PROPELLER FORCES STERN WALKS THE SAME DIRECTION PROPELLER TURNS

LONGITUDINAL THRUST

TRANSVERSE THRUST (SIDE FORCE OR PADDLEWHEEL FORCE)

COUPLE (TWIST)

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REFERENCES: CRENSHAW, CHAP 3

Notes:

THE PROPELLER WILL GENERATE BOTH LONGITUDINAL AND TRANSVERSE FORCES.

TWIN SCREW SHIPS CAN OPPOSE THE LONGITUDINAL FORCES TO CREATE A TWISTING MOMENT.

CRENSHAW COMPARES SIDE FORCE (TRANSVERSE FORCE) TO A PADDLE WHEEL AFFECT WITH THE PROPELLER WALKING ACROSS THE BOTTOM. WHEN GOING AHEAD, A RIGHT HAND SCREW WILL FORCE THE STERN TO STARBOARD AND THE BOW TO PORT. A LEFT HAND SCREW DOES THE OPPOSITE.