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Old 26-12-2007, 17:49   #1
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What is this black stuff?

We have a leek in a 1987 Catalina 27'. We started grinding and this picture shows an area at the very top of the keel on the starboard side about in the middle of the boat. This boat has a glass skeg keel of about 12 with the lead keel affixed to the bottom of that. The lead glass joint looks good. This picture is taken from the center of the glass skeg on the starboard side about in the middle. From the bottom looking up the picture clearly shows:
1. Red bottom paint
2. Gel coat,
3. Large Dark green band (very hard)
4. Small White band (Caulk like but rather soft)
5. Large Black band (Like putty very, very soft)
6. Tan, Pink (Very Hard)
It looks to me like #6 is good glass.
What is #5 it is worthless?
What is #4 it is not much better?
What is the #3 layer
The two layers of softer material white and black (about 1/8) is between the solid dark green layer and the tan pink layer #6 from the shaft log to as far as we have ground, which is now mid keel.
Also about half of the #6 layer is spider cracked and crumbling and we ground through the hull.
This boat was grounded before by the previous owner and repaired by the yard in an area of about 6 by 24 primarily with bondo directly behind the keel.
I can't seem to upload a picture.
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Old 26-12-2007, 23:08   #2
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Old 27-12-2007, 06:02   #3
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This is the picture
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Old 01-10-2017, 09:10   #4
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Re: What is this black stuff?

No idea, drill a 1/4" hole and see what comes out on the bit.
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Old 01-10-2017, 10:50   #5
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Re: What is this black stuff?

If that is the top of your keel it may be an oxide of lead.

I like the idea of drilling down a little. See if silvery unoxidized lead shavings come out of the drill bit.

Be sure to re-seal it well so water does not penetrate into the hole.
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Old 01-10-2017, 11:37   #6
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Re: What is this black stuff?

I'll give you my best guesses as to what the materials are. Though as stated by others, there's no way of knowing for sure without examining them live. Typically by drilling for a "core sample".
Quote:
Originally Posted by davidpm168 View Post
We have a leek in a 1987 Catalina 27'. We started grinding and this picture shows an area at the very top of the keel on the starboard side about in the middle of the boat. This boat has a glass skeg keel of about 12 with the lead keel affixed to the bottom of that. The lead glass joint looks good. This picture is taken from the center of the glass skeg on the starboard side about in the middle. From the bottom looking up the picture clearly shows:
1. Red bottom paint - Yep, bottom paint.
2. Gel coat, - Correct again
3. Large Dark green band (very hard) - Fiberglass, including resin. AKA the stuff the hull's made of.
4. Small White band (Caulk like but rather soft) - Probably a soft bedding compound.
5. Large Black band (Like putty very, very soft)- Probably a soft, flexible bedding compound, again.
6. Tan, Pink (Very Hard) - Either fairing compound, or a layer of hard bedding material. Resin mixed with structural fillers.
It looks to me like #6 is good glass.
What is #5 it is worthless?
What is #4 it is not much better?
What is the #3 layer
The two layers of softer material white and black (about 1/8) is between the solid dark green layer and the tan pink layer #6 from the shaft log to as far as we have ground, which is now mid keel.
Also about half of the #6 layer is spider cracked and crumbling and we ground through the hull.
This boat was grounded before by the previous owner and repaired by the yard in an area of about 6 by 24 primarily with bondo directly behind the keel.
I can't seem to upload a picture.
Sometimes when keels are fitted to boats, the first step is to smear the stub/sump that's part of the hull with a hard, structural bedding compound. Often resin mixed with a structural filler. And this is done to get the contour of the keel stub/sump to closely match the lead ballast keel.

Then the lead ballast keel is lowered, or the hull is lifted off of it, & a layer of flexible bedding compound is applied in between the keel stub/sump & the lead ballast keel. This fills any gaps left from the first fitting that used the structural filler. And it allows the keel to move ever so slightly in relation to the hull, as the hull changes shape under sailing loads, while keeping the joint watertight.

On some boats, racers in particular, the lead ballast keel is first bedded in a layer of structural filler. And then fiberglass & resin are applied overtop of this, & smoothed out via sanding, so that there's no visible joint between the keel & the hull. This is done so that theres less, or no drag caused by a seam between the keel & the hull. Though over time such joints can crack due to the keel moving around a tiny bit in relation to the hull as the hull flexes under sailing loads.

Also, sometimes people will put several layers of glass overtop of a flexible keel joint. One which has both hard & soft bedding compounds in between the keel stub/sump, & the lead ballast keel. It's possible that this is what was done to your boat, especially if the "hard green" layer is overtop of both the "hard brown" layer of what I think is structural bedding compound. Along with the fiberglass layer also being overtop of the layers of flexible bedding compounds that are in between the hard bedding (brown layer) & the keel sump/stub.
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Old 02-10-2017, 08:52   #7
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Re: What is this black stuff?

Greetings and welcome aboard the CF, David.
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Old 04-10-2017, 07:35   #8
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Re: What is this black stuff?

If nothing comes out on your drill bit, black and dark brown fiberglass is normally hydrolyzed resin. Not necessarily a void...

Basically polyester resin dissolves in water, and when you have a dry patch of mat or a shattered area of laminate that has cracked, or an area that was undercatalyzed from the start ... water is pulled in along the glass fiber and starts breaking down the resin into a weak acid and that changes the color.

If you grind into it, you can spray down the area with a mist bottle of distilled water just so it beads up. If you get an orange, reddish, or clearish yellow sticky goo in trails when it drys that is what you have going on...

It looks like you've got a pretty big repair area that was laid up with mat over the top and you might have dug down to where the last guy stopped. More than likely if everything is dry, the hydrolyzed area was patchy and they stopped there because they had enough area to get a good taper in without making things paper thin, and roughly followed the area that was damaged.

Did the old repair fail, or are you doing exploratory digging to see how they did it?

If you slick out with 80 grit on a grinder till the scars are gone, you can take some 120-180 grit on a DA and get a smooth surface, then wipe down with acetone and get a look inside the laminate while it is wet. Most of the time hydrolyzed areas look like little black rings around bubbles, or a smoked up window with fibers in it.
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