Keel bolt pockets in lead

[Lulworth]

Folks,

This is a bit related to the drilling lead topic but anyway ...

I am replacing bronze keel bolts that were installed 80 years ago using the usual herreshoff Manufacturing Co method: Thread both ends of a bronze rod, drill an undersized hole in the lead then screw one of the treaded ends into the hole. The theory was that the threaded bronze self-taps its way into the lead. The trouble with this method is that it is a bear to get the bronze to unscrew from the lead when the time comes. And, for me, the time has come!

In an operation, the memory of which continues to delight, I used the usual array of simple machines like wedges, levers, and rollers to move the 3500 lbs lead ballast out from under the elevated boat and it now lies alongside the hull with the bronze rods pointing skyward just begging to be removed. Yesterday I tried using locked nuts on the threaded top end to turn the first of the keel bolts out of the ballast but it sheared off at the lower threads 1/2" inch below the surface of the lead. Bugger, that lead is darn sticky (susceptable to spalling, if you prefer). Now my plan is to drill out what remains of the bronze -- anyone know how long the threaded section of the Herreshoff bolts on s-boats were? Then I intend to machine out a pocket that will accomodate a bronze nut, washer, and box wrench head. I need to do this for six bolts so any hints on mortices in lead would be appreciated!

David

[Nemo]

Sounds like a typical boat project (somehow becoming 3X the job envisioned).

I have to ask, and I don't know why, but wasn't there room to leave the keel in place, original bolts and all, and just drill "extras" in support of the originals? Sure seems like you've volunteered for a lot more work than I'd have thought necessary...

Hey, if I've written something really stooopid -- LAUGH! And sorry, I realize that I haven't helped answer your questions.....but me, I'd bolt that baby back in place and drill some more!

[ 12-23-2005, 01:58 PM: Message edited by: Nemo ]

[Lulworth]

Nemo, Naaa, not a stuupid question at all. In this case, just as the leg-bone's-connected-to-the knee bone's connnected to the ..., the ballast is connected to the deadwood and the deadwood is connected to the keel and the keel is connected to the floors, ... you get the idea. Well all of the above had to be replaced so away goes the lead for access.

[merlinron]

not ever having done it, but having a fair bit of experience with lead and woodwork for other operations, i would think you could drill the pockets to rough shape and pare them out with a chisel, much the same way you would work a large mortise in wood. lead actually chisels pretty easily and it doesn't splinter. as to how far the bronze is threaded into the lead, i wouldn't have a clue, but a series of small holes ( 3/16" or so) drilled at maybe 1 inch intervals would let you know. when the bronze chips quit showing up you're past the bolt. the holes could be repoured with lead or filled with epoxy afterwards. it's also possible that the length of threads at the upper end of the bolt is the same as what is in the keel(?).

[Adamant]

Hi Lulworth,
I'mthe one who posted the lead drilling question. I have had to replace the keel bolts on the boat I'm working on now and also last years project boat. I was able to get the bolts to move last year by first spraying them with PB blaster thed hitting them with a sledge hammer to loosten them up. I used a stilson wrench with a 3' cheater bar and got them turning. these were screwed into nuts in pockets. Pulling up on the wrench as I turned they came up about 1/16" every turn.
The next boat proved to be a bit more difficult. This time the bolts went all the way through the lead with a recessed nut on the bottom. Ha I thought it would be a cinch to drive them down with a drift and cut them off as I went along. I got them down just enough to be able to cut off the nuts.
Turning, pulling, jacking, cussing and swearing didn't help and in frustration I decided to cut them off flush and drill new holes. I haven't yet decided if I'll angle the new bolts just enough to clear the old ones or offset the new floors. The old floors had the frames in pockets on center and I can cheat them to a shoulder instead.
I can tell you tht the bronze down inside the lead was in much better condition than the part in the dead wood. You might find a stilson right at the top of the lead will grab the bolt good enough to get it moving. If it twists it off you can always try drilling them out as you said.

Good luck, Don

[RGM]

Sounds like the easiest solution is to weed whack the old bolts flush with the top of the ballast keel, note/mark there locations. Then drill for new bolts slightly relocated. Either install them as pocket bolts or go all the way thru to the bottom of the ballast (counterbored to house nuts and flat washers. Since you are apparently replacing most of the backbone structure in way of the keel bolts don't worry about retaining/using the old layout/method. Good luck. You can also use a combination of thru bolts and pocket bolts. Art Read did.

[ 12-28-2005, 10:01 PM: Message edited by: RGM ]

[Don Kurylko]

David, is it possible for you to apply heat to the keel bolts? Lead melts at approximately 620 degrees F.; Bronze alloy at about 1800 degrees F. The lead around the keel bolt will melt long before the bronze even turns red. It might do the trick. Same principle as loosening epoxied fastenings.

[Lulworth]

Thanks for all the suggestions. I've successfully unscrewed three of the nine (I mis-reported above when I said 6) bolts so I can now answer my own question: The 5/8" Herreshoff keel bolts in the S-boat were self-threaded into the lead with a 3" threaded section.

The keel bolt accounting goes as follows: One was broken off long ago in a hurricane repair job from the '50's and was never replaced, I unscrewed 3, I sheared off 3 in the lead, and the two that pass through the deadwood (about 24" worth of deadwood) remain. The two in the deadwood are proving to be uncoorperative in the sense that they don't want to unscrew and they don't want to allow the deadwood to move. The deadwood is one enormous piece of resinous yellow pine (I guess) that is in superb shape so I have to be careful. I am slowly wedging the deadwood up the bolts but it has taken a lot of sledge hammer work to move the dead wood up just 1 inch. Another inch or two (so I can grip the bronze with a pipe wrench) and I'll cut the bast$%^ds off and drive them out of the deadwood one at a time with a drift.

RGM's suggestion of rearranging the bolts is probably the thing to do. Since the lead is quite wide at the forward end of the ballast, pockets that extend to the centerline would be impractical. I am dreading the three or four inches of lead drilling that I'm going to have to do and I don't have easy access to the bottom of the ballast so going all the way through is probably not an option for me. I am a bit hesitant to change the original HMC configuration but there is a lot to say for off-center bolts. I'll have to decide between pairs of bolts on each floor or staggered, off-center bolts. Place your vote here!

Don, it's too late to try your suggestion but I suspect that the heat sink provided by the 3500 lbs of lead would make heating the bolts a tough chore (made a bit easier by the lower thermal conductivity of lead compared to bronze).

Adamant -- You are across the Bay from me, what are you working on?

[sdowney717]

perhaps heating the bolts will allow you to slide the deadwood off easier? char the wood a little where it touches the bronze bolts.
Any chance you could drill down into the broken bolts and ream them out?

[emichaels]

This could perhaps be the dumbest of all possible solutions, but I might get credit for thinking a little out of the box.......so........what if you heated the bolts with a torch, a lot, and perhaps enough heat will go down the shaft of the bolt in the lead and soften the lead and loosen the bolt. The bolt will also experience a slight swelling in diameter due to the heat perhaps helping to loosen by enlarging the hole slightly.

Now I have gone back and read the latest post prior to mine and see I am late to this party.

Eric

[ 12-29-2005, 11:26 AM: Message edited by: emichaels ]

[emichaels]

Looking in Machinerys, an intersting note for those of us suggesting the heat the bolt method: Bronze goes down to approx 56% of its normal strength at leads melting point (621).

Eric

[sdowney717]

That is hot strength?
So if you heat it thus expanding it and then cool it with dry ice, perhaps the heating and cooling will help loosen the bolt.

[emichaels]

Originally posted by sdowney717:
That is hot strength?
So if you heat it thus expanding it and then cool it with dry ice, perhaps the heating and cooling will help loosen the bolt.

Yes the chart shows the strength at elevated temps relative to strength at 70 F.

Yeah that could be, I wonder if there would be some case hardening then that might make the bronze bolt more brittle than before

[Don Kurylko]

Although I have had no experience heating keel bolts to extract them from lead, I did remove a 1” diameter threaded steel pipe from the meting pot I used for casting my ballast keel. Mind, there was only about three inches of solid lead deal with but, once heated, the pipe came out easily. The lead only needed to be heated enough to release its grip on the threads. I then simply “unscrewed” it from the lead - no great leverage was necessary. Any diminished strength of the pipe was never an issue, as I suspect it wouldn’t be with the Bronze bolts. No harm in trying. It may work. If not, no big deal.

[Lulworth]

Don et al,

I've managed to free the deadwood without cutting the bolts and while one of them unscrewed easily, the other is not turning so for the pure excitement of trying something new, tomorrow I'll use my torch to heat the last bolt and see if I can pursuade it to turn before breaking. Good point about the hot strength being much lower.

The fun continues...

David

[Chan]

After reading the posts in this thread I have definately decided to cast bolt holes in my proposed ballast keel. The plugs will be 3/4" dowels with 1- 1/2" dowels for nuts and washers on the bottom. The finished product will be thru bolted keel bolts, always accessible.
I'm amazed anyone would consider self tapping anything in lead.

[Lulworth]

Well I tried heating the last bronze rod with a simple propane torch. I foccused the heat on the rod above the top of the lead for about 10 minutes then I put the pipe wrench on the rod and ... ta da ... it worked! Yes the yield strength of the bronze decreases but that of the lead decreases even faster with increasing temperature (I won't quote #'s here but trust me!) I wish I had done this on the three that broke off in the lead.

In my view, Mr Chan, a sloppy fit cast-in hole running the depth of the ballast (laying right where casting shrinkage voids might make an appearance) offers, in service, more bronze rod-length overwhich failure might occur. If I were doing it, cast-in pockets might be an attractive option. For HMC self-threading bronze must have been the economically prudient thing to do -- I'd bet it's easier and the part that was threaded into the lead was pristine.

[Don Kurylko]

Right on David! [img]smile.gif[/img] Thanks for taking the effort and helping us all expand our WBF knowledge base yet again.

Cheers and good luck with the rest of your project,
Don