The Acorn machinery discussion contrasts Yarrow boilers with White-Forster boilers used by J. S. White. In the White-Forster arrangement, the tubes curved gradually so that they entered the main drums perpendicularly. That geometry made a strong, reliable seal easier to achieve and allowed higher operating pressure. The design is described as a development of the Yarrow type. Redpole, Rifleman and Ruby provide examples of White-built ships whose performance benefited from the boilers.
Notable Point · 1:02:38-1:04:03
White-Forster boilers: tube entries, seals and pressure
Curving boiler tubes so that they entered the drums perpendicularly helped make strong seals for higher operating pressures.