Re: Technique doesn't matter?

Teaplant wrote:
> postures, angles etc that can lead to the same bladework profile.
> However, the technique that matters is the horizontal force applied,
> and the length over which it is applied..this is the work done per
> stroke

The work done by the rower is always a lot more than the work that
actually moves the boat. The difference, the work lost in technique
inefficiencies, depends strongly on how the blade is controlled &
wielded. That is independent of strength & how the rest of the body
performs.

I was actually referring to the force the blade applies to the water
(the paragraph was about the blades, not about the rower) and I hope
this, and Newton's 3rd law, is sufficient to satisfy that you that we
are on the same page (as I keep saying).

I think my 'bladework' is your 'blade style' and my 'technique' is
your 'body style' . I maintain that poor 'body style' is what we
coaches should be correcting and improving, and that better 'blade
style' will come, Also that 'body style' is individual and a crew
won't always look uniform to be at peak performance. Too many coaches
look at the 'blade style' too much and then wonder why they lose - not
enough weights or ergo sessions usually being their conclusion.

teaplant.

We do agree on most of this. Where differences arise may be because we interpret words differently. I'm sure you & I understand this, but it may be worth my explaining this for the broader readership - RSR is always a communal experience - as it may help other readers, or it may just confuse :(

My concern, if I'm right, is that you see the blade as moving through the water. Newton does tell all we need to know, but we must first have the model right before letting him loose on it.

Think of the blade/water connection in the same sense as the tyre/road connection of a road vehicle. If adhesion to the road is perfect there is no relative movement & thus no work done between tyre & road. All the input work is given to moving the vehicle (accelerating its mass & overcoming all the other energy sapping process surrounding a moving vehicle). If the tyre skids a bit, _then_ there is relative movement & work is done (= shear force between tyre & road x speed of motion of tyre's contact surface relative to the road). But that work is all of it a dead loss; it produces noise, heat & smoke, but takes all of that away from the power delivered to the wheels by the drive train.

In an ideal world (for ultra-fast rowing) the water around the blade would bean inviscid but incredibly dense fluid. The thin blade would be able to cut end-wise into & through this fluid without any losses but would be completely unable to induce any motion in it. Thus no energy would be imparted to the water, so all work you put in would be 100% productive for propulsion. But there would be no movement by the blade, just rotation. There would be a virtual fixed fulcrum in the water. So force x distance, & force x speed, for the blade would be zero.

If the water now becomes a real fluid, of normal viscosity & density, then real fluid-dynamic consequences act to reduce propulsive efficiency by providing ways for energy to be lost from propulsion.

When you load real water with a real blade, it moves, because it is a fluid. Moving that fluid requires energy, in proportion to the mass of water moved x its velocity-change squared. In our earlier, infinitely dense, model the water was too dense to move at all, so no energy was given to it but, in real water, substantial water movement results, with significant abstraction of input energy which is later converted into heat by internal friction in the water, long after your stroke has ended.

How we row, absolutely governs how much energy gets given, in each stroke, to the water all around the blade. And that energy is stolen from what you put in. So all that remains for boat moving purposes is the difference. The ratio of energy left for boat moving to energy input is the overall propulsive efficiency, usually expressed as a percentage

Each part of the stroke has its own local propulsive efficiency. Some parts generate relatively more water motion causing a higher percentage of loss than others. How you load the blade in each part also alters the propulsive efficiency. So does the depth to which you immerse the blade. And there will be other factors....

In general, a less strong rower will have a higher propulsive efficiency since their blade loadings are lower, but will be less since the multiple of work done x efficiency will still be lower than that for a stronger person.

The point of all this is that you should be able to make useful performance increments by exploring the full potential of the 2 dimensions of the stroke (rotation & depth), plus the scope for redistributing the load through the stroke, & the way you engage the bits of your body, with their different strengths, response rates & masses, to apply these loads. I think that, in view of the time & money invested in the sport at all levels, we could & should do more to develop the science behind our technique.

Simply pulling harder, especially where that just digs a larger hole in the water, is a rather self-limiting approach. Getting the very basic science clearly understood & some of the popular misconceptions binned might be a good start.

Cheers -
Carl

--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: http://tinyurl.com/2tqujf
Email: carl@xxxxxxxxxxxxxxxxx Tel: +44(0)1932-570946 Fax: -563682
URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)
.

Relevant Pages

  • Hydrogen from bacteria?
    ... The mystery of how plants derive energy from sunlight by splitting water ... molecules into oxygen, hydrogen ions and electrons. ... machinery where water splitting occurs - the so-called "catalytic core". ...
    (sci.energy.hydrogen)
  • Re: The Future Navy Will Be Nuclear
    ... when it comes down to it the sun is the only reliable power ... With catalysts created by an MIT chemist, sunlight can turn water into ... dominant source of energy. ... would yield fresh water as well as electricity. ...
    (sci.military.naval)
  • Turning Power Plant Challenges into Clean Technology Opportunities
    ... Turning Power Plant Challenges into Clean Technology Opportunities ... Looks at Water and Renewable Energy ...
    (misc.invest.stocks)
  • Re: Best Books on Hydrogen Future Possibilities
    ... shift reaction of water with carbon to form hydrogen. ... energy from an outside source in addition to the methane feedstock. ... "Develop a comprehensive public education and outreach program. ... Commit resources for long-term education of students at all levels. ...
    (sci.energy.hydrogen)
  • What the oil companies dont get, the coal companies will: The lies about "clean coal technology"
    ... The WVDoE believes "that higher energy prices are providing and will ... Just this year, plans for a dozen new coal plants in Texas, Florida, ... Exacerbating the water crisis ... The answer is: toxic coal sludge. ...
    (alt.politics)
Loading