The machinery upgrade changes more than propulsion efficiency: the battleship's stability falls into a workable range. Armor can then be restored while keeping the design stable and efficient, which suggests that the basic steam-engine model may be feeding an incorrect value into the calculation. A later cruiser trial with triple-expansion machinery remains badly unbalanced, so the improvement does not solve every early-hull problem. Stability was a fundamental concern for naval architects, making the persistently extreme values suspect even within an early-technology campaign. The sequence leaves the engine calculation as a concrete hypothesis rather than a complete diagnosis.
Notable Point · 1:32:23-1:44:12
Triple-expansion engines narrow, but do not solve, the stability problem
A battleship refit becomes workable with triple-expansion machinery, but a later cruiser remains badly unbalanced, leaving the basic-engine calculation as a plausible rather than complete explanation.