Keel Bulb ideas

I’ve been looking locally for a weight to make a keel bulb for my Razor, but so far around here no one carries a torpedo sinker more than 4 ounces. I can find them on the internet, but the shipping cost is hillarious…

Any other way to go with a keel bulb?


Cast it - with normal care handling small quyantities of lead occasionally is less hazardous than crossing the street. Note the words CARE, SMALL and OCCASIONALLY.

If this were not the case, everyone who workeed in a lead foundy 50 years ago would have been dead inside a month!



Don’t know of lead sheet is readily available where you are - aka Flashing sheet. Many people cut the sheet to suitable shapes (kitchen scissors when the social advisor is not looking?) and epoxy together to make a bulb shape then after trials file smooth, fill with car body filler and paint.

This is an easy way to make a bulb - and leaving a slot for the fin comes easy, too.

Me, I fill a length of aluminium or copper pipe with lead, embellish it with pointy ends and call it a bulb, but also cast shaped bulbs in silicone molds too

any of these work for you?

Actually I’ve had a time finding much of anything Lead any more. I thought of flashing, but it’s not used and wheel weights, but they are being made of some alloy now. Seems like Lead is bieng phased out around here…

I’m sure I will find some sooner or later…

Belt weights for scuba… Try to find those supplied in heavy duty PVC sachets. Lots of very fine lead shot inside, which melts a lot quicker than the cast lead weights.

Please forgive the horribly commercial plug guys but…
Half way down the page.

I recently used the same bulb halves with slots cut in each to take struts mounted in the fin bottom. The halves are epoxied together trapping the struts which gives me a 1/8" narrower bulb.

(still casting bulbs and still here, I just wish I could remember where here is?)

This may sound daft, but it is easy to cast lead sheet to the accuracy we require - not very high.

Nail thin wood (1/8 ply) onto a plank of flattish planed wood so that it makes a wall round the area you want to have as sheet - I would suggest casting long thin strips about 1inch high and a foot long. Make sure the plank is dry. Level the plank reasonably and pour in lead to the top - you now have a molten spirit level! The lead cools very fast.
Really keen casters might line the wood with aluminium foil

Yes, the wood chars: Yes; the mold is expendable after 3 or 4 casts

But if you are doing this you might prefer to cut a female shape into the wood and mold half the bulb at a time and cut out the sheet stage.
I use thermalite block (foamed lightweight aggregate building blocks) and scratch out the half shape - then fill. Not complicated - make sure its dry before pouring.

Or, as Graham says get one from a supplier
Did I mention moulds have to be dry?

Thanks for all the ideas. For me, the casting is out. I don’t have a melting pot and my wife is adamant about using her stove. I love her cooking very much, so I leave her stove alone!:wink:
I thought about the copper tube and filling it. I could do that. I also have seen the weight at Graham’s site and most likely I will be doing that. I like the two piece design, since I am using a wood keel and I really like the looks of that bulb when it’s done.

I also wrote to an ebay seller and he will send me one 8oz. torpedo sinker for $1.35 and $4.00 shipping, so I may do that as well.

I did try on my own, but it was a mess. I bought two 5 ounce sinkers from Gander Mountain (haeviest they had) and pounded them down to make them torpedo shape. Then I drilled the blunt ends and used a screw to put them together. I used two part epoxy when I put them together. I did some filing and got something of a torpedo shape. I thought it was going to work, but as I was handling it, I dropped it from about 3’ and the epoxy joint broke and the screw loosened in the lead. Don’t think that’s sturdy enough for me, so I gave that up… Really looked pretty poor anyhow…

Thanks for all the help and information here!

i do cast 6 and 8 oz torpedo bulbs…

Thank you, I might need one in the near future. I just went with the 8 oz. torpedo sinker from a guy on ebay. $4.10 including shipping… I think it will work for now and he’s not too far away from here (Oklahoma)…

no problem. all i was charging was $1 for the lead and actual shipping charges. which is about the same.

Has anyone ever tried casting a bulb with lead shot & epoxy?? I’ve used it as fixed internal ballast or poured it into a hollow keel but I’ve never actually cast a bulb. I wonder just how dense you could make it. Maybe, it would end up being excessively large compared to a solid lead bulb?? Maybe, it would fall apart?? If it did prove to be dense & durable enough, the thought of casting a helicopter rotor blade into it as a keel fin has appeal.

Happy Yachting - Kip

Watch this space!

Incidentally, rotor blades tend to be a bit narrow!


depends on what scale craft you are pulling the rotors from. but they are also very $$$ and if I’m not mistaken unless you pull them from a stunt copter, the rotor will have some lift.

if you did a epoxy/shot bulb, why wouldn’t it work…I woudl be worried about adhesion and having the occasion shot fall off. but if you dunked in or coated it in epoxy after casting, it should be fine. but keep in mind that lead shot is usually around $2 per pound, and usually sold in 25# bags…unless you know someone who like shooting and makes their own shotgun shells…

Leadshot / epoxy is all i use.

I made the plug from pink foam, covered it with a few layers of epoxy / glass, cut it in half with a dremel diamond saw, removed the foam with acetone, and have two very quick mold halves.

Each half is filled with the desired amount of shot, then epoxy resin is poured over the shot to saturate it full. Each half uses 7 gm of epoxy, so 14gm is subtracted from the total I’m looking for.

My current bulbs are a 195gm, a 200gm, and a 225 gm.

They sand up nicely, and paint really well.

I used to offer thin glass bulb-shells, to be easily filled with shot and resin, but that mold is long gone now.

Here are the densities I dug up for the Yankee III book, in oz/cu in:

#7 Lead Shot: 3.4

Britannia Metal/Lead-free Pewter: 4.2

Copper and Bronze: About 5.1, depending on alloy

Bismuth: 5.73

Cast Lead: 6.0

Adding bronze casting powder to the lead shot/epoxy mixture raises the density a bit. As a rule of thumb, if you have a bulb shape intended for cast lead, you should multiply the linear dimensions by 1.2 for shot, 1.12 for Britannia, and 1.05 for copper alloys. There are a few art foundries in my part of the world and I’ve toyed with the idea of getting them to cast bronze bulbs but never got the energy up actually ask about costs.



I guess another idea instead of casting bronze or copper would to have one cut on a mettal lathe?

or just get a hunk of round steel stock about 3/4" in diamater and get yourself a grinder…:slight_smile: not as exact as a lathe but then we aren’t curing cancer here either…

Lead-free solder for use in soldering water pipes for drinking water has a nominal specific gravity of 7.1. I is available in wire form in 1 pound rolls for about $10, and is non-toxic to the sailor, his family members (young children), and to the environment (his sailing pond). It can be readily melted by a propane hand torch, into hollow molds gouged out of a piece of scrap wood. Two pieces can then be epoxied together. The metal is readily drilled, filed, and machined on a lathe, unlike lead which tends to bind to any cutting tool. One roll of Kester brand solder would be enough for three Footys.

I like that idea. Especially the non-toxic part!