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| A coxless pair, which is a sweep-oar boat; the rower on the left of the photo, or the bow of the boat, is rowing "starboard" or "bowside", the rower on the right of the photo is rowing "port" or "strokeside" |
Rowing is a cyclic (or intermittent) form of propulsion such that in
the quasi-steady state the motion of the system (the system comprising
the rower, the oars, and the boat), is repeated regularly. In order to
maintain the steady-state propulsion of the system without either
accelerating or decelerating the system, the sum of all the external
forces on the system, averaged over the cycle, must be zero. Thus, the
average drag (retarding) force on the system must equal the average
propulsion force on the system. The drag forces consist of aerodynamic
drag on the superstructure of the system (components of the boat
situated above the waterline), as well as the hydrodynamic drag on the
submerged portion of the system. The propulsion forces are the forward
reaction of the water on the oars while in the water. Note also that the
oar can be used to provide a drag force (a force acting against the
forward motion) when the system is brought to rest.
Although the oar can be conveniently thought of as a lever with a
"fixed" pivot point in the water, the blade moves sideways and
sternwards through the water, so that the magnitude of the propulsion
force developed is the result of a complex interaction between unsteady
fluid mechanics (the water flow around the blade) and solid mechanics
and dynamics (the handle force applied to the oar, the oar's inertia and
bending characteristic, the acceleration of the boat and so on).
