I'm not sure if there is a point or not. But to play devil's advocate, isn't 0.4 to 0.6 lbs of drag reduction (@30mph) which yields 1-2 mph (@45mph) still worth it regardless of how much drag your body is producing? Maybe there is so much turbulence in a field sprint that there wouldn't be any laminar flow around aero tubes anyway.AussieRob said:
Go back and read what art and aussierob wrote, they are both right. Also there is no way in hell the difference between an aero and non aero downtube is 1-2mph at 30mph so take all three of those things into consideration and you can see it doesn't matter to a guy that explodes over the last 100m of a 200km race.lefeur said:
Now now *****. I didn't say that aero tubing made a 1-2 mph difference @ 30mph. I said it reduced drag by 0.4 to 0.6 lb. force @ 30 (Actually according to www.cervelo.com aero frames can reduce drag by up to a pound at 30mph, but I reduced it 0.4 to 0.6 because mfg's. always exaggerate their claims). That translates into about a 0.8 mph gain around 30 mph. If you do the calculations, and I have, you will find that a 0.6 lb. force @ 30 translates into a 2.5lb reduction in drag at 45mph. This means that with the same power output one can go 1-2 mph faster when travelling in the 45mph range.wilmar13 said:
In a flat out sprint (as Aussierob said) you are all over your bike, the bike is swaying/leaning constantly and you never have streamlined airflow passing over/around the bike or the rider - these factors practicly reduce any theoretical gains you have calculated as wind-tunnel data is based on steady-state airflow. The movement of bike and rider in sprints disrupts the airflow and doesn't allow you to take advantage of aerodynamic efficiency of the frame. This means that stiffness is the biggest factor to ensure there is a little energy loss as possible (as Art mentioned).lefeur said:
Yeah what he said!lefeur said:
I had an unfair advantage - i did my engineering thesis some years back on aerodynamics (moreso on cars, but the principles are the same)lefeur said:
Some other points to mention is the importance of the rotating masses on aerodynamics - ie wheels and foot/pedals. They churn the air up big time so small improvements here are huge. The advancement in tech and materials has seen some pretty aero and stiff road/race wheels without the weight penalty. Zipp have also introduced dimples on their wheels now which act in a similar way to those on golf balls - ie keep the airflow attached and smooth as it passes over the surface. I could drop some 'nerdy' terms here but that would not be cool...Dini77 said:I had an unfair advantage - i did my engineering thesis some years back on aerodynamics (moreso on cars, but the principles are the same)
It's an interesting question - aero frames are important, but IMO not nearly as much as how the rider is positioned on the bike. It's funny, just small adjustments to get you flatter make a big difference. It's actually on this point that the sprinter can make big gains. Ever noticed how top sprinters keep low and have a flat back - this streamlines them and presents a lower body surface area to the wind. They also periodically drop their chins to their chest - this fills the void between head an chest and lets the airflow pass by more smoothly. It's a pretty interesting topic.
cheers
Nerd it up. We can handle it.Dini77 said:
No problem, Wilson.wilmar13 said:Yeah what he said!
Sorry for misquoting you above, I was in a hurry but I do understand your question, no matter how small the advantage, why don't they go for it? Again I would venture a guess that just as Art said, they go with what is available and stiffness takes priority.
I interpreted the cervelo data correctly. "Table 3" from Jim Martin's article http://www.cervelo.com/tech/articles/article5.html shows drag data using a standard frame, 3 body positions and aero wheels. "Table 2" from the Cervelo article http://www.cervelo.com/tech/articles/cervelo-calc.html shows drag for a P2 aero frame with 3 body positions and aero wheels. The only difference in the two data sets is the frame. I confirmed this with Gerard Vroomen the author of the Cervelo article. As you can see, there is a 0.76 lb. reduction in drag @ 30mph with the P2 frame regardless of body position. The P3 frame shows a 0.91 lb. reduction in drag @ 30mph.artmichalek said:
1) The P2 isn't legal for mass start races either. Even if it was, the geometry would make it handle horribly in a sprint.lefeur said:
Arty,artmichalek said:
He does? I have seen a lot of pics of his bike with Cosmic Carbones, but maybe they were older. Either way they are both about the same aero and maybe the Bora is as stiff as the Carbone (with the Bora being way lighter). Im not sure I agree with you dismissing it as stiffness though, for sure he uses them for the aero advantages as well, if he just wanted to use stiff wheels he would be on Hyperion or NucleonsPeterF said:
How much do we have to dumb this down for you? I didn't change track, and you didn't interpret the data correctly. A time trial bike is a time trial bike. A road bike is a road bike. If you need the details spelled out, find a UCI rule book. None of the comparisons that you cite from the Cervelo web site are at all relevant. All else being equal, which it really isn't in any of those tests, the aerodynamic advantage gained from using "aero" tubes is negligible. As for the power issue, a person+bike in a field sprint is not a steady state system. Next time please make an effort to understand the basic physics of the system before you start talking down to people.lefeur said:
