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Since this thread is about barrier coats, can I partially hijack it paj, please? I'll let you hijack one of mine down the road...

I just bought a boat, as y'all know, and it has...um...something...on the bottom of it.
Rough texture, dark color...some of it coming off in a few places.
How can you tell the difference between barrier coat, bottom paint, and...other stuff?
And for a trailered boat that will not likely be in the water more than a day or two, do I need to bother trying to "fix" the patches that have come off?

Try posting a photo of what you are trying to describe.

Ray

vizwhiz-
You could have a bottom paint that was applied over an unprepped hull surface, ie: wasn't sanded before paint applied. Mine is like that...I bought that way from the P.O. He kept it in the water all the time, I've had it in for up to six days at a time...don't need / don't want / haven't fixed the bottom paint. If you don't mind the way it looks on the trailer, then you don't need to fix it.
(Unless it's against the law!)

As an "about to be a new Mac owner", who intends to keep his boat in a fresh water slip all summer, I have many questions about this subject. Sorry, if some sound stupid, but I'm totally new at this: (1) Can barrier & bottom paints be applied while boat is on the trailer? (2) If so, how does one shift the boat so that he can paint where boat rested on the trailer, or bunkers? (3) Regarding the sanding, is that all by hand, or can a power sander be used? If so, what type? Are we talking a very light sanding to simply roughen the surface? (4) Once these barrier and bottom coats are properly applied, does the application need to be repeated annually, or can one simply keep touching up where the top coat (bottom paint) has visibly worn off? (Many thanks to the sailor who explained and illustrated his whole process here with many photos; that is really appreciated.)

Thanks!

Here is a copy of a post on the subject of bottom paint. You may wish to contact seacatcapt about his post to find out how the boat was moved in order to finish the job.

Ray

Re: Bottom Painting
by seacatcapt » Sun Sep 12, 2010 4:10 pm

I put on the epoxy and anti-fouling paint while the boat was on the trailer. Paid two college kids to do the rolling; one on a mechanic's creeper with a roller and the other sitting beside the boat re-wetting the roller. Other than paint-specked clothes, it was a breeze.

What I used in the Salt/Brackish water of the lower Chesapeake Bay.
http://www.macgregorsailors.com/forum/v ... =8&t=16258

mika wrote:As an "about to be a new Mac owner", who intends to keep his boat in a fresh water slip all summer, I have many questions about this subject. Sorry, if some sound stupid, but I'm totally new at this: (1) Can barrier & bottom paints be applied while boat is on the trailer? (2) If so, how does one shift the boat so that he can paint where boat rested on the trailer, or bunkers? (3) Regarding the sanding, is that all by hand, or can a power sander be used? If so, what type? Are we talking a very light sanding to simply roughen the surface? (4) Once these barrier and bottom coats are properly applied, does the application need to be repeated annually, or can one simply keep touching up where the top coat (bottom paint) has visibly worn off? (Many thanks to the sailor who explained and illustrated his whole process here with many photos; that is really appreciated.)

Thanks!

1. Yes, but it will be a real pain working around the trailer while sanding and painting.

2. Lower the tongue to the ground and block the back of the boat. Then raise the tongue and the boat will come free of the back bunk. Put the boat pack down on the trailer and raise the tongue and block the front of the boat and then lower the tongue and do under the front bunk. There are other ways, but removing the trailer would be the easiest way to work on the boat, but search how to do this and be very careful.

3. If the boat doesn't have a present bottom and/or barrier coat you need to sand to......



..... a dull finish with 80 grit for most paints. Make sure you wipe down with a wax/grease remover first so that you aren't sanding wax into the gel coat or you might not get a good bond. The sanding is to create scratches for the paint to grab hold of. If you have paint on the bottom first you had better figure out what it is and then post or talk to a paint rep.

4. No you don't necessarily need to do something annually. I put on 2 coats of black bottom paint over a barrier paint and the one coat of dark blue and will touch up when I see black. Different types of paints will be treated differently, so no pat answer. Decide what you want, making sure it is for a trailer boat if you are not going to leave it in a slip year round and then read the tech sheets on the paint.

I posted this link of what I did earlier, but will again. It might more thoroughly answer your questions....

http://purplesagetradingpost.com/sumner ... de-39.html

c ya,

Sum

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In order to paint mine on the trailer I used two 10ft 2x6 stacked on top of each other under the stern of the boat. I then jacked up one side then the other a little at a time piling first 2x4s under the 2x6s between them and the trailer. Then when I got higher I used cement blocks. I got about a foot clearance between my boat a trailer roller this way. I painted all my coat this way with centerboard removed and painted that separately. When I finished I simply lowered it in reverse order then painted where the boards were.

I'll take some pics tomorrow while I'm playing around with the boat** and post them...


**I can do that because it's such pretty weather down here...

Mika-
Here's a repost summary of what I did to apply a barrier coat while the boat stayed on the trailer:

Now for a report on the boat painting project - did it all while on the trailer. Washed the hull with cleaner and water rinse. De-waxed the hull with Interprotect Solvent Wash 202 (wear a respirator), sanded with 80 grit, and cleaned again with Solvent Wash 202 (charcoal filters are a good thing ). Masked the paint line with 1-1/2 inch 3M Painters Tape #2090 (great stuff). Hired two college-age friends for the painting and using a car mechanic's creeper (another good thing), applied 4 coats of Interprotect 2000E (alternating between grey and white) with 3/8 inch nap rollers (don't go with cheap rollers - the fibers come off). Then applied two coats of Interlux Micron Extra with Biolux (16 hours apart for the Micron Extra). When the initial painting was complete and dry, went to a boat launch and backed the boat off the trailer about 9 inches, applied a tie-down strap to the bow (VERY important as the boat is stern heavy on the trailer), and repeated the above painting process for the now exposed bunk areas. Hull is completely painted, and I'm hoping that between the epoxy and the the anti-fouling, I don't have to worry about blisters or slime . Pictures of the process are available at http://s984.photobucket.com/albums/ae32 ... 0Painting/. All in all, not too bad, particularly with strong, hired help!
-Randy
seacatcapt
Feel free to PM me if you have other questions.

As promised, pics of the (very ugly) bottom...uh...paint, I suppose...
From near the middle of the boat (amidships):

Near the front (bow):


Any ideas what this is and whether I need to try to salvage what's left (touch-up the patches) or just sand it down or let it keep flaking off...

For a trailered boat in the water one or two days, I would skip all bottom coats and just apply marine wax. Leave your present coating (looks like an ablative bottom paint to me) alone.
Second this advice if you are a cruiser and wont be trying to squeak out every 0.1 knot performance.

Thanks Cat...by "leave it alone" do you mean wax over it? don't scrape off the parts that are flaking off? ignore it completely?
I'm planning to polish/wax the boat, don't want to waste time with the bottom if I don't have to, but it sure looks crappy...

Ignore it completely. No point in waxing that nastiness imho..if you had a bare hull, the wax would make sense.

Nothing wrong with that paint from the pictures that I can see. It's about protection not looks with abative anti-fouling paint wears down like soap so it going to take all kinds of shapes and shades of color. If it is still there you are good. If you are not going to slip your boat in warm water for longer then a few days don’t wory about it at all. Boat in the water you don’t see the bottom. Any sailboat on a trailer that is not covered in barnicles is a beautiful sight.