Hi, John! Back in the saddle!

Literally got blown off the road today lol. Something is up with the weather these days...

A van got squashed by a tree today on Alpine Rd. Be careful out there.

Even a crosswind has two-thirds the vector force of a headwind so best to avoid windy areas by riding as early in the day as possible. Where my wife and I love to ride is along the coast and there is often a 15 mph wind to contend with and when we bought a couple of lightweight road e-bikes it made it a lot more bearable.

The air drag increases with the square of the rider/vehicle speed so pedaling at 15 mph and adding a 15 mph headwind quadruples the effort required. Hills are no problem, mentally, as I knew that my effort going up would be rewarded going down. But with wind that does not apply.

It can help with trip planning for a tour. I see people biking from the south to the north along the California coast where the prevailing winds are from the northwest direction. Going the opposite direction would result in less time fighting the wind.

Where did you come up with that?

Went for a first day of spring ride yesterday. NE wind and strong. Rode west about 20 miles with another 7 both north and south. (Roads laid out around rectangular farms.) Going out was easy. Coming back on the fix gear - hard! Out of the saddle, in the drops and lots of arm bend on tiny rises. Horizontal back most of the ride home. Last three miles, trees and shelter. TG! Aspirin to have any chance of sleeping last night.

Do the geometry of the vectors - the wind and the bike. See the bigger vector wind velocity. Calculate the wind force (proportional to the velocity squared for that bigger velocity. Apply the in-your-face proportion of the force vector.

Only way to avoid that phenomenon - stop! Eliminate your velocity vector. Cold hard reality. Yes, math and physics suck.

Where does the 2/3 factor come from?

It's not 2/3 written in stone. Just approximately what a cross wind of your speed gives you. (Actually 0.71 so a touch more.) Do the calcs I suggested and you will see.

It's not even approximately 2/3 -- it varies a lot depending on ground velocity, wind velocity, and angle of the wind.

Most of the forecast we look at give 'wind 10-12 from the xyz...HOWEVER, check an aviation forecast, it will tell you that the 10-12 mph wind starting at , say 11:00 will have gust to xyz (sometimes 2-3 times the speed the regular forecast is calling for.

The wind gust can make a huge difference, but the gust will change, so looking at an aviation forecast will tell you that 'if I bike from 200-4:00 it should be miuch better, while the regular forecast calls for the same wind all day

Or…Eliminate your velocity vector Victor. (Verily)

I live for days when the wind is only blowing 10mph!

This graph from Jobst Brandt’s article may help folks get a sense of the power requirement for a wind equal to riding speed. I’m not really sure what someone would mean by “two-thirds”. I have a vague recollection of integrating this over the full circle and getting an average 15% increase in workload. I.e. wind is a 15% net burden to your normal speed. This weekend I’ll add it up again.


https://cimg1.ibsrv.net/gimg/bikefor...faa1754f4.jpeg
Otto