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Stability Trials - Dieudonne`s Spiral - Coggle Diagram
Stability Trials - Dieudonne`s Spiral
Gives
Steady yawing rates
according to Rudder Angle
Speed does not affect
Procedure
Ship steadied straight course for 1 min
Rudder turned a certain angle and held until cte yaw angle
Rudder decreased a small amount and held until cte yaw angle
Keep going for repeated rudder angles
Straight line
goes and comes back straight
Controls-fixed straight-line Stability
Zero angle rudder - straight course
Negative
Directional Stability Index
Hysteresis Loop
Unstable
Larger loop, more unstable
Ship might continue to turn with Rudder at amidships
More than one turning angular veloc for a given rudder angle
Turn against rudder until suddenly swings to the other side
Positive
Directional Stability Index
Directional Stability
Similar to Heel Stability
in the Graph
