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Topic: Lead in the centerboard (Read 1002 times)
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Clem Freeman
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I\\\'ve made a mould out of plywood so I can cast a piece of lead to put in to the centerboard. My first attempt was reasonable but contained large air bubbles trapped at the bottom. Anyone done this before and have any tips?
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Anthony Huggett
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Hi Clem,
I (for one) would love to know how you did this.
How did you melt the lead?
Did you make a positive or a negative mould? i.e. did you pour the lead into a plywood box, or use the plywood to make a dent in casting sand? If the former, the latter might be the answer.
I think if I were going to try a plywood box for casting I\\\'d use a horizontal box, with a top with a reasonable sized hole for the lead to pour in, and small holes in each corner for the air to squirt out. A real pro mould would have a tapered hole for the lead to go in, to minimise the burr that will be left which you would need to file off.
Any chance of some pictures?
Anthony
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Steve Joyce
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Hi Clem, is the centreboard on the 17 a single piece of thick ply, or do you need to laminate it up yourself? On the 15 its a single piece, and although the instructions refer to putting lead in, they all seem to refer to making the board up, rather than it being already in one piece. Although I haven\\\'t really thought about this too much yet, I was thinking along the lines of a golf club weight, drilling out a hole with a forstner bit and dropping in pennies of lead chopped out with hole saw, and sealing up with epoxy.
My whole centreboard thing has been a bit of a trial. Its about the only part of the kit that didn\\\'t fit together well. I will update my build post with the latest.
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Clem Freeman
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Anthony,
I made a flat open mould out of ply and that is probably where I went wrong. The ply seems to have stood up to the heat pretty well, just a bit scorched. Mark 2 will be as you suggest with an upright mould where I can pour the lead in at the top. I melted the lead in an old saucepan on a camping gas stove. Not sure when I will get around to the next attempt as I was only trying this as the weather was to bad to get the S17 out of the garage to work on.
Steve,
The S17 centreboard is made up of 2 laminates of ply which have had hollows routed out. You could just lay the scrap lead in but I thought by moulding the lead to fit I could maximise the amount I could get in.
Clem
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Jeremy
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My guess is that the bubbles were probably caused by the ply outgassing, or not being totally dry. I cast a lead keel bulb many years ago, out in the garden, by making a mould from concrete cast around a shaped polystyrene foam master. Having been warned of the dangers of damp causing gassing and a possible explosion whilst pouring, I lit a fire around the mould and baked it for an hour or two to burn the polystyrene out before pouring the lead in (it was a lot of lead, around 500lbs or so of melted scrap). I melted the lead in an old cast iron cauldron over a charcoal fire, but it too four of us to tip the lead into the mould, via a feed runner made from a bit of old cast iron guttering.
I\\\'ve heard of people making smaller lost foam castings using plaster of paris as a mould, over a bit of carved foam. If gently dried in an oven you can apparently just pour the lead directly on to the foam so that it vaporises as a the lead is cast. Extruded polystyrene foam (the pink or blue stuff) is best, as it can easily be carved and sanded to shape. I\\\'d think that the same technique might work for making a shaped insert for a centreboard.
Jeremy
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gerald turner
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Anthony,
I made a flat open mould out of ply and that is probably where I went wrong. The ply seems to have stood up to the heat pretty well, just a bit scorched. Mark 2 will be as you suggest with an upright mould where I can pour the lead in at the top. I melted the lead in an old saucepan on a camping gas stove. Not sure when I will get around to the next attempt as I was only trying this as the weather was to bad to get the S17 out of the garage to work on.
Steve,
The S17 centreboard is made up of 2 laminates of ply which have had hollows routed out. You could just lay the scrap lead in but I thought by moulding the lead to fit I could maximise the amount I could get in.
Clem
Wotcha Clem!\\\'Tis Gerald here,Maybe it would be better to make a mould out of plaster, would need to be done in two parts with a pattern made out of scrap wood,I say this because I had a notion of making a Model yacht which would need a lead bulb. Why not ping John Perry, he can advise |
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Clem Freeman
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I\\\'ll give the plaster of paris a go and report back.
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