CDa estimate

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Wobblydrow
Posts: 42
Joined: Mon Jul 29, 2019 6:29 am

CDa estimate

Post by Wobblydrow »

Hi

How much variation can you expect with the CDa estimation value vs what real world may be...if you add your height/weight/riding position what is the likely range of value in the real world vs the 0.032 the software estimates (for my size), can it have a significant effect or is it unusual that it wil not be somewhere near that value?
Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: CDa estimate

Post by Velocomp »

Sorry, I do not understand your question. Please elaborate.
John Hamann
Wobblydrow
Posts: 42
Joined: Mon Jul 29, 2019 6:29 am

Re: CDa estimate

Post by Wobblydrow »

Apologies. Let me clarify. If the app calculates my cda at a value 0.032 for the parameters input, what variability could it really be i.e. would it be 0.032 +/- a fraction, , or could it be a wide range and the value given is just a best guess.

My question really is how much error can be present in cda values, and therefore in the power calculations for any given persons size?
Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: CDa estimate

Post by Velocomp »

Part of my confusion is the number you are using. A CdA of 0.032 is "low" by a factor of 10x. That is, CdA for most cyclists should be in a range of 0.2 to 0.4...

We estimate CdA based on height, weight, and ride position. The accuracy of our tables have been proven out over thousands of ride files over the years. Our estimates are within 2%.

The effect CdA difference has on overall watts accuracy is dependent on actual ride conditions. For example, a 2% CdA difference on hills is immaterial, because most of the power generated by the cyclist is used to climb the hill!
John Hamann
Wobblydrow
Posts: 42
Joined: Mon Jul 29, 2019 6:29 am

Re: CDa estimate

Post by Wobblydrow »

Thanks for explaining.
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