Re: Evers-Swindell technique

KC wrote:
Carl Douglas wrote:

copied to top:

The blade will work best if spreading its influence over a greater
volume of water by working not just laterally (in 2-D), as you already
see it, but also vertically.


Beg pardon, Carl, but I most certainly *do* consider the stroke in all
four dimensions, not just 2!!! (or even one) Give me *some* credit!
:^)

Errr.... only now you tell me do I know that you, too, see the stroke as having a necessary 3rd dimension rather than a 3rd dimension rolled up insignificantly small ;)


There'll undoubtedly
be a "too deep" but, just as there's a "too shallow", we can't easily
know where the (perhaps relatively flat) optimum lies.


Agreed.


There'll be a price to be paid in getting deeper immersion but IMHO it
is not going to be high.


Basically we agree on the fundamentals, just our oppinions on the
implications thereto differ. These oppinions as we've all said, can
not be easily proven.

As the expression goes, "oppinions are like a**holes, everyone's got
one and they all stink!" ;^)


The easiest way to explain is to consider the dipping & lugging whaler
stroke. This looks painful but is in fact well evolved for rowing a
heavy boat. The blade motion in the water is diagonal in the vertical
plane,


Which vertical plane? If +y is in the direction of boat travel, +x to
port and +z away from the water, both the y-z and x-z planes could be
described as "vertical". I'm just trying to see what you mean by
diagonal, as most of the blade motions are on arcing paths, as I see it
(relative to a CS fixed to the boat).

The transverse section of the oar, projected onto the y-z plane, moves thus:
1. -z, -y
2. +z, -y
with the z components exceeding the y



keeping a good enough flow over the diamond or elliptical blade
x-section to sustain good hydrodynamic lift as it cuts first down &
astern & then up & astern, with very little time to generate actual
stall during the reversal.




That's my point - vertical motion can reduce stall by maintaining flow
over the back of the blade. So I'd not advocate going deep right


True, but current blades (Crokers and C2 anyway) are designed to
optimize flow from tip to root and vice versa, not vertical flow.

Ummm. Are you _sure_ that "design to optimise" is the proper term?

Actually even macon and tulip blades are better designed for flow from
tip to root.

Not a lot wrong with the curved back of your typical cleaver, although I might tend to agree that the shorter chord of the older blades might be no bad thing.

Whether technique dictated oar design, or oar design
dictated technique, I'm not sure.

The chicken is the egg's way of ensuring there will be future generations of eggs.


through the stroke, but that the depth be greatest at about mid-stroke.
The blade will work best if spreading its influence over a greater
volume of water by working not just laterally (in 2-D), as you already
see it, but also vertically.


I'm not so sure about that... again given current blade design. I
don't think that we're going to gain much lift at all from vertical
motion of the blade through the water, as the AOA is nearly zero
(thanks to the 4-6 degree negative pitch most people row with). Take
that pitch away, and you might have a nice AOA going in, but you'd have
a mess coming out. To facilitate a clean catch and release, you want a
near zero AOA in the vertical directions of flow.

You might have missed my subtle (?) point. Fluid dynamic lift is so energetically economical as a means of providing a reaction because, by moving chordwise through the fluid, the foil moves very large masses of fluid by only small amounts, whereas a parachute influences smaller masses of fluid by large amounts, disspipating lots of energy. Varying the vertical displacement of the blade (& ignoring any resulting lift contribution) will, as well as curing the ills of cavity formation, allow it to influence a somewhat greater vertical thickness of water even in the stall phase, with a similar if less striking benefit.


That means you must go quite deep. How
deep is that? I really do not know, except that should be deeper than
most rowers go.


Again, I agree, I just think those All-Blacks in the W2x were on the
excessive side.

When they start losing, I might become just slightly more persuadable.


BTW, an afterthought: I'm primarily a sweep rower and coach. When I
envision technique it is with sweep blades. I don't have a good
intuitive sense for the feel of sculls and their bouyancy or lack
thereof compared to a sweep oar. So it's possible that my comments on
how "hard" it might be to keep the hands that high with sculls are
misplaced, since I probably was thinking more about the feel of sweep
oars. Although I would think the "net" feel of bouyancy would be
similar... maybe not.


Sweep rowing makes it so much harder to sense what's going on when you change anything, because what you do can only be felt for its full worth if everyone else changes in unison from A to B - which never happens!

I think your oar will possibly be harder to hold deep than a pair of sculls, partly because of the larger volume you might displace, but possibly because you have less (effective) leverage due to hand positions & are affected also by the lopsided rule in sweep, which can't apply in scull, that one hand does this & the other does that. The stroke arc is also shorter, giving less time to play with that z-dimension than the sculler. And you'll piss of the coach & the rest of the crew if you start digging, & upsetting the balance, & coming out later ...... which does somehow inhibit experiment.

Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing low-drag Riggers/Advanced Accessories
Write: The Boathouse, Timsway, Chertsey Lane, Staines TW18 3JY, UK
Email: carl@xxxxxxxxxxxxxxxxx Tel: +44(0)1784-456344 Fax: -466550
URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)
.

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