd be looking for in the pawn shop or surplus store.

If you can find an affordable 8" DA, you can skip the polisher tool at least as far as the bottom work is concerned.

Dave

[George ( Triton #236 )]

Thanks Tim, Dave, David and Bruce,


I appreciate all the good comments. I think I might try the chemical stripper route and then finish with the random orbit sander and a few passes with the long board. It's going to be a royal pain no matter how I do it.

The guys at the yard have been pretty up front with their concerns about sandblasting a hull that already has a fine racing finish on it so I'm going to pass on the sandblasting. I can get a really good deal on bulk marine chemical strippers so it's time to get gooey!


Thanks again for the info everybody,

George

P.S. - I do own one of the 3M full face mast respirators so I'll at least be able to keep my lungs clean if not the rest of me.

[Ray Henry]

Just stumbled onto the list here from who knows what direction....

Lots of WONDERFUL information here!!!

I don't have a Triton, but I am doing a complete restoration on a VERY poorly kept Nimble Kodiak Yawl.

Just wanted to put in my 2 cents on stripping the bottom. I look at and tried just about everything from grinders to strippers to scraping, etc.

What I ended up doing (and am in the middle of) is using a drill with a 5" sanding disk pad. I put a 7" sanding/grinding disk on (50 grit) and that leaves an inch of overhang all the way around for flexibility and not digging in too much.

The drill makes very quick work of the bottom paint (mostly). Change disks often. It also makes very quick work of my upper arms and shoulders as the hull is a sharpie and 90% of it is horizontal (upside down)!!!!

Then I follow up with a random orbital sander with 80 grit on it.

Here's a pic of the goings on on the port side. All the light-green areas have been hit with both the drill/sander and the ROS.



Anyway - that's what I'm using as we speak.

Good luck (and thanks for the great website!)

Ray Henry

[Dan]

George, after finishing college with a reasonably worthless BA degree, I got a job prepping and painting bottoms at a big yard in Seattle. I worked there about 6 months and painted 3-4 boats/day. Yes, it was a crappy job. When stripping bottoms, we'd tent the boats off with plastic and go at them with a large DA, one guy on each side of the hull. We could knock out a 40 footer in a couple hours that way (stripping, that is...not prepping or painting). The mess isn't even that bad with a decent paper suit and respirator. Its really not all that difficult, just takes some time and preparation (and air tools!). Having an accomplice would help too. As I owe you big time for the hatchboard help, would be happy to spend a day working on the new boat's bottom if you choose to go that route. Just let me know.

BTW, I stopped by and took a look last week after I called you. I love that deck layout...wide open spaces. Way cool.

Dan