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Thread: 600 lb Lead Keel Mold

  1. #1
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    Question 600 lb Lead Keel Mold

    Hello experts! I need to pour a lead ballast keel for my Sommes Sound 12 1/2 and I am to the point of creating the mold. A few questions:

    1) Is there a type of wood that is preferred, or, more importantly, should be avoided?

    2) Has anyone tried lining the mold with Hardi plank (concrete impregnated paper product)? I expect it essentially holds no moisture.

    3) One much older post reads: "Smear a layer of grease on the inside of your wood mold. I did it and it works. Make sure you get grease on any part that the lead will contact, including any cross braces at the top of the mold.
    The grease will smoke a bit and may even catch fire, a minor detail. But it will prevent any moisture from boiling out of the the mold wood and giving you a rough finish on the lead."

    I await your sage advice.

    Thank you!

  2. #2
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    Default Re: 600 lb Lead Keel Mold

    I built a mold for the 300 lb lead ballast for my Herreshoff Biscayne with plywood. It was open top, IIRC the mold for a Somes or Haven 12 1/2 is closed top. I think this thread has details for the keel pour for a Somes: http://forum.woodenboat.com/showthre...es-Sound-Build. I found it very helpful.

    I coated the inside of my mold with waterglass (Sodium silicate) and scorched it with a weed burner before pouring to eliminate any moisture. Any moisture in the mold will boil off when the molten lead hits it, with potentially very dangerous consequences.

    I suppose grease would also work, but then you may need to degrease the casting before you apply any coating to it.

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    Default Re: 600 lb Lead Keel Mold

    Quote Originally Posted by nrs5000 View Post
    I built a mold for the 300 lb lead ballast for my Herreshoff Biscayne with plywood. It was open top, IIRC the mold for a Somes or Haven 12 1/2 is closed top. I think this thread has details for the keel pour for a Somes: http://forum.woodenboat.com/showthre...es-Sound-Build. I found it very helpful.

    I coated the inside of my mold with waterglass (Sodium silicate) and scorched it with a weed burner before pouring to eliminate any moisture. Any moisture in the mold will boil off when the molten lead hits it, with potentially very dangerous consequences.

    I suppose grease would also work, but then you may need to degrease the casting before you apply any coating to it.

    Thank you. The mold is partially closed -- the first 3' or so from aft (the mold is build upside down. The plans call for a single vent, but I plan to put in two for good measure.

    I'm pleased to hear that you had success with Sodium Silicate. Residual moisture is what scares me, hence the Hardi idea.

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    Default Re: 600 lb Lead Keel Mold

    The fiber cement (Hardi) board idea is intriguing. It sure doesn't burn, but will degrade and crumble at wood burning temperatures. It wouldn't be strong enough to be the mold itself, but as a liner its possible. You'll want to make sure you don't get something that's pre-primed, which much of it is these days. Fiber cement board is made is many shapes and sizes now, you may be able to find something that isn't siding that is more suitable.
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    Default Re: 600 lb Lead Keel Mold

    Most boatyards also bury the mould in the ground and ram the earth well. Both for support and to contain any leaks.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: 600 lb Lead Keel Mold

    This is the thread Jeff put up specifically for the keel he poured.
    http://forum.woodenboat.com/showthre...-lead-for-keel

    I've not heard of this greasing the mold before, sodium silicate (aka "water glass") yes but not grease. Cement board has a lot of texture, the lead tends to come out a bit coarse anyway, something to consider? Don't over think it, I was there when Jeff poured his keel and the mold didn't burst into flames, neither did the one for a 400lb keel I did for my boat.
    Steve

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    Default Re: 600 lb Lead Keel Mold

    Allow for shrinkage. IIRC mine shrank about 1/16” per foot. Plywood with sodium silicate. If you do it in ground put a couple of chains under mould to pull it out.

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    Default Re: 600 lb Lead Keel Mold

    The chains are a good point. The other thing is to do a test-run of your pouring system, water will work, just dry things out before you pour for real. The key is to get a sense of how that molten lead is going to come our of the spigot. It is easy to over or undershoot the mold. How much of a splash zone do you need?
    Steve

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    Default Re: 600 lb Lead Keel Mold

    Quote Originally Posted by Andrew Donald View Post
    Allow for shrinkage. IIRC mine shrank about 1/16” per foot.
    1/16" sounds about right to me too.

    Bud McIntosh covers this in "How to Build a Wooden Boat". He says to pour your ballast as lofted and then build off the actual shape. Makes sense to me.
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
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    Default Re: 600 lb Lead Keel Mold

    I also used Bud McIntosh's book as my bible when I built my 20' Stadel gaff pilot sloop, but I got the instructions for building the ballast keel mold from page 169 of Chappelle's "Boatbuilding". Keel was 900 lbs.
    I don't remember if I scorched the inside or not, this being over 30 years ago, long before this Forum existed.
    Sure could have used the help back then!
    I had a foundry pour the lead and it all came out OK.
    Post #6 provided the link to the thread that should answer all questions.
    I was born on a wooden boat that I built myself.

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    Default Re: 600 lb Lead Keel Mold

    Re the Hardiplanks, I've built several houses that used them. They do hold moisture until they are painted after drying out, so be aware of that.
    There is nothing quite as permanent as a good temporary repair.

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    Default Re: 600 lb Lead Keel Mold

    I'm the Jeff that did the SS mold referenced by Steve. My thread contains photos that I had hosted by Photobucket which has gone beserk. But they are still mostly legible. I've more photos if you need. Do you have the plans from John Brooks? I don't remember if he recommends a material. I used common pine and coated with sodium silicate. I'd do so again. I suspect that hardiplank will blow up with the heat. I mean... it won't literally blow you to smithereens, but it will badly crumble and possibly contaminate the lead. You should certainly do a smallish test pour before using it for the actual keel. My best advice is to pour slowly. We filled the mold too fast and I has some shrinkage holes that had to be filled. I would not bother to bury this in the earth. I think that's for much bigger keels.

    Jeff

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    Default Re: 600 lb Lead Keel Mold

    You might also consider lining the wood mold with ceramic fiber. I put the waterglass over the fiber for a 1200# casting

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    Default Re: 600 lb Lead Keel Mold

    I did an 800 kg pour back around 2012. A plywood mold buried in weak cement. I had 3/4" wooden dowels where the keelbolts would go. The dowels turned to charcoal but it made drilling them easier.
    I would rather have questions that can't be answered than answers that can't be questioned


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    Default Re: 600 lb Lead Keel Mold

    +1 to post #11. I work with Hardie frequently and it definitely gets wet and takes time to dry. The installation specifications call for large clearances at roof lines and decks, presumably because it is vulnerable to moisture damage.

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    Default Re: 600 lb Lead Keel Mold

    I have cast a few keels in wooden (and other) molds and my experience has been is as follows:

    My first pour over 40 years ago now was a small one, 500lbs lead, a coal fire, steel pipe tripod with a 3/16" thick steel crucible rendered from an old 20 gal propane bottle. Poured into 2x wood boards screwed together to form a box with an open top, no problem.
    For my second pour I was talked into using Sodium Silicate coating. It takes a while to dry and made the worst mess of any pour before or after as it floated and flaked off the surface and contaminated the casting.
    I have tried steel molds it is more work and time in welding and there is a risk of the lead actually soldering itself to the mold.
    "Coatings" tend to burn off and can be potentially a health hazard. I would not do it, especially with a petroleum based product...
    I have tried green sand molds (same stuff that I used for bronze) and that contaminated the surface of the lead making it impossible to plane. Hateful...
    In about a half dozen pours, some over a thousand lbs, Dry Wood all by itself, carefully placed in a hole in the ground and backfilled with sand to contain any spill or leaks gave me good results.

    Well fastened 2x' planks with external cleats and threaded rod for bolts (about double what you might do to keep a concrete pour from bulging the form) with an open top carefully leveled.

    A way to note the temperature of the lead is a good investment.
    It doesn't want to be any hotter than it takes to make it liquid, about 650f A laser pyrometer that reads up to about 1000f is good, they don't cost much.

    A wood or coal fire is difficult to regulate and will tend to keep heating long after the lead is molten with no easy way to shut it down. Gas, or an oil burner worked the best for me. Those can have safety devices installed if you want that.

    When it is all ready to go and molten, the whole pour usually takes less than 5 minutes. There is a lot of preparation for that 5 minutes!

    My old 1914 machinery's handbook says for casting shrinkage allowance in lead, use 5/16" per foot in length. This is what I used to generate the molds and almost exactly what I experienced.

    Always keep in mind that molten metal is dangerous, and don't ever stop thinking about what can go wrong.

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    Default Re: 600 lb Lead Keel Mold

    Yes, I do have Brooks' plans (cost me an extra $50! ). The keel that results from his plans differ from the keel for the Haven, which is what much (most?) of the drawings seem to depict. So I built a foam keel "blank" that matches Brooks' keel plans and have been working around that.

    To your question, he suggests "very dry pine." My concern is "how dry is dry enough, i.e., *very* dry?" Since I live in FL (the AC capital of the world), I am considering bringing the lumber into the house for a few months to let the AC dry it out. Since I will be getting my lumber from a "big box" store I really have no way of knowing just how dry it is.

    Thanks for your reply!

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    Default Re: 600 lb Lead Keel Mold

    Excellent idea about the dowels for the bolt locations. Is a specific ply that you would recommend or avoid (e.g., OSB)? OSB, is, of course, nice and cheap. ;-)

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    Default Re: 600 lb Lead Keel Mold

    Thank you for this. Not trying to overthink it (although that is always a tendency for a first-timer), but also want to avoid an explosive event. ;-)

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    Default Re: 600 lb Lead Keel Mold

    The idea would be to use it as a lining, but given the many posts I've seen below, I expect I will go with either plywood (wondering if, for example, I should avoid OSB) or pine (as Brooks recommends). I'm thinking of setting up a small "foundry" to clean up lead and make ingots. Should I do that I may make a test mold with Hardi and see how that works out.

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    Thumbs up Re: 600 lb Lead Keel Mold

    Quote Originally Posted by Canoeyawl View Post
    I have cast a few keels in wooden (and other) molds and my experience has been is as follows:

    My first pour over 40 years ago now was a small one, 500lbs lead, a coal fire, steel pipe tripod with a 3/16" thick steel crucible rendered from an old 20 gal propane bottle. Poured into 2x wood boards screwed together to form a box with an open top, no problem.
    For my second pour I was talked into using Sodium Silicate coating. It takes a while to dry and made the worst mess of any pour before or after as it floated and flaked off the surface and contaminated the casting.
    I have tried steel molds it is more work and time in welding and there is a risk of the lead actually soldering itself to the mold.
    "Coatings" tend to burn off and can be potentially a health hazard. I would not do it, especially with a petroleum based product...
    I have tried green sand molds (same stuff that I used for bronze) and that contaminated the surface of the lead making it impossible to plane. Hateful...
    In about a half dozen pours, some over a thousand lbs, Dry Wood all by itself, carefully placed in a hole in the ground and backfilled with sand to contain any spill or leaks gave me good results.

    Well fastened 2x' planks with external cleats and threaded rod for bolts (about double what you might do to keep a concrete pour from bulging the form) with an open top carefully leveled.

    A way to note the temperature of the lead is a good investment.
    It doesn't want to be any hotter than it takes to make it liquid, about 650f A laser pyrometer that reads up to about 1000f is good, they don't cost much.

    A wood or coal fire is difficult to regulate and will tend to keep heating long after the lead is molten with no easy way to shut it down. Gas, or an oil burner worked the best for me. Those can have safety devices installed if you want that.

    When it is all ready to go and molten, the whole pour usually takes less than 5 minutes. There is a lot of preparation for that 5 minutes!

    My old 1914 machinery's handbook says for casting shrinkage allowance in lead, use 5/16" per foot in length. This is what I used to generate the molds and almost exactly what I experienced.

    Always keep in mind that molten metal is dangerous, and don't ever stop thinking about what can go wrong.
    Thank you for this wonderfully detailed reply. I'm thinking of building the form of 2x pine and keeping it inside the AC for a month or two to ensure it is nice and dry. The plan is to surround it in sand to contain spillage but not completely bury it. I expect that, by using 2x stock, it will hold up to the lead. As for the crucible/foundry, I will likely follow what Bob Emser did with his pour for his Haven keel on his "Art of Boatbuilding" YouTube channel.

    Thanks again!
    Last edited by bogolese; 11-10-2021 at 09:53 AM.

  22. #22
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    Default Re: 600 lb Lead Keel Mold

    lead gets "cleaned up" when the slag is raked off. you'll be doubling your work if you elect to do this twice..as long as the donor lead will fit into the pot, I'd call it "good 2 go".. i'd avoid adding wonderboard to the mold...try as i may to visualize it being used..I can't see any advantage. A thoroughly dried cement mold alone will do just fine. If possible dry the mold out in an , improvised oven for a week or three, before moving it into it's pouring position- don't allow it to reabsorb moisture, between the two steps
    Last edited by the_gr8t_waldo; 11-10-2021 at 10:35 AM.

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    Default Re: 600 lb Lead Keel Mold

    One thing I would like to add that hasn't been mentioned: make sure that your mold is TIGHT. Melted lead is as fluid as water but 10x the weight so it will push through the smallest voids. I learned this the hard way when about 50kg of my lead spilled into the sand around my mold.

    My final solution was a thin welded steel lining inside the wooden mold. My shape was a simple "plank" so this worked. Only problem was the steel lining expanding a little more than I anticipated so there was not enough room inside the box. This resulted in slight waves on the sides. Otherwise it worked great.

    14082013224.jpg

    ballast.jpg

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    Default Re: 600 lb Lead Keel Mold

    Thank you. Bob Emser built a very similar mold for his Haven build (see his "Art of Boatbuilding" YouTube channel), so I will reach out to him to see how he ensured his mold was tight. There was some flashing that he had to cut off where the lead worked its way into seams, which I expect.

    Also, the pallet jack is an excellent idea!

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    Default Re: 600 lb Lead Keel Mold

    It is not at all difficult to cobble up a means to melt a relatively small amount of lead. I use a plumbers melting pot and burner but one can just as well use a good camp stove and an old dutch oven. With this in hand one is ready to do a any number of test melts/pours that it takes to get used to the idea and to experiment with mold material. I heartily encourage this sort of experimentation for it will teach more in one go than sixteen days of reading on the internet.

    I had no problems using sodium silicate whatsoever. It dried rapidly to a hard coating. I did two coats on my forms as well as on the test mold that I did to, you guessed it, test the sodium silicate.

    bogolese, if you're concerned about the moisture content of your pine, a test will tell the tale. I had no problem with mine and I live in the PNW, a place not known for dry weather. The local lumber yard stores their pine lumber outside under a covered porch roof.

    Jeff

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    Default Re: 600 lb Lead Keel Mold

    I miss my time in PNW. Thank you. That makes me much more comfortable!

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    Default Re: 600 lb Lead Keel Mold

    We poured about 650 lbs. of lead for our Gartside 170 keel. The sodium silicate also worked well for us. Three coats as I recall. In addition, I applied muffler cement on all the seams. The mold was mostly construction lumber. There were no moisture surprises nor were there any leaks. I added some antimony to make machining easier. It seemed to help quite a bit. Not a whole lot melted as it has a much higher melting temp. than lead. Striking the keel with a hammer gave a nice gong sound. Striking the lead bricks prior to melting gave a dull thud.

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    Default Re: 600 lb Lead Keel Mold

    I made a thick slurry of sand and sodium silicate and ran a fillet of it in the seam between the bottom and sides of my mold. No leakage. I put the mold on a sun porch in my house for a few days before the pour to get it nice and dry.

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    Default Re: 600 lb Lead Keel Mold

    Wow! Sounds like Sodium Silicate is the preferred way to go, based on an unscientific poll of the posts here. I will most certainly look into it. I also like the ideas or sealing the seams. Thank you. So happy to have this wonderful resource.

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    Default Re: 600 lb Lead Keel Mold

    I have a 400lb one to pour and have made the mold out of well dried construction lumber planks. Going the open sided type of pour as it is 2" thick.
    For the joints, stove mastic and let it dry well and the dowls for the keel bolts.
    The lead pot is a propane cylinder with the top cut of and hinged. Trunnions welded to each side to pivot on axle stands and a the 'spout' a bit of tube welded near the bottom and coming up at 45. Think a tea pot, so it flows out from the bottom with the dross left on top.
    Heat is by a central heating diesel oil unit of 30kw with a sheet metal jacket round and under the pot, so the heat swirls around the pot a couple of times, then out of a flue.
    Canoeyawl's post is especially helpfull. Not going to silicate the wood.
    All this has been set up for a while, just work has got in the light and possibly a bit of 'trepidation'
    A2

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    Default Re: 600 lb Lead Keel Mold

    Quote Originally Posted by BBSebens View Post
    The fiber cement (Hardi) board idea is intriguing. It sure doesn't burn, but will degrade and crumble at wood burning temperatures...........
    Are you sure? I made a temporary forge from my BBQ by lining it with Hardi board. I got it as hot as any forge ever gets, and did a reasonable amount of metal-bashing. The Hardi board not only protected the steel BBQ container perfectly, but was every bit as good when it cooled down as it was before I started. I've put it away to use it next time the same need arises.

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    Default Re: 600 lb Lead Keel Mold

    Quote Originally Posted by Mike-in-Suffolk View Post
    Are you sure? I made a temporary forge from my BBQ by lining it with Hardi board. I got it as hot as any forge ever gets, and did a reasonable amount of metal-bashing. The Hardi board not only protected the steel BBQ container perfectly, but was every bit as good when it cooled down as it was before I started. I've put it away to use it next time the same need arises.

    Having just wrapped up a large house renovation, I disposed of some scraps with a small fire. This inadvertently included some cut-offs of fiber-cement siding. I saw it delaminate into layers and become brittle. I bought the siding from someone else who had extra left over from a project, so I can't exactly say what brand it was, or how long it sat outside in the rain unpainted, so that may have contributed.
    There's the plan, then there's what actually happens.

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    Default Re: 600 lb Lead Keel Mold

    I do not know the temperature characteristics of fiber cement, though I have heard it can make a good heat shield, but for the purposes of a lead pour I would be cautious. As with any cement based product, it absorbs a huge amount of moisture. It just has the advantage over wood of not significantly changing size based on its moisture content. I am currently working on a siding job in Oregon and I can tell you a 12' stick weighs a lot more from an open pallet on a rainy day than it does fresh off a dry pallet.

    I have not yet poured my 12 1/2 keel and won't for several months yet, but I know moisture is the enemy of lead pours. If the fiber cement heat characteristic are suitable, make sure you keep it dry after assembly and prior to the pour. On a house this means a proper rain screen gap. With a pour that may be buried in the ground, you cannot maintain such a gap (nor would you want to, as fiber cement has no strength in that direction to resist liquid lead at even a few inches of depth). If the fiber cement is in contact with the ground, for any wet surface directly it will wick significant moisture.

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    Default Re: 600 lb Lead Keel Mold

    For what it is worth, in my naivety some 40 odd years ago I followed Howard Chapelle's instructions to the letter on my first pour.
    He recommended wetting everything down before pouring the molten lead!

    It wasn't really much of a problem, aside from some steam ing but it was a small pour (500 lbs) in a wood mold. Now, I have welded on 50 year old concrete (well cured) and have it violently spall off chunks of concrete (There was nothing else for it, that job had to be done) and that is a nasty business. It is difficult to remove moisture from concrete (Portland cement) without a kiln and some time.
    I have also welded attachments next to wooden structures and aside from some smoke and smoldering it was a non-issue.

    I think the lesson is that Concrete is not forgiving of moisture and heat.

  35. #35
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    Default Re: 600 lb Lead Keel Mold

    I poured 1100 lbs in a plain wood mold with no issue. It does boil a bit as the steam comes out. Make the open top several inches higher than the final shape to account for that, you can't fill it to the brim. I did seal the joints with high temp stove caulk. Be safe it will go fine.

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