What's a tailwind?

[Leaway2]

If you did get a tail wind, is it better to get low on the bars to reduce wind resistance or sit up high and let the wind "push" you along?

 

[ufkacbln]

I once read a superb bit about head winds (Mike Burrows I think) which went back to vectors.

Stand on your bike, with your arms outstretched.

Any wind direction from in front of your arms will have a headwind component and slow you down!

 

[Archie_tect]

This looks more interesting!

 

[rollinstok]

Living on the west coast I experience some excellent tailwinds.. I can regularly cycle to the end of the prom without having to pedal
Getting back to the start is a totally different story !!

 

[Hawk]

If you did get a tail wind, is it better to get low on the bars to reduce wind resistance or sit up high and let the wind "push" you along?

If the component of tailwind that pushes you along is greater than your forward velocity then getting up high would work best.

So with a tailwind simply take the cosine of the angle it is to your back (where a wind coming from *directly* behind you would be at 0 degrees), multiply the cosine of that angle by the wind speed.

This gives you a value for how much a wind pushes you along (it's rare to cycle dead downwind so the cosine bit takes account of 'wasted' wind that just wants to push you sideways). If this is greater than your forward speed then sitting up and catching the wind will help.

Otherwise, being tucked down is still the best option - if I'm cycling at 20mph dead downwind and have a tailwind of 5mph, well, the air's still resisting my motion the same as it would be if I was jus cycling through still air at 15mph.

Interestingly though (extra technical bit) - the resistance the air provides varies with the square of your speed and the energy you have to provide per second is the force required multiplied by the velocity you apply it at (how fast the pedals turn). So you have to supply about 8x as much energy per second to go only twice as fast. That's a very steep increase!!

 

[thnurg]

If that was really geek mode, you would have used [ instead of { :P

Nah. Real geek mode would have used XML.
<geek>
</geek>

 

[gaz]

Nah. Real geek mode would have used XML.
<geek>
</geek>

Agree with the closing the tag with the standard / but i think [ still trumps < in the context of a forum where tags are written with [] rather than <>

 

[TonyEnjoyD]

If that was really geek mode, you would have used [ instead of { :P

Erm....you mean [Geekmode] then [/Geekmode]??

 

[MontyVeda]

Living on the west coast I experience some excellent tailwinds.. I can regularly cycle to the end of the prom without having to pedal
Getting back to the start is a totally different story !!

when i started reading this thread i was thinking; Morecambe prom going towards Hest Bank is the one place I've had a good consistent tail wind.

sometimes i've cycled to work in a headwind a thought, at least I'll get tailwind on the way back, but that seldom works out.

 

[rollinstok]

when i started reading this thread i was thinking; Morecambe prom going towards Hest Bank is the one place I've had a good consistent tail wind.

sometimes i've cycled to work in a headwind a thought, at least I'll get tailwind on the way back, but that seldom works out.

to Hest Bank is the one !! I lived on top of a hill in Blackburn for over 30 years and always had a big climb at the end of a ride
when I moved to Morecambe I was looking forward to some easy cycling... wrong, the headwinds are horrendous at times

 

[deptfordmarmoset]

A tailwind is the triumph of idealised theory over empirical experience.

 

[Sheepy1209]

Do you get troubled by the sea breeze in Morecambe? Here in Blackpool on a warm day (we do get them) a north-westerly sea breeze sets up in the afternoon, especially at high tide. So for most of the summer it doesn't matter whether the weather's calm or not, I'll always have a headwind going home.

 

[Orange]

If the component of tailwind that pushes you along is greater than your forward velocity then getting up high would work best.

So with a tailwind simply take the cosine of the angle it is to your back (where a wind coming from *directly* behind you would be at 0 degrees), multiply the cosine of that angle by the wind speed.

This gives you a value for how much a wind pushes you along (it's rare to cycle dead downwind so the cosine bit takes account of 'wasted' wind that just wants to push you sideways). If this is greater than your forward speed then sitting up and catching the wind will help.

Otherwise, being tucked down is still the best option - if I'm cycling at 20mph dead downwind and have a tailwind of 5mph, well, the air's still resisting my motion the same as it would be if I was jus cycling through still air at 15mph.

Interestingly though (extra technical bit) - the resistance the air provides varies with the square of your speed and the energy you have to provide per second is the force required multiplied by the velocity you apply it at (how fast the pedals turn). So you have to supply about 8x as much energy per second to go only twice as fast. That's a very steep increase!!

Aargh!!!! 'A'-level maths... memories of 30 years ago.

 

[MossCommuter]

<geekmode/>

 

[MontyVeda]

Do you get troubled by the sea breeze in Morecambe? Here in Blackpool on a warm day (we do get them) a north-westerly sea breeze sets up in the afternoon, especially at high tide. So for most of the summer it doesn't matter whether the weather's calm or not, I'll always have a headwind going home.

<style="shakes_fist">Bloody Wind</style>