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© 2009 Mark Kennett

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Boat design – stability analysis:
Intact statical stability curves for the Vergoyer 45

Click here for an introduction to intact statical stability, or find this article in the technical articles section. 

The Vergoyer 45, with its beamy, roomy hull, shows a GZ curve that is  characteristic of this type of hull form.

The curve shows a very steep initial rise, up to the  maximum GZ at about 35 degrees inclination. This is due to the form stability inherent in this type of boat.

At 45 degrees inclination the side decks are immersed and there is still a very strong righting arm and moment (124,730 foot pounds), even though the righting arm is beginning to decline.

At 90 degrees inclination, with the vessel on its side, there is a moderate righting arm, augmented by the fact that the wheelhouse is now partialy immersed, a condition common to most boats at his angle of heel.

This moderate righting arm is maintained through 135 degrees. This is of course  because the hull is partially floating on its superstructure, as with most motor boats when nearly upside down.

At no point does the Gz arm become negative.

Watertight integrity is, as usual, assumed to be maintained at all times .

See the actual graphs of statical stability and righting moment below. Note that they represent the hull in a light condition. Additional weights added low in the hull will increase both the righting arm and the righting moment.

GZ curve: Vergoyer 45

boat design: Vergoyer - gz curve

Righting moment: Vergoyer 45

boat design: Vergoyer - righting moments

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