Force curve for OTW rowing?

No, ergs don't yet float, but some of us do, and here's where you get to discuss that other form of rowing.
jbell
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Force curve for OTW rowing?

Post by jbell » June 11th, 2007, 4:12 pm

I was reading up on this issue and I have read two different views.
1: Have the graph peak early in the stroke and slowly decrease. These would be the same as getting the blade in and driving right at the catch.
2: Make the graph almost symmetrical. These would be hard finishes.
I know both of these are important in a stroke, but which one should I follow. If there is any interest, I will look for the website that had this info. I have heard the first point a bunch of times, but never heard of the second, although it does make sense. Any input?
PB's:
500: 1:39
2k: 6:43.3
6k: 21:44.1

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Re: Force curve for OTW rowing?

Post by PaulS » June 11th, 2007, 7:22 pm

jbell wrote:I was reading up on this issue and I have read two different views.
1: Have the graph peak early in the stroke and slowly decrease. These would be the same as getting the blade in and driving right at the catch.
2: Make the graph almost symmetrical. These would be hard finishes.
I know both of these are important in a stroke, but which one should I follow. If there is any interest, I will look for the website that had this info. I have heard the first point a bunch of times, but never heard of the second, although it does make sense. Any input?
#1 for sure, as long as you have good catch timing, otherwise what you get on the Erg may well be far from what you get in the boat.

You've never heard of #2? That's amazing! The "big finish" is probably practiced by the vast majority of rowers that think they are fast, yet consistently get beaten by those that can actually do #1.

They even labelled them #1 and #2 to make it easy.
Erg on,
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Post by jbell » June 11th, 2007, 7:34 pm

Thanks for the reply Pauls. It's not that I never heard of hard finishes, I just never heard of doing it on the erg. The only reason I was getting confused was on this site:
http://www.rowperfect.com.au/verificati ... rfect.html
This is the main pic that was screwing me up
Image
I realize that it is off the rowperfect webiste, but it should still apply to the C2, right? Also, I guess it would be to my benefit to make my stroke emulate that as much as I can? Thanks again.
PB's:
500: 1:39
2k: 6:43.3
6k: 21:44.1

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Post by PaulS » June 11th, 2007, 9:11 pm

Specifically the shapes would apply more to a C2 on Slides when comparing them to a RowPerfect, but even on the grounded C2 it makes sense to try to duplicate the Front loaded force profile, focusing on making sure that there is no pause at the catch and proper sequencing is maintained.

In the graphic below there are three distinct styles being used, the first and second of the top row are "coordinated" for good sequencing through the drive, the third indicates that the rower is openning the torso too early in an attempt to get the force on the handle quickly, but actual power production lags.

Image

Another thing that complicates the differences between the Erg and Boat is the difference between a chain/cog (solid) interface and the Blade/water (fluid) interface. The chain/cog will accept additional force at any time during the drive and issue a known reward for the effort, however the blade/water interface varies all through the drive, beginning with a very high efficiency which falls off rapidly, and near the very end (last 1/4) regains high efficiency (ONLY IF the fluid flow has not been terribly disrupted during the 3rd quarter).

From the RowPerfect graphic, if the "strong finish" were looked at in a mirror image, it would be what I would call very good indeed. A quick rise in force to a very sustainable peak, with a realtively fat middle, but the peak is reached and starting to fall prior to the mid point in the drive, where any hard pulling only causes more slip and reduces the efficiency at the finish. (Of course the rower will be producing a big washy puddle that looks impressive, it just does nothing to move the boat.)

There is another Biomechanics newsletter that discussed just this thing with respect to the Erg and it ends with the statement that a rower with the big finish is more likely to produce good Erg scores than move a boat quickly. (They will also be beaten on the Erg by the front loaded rowers [all things being equal], because the front loaded rower spreads out the power input in a more efficient manner.)
Erg on,
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Post by jbell » June 12th, 2007, 5:02 pm

Thanks for all the info Pauls. So even though I will be rowing on a grounded erg (mainly) I should still follow those diagrams? I guess I'm gonna have to work on applying power at the start of the stroke rather than the middle / finish. Any chance you have that Biomechanics newsletter? It sounds intriguing.
PB's:
500: 1:39
2k: 6:43.3
6k: 21:44.1

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Post by PaulS » June 12th, 2007, 7:47 pm

jbell wrote:Thanks for all the info Pauls. So even though I will be rowing on a grounded erg (mainly) I should still follow those diagrams? I guess I'm gonna have to work on applying power at the start of the stroke rather than the middle / finish. Any chance you have that Biomechanics newsletter? It sounds intriguing.
The specific RBN in question.

www.biorow.com
- will get you to all of the RBN that are online.

My personal preference is a combination of the Grinko and Rosenberg styles, Sequenced, but with a stronger torso than Grinko indicates.
Erg on,
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Post by ranger » June 22nd, 2007, 8:46 am

I didn't realize that, in the Rosenberg style, the torso is strongest lever, stronger than the legs.

Peak pressurse is reached when the back reaches its peak.

Interesting.

ranger

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Post by NavigationHazard » June 22nd, 2007, 2:24 pm

ranger wrote:I didn't realize that, in the Rosenberg style, the torso is strongest lever, stronger than the legs.

Peak pressurse is reached when the back reaches its peak.

Interesting.

ranger
The torso isn't the strongest lever, the legs remain stronger.

Kleshnev's depictions of the different rowing styles track POWER / output rather than FORCE / rower input. They're intended to show what happens to instantaneous watts (vertical scale is "POWER") as force is being applied sequentially to an oar sweeping through its arc from catch to finish (horizontal scale is "ANGLE').

The Rosenberg style aims to achieve maximum output as the blade is starting to approach perpendicularity vis a vis the hull. Thus it commits the trunk fully rather earlier than the other two styles. Because blade efficiency is approaching its highest at this point in the stroke, the comparatively early, full commitment of the trunk has a significant effect on peak power output. The downside, of course, is that power output falls off rapidly from that peak because the legs and then the trunk are 'used up.'

The Grinko style is considerably more 'front loaded' than the Rosenberg style, aiming to get the oar blade accelerated as quickly as possible after the catch. It commits the trunk rather later in the stroke than does the Rosenberg style. Because the legs have been 'used up' more quickly in the Grinko style than they are in the Rosenberg style, adding in the trunk later tends to extend the instantaneous watts curve to the right rather than increase its amplitude. That is, you get fewer peak watts from the stroke, but the power falls off less quickly from its peak.

The DDR style tries to commit legs and trunk together throughout as much of the stroke as possible. The net result is a comparatively symmetrical instantaneous watts curve that privileges a 'fat middle'.

The answer to 'which one drives a boat faster' is Olaf Tufte. :wink:
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Post by Ray79 » June 22nd, 2007, 3:27 pm

NavigationHazard wrote:The answer to 'which one drives a boat faster' is Olaf Tufte. :wink:
Mr Drysdale may have something to say about that..... :wink:

http://video.google.co.uk/videoplay?doc ... &plindex=8

http://www.youtube.com/watch?v=bvIONbiofFg -- World Fastest time
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where do I go from here

Post by mikvan52 » November 1st, 2007, 8:01 am

I'm primarily an on-the-water (OTW) sculler.

Getting into the "lull" between seasons, I'd like to revisit this thread and ask a couple of questions. The shift to Indoor Rowing prompts me, again, into thinking about the merits of the three styles Nav. Haz. describes:

(assume the following terminology):
NavigationHazard wrote: The Rosenberg style aims to achieve maximum output as the blade is starting to approach perpendicularity vis a vis the hull. Thus it commits the trunk fully rather earlier than the other two styles. Because blade efficiency is approaching its highest at this point in the stroke, the comparatively early, full commitment of the trunk has a significant effect on peak power output. The downside, of course, is that power output falls off rapidly from that peak because the legs and then the trunk are 'used up.'

The Grinko style is considerably more 'front loaded' than the Rosenberg style, aiming to get the oar blade accelerated as quickly as possible after the catch. It commits the trunk rather later in the stroke than does the Rosenberg style. Because the legs have been 'used up' more quickly in the Grinko style than they are in the Rosenberg style, adding in the trunk later tends to extend the instantaneous watts curve to the right rather than increase its amplitude. That is, you get fewer peak watts from the stroke, but the power falls off less quickly from its peak.

The DDR style tries to commit legs and trunk together throughout as much of the stroke as possible. The net result is a comparatively symmetrical instantaneous watts curve that privileges a 'fat middle'.
Let me add the following to the mix:

I have a problem balancing OTW rowing style with going for good performances OTErg. Elsewhere, I've been advised: "The problem is that the erg and boat are two different feels. The erg is lighter at the catch and then gets heavier to the finish. The boat is heavier at the catch and lighter at the finish."

I don't want to be faced with trying to master one form for the water and another for the erg. I don't even believe it can be done.

While my watts curve OTE (while I'm rowing without thinking about it) resembles the DDR style (tending sometimes to the Rosenberg form), I still wonder where improvements could be made in my quest for speed.

Now, given that "the erg is lighter at the catch" (than sculling): Doesn't this mean that it is easier to get god erg scores using the Grinko style of rowing? As can be seen above, I'm weak in the Grinko dept.!

On the other hand: During 700-800 k of OTW work this spring-fall I've been rediscovering the value of being able to propel the boat best at mid-drive. Heavy legs at the catch (Grinko style) seems to "pinch" the boat and, since I'm not a humongous beast of a rower, it's hard to push through to a strong mid-stroke over the course of a head race distance. I have the bias of thinking that Grinko style sculling will wear me out. The DDR approach seems to better suit me.

Load on the oars matters too: When I'm using longer blades I sweep through a powerful mid-drive employing a lower rate (spm). It hurts more but I seem to go faster over the 3mi.-5k distance by accelerating the blade a little more slowly and taking advantage of the efficiency of the mid-stroke (force vector parallel to the hull).

Where do I go with making changes in style from here?... I don't really know :?: :?:
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Post by PaulS » November 1st, 2007, 8:59 am

Remember that the "Style" paper is showing "Power" profiles and the PM3 shows "Force" Profiles, while they can, and should (IMO) be similar, they are in fact, very different metrics.

The main difference between what might make an Erg register a good pace and what will advance a Boat/Rower system well has to do with the way we connect with both. The Erg has a rigid chain/cog connection that is fixed, the rower has a fluid and dynamic connection with the water and the nature of that connection makes it even more important to execute certain things differently during the different phases of blade efficiency.

Two main, and common errors:
1) An early rise in force in a boat does NOT "pinch" the boat.
2) The point at which the shaft is perpendicular to the hull is NOT the time to be applying peak pressure. (unless you accept that shortening the acceleration impulse and wasting energy input by whipping up the water is a good thing.)

I like the characterization of the Erg going from light to heavy and the boat going from heavy to light (Erg+Slides may be more 'boat-like' in this respect), however if the difference is obvious, there are technical errors that need to be worked out for the best performances on either.
Erg on,
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Post by Nosmo » November 1st, 2007, 5:36 pm

In college rowing an 8, I was taught to have a very stong hard catch.
Since the beginning of July I've been rowing a 2x with a very experienced coach.
He has emphasized:
1) get the blades completely covered before applying any power
2) Matching the speed of the boat at the start of the stroke
3) Apply power smoothly and so the oar handle accelerates
continually and smoothly.

This is definitely not a hard catch, and the fast scullers that I've talked to in my club do not recommend a hard catch.

Comments on this advice?

My 2x partner/coach has a very smooth force curve that looks like the Rosenburg style, but has some hints of the Grinko. Mine is a bit more like the Grinko with hints of Rosenburg, but I am inconsistent and it very often has some small bumps in it. A couple of coaches who have seen me on the erg don't see anything that would cause the bumps. (one comment was "how do you do that?")
Even so I've been told we now look very good together in the boat and have convincing won 3 out of 3 head races this fall. The fourth next week should be tougher.

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boat pinching

Post by mikvan52 » November 1st, 2007, 8:37 pm

Paul S sez:

"1) An early rise in force in a boat does NOT "pinch" the boat."

I reply: I've been told (and it makes sense) that if you balanced a 1x on the surface of a frozen lake and went to take a stroke against two poles embedded in the ice: the single would not move. That is, the boat would be pinched by the vector forces of the drive against stationary points.
The slippage of the fluid water lets the boat move. A non-moving boat is "Pinched".

What I meant: any force at the catch pinches a boat.

So, an extention of this observation: It would make sense to me that more energy is lost at the catch than toward mid-drive (where the vector forces are parallel to the direction of the boat.

The erg doesn't have the physics of this built in....

An athlete OTW has a finite amount of energy he or she can apply on each stroke. Legs should come on quite hard at he catch OTW but not to the detriment of having a great mid, and mid/late drive where a high percentage of the energy will result in boat speed.
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Re: boat pinching

Post by PaulS » November 2nd, 2007, 9:00 am

mikvan52 wrote:Paul S sez:

"1) An early rise in force in a boat does NOT "pinch" the boat."

I reply: I've been told (and it makes sense) that if you balanced a 1x on the surface of a frozen lake and went to take a stroke against two poles embedded in the ice: the single would not move. That is, the boat would be pinched by the vector forces of the drive against stationary points.
The slippage of the fluid water lets the boat move. A non-moving boat is "Pinched".

What I meant: any force at the catch pinches a boat.

So, an extention of this observation: It would make sense to me that more energy is lost at the catch than toward mid-drive (where the vector forces are parallel to the direction of the boat.
Apologies, I hadn't realized that you are rowing a non-moving boat. :roll:

Boat Pinch Myth - Busted.

Old discussion, and there is a lot more.
Summary: Until you get to somewhere in the range of <15deg (and nobody does) you do not "waste energy" pushing water sideways.

But of course, I'm referring to rowing in boats that are actually moving, so may be taking undue liberties with regards to this discussion.
Erg on,
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Post by mikvan52 » November 2nd, 2007, 12:46 pm

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 :idea:

-thanks for your help
-Mike
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American 60's Lwt. 2k record (6:49) •• set WRs for 60' & FM •• ~ now surpassed
repeat combined Masters Lwt & Hwt 1x National Champion E & F class
62 yrs, 160 lbs, 6' ...

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