Apr 7 2019
These guys seem to be happy fiddling, but the combination of Sander, rowing electronics, and fiddling is not a pretty sight.
Today there was too much fiddling with the Quiske app. I had moved the sensor to under the seat, but I am always uncertain about the correct orientation of the pod, and there is no quick google answer to that. Quiske has a couple of user guides and other documents, but all I need is a simple table which I could print out and put on the inside of my locker door.
|Pod Position||Pod Orientation|
|Under Seat (OTW)||Oar handle from logo pointing to stern|
|On oar||Oar handle from logo pointing to rower|
|On oar||Pod facing towards bow during drive|
|Under Seat (OTE)||Oar handle from logo pointing to erg handle|
I think I got this correct, but I need to check it.
What added to my frustration is that the Quiske app sometimes doesn’t update the lines. The only way to get it to behave again is to go out of the application, kill it, and start again. Or, at least, that seems to be the procedure. On the water, of course, I am trying out all kinds of menu and settings combinations before I kill the app.
Anyway, enough about fiddling.
When I had finally set up my gear correctly at the end of the warming up, I was happy to find myself alongside another Masters team. In the spirit of GDPR, I shall not reveal who it was, but suffice to say it was a big, coxed, sweep boat. And there were eight ladies in it. Of varying age. The prettiest lady being Martin on stroke seat.
So, of course, I wanted to focus on technique, get some good Quiske curves measured at various stroke rates, but I also wanted the eight to not pass me.
We did three full lake stretches of about 3 kilometers each, and the score was 3-0 for the single sculler. Well, in the first two stretches the eight was also doing technique drills, but in the final one, they were rowing at a steady pace.
Workout Summary - media/20190407-172713-Sharing file: SpdCoach 2136923 20190407 0426PMo.csv
The summary table shows the splits for the pink intervals shown on the chart. Looks like it was a bit harder training than intended. Well, I don’t think it hurt me. A bit of good sparring with random other crews (preferably when they are not aware they are in a race) is always healthy, I think. It pushes me a bit further.
And now follows a whole bunch of Quiske charts.
An interesting observation. At 22spm, my seat is accelerating during the recovery, but as stroke rate increases this acceleration disappears and at 28spm (and higher) the maximum seat speed is during the middle of the recovery.
Seat speed during recovery is, for me on the single at least, an intuitive thing. I hope I am trying to not slow the boat down too much, but to be honest I am not sure how I determine the subtle things (or not so subtle things) I do on the recovery. I did not try to change my natural rowing style in this outing. I just wanted a good baseline of my current style.
By accident, I produced the above chart with the handy red lines on the Quiske web portal. I presume the lines coincide with, from left to right:
- Maximum deceleration of the boat (that is where Quiske places the start of the stroke cycle)
- Maximum acceleration of the boat
- Maximum boat acceleration during recovery (?)
- Seat speed reversal point
- Same as 1.
So what can we learn from this chart? To me the most significant point to notice is how much the boat slows down after the seat speed reversal. What Quiske cannot say if this is before or after the blade has entered the water. Here is a “powerpoint attempt” to determine this.
So what have I done here? I basically combined a few analyses from yesterday and today, selecting strokes at 27-28spm. I looked at the boat acceleration curves (not shown here) and determined that they were all very similar. From that, I conclude that these curves represent my typical (average) stroke at 28spm. Then I took screenshots of the oar angle velocity and seat speed curves (measured at different days) and in PowerPoint, I overlaid these charts, drawing a few vertical lines to indicate “significant” moments during the stroke. From left to right:
- Maximum boat deceleration point (Quiske stroke cycle start). Both the scull and the seat are moving. Quiske doesn’t tell if the blade is already in the water or not. During my rowing, I am making nice “V” splashes with the blade. That means that at entry, the blade is not moving in the reference frame of the water. However, because the boat has a non-zero speed, this means that I must be already moving the oar (and seat). At this point, the seat speed is about 0.56 m/s, the oar angle velocity is about 29 degrees per second from the measurements) and the boat speed is 3.1 m/s. If I wouldn’t open my back, then with my rig, the seat speed would translate to a blade speed creating a forward splash. If I look at the oar angle speed, the blade hits the water with a slightly negative speed, creating a backward splash. What happens in reality, I think, is that the blade enters the water a bit earlier than the Quiske stroke cycle start. The conclusion that I am opening my back still holds though. Interesting. Need video evidence.
- I have drawn the second black line at the point of maximum seat speed. What I find interesting here is that the oar angle speed curve shows a more pronounced bend than the seat speed curve. That would suggest that I stop opening my back here. After this point, the seat speed starts to decrease while the oar angle velocity keeps increasing. This is where I start the back swing.
- The third black line is at the point where the seat stops and my oar angle velocity is close to maximum. I suspect that this is close to the moment where I end the back swing and start the arms only phase.
- The fourth black line is at the point where the oar changes direction. This is slightly after the tap down.
- The fifth black line is at the point where my seat starts rolling again. Arms are away and, hopefully, the body is rocked over. Or is it?
- The sixth black line is at the end of seat acceleration. You can see that during the entire seat acceleration phase, the oar anglular velocity is roughly constant. That suggest that my body rock over hasn’t fully finished when my seat starts to go towards the stern. This is not necessarily a bad thing. After this line, there is a phase where seat speed and oar angular speed seem to be coupled well (taking a cosine by eye!), which indicates that during the second half of the recovery I am already in catch position.
- The seventh black line is the point where seat and oar angle reverse. These points coincide. Nice. This is also just before the catch.
Interestingly, this set of measurements shows no sign of any funny movement just before the catch, like an extra reach or anything. I am sure Olympian rower have better timing around the catch than I do, but all in all I don’t see any big flaws, apart from using a back opening to do the catch.
And that’s a long story to say I need side video analysis.