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  #31  
Old 04-22-2012
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Re: OK, so I'm Sanding My Bottom...

That's probably the worst looking bottom I've seen in 50 years--bar none. Squid, the first thing you want to do is get rid of that sander. The easiest and best thing I've come across for sanding a boat bottom is a tool used by sheet rock hangers for sanding spackle paste. It's a fairly coarse, stainless-steel screen fitted over a flat, cushioned pad attached to a relatively long handle. The screens and handle can be found at Home Depot, Lowes, etc..., the screens do an outstanding job, don't wear out quickly like sand paper, and you do the entire job wet. Just dip the head of the screen in a bucket of water, and scrub the bottom. The finish will be flat, smooth and ready to paint in just a couple hours. For some reason I thought everyone knew about this technique, but I guess I was wrong.

Good Luck,

Gary
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  #32  
Old 04-23-2012
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Re: OK, so I'm Sanding My Bottom...

I'll give the screen/pad a try to flatten things out on the next step when I fill and fair the bottom... I have the toolage here...

I don't think it would have worked on the ablative though, I needed the sander to "clean out" the divots without taking the whole hull down to fiberglass matt...

The divots were actually in the hull prior to ablative being applied as witnessed by the red ablative at the bottom of most of the "divots"... Looks like someone had ground out the blisters previously, but rather than fill just overcoated with the ablative...

Good news is there weren't any "new" blisters or soft spots forming in the 4-5 years the boat was in the water since the ablative was put on...

Here's an older photo from before I started, you can see the blister divots under the red ablative...

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  #33  
Old 04-23-2012
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Re: OK, so I'm Sanding My Bottom...

Squid,

I'm seeing red, white, blue and brown on your finished sanding. Lots of work, btw, nice job.

I assume the brown is where the blisters got into the mat. The red is remnants of the ablative, since you've referred to it.

I'm confused by what the porous white stuff is? Previous filler? Is it secure enough to apply over again? What's the blue?
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  #34  
Old 04-23-2012
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Re: OK, so I'm Sanding My Bottom...

The blue on that later picture is where I took off a larger rectangular screen box that was covering the brass sea screen seen..But it too was "paint" over the gray/white porus stuff, it just hadn't been sanded down in a previous "redo"...

What the white/gray stuff is ...I don't know...but it's been on there for awhile...although in most places it sanded out and "flaired back" nicely and seems "tightly attached".. a couple places (first pictures) show "air bubbles" in the mix, but they sanded out to tight material as well..

The only "history" I know on the boat is the PO bought it in the water 5 years ago and never had it out.. so everything we're looking at has been soaking for 5 years ... and/or "redone" 5 or more years ago...

The blister/divot/craters were "pre-ablative" and as far as I can tell no new blister/loose spots/cankers have developed under the ablative coating...

Also looks like in a previous "redo"... someone drilled and spot filled the blisters with another "something" seen as the perfect "yellow" circle in some of the blister craters...



I believe they predate the preablative divot creation...

Quite the premordial "chemical soup" I need to cover...
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Last edited by Squidd; 04-23-2012 at 09:16 AM.
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  #35  
Old 04-23-2012
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Re: OK, so I'm Sanding My Bottom...

Squid,

Couple of semi-educated guesses here:

o The beige colored repairs in your most recent post look to be made with resin thickened with West System Microlight filler. It could be either epoxy or poly resin, but I'd guess epoxy.

o The "white chalky" stuff is likely a poly filler (Bondo or an equivalent) with white cream hardener.
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Re: OK, so I'm Sanding My Bottom...

I would guess the yellow circles are some form of epoxy used to fill the early blisters.

I don't know how much time and money you want to spend on this, but you really dont want to kick the can down the road any more either.

Once you get it as clean as you can epoxy can fix a lot of past sins.

My opinion is if it doesn't leak, the surface is sealed, and the bottom is smooth after painting. You have a boat.

Regelcoating the whole bottom may not be what you want to do right now.
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  #37  
Old 04-23-2012
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Re: OK, so I'm Sanding My Bottom...

Exactly...

My goal is to fill, fair, put a sealer/barrier coat on and biocide paint...

See what it looks like next spring and "maybe" in a couple years a total redo...

But really it's a $3k boat...I'm not planning on putting $5k bottom job on it...
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  #38  
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Re: OK, so I'm Sanding My Bottom...

Quote:
Originally Posted by PorFin View Post
o The "white chalky" stuff is likely a poly filler (Bondo or an equivalent) with white cream hardener.

I've never had much sucess with that "stuff". My earliest memory of it is my uncle scraping it out of an old car repair to redo it.

The few times I've tried it, may have been from it sitting on the shelf of an auto parts store too long, but I got the same results.

Once the benzoyl peroxide cream, (yes the same stuff you put on zits), couldn't completly harden the resin leaving me with scraping out a mess the consistancy of silly putty mixed with bubble gum.

I've had good luck with polyurathane, and with polyester. I would skp the bondo.
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Old 04-23-2012
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Re: OK, so I'm Sanding My Bottom...

Quote:
Originally Posted by CapnBilll View Post
I've had good luck with polyurathane, and with polyester. I would skp the bondo.
Agreed. I'm not suggesting Bondo as the filler to use -- there are far better products out there. Selecting a filler that's recommended for below the waterline use would be prudent.

The colors of body fillers are usually imparted by the hardener used. Bondo comes with a red cream hardener, hence the pinkish tinge of the properly mixed putty. Other body fillers come with different colored hardeners (blue and green seem pretty common), but the base filler is usually white or grey.
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Re: OK, so I'm Sanding My Bottom...

If you'll look at the photo of the strainer, it is surrounded by white surface. I think that's your gelcoat. Everything on top of that surface is either old paint, or dirt or algae covered with old paint. I don't think most of the pits you are seeing are "boat pox." I think they are simply many layers of peeling paint. If you get all the red and brown and blue stuff off, eventually you'll get down to the white gelcoat, which is where you want to be. You don't want to remove the white gelcoat.

I wouldn't apply any filler to try to smooth it out, because I believe you'll be filling pits in old bottom paint and dirt, sealing them there forever. You have done a terrific amount of hard, nasty work, and smoothed out the original mess fairly well. My suggestion is that you apply one coat of ablative antifouling and enjoy sailing the boat for the summer, and then, next spring, have another go at it, and finish the job. After it's finally done, if you use no more than one coat of good quality ablative each year, you'll probably never have to strip it again. After you get rid of all that old paint, you'll be able to see whether there really are any osmotic blisters under it. At that time, you can decide whether you need to do anything about them.
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