Aero Question

[Dalakhani]

This may turn out to be a really stupid question, but here goes...

Say you're descending (for example a 10% decline) and there's a strong wind behind you. Does making yourself bigger - giving the air more surface area to hit you - speed you up?

You'd get more air resistance in your face, but does the "extra push" from behind more than make up for that?

I'm asking because I hit speeds today that I didn't expect to hit while sitting up in a tailwind.

 

[ElChingon]

Always tuck in.

 

[Kiara is a rational girl]

You'd get more air resistance in your face, but does the "extra push" from behind more than make up for that?

What push? You'd almost certainly be moving faster than the wind.

 

[BroDeal]

Without thinking about it too much, I would guess that with a direct tail wind speed greater than the non-wind speed there would be a benefit to catching more wind. I am not sure how much faster the wind would need to be. For example, if you were riding at a speed that would result in 20mph on flat ground with no wind, I am pretty sure that sitting up to catch a 50mph wind would increase your speed over crouching. I am not so sure about a 21mph wind.

With a 10% grade it would have to be a hellavu wind and you would probably be more worried about stability issues than going faster.

 

[Dalakhani]

What push? You'd almost certainly be moving faster than the wind.

Good point.

That would suggest my theory that I go faster down that hill when the wind is at my back is solely because I don't have the wind in my face. And, if there was such a thing as a perfectly still day (not here!), I would go just as fast as with a tailwind - unless the tailwind was faster than me.

Is that how it works?

Steve

 

[Alex Simmons/RST]

Good point.

That would suggest my theory that I go faster down that hill when the wind is at my back is solely because I don't have the wind in my face. And, if there was such a thing as a perfectly still day (not here!), I would go just as fast as with a tailwind - unless the tailwind was faster than me.

Is that how it works?

Steve

I think it's more complicated than we might think. Reminds me of the Mythbusters episode where they did the fan on a sail boat cartoon myth.

In any case, when you're doing 100km/h +, you have other things to think about.

 

[Shady87]

Unless the wind speed is greater than your own speed, in the same direction (vector addition and whatnot), you will be faster in the tuck.

That said, air drag is proportional to relative wind speed squared, so with a tailwind of say 20kph compared to still air, your 'airspeed' will be say 60kph compared to 80kph, which is a substantial difference.

 

[Thorn Cycling]

tuck. always tuck. unless tailwind is higher than your speed.