mikvan52 wrote:Paul:
I still don't see that you've addressed the crux of my question.
Let me put it another way by asking some questions:
Is it true that an oar blade entering the water at a typical catch angle creates a swirl behind it?
If so, does this swirl indicate a loss of energy in the blade water system?
If the water was unable to swirl, would the boat move?
Can this loss be expressed as a percentage of force applied?
Closer to mid drive: Is this slippage less or more?
I assume it's less.
Therefore: Regardless of the total force generated anywhere in the drive, is a higher percentage of force applied lost at the catch than at mid-drive?
All this being said: strong catches are needed because that is when the strongest muscle groups are called upon.Yet: A strong catch can be over done. Once the boat is a race speed: efficiency and the management of finite energy reserves becomes the key. Perhaps the "left-leaning haystack" shape so highly sought after on the erg is of less value (not no value) OTW because, less energy gets loss when the oar is moving closer to the perpendicular.
The graph you reference do not address the relative strengths of the different muscle groups in the body... the graph seems to show me (unless I'm missing something) that the most force is generated at the catch. I recognize and accept that.
I would like to be able to flesh out this examination some more as it bears on the relative values of the DDR, Grinko and Rosenberg styles as it applies to OTW rowing.
In my own private realm: I ask myself: "Why am I (w/a 17:49 5k erg time) able to beat another person in my age group OTW who is over a minute faster than me OTErg"? Could it be that I am more of a Rosenberg/DDR style than he? ( I assume that my competitor is a Grinko (left learning haystack) style erger....Or, is it isomething else entirely?
As you see, I've a practical purpose for these ramblings
-thanks for your help
-Mike
No, until there is some force on the handle there is no swirl created, just as with a wing lifting a plane, the vortex is the necessary byproduct for the “equal and opposite” force in opposition to our muscular force. “Turbulent flow” is the “wasted” energy.
If the Blade were unable to travel through the water (flowing along the blade) the boat would indeed be immovable. Quite unlikely this will happen, but on a similar note, air can be too thin for a wing to provide the designed capacity of lift for a given speed also.
There is far less loss near the catch and release than during the 15 degrees either side of perpendicular.
Blade Efficiency, note that 100% is up. And that inverting the efficiency profile would be a pretty good force profile. The only hitch being that we can’t really expect to increase the force at the release. But we can try to maintain it as long as possible.
That's the problem with assumptions, especially in rowing.
Discussion of force profile.
I would suggest that “the left leaning haystack” directly addresses the relative strengths of the muscles groups employed when rowing.
Why are you faster, you are likely a better rower in a 1x, lighter, or both. I’ll also add that the force profile produced on the Erg, may or may not be what actually gets produced in a boat. The Rosenberg is probably the easiest to take between the two situations because it requires less accurate timing at the catch. The Grinko is the most difficult, requiring the most accurate catch timing. Though for the same input energy the Grinko will produce far faster Avg speeds in the boat due to using the blade more effectively/efficiently.
I row with a Rosenberg or DDR every so often, and it’s easy to get the boat as fast as they think it should go for the effort, but the boat is still moving far slower than what I would like it to go for the input. I can demonstrate very easily with a short exchange of individual rowing in a 2x at “comfortable” pressure. The strange part to the “rider” is that they feel what they interpret as “check” (negative and subjective) but then see the actual speed increase in the objective instruments. Often leading to a question “Why?”, which I try to answer with much of the same information being relayed here.
The fastest boats have a front loaded force profile. i.e. 8+ Vs “everything else”, the faster the boat the more front loaded the drive. Now the real question is: Are the boats faster because of the front loaded drive or does the front loaded drive happen because of a faster moving boat? The former makes sense, the later simply doesn’t. For instance, just because I ask you to “get on it quicker” doesn’t mean you will be able to; in fact it’s highly unlikely that you can make such a sudden change without sacrificing some other part of technique.
If you have the time, spend a good amount reading and thinking about the various data collections at
www.biorow.com sometimes the interpretations are not as good as I'd like, but the data is quite good.
I don't think I'll be back OTW 'til next March (I live in VT and will travel to Florida for some preseason work then)