🔍 Key Concepts

• How shaft weight and propeller forces act on the shaft line (direction of load) • Why most line shaft bearings can support the shaft with only a lower shell • Which bearing is closest to the stern tube and propeller and how that might change loading

💭 Think About

• Visualize the shaft from the thrust bearing all the way aft to the propeller. Where are the largest and most variable bending forces likely to occur? • Ask yourself why engineers would bother installing an upper half bearing shell at one location if gravity alone usually keeps the shaft on the lower shell. • Consider which end of the shaft line experiences the most motion and possible shaft lift in heavy seas or when the propeller is highly loaded.

✅ Before You Answer

• Identify which bearing is closest to the propeller and stern tube among the choices. • Confirm that most intermediate line shaft bearings typically carry the shaft on the lower half only, under steady downward load. • Think about where there is a greater risk of the shaft lifting or whipping, making an upper half shell more necessary.