Quote:
Originally Posted by JulianEdgar
Looking at the table I posted, and remembering that required power goes up with the cube of the speed (ie your nominated speed of 50 km/h will require 2.7 times the 36 km/h aero power shown in the table), I wouldn't think you'd be able to get the Cd down sufficiently to achieve that outcome.
Using the table, at 36 km/h, a bike with a frontal area of 0.35 square metres and a Cd of 0.13 requires a total (aero + rolling resistance) power of 50W (of that 24W is aero power, so a total of 90W at 50 km/h).
So that would imply that to meet your criteria, you'd need a Cd of something like 0.13  pretty hard.
Happy to have someone check my maths  never my best area.

Cd 0.13 seems very plausible.
I was unsure of the allup weight, and used data for the 0.40 msquared rig, thinking Grant53 might be able to tuck his head inside the enclosure.
* If the RR was 38Watts @ 36 km/h, and tires were below standing wave, and increasing resistance arithmetically, then @ 50 km/h, RR power would rise to 52.7Watts. Leaving 47.3 Watts budget at the higher speed for aero.
If it's 47.3 @ 50 km/h, then it'd be 17.65Watts @ 36 according to the cube law.
One of the bikes had a 24.2W aero power consumption with CdA = 0.044 msq.
Adjusting for 17.65W available power, the CdA would need to fall to 0.0325 msq.
Dividing by 0.40msq, Cd 0.0813 falls out of the equation.
Really low!
At Battle Mountain, Nevada, the 'laminar' bikes doing 85mph ( 137km/h ) are around Cd 0.11 according to the university teams.
It's okay checking my math as well. I stayed with metric, where typically I switch to US standards, then convert back.