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Thread: Lead keel construction method

  1. #1
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    Default Lead keel construction method

    LFH was an advocate of eliminating the largest, most rot prone and possibly the most challenging part to replace in a sailboat, the timber keel, and replacing it with the lead ballast keel. He maintained that lead with the appropriate % of Antimony added has the same strength as an equally sized piece of White Oak. If this is the case, would it be possible to build an epoxy laminated style construction as advocated by the Gougeon brothers and eliminate the timber keel? I imagine you'd need something to fasten everything to while building. You'd want to build upside down to facilitate construction. It would need some strength in order to flip the hull over. What I envision is a 3 inch (maybe more, maybe less) thick plank/plug that you build on and once the hull is flipped upright, you cut it out with a reciprocating saw, plane the hole smooth with an electric plane and possibly slicks, chisels etc. then lower the hull onto the lead keel. Fastening would be with typical heavy keel bolts through the floor timbers/castings and possibly large screws through the garboard area. Keels are supposed to be held by the floor timbers anyway so that shouldn't be a problem. You've removed a large expensive rot prone part and possibly added weight down low where it does good.
    I'm talking large vessels in the 40-60 foot plus range.
    Would this be hull shape dependant? I'm pretty sure big Ti was built this way and she's 72 feet. Nereia was built that way, as were many of the Ticonderoga style hulls if my memory serves me correctly.
    Any thoughts on how this might be done or why it could not be done, with this style of construction?
    Picture one of Peterson's Coaster schooners for an example of hull shape I'm anticipating if hull shape makes a difference.
    Thanks guys,
    Daniel
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    Default Re: Lead keel construction method

    Are you talking about having a vertical sided casting with the garboards stem and stern post lapping down the sides and ends?

    If so, why not use the plug that you will cast the keel from as a dummy including the keel bolt holes, wax it or apply some other release agent and build the boat round that. Then pop it out, send it to the foundry and lower the boat over the result.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Lead keel construction method

    Nick is ahead of me here, as usual, but I am in accord with his idea. The garboard rabbet is, normally, made directly into the mold plug for this kind of construction. It was the R boat "Live Yankee" that L. Francis fist used this concept with. "You could walk on her lead" was his comment about it. I might add that the floors would best be made of bronze castings that bolt directly to the ballast keel. Another way would be to make floors of sheet bronze that is Tig or Mig welded for the flanges that support the garboards.

    Also, "Live Yankee" was beaten by the R boat "Pirate" at the Larchmont R boat nationals in 1929 with skipper Matt Walsh at her helm. None of the LFH clipper bowed ketches had their wooden keels eliminated by this form of construction. "Bounty" recently had her keel replaced but, I believe it was of wood. This was done before she was taken to France, bny her new owner, several years ago.
    Jay

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    Default Re: Lead keel construction method

    I thought the Ticonderoga models were usually without keel timbers, my mistake. Either way, the idea was used by LFH. As for your question Nick, what I envision is the same shape of keel that any other ballasted keel boat would have. In this case, a long rectangular in profile, wider mid length and tapering toward the ends when viewed from above. A rabbet cast into it at the top, as the keel timber would have to accept the garboard planks. Only in this case, the "garboard planks" would simply be the bottom edge of the laminated construction. Still requires screws through into the rabbeted lead casting. The ends are "scarfed" and bolted to a keel timber where the after end of the keel would be and the stem would connect. Of course the ends would be nibbed so as not to taper off to a fine point. I guess structurally, I envision simply casting the keel taller than called for, into where the timber keel would have been and not really changing anything else. Might mean shortening the length of the keel casting as there's more weight concentrated toward the center of the length of it. The portion of the keel abaft the lead wouldn't need to be so long so it would be easier to find timbers. That part would remain the same as original. Is my idea out to lunch. It makes so much sense to me that I don't understand why nobody else has done it. But if LFH has managed to do it successfully, why can't someone else?
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    Default Re: Lead keel construction method

    Unless I'm missing something are you suggesting there wouldn't be any frames or floor timbers, whether wood or metal (as Jay mentions)?
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    Default Re: Lead keel construction method

    NO, I'm suggesting that cast bronze floors would tie the frames (Laminated) into the lead keel with keel bolts as in any other classic traditional construction. Just that the wood between the floors and the lead would be eliminated and replaced with more lead.
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    Default Re: Lead keel construction method

    Lead antimony is not as strong as a small, perfect specimen of dry white oak. As for a large wet timber with the knots, checks and other flaws, the casting is likely to be at least as strong, or stronger.
    http://www.wood-database.com/white-oak/
    http://vulcangms.com/cast-lead-antim...ys-properties/

    There are some issues to consider;

    A shorter, taller casting will have a higher CG and different moment of inertia.

    Sealing requires attention if, as it sounds, the lead is exposed inside the hull.

    Nick's idea to use the plug as a pattern sounds good as long as the solidification shrinkage issues in the casting are accounted for. The bolt holes will move, so it might be better to use the plug as a drilling guide to locate the holes after casting.

    Referring back to Nick's signature about the power of the web, there is a knee jerk reaction to suggest an unwanted alternative approach. Plasma or water jet cutting of thick steel plates as a lower cost, higher strength alternative comes to mind. You can produce a keel with the same weight as lead with the advantages of smaller deadwood while keeping the CG and inertia problems associated with a different shape. As a bonus, corrosion issues will arise.
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    Default Re: Lead keel construction method

    Quote Originally Posted by Sailor View Post
    As for your question Nick, what I envision is the same shape of keel that any other ballasted keel boat would have. In this case, a long rectangular in profile, wider mid length and tapering toward the ends when viewed from above. A rabbet cast into it at the top, as the keel timber would have to accept the garboard planks. Only in this case, the "garboard planks" would simply be the bottom edge of the laminated construction. Still requires screws through into the rabbeted lead casting. The ends are "scarfed" and bolted to a keel timber where the after end of the keel would be and the stem would connect. Of course the ends would be nibbed so as not to taper off to a fine point. I guess structurally, I envision simply casting the keel taller than called for, into where the timber keel would have been and not really changing anything else. Might mean shortening the length of the keel casting as there's more weight concentrated toward the center of the length of it. The portion of the keel abaft the lead wouldn't need to be so long so it would be easier to find timbers. That part would remain the same as original. Is my idea out to lunch. It makes so much sense to me that I don't understand why nobody else has done it. But if LFH has managed to do it successfully, why can't someone else?
    Herreshoffs designs bolted the stem and stern knee to the top of the full length casting. If you are envisioning a three part structural keel you are building a weak boat for very little saving in time or effort.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Lead keel construction method

    Why so complicated if it's epoxy construction? Just use a plank instead of the keel, plywood would be good, sheath the exterior then bolt on the lead ballast. Laminated inner stem and sternpost continue over the ballast to be bolted to it. Laminated outer stem and sternpost to be bolted to the ends of the ballast (bolts in pockets). No rabbets, no knees, no scarfs. Laminated leaf spring floors inside to bolt the ballast to. Thickened epoxy between ballast and plywood keelplank to even out all the irregularities and assure a perfect fit and glue the ballast to the boat. Build can be upside down or right side up, as you wish.

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    Default Re: Lead keel construction method

    I'm not seeing any particular advantages to your contemplated option, either in material saved or labor (which sounds even greater).
    "It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so."

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    Default Re: Lead keel construction method

    Quote Originally Posted by Rumars View Post
    Why so complicated if it's epoxy construction? Just use a plank instead of the keel, plywood would be good, sheath the exterior then bolt on the lead ballast. Laminated inner stem and sternpost continue over the ballast to be bolted to it. Laminated outer stem and sternpost to be bolted to the ends of the ballast (bolts in pockets). No rabbets, no knees, no scarfs. Laminated leaf spring floors inside to bolt the ballast to. Thickened epoxy between ballast and plywood keelplank to even out all the irregularities and assure a perfect fit and glue the ballast to the boat. Build can be upside down or right side up, as you wish.
    I can't for the life of me imagine why anybody would spend the money on things like cast bronze floors and even lead ballast on a plywood boat the likes of those described in this thread. I mean, really.

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    Default Re: Lead keel construction method

    Is rot in the keel really a common problem? In decks, in planks, in frames, sure. Worms in keels, OK. But I'm surprised to read that rot in the keel is a common enough problem to be deserving of an off the wall solution.

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    Default Re: Lead keel construction method

    I have no intention of using ply Bob. Not a chance. I guess the reason I'd contemplate this is that flipping a boat with a lead keel that was built into it upside down is a bad idea. By adding the lead afterwards, you're not flipping 10 tons of lead as well as a boat. I guess I'm thinking out loud in creating this thread with the added bonus that the voices can talk back to me and have intelligent things to say instead of simply "yes, great idea." or "no, that's terrible". I am looking for the why and how of it all I guess and if the why or how has no answer or the answer steers one clearly away, I'll stick with a known method of construction. But no way no how will there be plywood in the boat I want to build. At least not in any structural capacity. I'm not hanging 10 tons of lead off a few glued up sheets of plywood.
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    Default Re: Lead keel construction method

    If so, why not use the plug that you will cast the keel from as a dummy including the keel bolt holes
    The reason *not* to that pops into my mind is that lead has a considerable amount of shrinkage when cast. You'd need to figure out a way to account for that --possibly by gluing in strategically-located splines during the final process of fitting the lead to the wood?

    And I suspect that's about the entirety of my useful knowledge in this conversation.

    Alex

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    Default Re: Lead keel construction method

    Quote Originally Posted by Pitsligo View Post
    The reason *not* to that pops into my mind is that lead has a considerable amount of shrinkage when cast. You'd need to figure out a way to account for that --possibly by gluing in strategically-located splines during the final process of fitting the lead to the wood?

    And I suspect that's about the entirety of my useful knowledge in this conversation.

    Alex
    How much is considerable, have you a percentage? Anything that could not be accommodated with thickened epoxy?
    Not to say that this is a good strategy anyway, but just curiosity.

    OK, about 1/8" per side on an average keel, http://www.frederickspassage.com/new...assage_020.htm

    So the length would be an issue if the forefoot is to be wood.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Lead keel construction method

    My limited experience in restoration shows keels generally crap out after 50 years, some earlier, some later, much depending on the quality of wood, where the boat is used and how it has been maintained......how long are you expecting to live?

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    Default Re: Lead keel construction method

    The cutout hole could be cut after the keel is cast so the hole size matched to whatever size the casting comes out to. I'd make the casting to accommodate shrinkage of course. I don't imagine I'll be sailing her 50 years from now but I would love to still live aboard and sail at 90 if the health gods care to smile on me for that long. Heck, at the rate I'm going, I may still be building her in 50 years. LOL
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    Default Re: Lead keel construction method

    May I ask why you insist on sealing the planking to the lead casting? The only thing you gain by it is raising the lead a few inches and create additional construction problems. LFH had no other choice but you have. Ok, you don't like ply, use something else. You need a hard chine and a flat surface to bolt the keel to, create them however you like. The strenght will come from the lead anyway, as long as you bolt stem and stern onto it. But of course then you can not "walk on the lead" like LFH did.

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    Default Re: Lead keel construction method

    How much is considerable, have you a percentage?
    Depends a bit on the alloy, from what I know. A quick search is getting me anywhere from .65% for lead + tin + antimony to 1.13% for pure lead. Check the shooter's forums for details. Shrink data is a lot more critical for bullets measured by the thousandth of an inch than for keels measured by the sixteenth. But the takeaway message would seem to be that the greater the expanse of lead --length or width of a keel-- the more that percentage will become an issue to account for.

    I haven't a clue whether thickened epoxy could compensate. That's way, way outside my realm of experience --as is most of this thread's line of enquiry.

    Alex

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    Default Re: Lead keel construction method

    I guess I like the idea of removing such a large expensive rot prone part. If it's not practical, I have some/will get some Black Locust that would suit just fine for the purpose of plank keel to mount the lead on. And deadwood forward and abaft the lead too. Stem and sternpost.... I'll use BL in as much of the structural components as I can, it will likely be availability dependant.
    Last edited by Sailor; 07-14-2017 at 10:11 AM.
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    Default Re: Lead keel construction method

    The shrink factor of lead is so minimal as to not be any any significance when casting a keel. Bronze is another matter and I use a shrink scale when I design or make a casting pattern.
    Jay

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    Default Re: Lead keel construction method

    Quote Originally Posted by Sailor View Post
    I guess I like the idea of removing such a large expensive rot prone part. If it's not practical, I have some/will get some Black Locust that would suit just fine for the purpose of plank keel to mount the lead on. And deadwood forward and abaft the lead too. Stem and sternpost.... I'll use BL in as much of the structural components as I can, it will likely be availability dependant.
    If it is not a full length ballast keel but has timber dead woods ford and aft, the keel must be cast with a scarf at each end, long enough to take at least 3 bolts into the wood.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Lead keel construction method

    Quote Originally Posted by Jay Greer View Post
    The shrink factor of lead is so minimal as to not be any any significance when casting a keel. Bronze is another matter and I use a shrink scale when I design or make a casting pattern.
    Jay
    In theory, I'd agree. However, I've cut up a number of lead keels and they are often full (or empty, as the case may be) of surprises. The uniformity of the shrinkage is dependent upon the uniformity of the cooling rate of the casting. The cooling rate can be quite variable in a large lead pour because the outside hardens much faster than the interior of the casting. I've seen many keels that shrank across the top of the pour as they cooled, indeed, I'd say that's to be expected in most all ballast keels. This creates a depression of as much as an inch deep in the top of the keel in the mold. This can be accommodated by pouring a bit of additional lead into the depression as it develops. That won't guarantee a solid casting between the two surfaces, but will that won't probably cause be any problem as the keel bolts will go right through into the main body of the casting.

    What I was surprised to find the first time I encountered it, was what I call a "geoded casting" but is properly termed "shrinkage porosity." I've seen maybe three of them when cutting up keels for recycling. Shrinkage porosity occurs when the outside of the casting cools first, while the inner part cools at a slower rate. The cooled outer part has done its shrinking at the surface and is hard and stiff, but the inner portion of the casting is still molten and continues to cool and shrink as it cools. As it shrinks internally, the metal pulls itself apart creating a void, the sides of which have a crystalline surface, like a geode. These voids aren't all that large, or so it seems, generally not more than several inches in length the few I've seen. It's all the same amount of lead that's poured, so the weight isn't affected, but sometimes the shrinkage occurs inside the ballast keel as well as outside the keel, the former not affecting the shape of the casting as the latter does, resulting in an apparently smaller shrinkage factor than one would expect. (This is, of course, theoretical and isn't likely to make a lot of difference in a keel casting.) This is different than "gas porosity" or "blow holes," where gas trapped in the molten metal leaves "bubbles" in the casting or pits on the surface where the gas "blew out" of the cooling pour.


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    Default Re: Lead keel construction method

    Quote Originally Posted by Sailor View Post
    I guess I like the idea of removing such a large expensive rot prone part. If it's not practical, I have some/will get some Black Locust that would suit just fine for the purpose of plank keel to mount the lead on. And deadwood forward and abaft the lead too. Stem and sternpost.... I'll use BL in as much of the structural components as I can, it will likely be availability dependant.
    I understand part of your reasons. No big keel, no rot. What I don't understand is why do you assume a big keel timber if using epoxy methods. A vessel 60' plus buildt using epoxy is either sheated strip, cold molded or a combination. You do not use a traditional big timber keel on such a vessel. The keel is usually laminated and sheated along with the hull then you build up the skeg, sheath it, then you bolt on the ballast. And laminating timber is making your own plywood after all.

    Take a look at this build: http://forum.woodenboat.com/showthre...ht=Venus+ketch
    This is exactly what you want. Bruce bolted the ballast only to the inner keel, so his is substantial. If you bolt to the floors and also bolt the stem and sternpost to the ballast the inner keel is reduced to providing a place for the planking to land and asure water does not come in. There is nothing to rot except the planking. The false keel is protected by the ballast. If yoh choose your underwater shape well you also don't have any traditional deadwood.

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    Default Re: Lead keel construction method

    The shape is chosen for me by the architect. That's not variable. I understand I'll be casting the scarf joints into the ends. I guess I envision large timber between the floors and lead as in a traditional boat rather than a thinner build in place "ply" between them. I want to build upside down to facilitate work on the planking, hull fairing etc but don't want a big chunk of lead waving in the air or having to be rolled over once complete and figured assembling the lead to the hull after righting the hull would be less work. Maybe I just build her so the rabbet portion is timber and keep the keel square in section without rabbets cut out at the top....
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    Default Re: Lead keel construction method

    What are you talking about, of course it's variable. You tell the guy long keel, short keel, deep forefoot, cutaway forefoot, fin keel, skeg or no skeg, underhung rudder, transom rudder and all your other wishes. He then tells you the price.
    By the way if you plan on doing it like you propose tell the arhitect, moving 10t of lead up a few inches changes the balance of the boat and you might end up with a tender one that does not sail as designed.

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    Default Re: Lead keel construction method

    A local friend had his lead casting done by a company that's widely advertised and commonly recommended. It was a disaster when it arrived, late and misshapen. .
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    Default Re: Lead keel construction method

    ...an epoxy laminated style construction as advocated by the Gougeon brothers...
    is plywood to a traditionalist.

    You are only talking about 3" +/- removable plank, so just how deep would the final keel be? A better description of the final geometry would help. Moving the CG an inch is one thing, a foot, is another.

    Nick's link in Post 15 gives a shrinkage factor of 5/16inch per foot, 2.6%. That is close to 3" in 10 feet. http://www.riparia.org/ketch/keelpouring.html has some good anecdotal information on shrinkage and bolt holes shifting. As usual, you keep finding the information you want to link on this forum. Thread: Shrinkage in lead casting? It is worth a click just to read Jay's story about Squeaky and the gophers. Nice pic of a shrinkage cavity in post #22 too.

    Interesting link to Bruce's build thread. The density of a 60% lead to 40% concrete mix by volume has the same density as steel.


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    Default Re: Lead keel construction method

    The plans are purchased, the shape is fixed. I understand fully how adjusting ballast can have an affect on GM, transverse, longitudinal, ultimate and initial stability. I've studied it enough to know what the effects would likely be and won't go moving weights around without Bill's advice. The boat was designed to be plank on frame and I have to accept that I will never have the skills nor the time to build her that way. I will go ahead and cold mold her on laminated frames, or strip planking with some diagonal layers over top. Not sure exactly how the hull will be laid up yet but I've discussed it with Bill when I visited him to purchase the plans. I'm just exploring ways to remove rot prone parts, simplify the construction etc. I had mentioned earlier the design was one of Peterson's Coaster schooners to give an idea of hull shape. I wish I could post images, I'd show how the lead (or iron if I want) is designed.
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    Default Re: Lead keel construction method

    "rot prone parts". How about looking at why the parts are prone to rot and fix that, rather than removing them. How about having a modern tight leak proof deck for starters rather than a traditional laid deck?
    Acetic acid in the wood is prone to cause "lead rot", you might want to look into that a bit more.

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    Default Re: Lead keel construction method

    You mean one of this things? http://uk.boats.com/sailing-boats/19.../#.WWnWyIGxVDs

    It will not work, the lead needs to extend under the stem and sterpost knees.

    A blog about a build of asmaller one. Epoxy strip plank. http://provincetownwoodenboat.blogspot.de/2013/

    FAQ page has instructions about posting photos.

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    Default Re: Lead keel construction method

    Quote Originally Posted by Sailor View Post
    The plans are purchased, the shape is fixed. I understand fully ... I had mentioned earlier the design was one of Peterson's Coaster schooners to give an idea of hull shape. I wish I could post images, I'd show how the lead (or iron if I want) is designed.
    Sorry, you did say. Like a larger version of this then? http://images.boats.com/resize/1/5/4...00&w=600&h=600
    As for the time to build traditionally, this title says a lot: Thread: 38 years of work launched
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    Default Re: Lead keel construction method

    Machinery's Handbook "casting shrinkage allowance" say's...
    "The usual allowance for each foot in length", Lead = 5/16 inch per foot.

    I have cast quite a few lead items from 6 to 8 foot long keels and many 100-300 lb window weights for large double hung windows, all in wooden molds and this allowance is pretty typical. Early on I was shy and added some extra, but after days of planing it back to size I will now say that this is pretty accurate.
    (There may be a wild card with Antimony as it does expand when cooled, but I have always ignored that and it never showed up. I think it would take a lot of Antimony to change that allowance. This was all before Google and curiousity led me here http://nvlpubs.nist.gov/nistpubs/jre...n5p697_A1b.pdf)

    So... Today I would make a 10 foot long keel mold 50/16's of an inch longer than the finished product, or 3-1/8 inches. I would use the same formula for the width and depth.

  34. #34
    Join Date
    Feb 2002
    Location
    Shubenacadie NS
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    3,689

    Default Re: Lead keel construction method

    Maybe I just follow the good brother's book and build her upright. At the size she is, turning the hull may be more trouble than working overhead to laminate her hull up.
    If one advances confidently in the direction of his dreams, and endeavors to live the life which he has imagined, he will meet with a success unexpected in common hours.
    -Henry David Thoreau-

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