Ford/Ironman Wind tunnel testing article and results, that Tom D worked in conjunction with.
I don’t see that this changed anything. Why am I suspicious of this?
Amazing!
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Draft benefit decreases as the riders get further apart!
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Even at three bike lengths there is still some level of draft benefit!
Instead of using a grossly expensive wind tunnel to get these results couldn’t they have just observed athletes at a local race?
Ford/Ironman Wind tunnel testing article and results, that Tom D worked in conjunction with.
http://vnews.ironmanlive.com/vnews/topstories/1121463254
It looks to me like they absolutely tested the worst case results to see what the maximum effect could be. A big rider in front and then not even in a very aerodynamic position to block as much wind as possible and a small rider (her head appears to be at the level of his butt) behind in a more aerodynamic position AND the wind coming directly from the front, something rare in the real world.
The next test they should test with the wind coming from 5 or 10 degrees from the side and I will bet the drafting effect if the rider is directly behind almost disappears at 3 bike lengths.
Anyhow, nice to know they have data now that can justify the rule, even in the worst case. Kudos to Ford and WTC.
What a bloody waste of time. Like they did not know this before.
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What a bloody waste of time. Like they did not know this before.
I knew there was an effect. I did not know the magnitude. From the article: " “We always welcome a chance to do something that’s never been done before,” said Ford Technical Specialist Paul Schulte," If you knew this before tell me what the number is, how big is the effect at 1, 2, 3 and 6 bike lengths? Cyclists don’t really care about this because they are allowed to draft and know that the closer the better so why would they get this data or even care?
It’s fun to watch you guys play with this.
If you knew this before tell me what the number is, how big is the effect at 1, 2, 3 and 6 bike lengths?
Guys with powermeters know the answer already. The first answer is, “It depends.”
If I’m following a guy my size in an average position, I see from 10-25 watts at 3-4 bike lengths. 10 if it is a mild cross-wind (riding a little bit to one side); 25 watts if in still air or a headwind. At 6 bike lengths, the wattage savings drop down to 10 max, and just about nothing if there’s a cross wind.
Note that they didn’t test anything more than 3, yet reached a conclusion anyway (I am more than a little skeptical about their “extrapolation”). I guess if you have to justify your 3-length rule, that’s one way to do it. People that actually ride bikes know that there is a huge difference between 3 lengths and 6 lengths.
Bottom line is – a 3 bike length distance would allow you to follow another rider around the course who would normally ride 10-15 minutes faster than you. A few guys working together could all ride 10-15 minutes quicker. And it happens all the time.
Another effect – if you follow a pack of riders at 3-4 bike lengths, you can save as much as 30-40 watts! I sat ~4 lengths off the back of a 6-man pack last Thursday night at Fiesta Island for 5 miles. On 215 avg. watts, I went 24.4 mph. That’s about 40 watts less than I would normally need to go that fast with that bike setup.
YMMV.
Very good answer.
It’s nice to see ya still have a sense of humer about this since WTC wacked your pee pee! 
Tom,
A word of advice. Don’t. Just read and know most of us know what you are thinking.
I appreciate you, I hope that means something.
It does and I do. Thank you.