I have created a set of files for use by everyone interested in making their own US1M bulb. These bulbs files are based on the current bulb and mold design used to cast ballast bulbs for the US1M class, but may be appropriate for other sailboats in the one meter range. (Special thanks to Steve V. for sharing his bulb design)

In the folder there is a dimensioned JPG file of two bulbs and two casting molds. There are also 3d versions in STL and STP for developing into 3D prints or toolpaths for machining. These files also have points locating the CG of the raw bulbs.

The two versions have different finished weights. One is the "standard" ~4 lb bulb, the other is a "lite" version at ~3lb 6oz. (This second bulb may be a good choice for DF95/US1M conversions also)

These molds are designed as half molds for open pouring. You cast each bulb half, then epoxy them together, fill the seam with body filler, sand smooth, and machine the plug for the fin and mounting hardware, then finish as desired. By varying the depth of lead fill during casting or drilling out a bit of lead from the finished halves, you can fine tune the weight.

---You will notice in the JPG the weights are listed slightly higher than the finished weights. Those annotations are the raw plug weights from a 100% lead filled plug. The mold and plug are slightly oversized to account for shrinkage and machining lead away for the fin slot and mounting hardware.

All files are formatted in inches.

You can follow along with this build here: https://www.rcgroups.com/forums/showthread.php?4080263-Learning-to-cast-a-sailboat-bulb-in-7-000-easy-steps-an-epic-tale-and-tutorial/page4