Concept2 Forum

Good Morning,
I was looking at my personal best' and thought to myself "I can beat this one " my pb was from 2010. And I beat it the other day, so that's good. My question is if I had the damper set at 3 in 2010 and the other day it was set at 5 does that actually change the time? I'm sure the drag factor in 2010 was maybe 90 but the other day it was reported at 110. I probably should re row it at a 3 damper just to see.

Thoughts?
Have a great day and thanks for reading.
Chris

C2 adjusts for the drag factor. Please note that you should always rely on the Drag Factor (the 90 / 110) as this varies with temperature, anything covering inlet or outlet from fan and dirt in the fan. Of course the stroke is different, so you need to find what setting works best for you.

Changed drag factor does not change the time, but it indicates the flywheel decelerates faster or slower (higher drag or lower drag) and it's acceleration also feels different (heavier or lighter).
There is no right or wrong setting, like iain wrote, it's a personal preference. Lighter drag enables a faster acceleration, if you are fast. Heavier drag is probably better suited for more strength related or not so fast people. You have to find out what group you're in

Sakly wrote: ↑

August 28th, 2024, 10:16 am

Changed drag factor does not change the time

A nuance to this remark. As Iain indicates, a higher drag results in a higher pace and larger distance travelled for a specific movement of the flywheel. The PM5 calculates drag and will compensates for this. Drag behaves a bit like gears or using a longer oar: a higher drag will make the stroke heavier, bit you'll move more per stroke. A lower drag results in an easier/lighter stroke but less displacement.

As said, most people have a preference for the one or the other.

JaapvanE wrote: ↑

August 28th, 2024, 10:42 am

Sakly wrote: ↑

August 28th, 2024, 10:16 am

Changed drag factor does not change the time

A nuance to this remark. As Iain indicates, a higher drag results in a higher pace and larger distance travelled for a specific movement of the flywheel. The PM5 calculates drag and will compensates for this. Drag behaves a bit like gears or using a longer oar: a higher drag will make the stroke heavier, bit you'll move more per stroke. A lower drag results in an easier/lighter stroke but less displacement.

As said, most people have a preference for the one or the other.

This is not true. A higher drag only leads to a greater covered distance, if you can accelerate the flywheel with the same speed at the same stroke length. If you cannot pull the same stroke speed and length at the higher drag, the calculated distance will probably be the same as on lower drag with a higher acceleration.
This is why drag alone isn't the solution.

Sakly wrote: ↑

August 28th, 2024, 12:01 pm

A higher drag only leads to a greater covered distance, if you can accelerate the flywheel with the same speed at the same stroke length.

Hence my explicitly stated point about a specific movement (=angular displacement) as a requirement. Please note that acceleration is NOT in any way part of the pace or distance calculations of a PM5. Only average flywheel speed across the entire stroke is. This provides some interesting opportunities to change the stroke to keep the average flywheel speed the same while requiring less flywheel acceleration (i.e. change the ratio of the stroke).

Sakly wrote: ↑

August 28th, 2024, 12:01 pm

If you cannot pull the same stroke speed and length at the higher drag, the calculated distance will probably be the same as on lower drag with a higher acceleration.

I admit that drag isn't much of a compensation for a lower average flywheel speed, but you can't rule it out either. When calculating linear velocity u across the stroke, the PM5 seems to use

u = (k/C)^1/3 * ω

where ω is the average angular velocity in rad/sec across the stroke, C is 2.8 and k is the dragfactor/10^6. k is included in the cuberoot, so it will not do much, but it is more than nothing.

In theory, you can actually pull slower and get the same or higher speed as long as the drag can compensate. Mathematically, this is possible. In practice, to have meaningful impact, it is very difficult as you are taking the cuberoot out of a small number, and doubling the dragfactor (!) then only has a very limited effect.

JaapvanE wrote: ↑

August 28th, 2024, 10:42 am

Sakly wrote: ↑

August 28th, 2024, 10:16 am

Changed drag factor does not change the time

A nuance to this remark. As Iain indicates, a higher drag results in a higher pace and larger distance travelled for a specific movement of the flywheel. The PM5 calculates drag and will compensates for this. Drag behaves a bit like gears or using a longer oar: a higher drag will make the stroke heavier, bit you'll move more per stroke. A lower drag results in an easier/lighter stroke but less displacement.

As said, most people have a preference for the one or the other.

Quoting this again - sorry, I've missed to read that specific part properly. Sometimes I respond too fast

Sakly wrote: ↑

August 28th, 2024, 1:25 pm

Quoting this again - sorry, I've missed to read that specific part properly. Sometimes I respond too fast

Happens to the best of us. No problem.

"Distance" on the Erg is a completely contrived quantity. It measures work and time and converts to distance using a somewhat arbitrary formula.

The amount of work you do depends on: how hard you pull; how far you pull; how often you pull.

If you set the drag factor low and can pull with the same force for the same distance, you do the same amount of work per stroke. As a bonus, your stroke is completed more quickly, so you can have a slightly more relaxed recovery while achieving the same stroke rake.

gvcormac wrote: ↑

August 28th, 2024, 6:02 pm

It measures work and time and converts to distance using a somewhat arbitrary formula.

The formula isn't arbitrary at all. It is an extremely elegant application of the law of conservation of energy. In essence, they say the power in the rotational system (P = k * ω^3) must equal the power in the linear boat (P = C * u^3). In essence, C is the drag of a hypothetical boat (also named a magical constant by some). The founders of C2 found that setting that drag to 2.8 matches their experiences with OTW rowing. Both being accomplished Olympic rowers, they nailed it pretty well. More advanced competitors like RP3 also use the same values, but allow setting a different boat type (thus changing the constant C. But their "seat if the pants" approach of determining a racing shell's dragfactor still sets the standard.

Ooof,
Thank you all for that great input. I am by no means gonna fake that I understood most of that. I think I will be happy thinking that - for me my pb is what it says it is regardless of the df or the damper setting.
Thanks to all I appreciate it .

Chris

fake that I understood most of that

No need. Power, which is what the erg measures, is Force x Speed. Ergdata lets us see both as generated during each stroke pull.

So we set the drag to a level that lets us use our best combination of the two, using standard rowing style as ilustrated by C2.

Pull speed might be 2m/s, and pull force (in Newtons) half your weight x 10. At rate 20, enough to keep you fit.

solomon wrote: ↑

August 28th, 2024, 8:34 pm

I think I will be happy thinking that - for me my pb is what it says it is regardless of the df or the damper setting.
Thanks to all I appreciate it .

Chris

Exactly right. Unless they (incorrectly) think that a specific df is the magic bullet, no one cares what df you used to get a result. It certainly doesn't make it better or worse, albeit I am astounded by the outliers who can row everything at circa df200.

JaapvanE wrote: ↑

August 28th, 2024, 6:46 pm

gvcormac wrote: ↑

August 28th, 2024, 6:02 pm

It measures work and time and converts to distance using a somewhat arbitrary formula.

The formula isn't arbitrary at all. [ . . . ] But their "seat if the pants" approach of determining a racing shell's dragfactor still sets the standard.

OK, substitute "seat of the pants" for "arbitrary." Watts (e.g. work per unit time) gives you a linear, much more interpretable, reading of effort than "distance" or "pace" or "speed" which are often speciously equated with stroke rate, or flywheel rotational speed.

gvcormac wrote: ↑

August 29th, 2024, 7:43 am

Watts (e.g. work per unit time) gives you a linear, much more interpretable, reading of effort than "distance" or "pace" or "speed"

My work as a person isn't accurate anyways as a huge energy expenditure is omitted in C2's calculations: me constantly accelerating and decelerating about 100Kg up and down a slide.

To be honest, I have huge difficulty in rowing 100WHours or 10KJoules, especially since it lacks any indication for intensity of the effort. And I absulotely dispise rowing for a fixed time. I hate every second of it. With a fixed distance I have a feeling of more control: if I want to get off the machine, just increase the pace. So I'll take a 10K @ 2:05/500m much easier than row 125 WH at 179W.

gvcormac wrote: ↑

August 29th, 2024, 7:43 am

"distance" or "pace" or "speed" which are often speciously equated with stroke rate, or flywheel rotational speed.

I hate to bring it to you, but everything you do on a PM5 (or any rowing monitor) comes down to one variable: angular velocity of the flywheel. That is the only thing actually measured. Rest of the metrics depend on it, including dragfactor. When you can accurately calculate angular velocity and dragfactor, the rest of the metrics is a given.

Strokerate is just a means to produce average angular velocity in a specific way. From a metrics perspective, strokerate (and thus stroke detection by the PM5) is only relevant as it provides a convenient way to present metrics (and allows for drag calculation as that needs a recovery). With ORM we actually designed algorithms to be robust against missed stroke detections, aside from some lack of update of specific metrics, it doesn't make one iota difference.