Stability Criterion

Sway

image

Ship with acceleration +˙v

Inertial reaction \(-Y\)

image

Yaw

image

Bow and Stern Counterpose

\(Y=-\dot{v} \)

image

Situations

If bow dominates

Usually, \(N_v\) negative

If Bow and Stern Equal effect

If stern dominates

Usually, \(N_v\) positive

\(N_v \) =0

\(\sigma\) stability

not speed dependent

at low and moderate Fr numbers

So

Ship has controls-fixed straight-line stability low speed

will have at higher speeds

Contributes more with Rudder

Contributes to CORRECT and keep straight line