🔍 Key Concepts

• Hogging vs. sagging — think about whether the bow and stern are pushed up or down relative to midships • Where the weight (cargo/engine) is concentrated and how that affects the ship’s vertical bending • Difference between tensile stress (stretching) and compressive stress (squeezing) on the deck vs. on the keel/bottom when a vessel hogs or sags

💭 Think About

• If the heavy weights (cargo, machinery) are concentrated in the ends and the middle is relatively lighter, will the hull tend to bend upward or downward in the middle? Visualize the ship as a simple beam supported by buoyancy. • When the hull bends that way, is the main deck being stretched or squeezed? What about the bottom structure/keel? • Try drawing a simple side-view sketch of the ship with arrows showing weight and buoyancy, then show which way the hull curves and mark where you’d expect tension vs. compression.

✅ Before You Answer

• Be clear which condition is hogging (ends down/mid up OR ends up/mid down?) and which is sagging. • Match hogging/sagging with the correct combination of tensile vs. compressive stress on the main deck. • Confirm that your choice is consistent: if the deck is in tension, then the bottom must be in compression, and vice versa — they can’t both be in the same state.