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So a stupid, probably pointless question for you guys - whats more aerodynamic for a standard bike bottle - in a seat tube holder or down tube holder?
 

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i would postulate that the down tube holder is more aero. by angling the bottle you are reducing frontal area (just like swept wings on an airplane). also, we all know that the closer you get to the rider in front of you, the better the draft. well, the bottle is drafting off the down tube instead of leading the seat tube. makes sense. i think.
 

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suprcivic said:
i would postulate that the down tube holder is more aero. by angling the bottle you are reducing frontal area (just like swept wings on an airplane). also, we all know that the closer you get to the rider in front of you, the better the draft. well, the bottle is drafting off the down tube instead of leading the seat tube. makes sense. i think.
Except that it's beneficial for the big, aerodynamically 'noisy' rear wheel to draft off of a water bottle on the seat tube, which is widely regarded as the 'correct' answer.

Here's one take on the topic.
 

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so i guess the question should read, 'what is more aerodynamic overall' rather than "whats more aerodynamic for a standard bike bottle." :)
 

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danl1 said:
Except that it's beneficial for the big, aerodynamically 'noisy' rear wheel to draft off of a water bottle on the seat tube, which is widely regarded as the 'correct' answer.

Here's one take on the topic.
Except that Cobb's wind-tunnel data in the linked article show the opposite: a slight reduction in drag with the seat-tube bottle, but a greater one with the downtube position.

The question may or not be stupid or pointless, but it appears that people as smart as John Cobb have been thinking about it and doing actual research for more than 20 years.
 

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suprcivic said:
so i guess the question should read, 'what is more aerodynamic overall' rather than "whats more aerodynamic for a standard bike bottle." :)
That's in Cobb's data.

Here's another (later) reference by Cobb, which comes to the conclusion that the seat tube is better, though it depends on apparent wind angle assumptions somewhat (which isn't fully addressed in this summary):

http://www.analyticcycling.com/RiderAeroStudy.html
 

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??

danl1 said:
That's in Cobb's data.

Here's another (later) reference by Cobb, which comes to the conclusion that the seat tube is better, though it depends on apparent wind angle assumptions somewhat (which isn't fully addressed in this summary):

http://www.analyticcycling.com/RiderAeroStudy.html
I don't see that conclusion in either the graphs or the narrative. The graphs show the downtube rider ahead of the seattube rider. And behind the seat is worse, though still better than no bottle at all.
 

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suprcivic said:
i would postulate that the down tube holder is more aero. by angling the bottle you are reducing frontal area (just like swept wings on an airplane). also, we all know that the closer you get to the rider in front of you, the better the draft. well, the bottle is drafting off the down tube instead of leading the seat tube. makes sense. i think.
At the risk of being pedantic, and off the original topic, the main reason that aircraft wings are swept is to reduce the drag at high Mach numbers. An oblique shock has less of a pressure rise across it than a normal shock at the same Mach number.
 

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JCavilia said:
I don't see that conclusion in either the graphs or the narrative. The graphs show the downtube rider ahead of the seattube rider. And behind the seat is worse, though still better than no bottle at all.
Only at zero degrees, which he notes (tho not here) is rarely the case in the real world. At all other angles (in the tested 5 deg increments) , seat tube is equal to or ahead of down tube.
 

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the_gormandizer said:
At the risk of being pedantic, and off the original topic, the main reason that aircraft wings are swept is to reduce the drag at high Mach numbers. An oblique shock has less of a pressure rise across it than a normal shock at the same Mach number.
Yeah... But I don't pedal quite that fast anymore. Gettin' old.:D
 

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It wouldn't change the world if it's one or the other. Cervelo's P4 possibly has the best bottle design as it changes the shape of the bottle altogether.

There's also this one tri-bike I saw in Triathlete magazine that an aerobar-mounted bottle, but it was covered with some type of small mid-fairing. I always wondered how fast one could go if they duck under it. Never found it online and wished I picked up the magazine.
 

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OK, ok, as an aerospace engineer and a cyclist, I'm going to say that the bottle placement dosn't make that much of a difference. I'll even go so far as to say that the difference is so close to nill, there's no point in doing the testing. We're not going fast enough, the wind is never straight in our faces. Sure, someone might say one spot is better than another in a wind tunnel, but did they account for cross wind? Did they have a rolling treadmill in the wind tunnel? Did they account for the body position differences when reaching for the bottle? What about where it was placed on the tubes.

It all comes out in the wash...put the bottle where you like it.
 
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