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W/CdA Charts like Coggan-style W/kg Chart?
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Hi all,

Long time lurker, first post.

It's a long one so tl;dr right here and skip to the end for the example:

I'm coming to see if an Andrew Coggan-style (Watts / CdA) chart exists like the classic (W / kg) chart?

====== Context ======


My goal is to understand what other are accomplishing by looking at the statistical spread. Part of my selfish reasoning is I'd like to see where I stand. I understand I shouldn't compare myself with others, but it's a source of aspiration and motivation for me when I see what the hardworking and gifted ones are accomplishing. Seeing the upper bounds helps with this.

But right now, I don't know what the "spread" looks like in regards to WCda, let alone CdA. So I took a stab at making my own which I've attached at the bottom, but I don't want to reinvent the wheel.

The background is I've recently begun measuring CdA and cross-checking them with arm-chair calculators. The approaches:
  • RChung Method using halfpipes + GC Aerolabs
  • myWindSock Premium
  • https://www.gribble.org/cycling/power_v_speed.html
  • Wunderground
  • https://www.gribble.org/cycling/air_density.html
  • Strava Rides
  • BicycleRollingResistance

Using these tools, my cross-checking methodology is loosely:


A. Measure "Real World" CdA average
1. Go on solo "real-world" rides recorded by Strava. Focus on holding aero position.
2. Use myWindSock to assess quick & dirty CdA
3. Target key laps on Strava/myWindSock, and use Gribble calculators to crosscheck estimated CdA
4. Use WUnderground, Gribble Air Density Calc, and BRR to crosscheck Rho and Crr


B. Measure Focused RChung CdA (Baseline Control)
1. Crosscheck above with Aerolabs RChung Method, on a halfpipe
2. Again using calculators to crosscheck Rho, Crr

Result: The RChung CdA sits in the middle of the Real World CdA, with the RW CdA having a larger spread, which is what I expect. The myWindSock data's accuracy varies based on the windiness and road conditions of the day. A certain level of inaccuracy is also expected given that myWindSock is making larger leaps based on just a few estimated variables.


Because I just started last week, I'm using GPS instead of a speed sensor. Secondly, I'm still honing my RChung technique. My speed sensor is arriving in 2 days. I'd like to share deeper data once I get the speed sensor AND once my technique improve over the next few weeks. But today, I have prelim numbers to work with:


Rchung Measured: 0.2765 CdA
Gribble Calculator: 0.2750 CdA
myWindSock Full Ride Avg: 0.261 CdA


Course & Ride:
* 28.73 miles / 436ft elevalation (pancake flat, large square loop, country roads)
* 23.0mph
* 229 W avg / 241w (NP)
* 1.187 kgm^3 Rho


Bike Equipment:
* Allez Road Bike (7.6kg)
* 25mm Turbo Tires 80/80psi (0.00489Crr *1.13 = 0.0055)
* guesstimate to correct for rough country roads
* Drivetrain loss 3% (dirty chain, can't clean right now)


Rider Equipment:
* Tight fitting jersey + bib
* Kask Mojito Helmet
* No gloves
* Arm warmers
* Long socks
* Fizik Tempo R5 Boa shoes


Rider & Position
* 5'6, 143lbs (64.86kg)
* Total system weight accounting for water/food/tools: 75.06kg
* Elbows in 90° Bend: Grip on Shifter Hoods


====== EXAMPLE ======

Here's my stab to demonstrate what I'm looking for. Watts on the Y, CdA on the X... I got the "spreads" and "categories" researching a ton of website, but as you know none of the data is normalized, cleaned, or polished in anyway so these are ball parked figures. One example: https://gccoaching.fit/...flat-roads-wattscda/


Again, my goal's to see if CdA statistical data exists for different riding positions so that I can label categories and spreads. If I used my own data, I can see that my CdA still has lots of sheds to get to that lower bound of 0.24 CdA for road. And plenty more if I jump on a TT bike.





I did another version that takes the cubed root of the Watts/CdA. Just to get the final number down to single/double-digits.



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Re: W/CdA Charts like Coggan-style W/kg Chart? [breakfast4lunch] [ In reply to ]
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That would be reasonably estimated by a flat TT speed chart.


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Re: W/CdA Charts like Coggan-style W/kg Chart? [RChung] [ In reply to ]
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Wow thanks RChung for the quick reply! Great chart given that it bakes in Crr and assumed weather conditions to derive speed.

My follow-up question for you or anyone out there that is knowledgable....

Have there been attempts in the past to study or characterize the spread of CdA's achieved by a population of athletes, based on key attributes?



For example: Best measured CdA per athlete based on height, or weight, bike position, body composition (endomorph, ectomorph, mesomorph), torso length, leg length, etc.

I'm honestly just looking for anything that studies a population of CdA's. Ideally, the sample set includes a mix of Average Joe/Jane's, enthusiasts, and elite. But I'd be happy to review anything even if it has noisy data or tiny sample sets -- and review them with a grain of salt.

Maybe the answer is no, because CdA is highly individual and there's too many variables to bound and thus no correlations have been found.

But even knowing what has been attempted and failed in the past would be very useful. Do past examples come to mind?
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Re: W/CdA Charts like Coggan-style W/kg Chart? [breakfast4lunch] [ In reply to ]
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Look for some posts by Alex Simmons, he used to have a blog (although the name escapes me at the moment) that has a w/cda chart for the individual pursuit.

There are also a few spreadsheets floating around that did a fair job predicting outcome when enough known variables were plugged in.

My Blog - http://leegoocrap.blogspot.com
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Re: W/CdA Charts like Coggan-style W/kg Chart? [Morelock] [ In reply to ]
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Thought I remembered seeing that same chart, so I went and dug up some of the links:

He hasn't posted in a while, and is apparently using https://wattmatters.blog/ now, but there's a ton of great info in the older posts.
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Re: W/CdA Charts like Coggan-style W/kg Chart? [RunningChoux] [ In reply to ]
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@Morelock & RunningChoux, thank you!

Little golden nuggets, very cool.
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