This topic is most interesting to me, as a fluid dynamicist, as the
explanations for the results claimed run counter to my expectation.
Thus there's the stated assumption that immersing more than the blade
itself reduces propulsive efficiency: if we, for now, ignore the catch
& finish phases, which should already be rather more efficient (less
loss-making) than the stalled mid-stroke, that leaves the stalled
mid-stroke. It is standard knowledge that the reaction force against a
plate immersed square to a steady flow - the stalled situation -
increases with its depth of immersion & continues to increase as the
depth of its upper edge below the water surface increases. On that
basis, a deeper blade should suffer reduce slippage through the water &
so be a more effective propulsor.
I know the old coach's argument that the shaft of the blade should be
kept out of the water as, if immersed, it must be backwatering. Yet if
any of the shaft is significantly backwatering (enough to generate
measurable deleterious drag), that implies that part of the blade is
also backwatering. Observations tend to show this to be untrue, with
the "turning point" of the oar being inboard of the inner end of the
blade itself. In which case there is no drag penalty from a modest
length of shaft being immersed (& remember that drag is proportional to
the square of velocity, so is very small at low relative velocities, &
the shaft is of circular cross-section which is also a low-drag form at
low relative velocities)
I will return to this as more info & comments become available, & please
understand that I don't challenge your observations. All I would say is
that, reading between the lines, the Randallfoil appears to give you
much better control of your blades which, alone, might explain at fair
part of the benefit you have gained.
I would be very reluctant to criticise the technique of a 2x Olympic &
5x World Champion (plus 3 silvers and a bronze) of nearly 40. How many
of the world's very top athletes are as old? And your criticism of
Mahe's deep stroke technique should equally apply to that other great
Kiwi champion, Rob Waddell (1 Olympic & 2 World Golds). I think I'd cut
Mahe a bit of slack & allow him a less stellar season from time to time?
I'm not saying the system does not work, as clearly it works for you
right now, but I would look for a more solid fluid dynamic basis & more
Let's hope it really is a great step forward, but let's establish as
scientific basis too.