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Home Aerodynamics Misc Frontal Area: KW Position

Frontal Area: KW Position

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Last weekend I was fiddling with my frontal area measurement setup and also working on my position a bit.  I was able to verify again, that I am able to reduce the data pretty consistently - on the order of 1% variation using the same photo.  I also found out that it is best to take the pictures without a flash, since the background will show a shadow and increase frontal area by 25% or so (the previous setups were done outside while this time I was in my garage). 

FYI, I am 162 lb and 6 feet tall and all area measurements are in square meters and represent the average of four foot positions.

I tried several different positions and this is what I found:

Normal position: area = 0.308 

Roll position (rolling the shoulders in and ducking head a bit - like trying to touch your ears to your shoulders

or "shrugging"): area = 0.294 - this is the "Danny Pate" frontal area profile shape.


Tip position (on the tip of the saddle): area = 0.315

 

Back position (on the back of the saddle): area = 0.300

Choke position (normal saddle, but grasping the aero bars halfway back - not at the ends) area = 0.318

Wide position (normal saddle and hand position, but placing my elbows out by the brake levers - really bent over and low): area = 0.349

Drops (sitting upright): area = 0.433

Here is a table that shows the areas and the % difference from the minimum area (roll position):

Here are some side views of the normal, tip, and back positions (yeah, I know that my garage is a mess):

normal position

tip position

back position

I regularly employ all these positions when riding.

Observations

The 10,000 foot analysis suggests that in my normal position, the frontal area is fairly consistent whether I am in the front/normal/back position (a few percent variation).  However, it appears that as I slide forward, my front end comes up a bit and increases frontal area - darn near linearly, huh?

I also noticed that I may have a bit of a pedal stroke flaw when contorting myself into these positions - check out these animations (forgive the website name across the images, but I had to do it since last time I posted stuff like this, I had some "borrowing" issues) -
 

You can see that in one of the frames, my right leg flares out a bit.  The instantaneous frontal area on these frames increased by ~ 8%.  This illustrates what we all know about the importance of keeping the knees in for best aerodynamics.

It also looks as if the "roll" position that Danny Pate employs also presents a smaller frontal area for me.  I have used this position for short periods (75% of a 20k TT), but staying in that position for a long time requires concentration and generally makes me get headaches later in the day - eye strain from looking "up" without moving my head, I reckon.

I could also probably benefit from doing something with my "fat" brake levers - those things are huge!  Also, the area behind my head looks like it could benefit from a head fairing.

Anyway, I am no positioning expert, but figured you all might be interested in what I found out.  As always, all comments/criticisms are welcome.

Last Updated on Sunday, 24 January 2010 05:25  

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