Did the 'boats take off in a curving path ? Did they typically go westbound, into wind, and then land back just skimming Rochester Bridge ?
Yes,
WHBM, they followed a curving path for part of the take off run, which could be over a mile in length. They could take off and land in either direction to suit the wind direction. For example the maiden flight of the Empire class "Canopus" on 2 July 1936 took off from a position close to Rochester bridge, travelling westwards, and a photograph shows it to be already "on the step" some distance past the castle keep and cathedral spire.
On the occasion of a royal visit to the works by King George VI and Queen Elizabeth on 14 March 1939, they witnessed a newly built Sunderland take off for its first flight travelling eastwards, lifting off and climbing over the bridge.