Keel: an idea

I was just thinking how useful it would be to have some lead weights to hold things down as they glued. So, given that I will need lead to make the ballast keel and bricks at some point, I started to think about a supply of lead, and as usual this train of thought got me totally side-tracked. I am nowhere near ready to be making keels, but when eureka moments strike, they need to be given a bit of space.

I have given at least some thought to most aspects of the build already, and one that has been worrying me was the casting of the keel. Casting small weights and the like holds no fear, but the idea of pouring 455kg of lead has been troubling me. But that was before my idea. Like most ideas, it will either prove to be a good one and has therefore been done a million times before, or it will turn out to be the ‘other’ kind. However, to date, I have not come across it elsewhere.

Here is my thinking: instead of finding an enormous crucible of some kind, making a wooden mould and then risking life and limb by trying to pour the molten lead in, why not use a mould that can be heated up, and lob chunks of lead in until it looks about full? The shape of Haiku’s keel is essentially a couple of flat bars, each one about 10′ long, 10″ wide, and 2″ thick, with the lower two edges rounded over. So what, I asked myself, is about this shape and is made of something that I can heat up? The dazzling flash that came to me was… the web of a steel beam. If I can find an I-beam of the right sort of size, I can weld a plate to each end, mount it on its side on some bricks, put some burners underneath, and voilà!

4 thoughts on “Keel: an idea

  1. A 250 x 250 mm H beam (a standard size) weighs in at something like 72 kg/m so your 3 metres length gives you a 200 kg mould to handle, and 650 kg once leaded up. OK – that sounds doable. But I am wondering about what to use as a parting agent, as I suspect the lead might bond rather well to the steel. Perhaps after setting one could gently re-heat to melt the steel/lead bond, invert and tap it out…
    But I really like the principle of not having to pour lead.
    PS I have some scrap lead if you are interested…..

    • Hi Roger!
      Good point about the release agent – I hadn’t got that far. It would have to be something that survived heating, which may take temperatures up pretty high especially where the burners are sited.
      Thanks very much for the offer of lead – I will be in touch.

      • Hi Barnaby, I regularly make patterns for castings from wood and take them to Andrew Laing who runs Laing’s Foundry in Edinburgh. The patterns are moulded in sand, then removed and the metal is cast in the void. The cost is quite reasonable. My castings have been iron and bronze but perhaps he can handle lead too. You just need to make the pattern slightly larger to allow for the shrinkage – there are tables for this. Nice project – best of luck, John

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