The following 3 stability curves give examples of the variations in righting arms and points of vanishing stability (PVS) which can occur with different vertical centres of gravity (VCG).
This lift bulb keel racing yacht had an inclination experiment conducted, with the yacht in measured condition i.e. no loading, and the VCG of the yacht was established. The first 2 curves show the yacht with keel fully down and fully raised in its unloaded condition. Even with the keel fully raised, the PVS on this yacht is still 141.5 deg. The bulb keel arrangement gives a very low VCG for the ballast.
The third curve shows the yacht loaded with all of the crew weight and gear weight for racing located at deck height and on centre line. The PVS is still 153.7 deg with keel fully down. The area under the righting arm curve up to 180 deg is very small. This yacht would be difficult to capsize and would right quickly.
3.25m lifting bulb keel - VCG 577mm below DWL - PVS 165 deg
3.25 lifting bulb keel at 1.95m draft - VCG 123mm below DWL - PVS 141.5 deg
3.25m lifting bulb keel - VCG 378mm below DWL - PVS 153.7 deg