Coal-conversion weight, conservative machinery, and the 25-knot result

Were the Queen Elizabeths thousands of tons overweight, and why did a design associated with 28 knots settle near 25 knots?

The 900-ton figure concerns inefficient use of weight after the move from coal to oil. Conservative machinery and hull form constrained speed, while differing displacement figures did not establish a 5,000-ton design error.

The 900-ton figure refers to space and structure provided for coal that became inefficient after the change to oil. It does not mean the ships were 900 tons overweight. The competing displacement figures also require clarification before they can establish a 5,000-ton design error. A hoped-for 28 knots depended on small-tube boilers and geared turbines, while 25 knots was a more realistic aim for the conservative machinery chosen. Armour and hull form affected the result as well. Later hull refinements and the projected longer Agincourt offered ways to improve speed.