Carl Moesly's Ballast Tank Design Applied

[Blue_Heron]

Well, Almost. Check out the PT Skiff. Scroll about halfway down the page to the rendering of the internal structure. Like Carl's design, it has an automatic ballast tank intended to make the hull less tender at rest. But it is simpler, with a single chamber as opposed to Carl's two chamber setup. I believe Carl's design was intended to also limit bow rise during the transition from displacement to planing speed, thus the slower draining forward chamber. I think the PT Skiff's tank is only designed to keep it from rolling excessively at rest.
Dave

[RS]

I believe Carl's design was intended to also limit bow rise during the transition from displacement to planing speed, thus the slower draining forward chamber. I think the PT Skiff's tank is only designed to keep it from rolling excessively at rest.

A two compartment design also limits instability due to free surface effect of a partly filled tank. The PT design appears to be more prone to porpoising as the ballast transitions from full to empty and vice versus.