Let’s assume he goes with 35.46 km/h into the headwind for 10 km, it will take the rider 0.282 h. He is going back with a tailwind averaging 40.50 km/h for 10 km, it takes him 0.247 h. 20 km divided by the overall time of 0.529 h gives an average speed of 37.8 km/h, slightly slower than 38.0 km/h.
(Assuming a ground speed of 34.0 km/h into the headwind and 42.0 km/h back with the tailwind the average ground speed becomes 37.6 km/h)
yes, your averaging is more accurate than the ballpark I put out there. And the difference could be accounted for .003 CdA, about the margin or error when testing an ordinary cyclist on a bike.
Not to you specifically but to go back to the direction this thread has gone
A person asks, how many watts for 38kph.
We see a few estimates for “bad”, “average”, “good” and Remco
We get into a theoretical debate laminar/turbulent, reynolds numbers, viscous and pressure drag, drag crisis and how CdA is “nonsense” and can’t be used to compare people or speeds.
So Robert (the creator of the Chung method for those who didn’t know) comes along and produces a very useful chart showing that it can. As a matter of fact it matches numbers people see on some real rides.
Then we get in a debate that testing numbers and racing numbers are different things. Which they aren’t.
So we try to illustrate wind isn’t “that big a deal” but there is a delta of about 0.003 in Cda in the example, again, roughly the margin of error when testing a cyclist on a bike.
I think the best thing for your average ST to do is figure out where they are in the Aero Spectrum and how to set realistic expectations for improvement.
I followed this thread and I like to think of myself as having a clue about virtual elevation i.e. the Chung methode. Maybe I misinterpreted the statement of longtrousers. However, I agree that in “real” situations, i.e. when there is wind and some elevation, one always needs a higher power to achieve a certain mean ground speed than a model for no wind and for a flat course would predict. The time lost in the slow parts of the course can not be gained in the fast parts.
And all I am saying is Robert’s model works well in “reasonable wind” as well
It is a whopping 3 watts off (out of 220w) in our 4km/h headwind/tailwind example when I use an average computed the way you suggest.
Robert’s chart are pretty good, even in “real” situations
That’s actually a lot for some of us age groupers. I lost spare 10 kilos between February and July. I didn’t realize that apart from easier climbing/accelerating and (most of all) quicker running I was gaining 4 watts on a dead flat with no U-turns or corners just through weight loss! Compared to my normal race weight (as opposed to February weight), it was still up to 3 watts, that’s more than 1% of my race power.
Depends where you store your extra weight. On the shoulders or legs (where it’s in the wind directly) may be different than chest or gut (where filling in the hollow with a bottle has been shown to be free speed)
I never thought about my gut as an aero device… some race participants should get a DQ for the use of fairings I tellya