DIY Lead Keel for a sailboat.

Discussion in 'Boatbuilding' started by Omeron, Feb 5, 2009.

  1. Omeron
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    Omeron Senior Member

    Manufacturing a Lead fin and bulb keel for a sailboat of 35 Ft seems to be one of the most dounting jobs for an amateur builder, as well as one of the most expensive items if built professionally.
    I have long been thinking about a method, which did not need a furnace, and handling of large quantites of heavy molten stuff. And would ask your opinions on its feasibility.
    I guess any keel requires a pattern to begin with.So i would start with that but a half model cut in half along the span of the foil and the bulb.So you need to cast it twice to get the two halves. This ofcourse requires the bulb to be symetrical fore and aft, so that they dont face opposite directions when brought together.
    The pattern is then laid flat in a hole made in the ground and lined by a suitable material such as sand,concrete mixture or else.
    Once you have your mold ready, you have half of your keel with an open surface. This void in the ground is then filled by lead shots, wheel weights or any lead particles which you may have and melted by a propane torch used by roof makers.
    You only need to place a bit of lead in the mold and melt it. As it doesnt need to be forced into any cavity, the gravity will do the work. So add bits and melt, add bits and melt. It can take as many times as you wish to fill it to the surface. You can also place big chunks in the middle, and fill the gaps around it. All you need is a bit of molten surface to stick to the other piece.
    No bubbles, no void spaces.
    When nearing the surface, place any steel structures, bolts,what have you and continue encapsulating.
    The two halves can then be ground, faired and bolted together to make the finished keel. Infact you can place round objects wherever you want to create the bolt holes.
    This to me looks like a childs play, and does not require any special tools or skills or create a hazardous, irreversible situation like making a mistake during melting and pouring molten lead.
    What do you think?
     
  2. TeddyDiver
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    TeddyDiver Gollywobbler

  3. Omeron
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    Omeron Senior Member

    Thanks for the link. Very interesting. But this is exactly what i am trying to avoid. Huge quantities of molten lead,a massive furnace, a highly controlled pouring job, etc.
    In the method i described, you dont need any preparation at all. You can spend half an our each day, at your backyard,and build it up gradually.
     
  4. PAR
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    PAR Yacht Designer/Builder

    The lead has to be poured in one, molten shot or you'll have voids, but more importantly you'll have lots of layers of lead that aren't stuck to each other. In other words, melting some lead over cold lead will not create a bond. The net result will be lots of layers of lead, stacked on top of each other.

    Secondly, a symmetric foil section will stall very easily, making for a poor appendage.

    Pouring lead isn't especially difficult, but it does require some nasty work and the setup to handle the weight, melting the lead, pouring the lead, etc.
     
  5. Omeron
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    Omeron Senior Member

    PAR, thanks for replying.
    The main fin body doesnt have to be a symmetrical section. As long as it has a constant chord length, you can turn one casting upside down and you have a non symmetric one piece fin. Actually the same also true for the bulb.
    If you melt the existing layer, by a torch,and you get a little pool of molten lead before adding another layer, would you still get poor bonding?
    If you have a steel structure to carry all the weight and bending stresses, would that relatively poor bond be still a problem?
     
  6. TeddyDiver
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    TeddyDiver Gollywobbler

    Quite a torch you need.. a laser sword could work thou. Have you seen how Qui Gon ''torches" blast doors in Trade Federations flag ship..:p

    Steel would be the problem.
     
  7. Omeron
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    Omeron Senior Member

    C'mmon Teddy, Lead melts at 325 Deg.C. Almost possible in your domestic oven. I have seen those doors. They are massive and built out of unmeltium. I dont think i can afford those torches.
    Whats the problem with a steel structure then? Well you are not easy to please are you?
    How about a platinum inner core, embedded in gold and titanium sheated.
     
  8. TeddyDiver
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    TeddyDiver Gollywobbler

    It's not the temp.. it's the amount of lead to warm. And doing the whole process multiple times..
    Actually many homebuiders have used steel structure and most of them have (or are going to) serious corrosion problems..
    Gold would be great.. as well uranium :D
     
  9. PAR
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    PAR Yacht Designer/Builder

    I've often wished I could get some of those epoxy coated spent uranium pellets that are cut up fuel rods. They'd make great ballast and if I just happen to have Phalanx system handy . . .
     
  10. Omeron
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    Omeron Senior Member

    Seriously though, what is the reason for steel corroding in encapsulated lead?
    Is it due to play inside the lead,near the bolts, and moisture seeping in?
    I cannot imagine any substance penetrating lead otherwise and reaching the steel core. Even sulpheric acid would find it difficult.
    How about 316 SS?
     

  11. TeddyDiver
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    TeddyDiver Gollywobbler

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