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Bottom Job question(s)

10K views 19 replies 10 participants last post by  rookie00 
#1 ·
All,

I am embarking on my first bottom job over the coming few weeks before launching for the season. I have purchased 2 gallons of bottom paint (ablative) that I am hoping will allow me two good coats on the hull of a 30'' sailboat. The bottom is in good condition and the existing bottom paint has 3 coats (1, base, is black with 2 coats of blue over the black). In only a few spots is the black showing (in and around the rudder) a little bit. I want to prepare the bottom for fresh paint and I don''t want to over look anything, hence this e-mail. I see people in the boat yard scraping and sanding with industrial sanders, chemicals, and all sorts of gadgets. I have 2 gallons of paint, sand paper, and a couple of rollers, tape and some misc painting supplies. I don''t know if I should be laughing at myself or start painting - after I do some sanding. I am trying to determine what is an acceptable amount of preparation for this seasons bottom job (which I plan to do yearly or as required). I am planning to sand the bottom only to the point of providing the fresh paint a surface to bond to. Is this enough or should I take it down further? How much is enough and too much. After sanding I am planning to apply 2 coats of fresh paint over the course of 1-2 weekends as required. Does this sound right or am I missing something. I keep seeing all these people with mountains of equipment and gadgets and I think I am ill-prepared. Please help a Rookie.

Thanks in advance,
Rookie
 
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#2 ·
Rook,

You''re on the right path. Main thing is to be sure the old paint is adhering well and not loose in spots. Sand the old paint enough to give it "tooth" for the new paint to adhere to, wipe off the dust with solvent or denatured alcohol and paint away. Two coats will be fine, and easily doable in 1-2 weekends from start to finish. Remember to save some paint and a disposable brush for touching up the spots where the jack stands are when the boat is in the slings.

All the others with sanders and such probably have lots of loose paint to get off, or maybe 10 coats of old, hard paint they want to remove.

Using ablative paint is the way to go, btw. No build-up of coats to become a major pain to remove down the road.

My 2 cents worth.
 
#3 ·
What a relief. When I saw everyone else with their serious equipment I thought I might be fooling myself for thinking I can get away with doing a bottom job economically. You mentioned a couple of other points I would like to address. You mention ''solvent or denatured alcohol''. What kind of solvent and what purpose does it serve? Is a wash with water inadequate? I was think about having them move the stands because - 1) the boat will only be in the sling for a short period of time - is this sufficient for the paint to dry and 2) I assume they will apply only one coat of paint - would this be sufficient? Thoughts? I sail on the C.Bay and don''t want to risk potential damage in the long run - Blister, etc. I''ve read and heard so many horror stories about bottom peels, blisters, barrier coats, etc, etc. Am I just being too paranoid? If I can leave a used brush and some paint and get the job done, it makes my life much easier. Thank you.

Rookie
 
#4 ·
First you need to find out what type of bottom paint is on there now and make sure that the ablative paint you have will adhere to it. If the bottom is in good shape as you stated, you want to give it a good sand with some med. grit paper. This is more to give a good adhesion surface vs. "getting rid" of what is on there. Many boatyards require that you either put a tarp under your boat while you sand or use a power sander with a vacuum attachment. Bottom paint is 40%+ copper which is posionous to marine life (obviously) and to humans and other animals. As such, invest in a tevek suit to sand and paint in as well as a 3M (or similar) respirator with replaceable filters. I would also recommend goggles and latex or similar gloves. (No, Im not a paranoid.) NEVER use water to wipe off the hull after sanding; use the solvent recommended by your paint manufacturer. I wud also strongly recommned a low-tack tape like 3M''s Blue line to mask off the hull. This comes off very easily and leaves no residue. Generally I use a roller for most of the bottom and CHEAP brushes for places where you cant get at with a roller. MAKE SURE YOU MIX THE PAINT VERY WELL at the beginning of the process and occasionally while painting as the copper tends to settle at the bottom of the car otherwise. Paint around the jack stands one weekend and then ask the boatyard to move them so you can paint the bare spots the next weekend. Dont move them yourself. Good luck. It gets easier every year.
 
#5 ·
You have gotten some very good advice here but let me fill in some of the gaps....

Ablatives, like all bottom paints, over time eventually loose adhesion on the lower most layers. When this happens, ablatives have fewer layers of paint to remove than other harder forms of paint. Ablatives are prone to paint sickness (as are most other paints) and it shows up as small spider crack, or as peeling paint. Those areas where peeling or spider cracking is occuring should be sanded down to a base layer that ideally is solidly adhered.

The presence or absense of ablative anti-fouling bottom paint has no impact on blistering. Typically the gelcoat and when present the barrier coat, are the water resistant membranes that form the defensive line against osmotic blisters.

It is a good idea with ablatives to sand down through ''last years paint'' so as to prevent a build up. Too much paint is far worse than not enough.

Sanding should be done with increasingly finer grades and the strokes should run the direction of the water flow. I typically use 180 grit to prep for the first coat of bottom paint and 220 for the second coat.

Wearing gloves, I typically wipe down the hull with denatured alcohol, which typically removes any dust and any oils or greases or other contaminants that might compromise adhesion. Frequently change paper towels or clean rags so that you are not simply redistributing the same contaminents.

Masking tape off the waterline and the depthsounder transducer.

Two gallons is a lot of paint to paint the bottom of a typical 30 footer. I typically got 2 1/2 coats out of a gallon on my prior boat, a 28 footer. With ablatives, I would typically ''spot in'' (with an extra coat) the bow, waterline, keel (leading edge and bottom) and rudder as these areas experience more erosion than the rest of the hull.

I would typically roll on the bottom paint with a tight nap roller in a couple square foot area at a time and then ''tip off'' (drag the tip of a brush over the surface of the wet paint) the surface with a foam brush stroking in the direction of the water flow. Tipping off does several things. It levels the high spots in the rolled on paint which greatly helps with light air performance, but more importantly it increases adhesion and removes bubbles from the paint layer. I typically apply several coats of paint in a weekend and feather edge the paint maybe 6 or so inches away from the jackstands and then have the yard move the jackstands applying saranwrap to the top of the jackstand to prevent damage to the new paint and then feather in the paint at the jackstands.

When the paint has dried, I typically wetsand with 400 grit in the direction of water flow to knock down highspots in the paint for performance reasons.

The advise about a high quality dust mask, tyvek suit and goggles is very important. You expect to be around for a while and playing casually with toxic paints is not worth taking a chance with.

Lastly, here on the Chesapeake most of us stay in the water year round and so only paint our bottoms every other year. You can typically get a year per coat out of bottom paint depending on whether you use a diver and how often.

Good luck,
Jeff
 
#7 ·
Thank you all for all the great advice. It has made all the difference in my first bottom job attempt. I will be starting the job this weekend, since we are finally getting some favorable weather here in the DC Metro area. All the responses have sparked a couple of additional questions. With regards to sanding is this something that is easily done with a simple electric sander or by hand? Rollers - since the paint is toxix are special rollers required or can I simply go to Lowes or Home Depot and by several there? If I do not use both cans of paint will I be able to save the unused can for next year?
Thanks in advance for all your great advice.

Rookie

PS: Jeff we are in Harrington Harbor North. Where are you?
 
#8 ·
One thing I learnt years ago from the glass and awlgrip guys in the yards from St. Thomas to Southwest Harbor: DON''T bother to wipe down with acetone after sanding raw glass, epoxy, paint or bottom paint. Clean with air under pressure and tack rag, if you must. All you do by wiping with acetone, and, yes, I still catch myself doing it occassionally, is spread contaminants around.
 
#9 ·
If you use an electric sander (like a handheld Makita) you''ll be there all day. If you do it by hand you''ll be there all weekend.

See if you can borrow/rent a pneumatic rotary sander that takes 6" sanding discs. Your progress will be a LOT faster. Use 80 grit and a gentle touch, just enough to rough up the old paint. Also a lot quieter and lighter then the electric sanders (your arms will thank you at the end of the day).

Also be sure to check with the yard if you need to have a vacuum attached to the sander, I believe Herrington Harbor N is a "Maryland Clean Marina" and may require it.

Use a 1/8 nap roller to roll it on.
 
#10 ·
Rookie,

One thing coming out in these posts is the difference between racers and cruisers. If you plan to race, follow Jeff''s advice of fine grit sandpaper. If you are a cruiser (as am I), sand with 80 grit paper -- which is what most paint manufacturers recommend.

The roller needs to be solvent resistant, so buy it where it''s cheapest (probably anywhere other than a marine store.)

As for compatibility, the West Marine catalog has a good chart covering that - as long as you know what kind of paint is on there now. The primary problem paints are those with vinyl or teflon in them. In general, ablative paints will go over just about anything else.

I have been using Pettit ablative paints for many years and like them. As stated before, I sand/scrape off any and all loose paint to get down to a solid surface for adhesion. If the ablative paint is loose (cracking, flaking, etc.) the problem is due to the first (hard) coat of paint the dealer put on my boat when it was new years ago. That paint has lost its adhesion to the hull taking the newer ablative layer with it. All that has to come off in those areas. I feather in a layer or two of new paint in those areas to make them as smooth as possible.

I then sand the rest of the paint with 80 grit paper sicne I''m not a racer. With ablatives, I''ve found that I don''t have to sand all that much to remove the outer "dead" layer to get to a fresh layer the new paint will adhere to. That may be due to the Pettit paint I use -- or not. But there''s no need to arbitrarily sand through last year''s paint if it''s still adhering.

About painting where the jackstand pads are, I''ve done it both ways. The preference if you have the time is to have the yard move the stands so that you can do those areas properly. But a couple of times I''ve been rushed and had to sand and paint those areas with the boat in the slings. Even though the paint didn''t have the recommended time to dry, it did fine those seasons.

The last thing I do to smooth out the high spots is to go over the entire bottom with a sanding device on a pole used for drywall. Much easier than hand sanding and you can buy varying grits of sanding screens for the head to suit your needs.

With two gallons you will have paint left over and it will keep until next year. I put a piece of plastic wrap inside the can right on top of the left-over paint to provide some protection, and that works pretty well.

I sail the Chesapeake, too, out of the mighty Patapsco river.

Finally, two sites to visit for more info:

www.yachtpaint.com (Interlux paint site)
www.pettitpaint.com
 
#11 ·
Wow - Everyone, thank you so much for all the great information. I am much better prepared for my first bottom job then I was yesterday. It will probably take me a while longer on, this, my first job, since I will be using a hand electric sander, but I don''t mind a little sweat equity in my boat, I am sure by next year I will be better prepared. I did check with the Marina and yes, they do require a ''Dustless'' sander. So thanks again. This forum has been a wealth of information. I don''t know what we did before the internet... thanks again for the all the valuable information. We sail a P30 (sv Agenda) if you ever since, please say hello.

Rookie
 
#13 ·
Hey Kokopuff........doing fine. All this bottom chit chat is getting me psyched to start on Minstrel. No splash date yet either, but probably a month away. Glad to know you''re still kicking in Tar Heel land.

And Rookie, if you have a P-30 you need to join the Pearson Sailing Assoc. of the Chesapeake Bay. Check it out at www.cbpsa.org. But watch out for the new commodore.
 
#14 ·
I have a method that results in a good fair bottom that doesnt require all that much finish sanding and works with VC17 or ablatives:
I sand with 180 grit to flatten and fair the old coats with the object to "square off the tops of the ''prominences''. Then with a very fine knap roller apply a coat of new while using a long polyethylene blade with a tapered edge to immediately fair the surface - just like one would do when hand-laying up a surface top-coat of epoxy or polyester. I do this in 3ft X 3 ft. non-adjacent sections and go back and complete the fairing when the paint first starts to cure (not just set). With a little practice (and clean paint and blade) you can almost imitate a sprayed on finish. Since the paint is not dry to a ''hard cure'' you then can keep on applying more thickness without resanding. Obviously for a racing bottom you will need to finish with fine sand paper (or paper wad "burnish" with Teflon filled VC finishes).

The advice from JeffH about keeping the thickness build up to minimum is a very good one. Use a different color base coat and only consider to apply when the base ablative coat starts to show through the successive (different color) coats.
 
#15 ·
JEFF:
We had a discussion about bottom paints on this board or CWBB last year and I told you I used the least expensive of the West Marine Bottom paints, something like $39 per 1/2 gallon. On Teacher''s Pets bottom, doing both the dagger board and the center board, I roll on just about a pint less than 3/4 of a gallon. Because it is so easy to clean our boats bottom I repaint every other year. Right now we are having some rather low tides in the Braden river and last week I had two inches of water on the keel. Took one hour to really get a nice clean bottom without the need to repaint.
Respectfully Gene S/V Teacher''s Pet III and
21'' Windjammer First Born.
 
#16 ·
I think that you got just about all of the information that you could possibly use. There are a few points that I disagree with. I strongly disagree with the idea of not washing down the bottom with a solvent. In our climate, especially in Herrington Harbor where you are under the landing path for BWI, the boats end up with an oily residue which the heat of sanding moves around the surface. I do not recommend using acetone as it is tends to pull these contaminants into the pores of the paint. I do suggest using alcohol and frequent rag or paper towel changes to wash the contaminants off of the surface. Leaving this oily residue on the surface will increase the likelihood of bottom paint developing paint sickness.

I also have mixed emotions about using bottom paint after a year. Even bottom paint that has not been opened has less than a one year shelf life so I can''t imagine using year old paint that has exposure to the air. I do like the idea of putting plastic into the paint to keep it fresh and have used that technique with varnish as well.

To answer your question, I work in Annapolis and although my house has an Annpolis address it is really just north of the Severn on Mill Creek. My boat lives behind my house on Mill Creek.

Jeff
 
#17 ·
rookie00,
You don''t have to sand before painting over an ixisting coat of ablative paint if the power wash was done right. This is not true! I have never done this on my boat or on any of the other many many boats either, and I have never had any problem at all. NONE! However...if you wish to sand off paint that is perfectly good and you have paid $150-$200 a gallon for...go ahead.

Dennis
 
#18 ·
All - Thank you for the all input. Over the weekend I completed my bottom job. This is what I did. I rented a ''Dustless Sander'' from the marina at a cost of $15/hr. The last bottom paint was three coats (base different color) with two top coats. The base color was beginning to show in some areas. I used 80 and 100 grit sand paper (mostly 100 and 80 near the waterline to get all the scum off). I sanded the old paint, which came off very easily, to give the new paint something to bond to. I rubbed down the surface with lots of clean rags and de-natured alcohol. I applied the first coat on Saturday afternoon and the second coat yesterday. I only needed the sander for about 1.5 hours (I have a Pearson 30) Everything went very smooth thanks to all the feedback I received from everyone here. I applied two coats using 1 gallon of West Marine CPP Ablative paint. They told me this was the same as the Micron paint. My primary use of the boat is for cruising, though we tend to be rather competative when we have another boat in sight (and I don''t know why?). Next weekend we will wash and wax. Thanks again to everyone who provided input.

Rookie
 
#20 ·
Allcystemsgo,

I hope I go it right, it looks great. I purchased two gallons of West Marine CPP ablative paint. West Marine told me that their brand is the same as the Micron paint, so I decided to give it a try. The Micron paint was used previously. I have a Pearson 30 and I used 1 gallon for two coats of paint. I have tiny bit left, which I am hoping will cover the jack stand spots. The first coat seemed to take more than the second coat. I thought I was going to have to use some of the second gallon, but it worked out perfectly.

I purchased a gallon of de-natured alcohol from Lowe''s and I used quite a bit, I don''t didn''t notice how much I used, sorry.
 
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