Resistance Issue

[iain]

... Most would not find a clean machine on D10 ideal for a fast full length pull, especially if using mostly their arms.

Sorry to be a pedant as your point is well made, but I would dispute the "arms" point. I agree that you would expect that the weaker muscles capable of contracting more quickly would expect to benefit from a lower DF, but my (admittedly subjective) experience is that a higher proportion of the power is generated by the upper body at higher DF. I have assumed that this is because these elements come in when the speed is higher and so are potentially producing lower power at faster speeds as well as acting for longer due to a slower power stroke. This effect is most obvious on new rowers who under use their legs who have a proportionally greater increase in pace at higher drag.

[JaapvanE]

I didn't know the age of the topic poster nor his technique, but probably neither did you. I prefer to extrapolate from a serious scientific study about the effect of the drag factor, even if the populations might not match.

The main question is if one can if the populations do not match. And N=10 is hardly a serious scientific study, especially when one conducts a quantative study that is focussed on a single rowing club. Club training policies are too dominant in such an experiment to make this well generalizable beyond that point (for example: are people systematically training at DF225?).

The experiment conducted only shows that 10 collegiate rowers at that specific club can achieve the same pace on DF's between 100 and 150 for three minutes. We don't know about the specific club policy or even mandates, but national teams mandating DF130 for all time trials and training is far from uncommon. So (without any knowledge about their usual training regime), effectively, this study seems might only suggest that 10 20-year olds can cope with a variation of +20 and -30 with respect to their normal DF for 3 minutes. Given the aerobic and anaerobic tolerance of your average 20-er, hardly surprising. Extrapolating this to older age groups or distances seem unreasonable to me, as this tolerance is decreases when people age and this tolerance will also disappear for all age groups when the piece gets longer.

Extrapolating the N=1 experience from someone in a rehab phase who's mind is worried about pulling too heavy, seems rather odd to me.

Nah, when rowing I'm the same mindless monkey I was over a year ago. I'm not the worrying type, I blame my old primary sport where mistakes can be fatal and serious injuries were aplenty. I did my one of my best races with a broken wrist, and the currently reigning world champion broke his hand days before winning the most important race of the 2023 season.

I want to extend this debate for one specific reason: it is not the first time on this forum that club or gym ergs that in the well-known phrase of Citroen are suspected to be "full of dust, crud & cruft" are also conveniently thought to be the explanation for significantly lower 500m splits (or a much higher wattage).
My question to those who support this explanation is : by what mechanism ?

If a lower drag factor from dust, crud & cruft improves the 500m split, why don't we all emulate such a poorly-maintained erg by setting the drag factor on the home erg much lower? Doesn't C2 teach us that when set at the same DF, all ergs behave similar ?

All Ergs may be created equal, but as any mechanical engineer or car mechanic will tell you: its life afterwards and maintenance make a huge difference in mechanical performance. I read Citroen's "full of dust, crud & cruft" as a shorthand for "a total disregard for any decent maintenance procedure". Where obstruction the airflow and mechanical movement of the flywheel is indeed part of the dragfactor, 95% of the mechanical issues are not. Bluntly speaking, unless the one-way clutch locks up, any mechanical issue isn't accounted for in the DF. There are quite a number of bearings in a C2, and a mechanical chain, where a machines life history will have a significant impact on machine performance without being seen in the DF.

And these mechanical effects are numerous and potentially significant. Some effects of a machine are positive: initially a machine will "wear in": bearings and chains will get less friction due to the wearing in. That is why you need to be careful with your car engine in the first couple of hundred kilometers: the engine and drivetrain have to set and wear in. And yes, a good mechanic can tell you if the wear in period has been right or not (my father did performance tuning of race cars, and it was actually one of their services for professional teams). So it might very well be that a home machine with a couple of million kilometers on it might feel heavier than a intensely used machine in a boathouse with tens to hundreds of million kilometers on it. Lack of maintenance and wearing out might have a negative effect on this, as the chain stiffens, bearings run dry, etc.. But lack of use is very well known to cause issues as well. Cars, airplanes and many machines actually require inspection or even revision if they have been standing still for too long: oil will have dried out, bearings might have been standing still for a long time, rust has a chance to form, etc.. So you could encounter a (well maintained intensely used) machine that might feel like a knife through butter, where another (new) machine might feel heavy.

Aside the mechanics, I like to think that C2 has added the dragfactor mechanism for a reason. If it wouldn't matter for the user, why would C2 bother with the complexity?

Your position seems to be that DF does not matter for the times that can be achieved. So lets go to the extremes and I dare you to repeat the experiment I performed over a year ago, and row a 10K on DF70, DF135 and DF225. My conclusion is that there is a huge difference as you switch from a primary aerobic approach to a primary anaerobic approach. Thus by sheer interpolation on a completely analogue system, this must also present in between these values, although less pronounced. I realise there are some thresholds present. One extreme threshold is where the flywheel is too fast for the user (DF too low and user can't accelerate enough to catch it), so you have an ineffective catch where the power loss can be huge. The other extreme threshold is when the DF is too high, the flywheel is too slow and thus requires greater forces to get going again, potentially going beyond the physical capabilities of the user in the long run (i.e. power-endurance is lacking). But in between, you will see a gradual shift between aerobic and anaerobic power generation, where somewhere in that spectrum a personal optimal balance is present.

As James already said: DF is an essential part of the transfer of power from the user to the flywheel. The rowing motion isn't a simple mechanic drive where power is transferred continuously. That transfer is quite a fragile narrowly-timed interaction (you are talking 0.05 sec range precission timing) between a user and a flywheel, and when you touch the DF, you change the rhythm and powers involved. And, as I tried to exemplify by my own practical experience: changing the rhythm can have a significant impacts, even if one goes beyond a one-off row and invest significant time in adjusting the timing. These timings can have subtle impacts, and break the flow of the stroke. Not getting the catch well can play havoc with your entire stroke, and thus with the power transferred.