# Non drafting sections or cross wind sections

Make it possible to add cross wind sections in races. Simply put turn of drafting for shorter sections Almost like a short TT section. Climbs creates thinner packs due to w/kg differences. Cross wind sections would do the same, but give strong riders the same benefit as for climbers going uphill.

O yes wind in game will give us more options for strategy.

The founder has talked about doing cross-winds in conjunction with the steering feature to get echelons (I think this was on the CyclingTips podcast, but probably also mentioned on the Zwift podcast). The pack position intelligence isn’t sophisticated to handle this fairly otherwise. But the idea of eliminating drafting completely in cross-winds is interesting.

My thinking was just to have wind from a direction (arrow on the map) so a rider that pay attention can attempt to do a breakaway on a section when the wind is from behind.

The wind does not change direction for the whole event. So it is just changing the cda as we go around the course, so a head wind will have cda+x and a tail wind cda-x

This Look Interesting:
https://www.sheldonbrown.com/brandt/wind.html

Right – it’s not actually CdA that changes, but the relative speed for calculating the wind resistance force (to go from force to power still uses the bike speed). That would handle the issue of headwinds (easy to draft) versus tailwinds (harder to draft) but wouldn’t result in guttering (limit on number of riders who can draft).

You are 100% correct. I should have been more clear, Wind speed and bike speed squared is multiplied by Cda. So Zwift need to add the Wind factor.

the bike power formula look something like this. My guess is Zwift uses a factor of 1 for wind (W).

Wind isn’t a factor here – it’s a velocity. Zwift would likely use W = 0. I don’t recognize that formula, actually, for example I don’t know what Cm is, or Frg, or CrVh. But the dependence on wind for the CdAρ/2 part appears correct.

Here’s the formula I would have used:

P = v · [ (Cd A ρ/2) (v + w)² + M g ( [ gr / sqrt(1 + gr²) ] + Crr ) ]

where w is the headwind relative to the ground (v + w is the relative wind, assumed > 0), g is gravity, gr is the road grade, Crr is the coefficient of rolling resistance (for example, 0.004 in Zwift with a road bike on smooth roads), M is the total mass.

This is power at the rear hub. To get power at the pedals divide by drivetrain efficiency. (for example, 0.97).

O sorry @Daniel_Connelly my bad I should have linked the source of the formula. Here you go http://www.kreuzotter.de/english/espeed.htm

You keep finding my mistakes (good job)

Yes you are correct Zwift probably use W=0.

So If they track which direction you are riding they can use a function to calculate W.