Study on correlation of C2 performance to OTW

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

Study on correlation of C2 performance to OTW

Postby strider » February 14th, 2018, 10:34 am

Have there been any studies, or individual reports of general correlations of Concept2
erg performance time to actual on the water performance time ?
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Re: Study on correlation of C2 performance to OTW

Postby c2jonw » February 14th, 2018, 11:03 am

Not really a study or report as such, but interesting reading on the topic here:
http://eodg.atm.ox.ac.uk/user/dudhia/ro ... index.html
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Re: Study on correlation of C2 performance to OTW

Postby jamesg » February 14th, 2018, 1:19 pm

The erg measures Power in Watts using Newtonian mechanics, and calculates speed using W=kV³. A cube law, because the resistance of water and air are related to the square of speed, and Power = Speed x Force. The k used is 2.8 so that an erg shows approximately the boatspeed that the same oarsmen in a 4- can deliver with no wind.
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Re: Study on correlation of C2 performance to OTW

Postby strider » March 21st, 2018, 10:28 am

The erg also gives power output for handle height that might not have an oar in the water.

One can watch elite rowers on the water miss 3-4 feet of water per stroke.
The erg handle would register power in that motion.

They also wash out, rather than have a skilled finish, pulling in to their waist, not pulling high to near the chest.
As the oar handle lowers, power to the water is reduced. On an erg, no power reduction.

The erg clutch ought to slip at wrong handle heights, no power recorded, just like a boat.
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Re: Study on correlation of C2 performance to OTW

Postby jackarabit » March 21st, 2018, 12:15 pm

Hard to learn to drink water by touching an empty glass to the lips. :wink:
There are two types of people in this world: Those who can extrapolate from incomplete data

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Re: Study on correlation of C2 performance to OTW

Postby gregsmith01748 » March 21st, 2018, 4:00 pm

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Re: Study on correlation of C2 performance to OTW

Postby jamesg » March 23rd, 2018, 4:05 am

One can watch elite rowers on the water miss 3-4 feet of water per stroke. They also wash out


Must have been a bad day, or maybe I need a new dictionary.
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Re: Study on correlation of C2 performance to OTW

Postby gregsmith01748 » March 23rd, 2018, 10:35 am

One other reference. Kleshnev built a model that allows you to plug in erg results, along with weight and it will predict on the water performance (if you have "elite technique"). Here's the link. I use it as a benchmark for steady state paces and interval paces. I am consistently a couple seconds slower on pace than what it predicts for my speed on the erg. I think that's fair given the amount of technique work that I need to do.

http://www.biorow.co.uk/RigChart.aspx
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Re: Study on correlation of C2 performance to OTW

Postby Paul N » March 27th, 2018, 11:34 am

jamesg wrote:The erg measures Power in Watts using Newtonian mechanics, and calculates speed using W=kV³. A cube law, because the resistance of water and air are related to the square of speed, and Power = Speed x Force. The k used is 2.8 so that an erg shows approximately the boatspeed that the same oarsmen in a 4- can deliver with no wind.


Hi James - is a 4- a coxless four (sweep); and a 4x is a sculling quad?

So does this mean the C2 erg pace I see is (roughly, perhaps very roughly) equivalent to what four of me in a four shell (sweep) could produce?

Thanks, Paul
Row: 500m 2:04.7 | 1k 4:19.4 | 2k 8:55.4 | 5k 23:13.7 | 6k 28:43.9 | 10k 49:31.8 | 1min 257m | 4min 908m | 30min 6,328m
Ski: 1k 5:18.5
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Re: Study on correlation of C2 performance to OTW

Postby lwtguy » March 27th, 2018, 4:11 pm

You are correct. The erg is calibrated to what four 180 (I think) lb men in a boat on flat water, perfect conditions, and perfect technique should be able to do. A 4x (sculling) is marginally faster than a 4-. The results would be fairly close though.
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6K 21:11.2-- 30' 8342m-- 10K 35:54-- 60' 16209m
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Re: Study on correlation of C2 performance to OTW

Postby Remo » March 27th, 2018, 9:46 pm

There is a line often bantered about by the on the water folks that, "Ergs don't float"

Notwithstanding, there is a strong correlation between C2 (weight adjusted) performance and OTW performance. The major difference is the C2 measures power whereas OTW performance is based on both power and efficiency (otherwise known as "technique"). There is a limit on your boat speed based on your power output. The better your technique the closer you can come to reaching that ultimate boat speed.

Every Olympic or National Team rower (apart from the coxswain) rows a big erg. And if you drop down to the collegiate, club or school crews, the boating will tend to reflect the rower's weight adjusted erg score, the better scores will tend to be in the first boat. And the winning teams will tend to have better weight adjusted erg scores then the defeated.

However, technique does count. A college friend of mine failed to make the US national team even though he had one of the biggest ergs in the country. In hindsight, his problem was he had trouble adjusting to the ever changing lineups at the training camps.

I also know a current age group world record holder for the 2k (he rows at my gym). If you watch him row, you would not guess that he is a world record holder. He does too much loopy stuff which distracts viewers from recognizing the power he generates. A few months ago, I asked him about his on the water experience. He told me that he first tried on the water rowing and never could sync up well with his teammates and he never mastered rowing a single scull. In other words, he failed to master on the water technique.

As far as correlation, C2 offers a Weight Adjustment Calculator http://www.concept2.com/indoor-rowers/training/calculators/weight-adjustment-calculator -- put in your weight, 2k time, and 2000m and out pops out a fairly realistic estimate of an 8+ (avg. weight and avg. 2k time), assuming flat conditions, excellent technique and 70 degree water.
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Re: Study on correlation of C2 performance to OTW

Postby Remo » March 28th, 2018, 2:18 am

jamesg wrote:The erg measures Power in Watts using Newtonian mechanics, and calculates speed using W=kV³. A cube law, because the resistance of water and air are related to the square of speed, and Power = Speed x Force. The k used is 2.8 so that an erg shows approximately the boatspeed that the same oarsmen in a 4- can deliver with no wind.


Not quite, the "k" factor is an artifact which dates back to to maintaining compatibility with the original Model A erg. The flywheel on the original Model A was bicycle wheel with a couple of plastic flaps attached to provide resistance air resistance. It had a single gear and a mechanical speedometer/odometer. Rowing hard, approximately every ten strokes, the speedometer/odometer would tick over and add another 1/10th of a km. When you got to 2.5, you had rowed 2.5k and if you were ahead of everyone else, you had won a hammer. Here is what the odometer looked like: Image

To maintain compatibility when they upgraded to electronic monitors, C2 programmed in a k factor to maintain the same ratio of Watts to Velocity as the original so that a score would be the same.

I doubt that in designing the initial erg, the Dreissigackers had any thoughts of approximating the boatspeed of either a 4x or 4-. Far more likely would be a USA collegiate 8, as that was both their personal experience and their market.
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Re: Study on correlation of C2 performance to OTW

Postby Paul N » March 28th, 2018, 4:28 pm

Thanks both - the main point then for me is that my erg times are not in any way to be taken as being equivalent to my best potential (i.e. assuming perfect technique) OTW times in a 1x.
Row: 500m 2:04.7 | 1k 4:19.4 | 2k 8:55.4 | 5k 23:13.7 | 6k 28:43.9 | 10k 49:31.8 | 1min 257m | 4min 908m | 30min 6,328m
Ski: 1k 5:18.5
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Re: Study on correlation of C2 performance to OTW

Postby gregsmith01748 » March 28th, 2018, 4:58 pm

Paul N wrote:Thanks both - the main point then for me is that my erg times are not in any way to be taken as being equivalent to my best potential (i.e. assuming perfect technique) OTW times in a 1x.


That's right. To put summarize. Speed in a boat depends on weight, the erg doesn't. Here are calculated "best case" paces for different weight rowers, assuming each of them can pull a 7:00 2K (1:45 on the erg) using the biorow model.

60kg - 1:53 (8 seconds slower on pace than the erg)
70kg - 1:55 (10 seconds slower)
80kg - 1:57
90kg - 1:59

In practice, I have never been able to come close to these numbers. I am about 4 or 5 seconds slower on pace than the predictor. The main reason is that I'm, frankly, too fat and too short. But I also need to work on my technique.
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Re: Study on correlation of C2 performance to OTW

Postby lwtguy » March 29th, 2018, 11:01 am

In a 1x, technique is the most important thing IMO. Followed closely by fitness. If you row poorly in a 1x you will never go fast. If you have OK technique, you might be competitive but people that have mastered the technique will always beat you.

The larger the boat, the more the buffer between technique and speed. You can still go pretty fast in an 8+ or 4X even if your technique isn't the best.
Bill, 23, 160-165 lbs.
PBs-- 500m 1:28.9-- 1K 3:08.9-- 2K 6:37.7-- 5K 17:27.6
6K 21:11.2-- 30' 8342m-- 10K 35:54-- 60' 16209m
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