🔍 Key Concepts

• Effect of a single screw turning ahead or astern on the ship’s heading and transverse thrust (“walk”) • How twin screws (port and starboard) interact when one is ahead and the other is astern with rudders amidships • Difference between pivoting in place vs. sideways movement vs. ahead/astern movement

💭 Think About

• Picture the port propeller pushing water when going ahead: which way does it tend to push the stern (and thus turn the bow)? • Now picture the starboard propeller going astern: which way does its transverse thrust tend to move the stern? Do these two effects work together or cancel? • If the stern swings one way under these combined effects, to which side does the bow pivot?

✅ Before You Answer

• Verify how a right-handed propeller behaves when going ahead versus going astern (which way the stern “walks”). • Assume a conventional twin-screw ship with both propellers right-handed unless told otherwise—how does that affect the net turning moment? • Confirm whether the described condition would more likely cause a pivot about a point, a sideways walk, or straight-line motion.