Broken Bulb

While repainting, dropped my fin and bulb. Rear or bulb cracked off leaving rod soliid but bent. Straight rod end with pliers but how due I add material to rear inch or so?

If no repair possible how do I get new bulb, current oe is a replaceable type?

Hi Ernie, If your bulb is the Bantock style, with the brass rod in the centre, then what may have broken off is the epoxy fairing. If so, mix up some epoxy and filler and rebuild it. If some lead broke off, then can you epoxy it back on the end and refair.

I think that Don Ginther sold the molds for making the ballasts to Brighton Boat Works, so contact them for a new one.



I would use JB Weld from the local hardware, auto or big box store rather than epoxy if you have to bond lead to lead. The JB Weld has much more strength than regular epoxy and sticks to lead much better. And definitely do not use 5 min epoxy as it is not waterproof.

After roughing the surface with 60 grit paper, I use JB Weld to bond the halves of the lead ballasts I pour and have never had the joint fail.

Steve Vaczovsky
US1M #370 Venom
Infinity-54 #62
Santa Barbara #413
Seawind #380

Sacramento MYC & Elk Grove MYC

Thanks. but problem is last inch or so was crushed and not jst broken. So I just have the bare rod sticking out. I have to build some structure around he rod than sand and fair.


Then I would take some lead shavings (I save the “dust” when shaping a bulb - for both environmental reasons and to mix up as filler to pack in around the slot I mill in the bulb for the fin) or small diameter shot and make up a paste of the lead, some epoxy and some fumed silica (Cabosil). Just as it starts to get sticky, you can mold it on the broken section. Bondo also works well as the binder and can be applied layer by layer. Then sand and paint as usual.

You can solder lead quite nicely. A small torch, a little flux and a popsicle stick to form the solder and Bob’s your uncle.

I agree with Don, but a picture would help for better understanding.

Does anyone in North America make IOM Bulbs, several builders in England and Europe, but shipping costs extremely high

If you know the weight - try Tippecanoe or Brighton Boatworks

why you don’t try to make it yourself like I do every time when I need one ? Just some lead foil used by carpenters and cyanolite glue …
see :



Unfortunately, the only US source, Don Ginther of RC Ballasts, finally retired and no one else is making bulbs commercially right now. He was using a Bantock mold and I think I read somewhere he sold it to Midwest Model Yachts. You might email Brian at Midwest and see if that rumor is true and if he will do a one-off for you, or if he knows who has the mold. I had a conversation with Don right after he stopped making the US1M bulbs (I eventually bought his US1M pattern) and he said that IOM mold is a very nicely milled two piece aluminum job with notches for the brass rod and makes the bulbs in one pour.

If you don’t want to make your own bulb the way Claudio does, I make US1M ballasts for myself and a few for others in the class and could make an IOM bulb for you without the brass rod at a reasonable price if you have a full scale profile drawing or a set of dimensions to use as a starting point.

I would take the drawing and turn a hardwood plug for the master. From that I would make a cement half mold, pour the two halves and mail them to you - USPS Flat Rate (<$20). You would have to glue them together (JB Weld works) and cut your own slot for the fin. I can do the gluing and/or the milling the slot, but that increases the cost substantially due to the added labor.

My bulbs are made from scrap range lead and are not as hard and therefor difficult to cut the slot as Don’s, as he used an alloy of lead and antimony, but being softer, mine bend rather than shatter if you drop them. :wink:

Unfortunately, due to all the labor to make the plug and mold, just the halves would be about as expensive as one of Don’s finished bulbs. However, if you are interested, go onto RC Groups, find my profile (under FoamCrusher) and PM me and we can talk price to see if it is worth it for you.


Thanks Steve, right now a friend who does auto restoration thinks he repair it with fiberglass and is trying, I will get it back tomorrow and see.

If he does auto restoration he should be able to fix it with lead.