Hi there, at university we made 70cm long RC sailing yachts for a project. The university provided the bulb keel and once the project was over the keel bulb was returned. Now I’m looking for how I can get a new keel bulb made. The original was brass, about 250mm long and mass of 1kg. I’ve made a 3D model of keel bulb so does anyone know where I can get one custom made? Thanks

Talk to your local foundry. The reason I say local, is you could end up paying more for postage than the actual one off bulb.

Hi Giles

If this was a brass ballast a local machine shop should be able to assist you especially if you have a model or drawing of it.

A local technical college may also be able to assist for a donation! Using it as a machining exercise for one of their students.

The other alternative would be to approach a local model engineering or rail enthusiasts club. I say rail enthusiasts club as members producing their own engines or rolling stock would probably have a lathe and milling machine.

Regards Eric

The old HFM 590 model yacht kit used a plastic moulded shell filled with lead fishing shot bound together with epoxy resin - maybe another approach?

If lead was ok you could sand cast one at home using your pattern then file it down to weight. Lead is toxic so health and safety precautions would be needed.  By lead sheet from a builders yard for melting down. 

Hi Giles

Try checking out a DF95 ballast weight. I think it could be approximately the weight you are looking for? If the size is different providing you get the C of G correctly positioned as this is a one off yacht the actual size should not matter too much. The ballast may be smaller which should reduce drag.

May not have a slot but that should not be too difficult to produce.

May be worth visiting a club that sails this class with a tape measure and scales. (Check with club before visiting to ensure they will be a DF95 available.)

Being a commercially available ballast I would think a cost affective solution. 

Regards Eric 

If your original yacht was a Strathclyde 70, this design morphed into the Wee Nip. My club uses this (with Bermuda rather than una rig) along with Two Islands and Emberton clubs. We still sail and promote this, and one of our members occasionally casts suitable leads.

Edited June 29, 2025Jun 29 by tiggy_cat

Hi Giles, it has been sometime since the original post for help.

For Information, did you source a ballast for your yacht? If so from where did you obtain it?

Hello, thanks for all the replies. I haven't yet sorted the keel bulb but will probably get a brass rod of required dimensions and then get it machined by a friend that has a lathe and milling machine.