Page 2 of 2 FirstFirst 12
Results 36 to 47 of 47

Thread: 600 lb Lead Keel Mold

  1. #36
    Join Date
    Sep 2010
    Location
    Bainbridge Island WA
    Posts
    4,457

    Default Re: 600 lb Lead Keel Mold

    Concrete suffers from thermal spalling at around 570 degrees Fahrenheit (300 Celsius) the melting point of lead is 620F (325C).
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
    H.A. Calahan

  2. #37
    Join Date
    Jun 2003
    Location
    Central Coast, Ca
    Posts
    32,962

    Default Re: 600 lb Lead Keel Mold

    And it sounds like someone is shooting a gun...

  3. #38
    Join Date
    Feb 2001
    Location
    Seattle, WA USA
    Posts
    15,134

    Default

    Quote Originally Posted by stromborg View Post
    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.

    This says 5/16 per foot for lead.

    https://www.nonesuchtools.com/pmkr/shrink.html
    You would not enjoy Nietzsche, sir. He is fundamentally unsound. P.G. Wodehouse (Carry On, Jeeves)

  4. #39
    Join Date
    Sep 2010
    Location
    Bainbridge Island WA
    Posts
    4,457

    Default Re: 600 lb Lead Keel Mold

    I didn't measure the actual shrinkage of my keel pour which is 5'-6" long and m/s roughly 5"x5" but it didn't go from 5'-6" to 5'-4 1/2" in the cooling process.
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
    H.A. Calahan

  5. #40
    Join Date
    Jun 2003
    Location
    Central Coast, Ca
    Posts
    32,962

    Default Re: 600 lb Lead Keel Mold

    mine did, almost exactly

  6. #41
    Join Date
    Jan 2021
    Location
    Orlando, FL USA
    Posts
    22

    Default Re: 600 lb Lead Keel Mold

    Okay, now I'm rightly confused with regard to this shrinkage thing. Yes, there is no doubt that lead shrinks on "freezing" and that the rate is 5/16" per foot (2.6%). HOWEVER! As seen from some of the mold pours that I've viewed on YouTube (most specifically Bob Emser's "Art of Boatbuilding" and Steve and Alix's "Acorn to Arabella") the solid lead didn't seem to pull away from the walls or ends of the mold (or from the centerboard slot blank in the case of "Art of Boatbuilding").

    So, my MOST IMPORTANT QUESTION is: Does lead shrink *evenly* (from all dimensions) when cooling in a mold? Or does it *just* shrink from the open top?

    My mold is roughly 8' long, so allowing for shrinkage, should I make it 8'2" long? I will reach out to Emser to get his experience, but it certainly seems like the cooled lead was *very tight* to the mold when he broke off the mold wood.

    Thank you again for your sage advice and experience.

  7. #42
    Join Date
    Jul 2021
    Location
    Greater Northern Arizona Republic
    Posts
    839

    Default Re: 600 lb Lead Keel Mold

    Not actually knowing, I would think shrinkage would be concentrated wherever cooled fastest and that some of the variation people see involves their setup.

  8. #43
    Join Date
    Oct 2017
    Location
    Berkeley, CA
    Posts
    362

    Default Re: 600 lb Lead Keel Mold

    If the pour cools unevenly molten lead gets drawn out of hot of hot areas to those that are cooling. To prevent voids from forming it is often recommended to heat the pour area to keep a pool of molten lead that can flow into the voids. If enough molten lead is drawn away like this the vicinity of the pour has less metal in it. This process isn’t shrinking per se but the end result is that there can be less lead in the area of the pour than elsewhere. My pour ended up with a slight low spot and was also pinched inward just a hair in the area of the pour. I faired it with fairing epoxy.
    Last edited by nrs5000; 11-13-2021 at 12:04 AM.

  9. #44
    Join Date
    Feb 2001
    Location
    Seattle, WA USA
    Posts
    15,134

    Default

    Quote Originally Posted by nrs5000 View Post
    If the pour cools unevenly molten lead gets drawn out of hot of hot areas to those that are cooling. To prevent voids from forming it is often recommended to heat the pour area to keep a pool of molten lead that can flow into the voids. If enough molten lead is drawn away like this the vicinity of the pour has less metal in it. This process isn’t shrinking per se but the end result is that there can be less lead in the area of the pour than elsewhere. My pour ended up with a slight low spot and was also pinched inward just a hair in the area of the pour. I faired it with fairing epoxy.

    That is a whole 'nother issue than shrinkage.

    If you heat, or cool, a metal/crystal/pretty much whatever, it expands or shrinks respectively. By a very predictable amount.

    Water (ice) is the anomaly. It contracts (shrinks) until it hits c. +4 deg C, its point of maximum density. Then, as it gets colder, it starts expanding again. Weird stuff, water.

    It would probably be better to describe shrinkage in terms of percentage -- e.g., 1 cubic foot of molten lead shrinks xx% from molten to ambient temperature -- but that's not terribly useful to the pattern maker who has to make the pattern or mold.
    You would not enjoy Nietzsche, sir. He is fundamentally unsound. P.G. Wodehouse (Carry On, Jeeves)

  10. #45
    Join Date
    Feb 2002
    Location
    Uki, NSW, Australia
    Posts
    34,460

    Default Re: 600 lb Lead Keel Mold

    Quote Originally Posted by bogolese View Post
    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. ;-)
    It was nothing fancy I know that much.
    This was the mold, I got Peter Sibley to make it for me.
    Mold.jpg

    Mold in the ground and pouring.
    pouring.jpg
    It wasn't that pretty when the mold was removed.
    Mold removed.jpg
    Cleaning it up was messy but the end result was pretty good.
    Cleaned up.jpg
    I would rather have questions that can't be answered than answers that can't be questioned


  11. #46
    Join Date
    Jun 2003
    Location
    Central Coast, Ca
    Posts
    32,962

    Default Re: 600 lb Lead Keel Mold

    The cheapest power-plane you can buy will make about 500 lbs of chips before you toss it in the recycle bin...

  12. #47
    Join Date
    Feb 2007
    Location
    N62 5352" E27 4110"
    Posts
    379

    Default Re: 600 lb Lead Keel Mold

    Quote Originally Posted by Canoeyawl View Post
    The cheapest power-plane you can buy will make about 500 lbs of chips before you toss it in the recycle bin...
    +1. Exactly what I did, although mine was an ok unit but almost at the end of its career when I used it for the ballast.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •