check this out: http://biketechreview.com/...ance/ruleofthumb.htm The Straight Aero Bar Extension Trend Jan Ullrich, or was it Jens Voigt, has made the straight aero bar extension the latest fad/trend in the TT product world. The internet is full of people describing just how they took a hacksaw to their $400 one-piece bars (like the Easton Attack, CSC Vision Tech, Profile Carbons, etc...) so that they could adopt the Ullrich/Voigt hand position. I mean heck, those guys are winning with those style of bar extensions, so it MUST be fast, right?
Applying the tenuous “constant Cd” assumption discussed previously, I set out to see how these straight aero bars, or more precisely, the resultant hand position required to grab onto that style of bar affected measured frontal area. The reasoning goes that if the frontal area was smaller with a particular hand position, well, that would be the aero bar extension that everyone’s just “gotta” have…
The experiment consisted of sitting myself in a chair while wearing lots of black (so that my hands would be easy to extract from the digital picture) and rotating my hands downward in ~ 10 degree increments.
Figure 1. Wide angle shot of the hand position frontal area sweep setup.
After processing these images to determine frontal area, I was able to create the following table:
Figure 2. Straight aero bar extensions put your hands in a position somewhere between #3 and #4 above.
I would estimate that the hand position necessary to grab onto the straight style of aero bar extension is somewhere between that illustrated by position #3 and #4 above. Interestingly, the frontal area measurements show these two positions to have the highest frontal area by up to 20% as the chart below also illustrates:
Figure 3. Hand position and frontal area.
It should be noted that the minimum frontal area was measured with hand position #2. Upon closer inspection, the minimum frontal area hand position can best be described by looking at the relationship between the thumb and the forearm.
Position #2 is obtained when the thumb is parallel to the forearm and the forearm is also held parallel to the ground. An easier way to visualize this relationship is if one places a ruler on top of the forearm. Ideally, when the minimum frontal area hand position is achieved, the ruler should touch the forearm and thumb along its entire length as seen below:
Figure 4. The rule of the thumb - keep it inline with the forearm for smallest frontal area.
Hand positions #3 and #4 significantly deviate from the line projected off the forearm as is illustrated in figure 5.
Figure 5. This hand position results in a larger frontal area.
My “Rule of the thumb” should be clear by now; I think that for best aerodynamics people should keep that thumb and forearm in contact with a “virtual” ruler that extends out from the forearm. The resulting hand position based on the “rule of the thumb” setup has been shown to present a slightly smaller frontal area and perhaps, ultimately, faster TT times. In summary, the thumb metatarsal should be kept as flat as possible, and honestly, that’s quite tough to do when one lops off the upturns on their appropriately shaped conventional aero bars and opts to go the straight bar extension route.
And to think that someone had the audacity to claim I had too much time on my hands…
Tom Demerly
The Tri Shop.com
i guess there aerobars are hard to describe but definitly a broke wrist......not sure it s very aero in his case but he says he really like them..... 
not sure what the ski bend is but yes....his wrist as a slight bend...not much still not a neutral anatomic position. 
