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post #11 of 20 Old 10-13-2011
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Think I'd want to know how the existing bolts are attached: threaded or cast in place. If they can be backed out, replacing them would be the way to go if you even suspect they are corroded. You can make your own to match from the same or better s.s. stock and a set of dies. I'd also want to do a little research on Sn/Pb content to really evaluate the engineering of that keel. A 1/2" gap sounds like a symptom of some underlying issue.
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post #12 of 20 Old 10-13-2011
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Your problem may not be bolts pulling out of keel, rather it may be caused by compression of filler material in the hull's keel stub. It was not uncommon in that era to put a wood filler / stiffener in the keel stub.

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post #13 of 20 Old 10-13-2011
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Here's what's inside the keel - maybe!

Northstars were built in Ontario - I believe the keel is lead, if so there is 1) a series of bolts welded to a common plate and held in place when lead is poured, OR 2) J-bolts cast in place. Not likely drilled and tapped. CS 27 shoal draft are lead with bolts cast in while deep fin keel is iron with bolts drilled and tapped.
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post #14 of 20 Old 10-13-2011
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This will give you an idea of how a cast lead keel with embedded "J" bolts is repaired;


From MarsKeel

• The damaged bolts are identified when the keel arrives.
• The bolts are removed through one side of the keel. This is done with a great deal of skill with a torch taking
the upper surface of the lead away.
• The old bolt is used as a pattern for the production of the new bolt. Most keel bolts are J hooked or bent in
some manner.
• Once the old bolt is removed there is a “saddle” of lead remaining, creating the position for the new bolt to
be held.
• The new bolt is fabricated from new matching material.
• The new bolt can even be welded back into the bolt cage right in the keel.
• The new bolt is fused into place. Lead is melted back on top of the new bolt, fusing the original lead and
the new lead, making the repair as strong as the original keel.
• The entire surface of the keel is faired, both sides.
• The root cord is cleaned.
• The remaining original keel bolts are cleaned and readied for installation on the boat.

Disclaimer: No affiliation with MarsKeel etc...
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post #15 of 20 Old 10-13-2011
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That is a really interesting picture. Do you know what process they use to get the new lead to fuse with the old? It would seem that the newly poured lead would have a hard time sticking to the mass of cold lead. The guy in the picture needs a better vapor mask, breathing in those lead fumes!

Last edited by smurphny; 10-13-2011 at 06:08 PM.
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post #16 of 20 Old 10-14-2011
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For details on the process, follow the link I posted above. I agree - the guy should be wearing a respirator.
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post #17 of 20 Old 10-14-2011
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I wonder if it would be an option to just drill all the way through the lead so that a T-shaped rod could be countersunk and lead-filled from the bottom rather than trying to re-cast a bond between the large mass of old lead and new. I question whether the new material can be made one with the old. It would seem you'd have to recast the entire mass to fully incorporate the new material. Would like to hear from a metallurgist on the topic.
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post #18 of 20 Old 10-14-2011
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The hot lead will melt into the existing lead keel and the material will be as one piece of lead. it is the same process as when you do a lead repair on a car body. you melt on layer after layer of melted lead, can be done in any position. It does take some skill but not that hard to learn. He is not wearing a resperator because there are not fumes coming of the lead when heated to melting temperature, they are not heating it up high enough to vaporize it, just hot enough to melt it. melts at 630 degrees F and boils and vaporizes at 3200 degrees F.

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Last edited by overbored; 10-14-2011 at 11:19 AM.
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post #19 of 20 Old 10-14-2011
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Lightbulb Another way to accomplish it

Quote:
Originally Posted by smurphny View Post
I wonder if it would be an option to just drill all the way through the lead so that a T-shaped rod could be countersunk and lead-filled from the bottom rather than trying to re-cast a bond between the large mass of old lead and new. I question whether the new material can be made one with the old. It would seem you'd have to recast the entire mass to fully incorporate the new material. Would like to hear from a metallurgist on the topic.
Kinda similar to how a yard in the NW did a keel bolt replacement of most of the "bolts" in a fin keel sloop several years ago. They bored a round hold thru the keel from the side, and then inserted an large ss rod with a threaded hole thru it. New bolts were threaded in from top and centered with the existing holes in the hull. They filled the remaining small gaps with thickened epoxy IIRC. No melted lead was involved, FWIW.

L
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post #20 of 20 Old 10-14-2011
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Quote:
Originally Posted by olson34 View Post
Kinda similar to how a yard in the NW did a keel bolt replacement of most of the "bolts" in a fin keel sloop several years ago. They bored a round hold thru the keel from the side, and then inserted an large ss rod with a threaded hole thru it. New bolts were threaded in from top and centered with the existing holes in the hull. They filled the remaining small gaps with thickened epoxy IIRC. No melted lead was involved, FWIW.L
That is just a variation on the "window" method. This can be found on the web.

I, myself, personally intend to continue being outspoken and opinionated, intolerant of all fanatics, fools and ignoramuses, deeply suspicious of all those who have "found the answer" and on my bad days, downright rude.
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