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  #1  
Old 03-11-2011, 08:42 AM
Triman Triman is offline
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Building a lead bulb

Hello,
Im' building a 7m sailboat and I'm now thinking about how to build the lead bulb (aprox. 160 kg). The idea is to make a mold and then a fiberglas skin (two halves joined), then melt the lead inside, cooling the skin with cold water. Ideally, this would give a ready bulb with a nice outher skin, if it works... Anyone has experience with this or other ways to do the stuff?
Thanks for any suggestion!
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Old 03-11-2011, 11:14 AM
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gonzo gonzo is offline
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It will set the fiberglass on fire. The mold can be made of wood with a whitewash coating, casting sand, plaster, etc.
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Old 03-11-2011, 01:36 PM
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Doug Lord Doug Lord is offline
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You don't want to get water anywhere near molten lead. You can make a wooden plug and then use a ceramic material to make a mold. I've made dozens of very small lead bulbs this way but I don't recommend that an inexperienced person tackle such a large job. Definitely do not use fiberglass to pour lead into!
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Old 03-11-2011, 01:39 PM
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bntii bntii is offline
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Look here:

http://www.youtube.com/watch?v=ZLcXt...eature=related
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Old 03-11-2011, 09:25 PM
tazmann tazmann is offline
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I didn't see any of them wearing resperators
Tom
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Old 03-11-2011, 10:43 PM
bruceb bruceb is offline
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Glass molds

I have a fiberglass mold that has been used several times to cast lead bulbs. It does work. Lead melts at a lower temp than fiberglass ignites. You do have to be careful. B
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Old 03-11-2011, 11:06 PM
Earl Boebert Earl Boebert is offline
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Quote:
Originally Posted by tazmann View Post
I didn't see any of them wearing resperators
Tom
Very bad idea to pour indoors without breathing protection. Plus no visible temperature control on the pot to prevent overheating and outgassing. Breathing lead fumes is one of the easiest ways to get a dose. If you try this, please be more careful.

Cheers,

Earl
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Old 03-12-2011, 12:23 AM
michael pierzga michael pierzga is offline
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Quote:
Originally Posted by bruceb View Post
I have a fiberglass mold that has been used several times to cast lead bulbs. It does work. Lead melts at a lower temp than fiberglass ignites. You do have to be careful. B
The fiberglass mold will work for one pour of small stuff.....

Also a styrofoam bulb form inserted into concrete works. The lead melts the foam. Once cooled break the concrete apart. Ive used foam in concrete to make complex shape bilge ballast blocks. The skin off the lead bulb will be crude so make it larger , then powerplane to shape. Lead shaping can be done with a chain saw and powerplane
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Old 03-12-2011, 07:52 AM
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bntii bntii is offline
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Make sure to look at how they formed the plug- it looks good and I believe they are getting high form integrity.

One problem I saw was pouring a bit too fast at the end and they ended up with voids along the top of the form.

http://www.youtube.com/watch?v=ZLcXt...eature=related

Respirators and safety glasses and boots instead of tennis shoes...



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Old 03-12-2011, 11:48 AM
anthony goodson anthony goodson is offline
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I really don't know anything about this ,but I have to ask.If you are using the fibreglass moulding as an outer shell ,why melt the lead at all. Why can't you just fill the moulding with lead shot and resin ? Just wondering here in the rain in Spain .
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Old 03-12-2011, 01:49 PM
messabout messabout is offline
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Anthony; lead shot and resin is a workable solution but to achieve a specified weight the volume must be larger. That is to say that shot and resin are not as heavy as solid Pb. For least drag, the pod should be as small as can be, so extra volume is undesireable.

Plaster of paris will make a good quality mold. But there are hidden dangers when using plaster or concrete. Either material must be allowed to dry very thoroughly or all hell will break loose when the hot lead hits it. Dougs remark about not letting water get anywhere near hot lead is to be taken seriously.
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Old 03-12-2011, 02:12 PM
anthony goodson anthony goodson is offline
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Thankyou messabout I can stop wondering now.
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Old 03-12-2011, 02:52 PM
michael pierzga michael pierzga is offline
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Glass encapulated lead beads makes a poor keel. Keels like to be make of metal so you can touch a rock or handle the boat out of the water without damaging the bottom of the keel. Plastic is fragile.
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Old 03-12-2011, 05:15 PM
tazmann tazmann is offline
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A freind of mine tried resin and lead shot for a bulb and for whatever reason the resin didn't kick, what a goey mess. needless to say he scraped that idea.
Tom
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  #15  
Old 03-13-2011, 12:45 AM
wheels wheels is offline
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an idea that I've been pondering since I heard about it would be to use parafin/wax and lead shot/bb's to keep things in place.

Mix molten wax and the lead shot in a metal cooker used for deep frying turkeys. pour into mold/shell. If you want to tune the weight have a removable cover, use a heated icecream scoop if you need to reduce weight. adding weight would involve scooping out a hollow and placing larger chunks of solid lead inside.

a custom motorcycle shop could probably make you a hollow bulb out of metal using the same techniques that they use to make custom gas tanks if you are objectionable to using fiberglass.

just food for thought
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