Hull form governs small-ship speed and seakeeping

Why does tonnage alone not explain the seakeeping and performance of different small warships?

Hull proportions and engine power determine how a small craft turns, meets rough water, and sustains speed, so vessels of similar tonnage can behave very differently.

Long, narrow hulls favor high speed, while shorter and broader forms can improve maneuverability and the angles at which a vessel meets waves. The German S-boat example shows how rough conditions could erase an expected speed advantage and allow supposedly slower British motor craft to catch up. Engine changes also complicate a simple comparison because a light craft has limited reserve power with which to overcome a poor hull form. This sensitivity resembles interwar aircraft, whose performance could be transformed by engine horsepower before refinements in wing form became decisive. The answer therefore directs viewers to compare hull, machinery, range, and sea conditions together rather than treating displacement as a complete measure.