For a boat and rower, there are three associated velocities:
velocity of the rower
velocity of the boat
velocity of the system
They are all different:
The velocity of the overall system (rower and the boat speed together) is highest at the end of the drive derived from the propulsion from the blades. That highest velocity of the end of the drive is a cumulative reaction that comes from the beginning of the drive + the trunk movement. So if the beginning of the drive is weak and the second half is disconnected, the velocity of the overall system will be slow and there is no way you can contribute much to the speed of your boat. The most important thing is connection on the blade through the footplate. Again - no connection on the second half = weak propulsion = low velocity at the end of the drive. If we look at the velocity of the boat, it is highest during recovery (when over rate 24).
Below are two short sculling clips to watch. The one from World Rowing breaks down the stroke and explains how and when to move. (https://youtu.be/OpZbV8LyT_c) The clip of Victoria Thornley preparing for Great Britian's trials is a very good study in how to row. (Per Maksym Kepskyy: Her upper body movement considers the system's peak velocity which is why it looks like the upper body is doing the job to propel. It adds to the movement. The rower has a really good connection on the blade.) (https://t.co/2LpTzXw5kA)
