A longer, narrower hull generally tends to gain speed for the same horsepower when displacement remains broadly similar. The corrected figures leave the D class slightly longer than the late C-class ships and only somewhat wider in beam. Those proportions suggest about 29.5 knots, yet the cited speed is 29 knots. The half-knot mismatch remains an open design question, with propeller shape proposed as the next variable to investigate.
Notable Point · 5:54-6:45
Hull form, power, and the speed question
The revised dimensions leave a half-knot speed puzzle among ships of similar weight and power, with propeller shape identified as a possible variable.