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 Post subject: Re: Zipp SL-70 Aero
PostPosted: Thu Jul 17, 2014 3:11 am 
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I'd say 6 Watts constitutes "quite well." Your assumptions that the data was obtained without rider and that the presence of a rider negates any aerodynamic effects are both incorrect.

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 Post subject: Re: Zipp SL-70 Aero
PostPosted: Thu Jul 17, 2014 4:02 am 
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Waldo. How does hand position and the installed brake levers come into play? I know you guys are pretty thorough with your aero data.

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 Post subject: Re: Zipp SL-70 Aero
Posted: Thu Jul 17, 2014 4:02 am 


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 Post subject: Re: Zipp SL-70 Aero
PostPosted: Thu Jul 17, 2014 4:48 am 
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Waldo wrote:
I'd say 6 Watts constitutes "quite well." Your assumptions that the data was obtained without rider and that the presence of a rider negates any aerodynamic effects are both incorrect.


I'm just saying it would be nice to see that data to support the claim. Many of the claims made about aero gear turn out to be exaggerated when you look at the wind tunnel results.


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 Post subject: Re: Zipp SL-70 Aero
PostPosted: Thu Jul 17, 2014 5:47 pm 
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Ergott, I don't have access to the data anymore, but my recollection is that hand position didn't affect the results. We did see some interesting things with hand position relative to different bar widths but that data hasn't been released and I'm not at liberty to discuss it. This testing was only done with SRAM levers (non-hydro). I suspect that the difference going to a larger lever assembly like the hydro would be lost in the resolution of the tunnel.

Dunbar42, if you would like the data contact Zipp. I'm not sure what you're getting at stating marketing claims being exaggerated relative to wind tunnel data, since we're clearly discussing tunnel data at this point. If you're trying to insinuate that there's some manipulation of the data, that's completely off-base. All you need to do is look at historical data Zipp has released relative to magazine and even manufacturer tests to see Zipp has been conservative with data. Most of the recent data from other companies removes the strut tare from the data, which I certainly think is incorrect (it was never done with our data). That's why you see some of these relatively shallow rims yielding "negative" drag.

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 Post subject: Re: Zipp SL-70 Aero
PostPosted: Thu Aug 21, 2014 6:53 pm 
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A traditional round-tube section creates drag of about 0.74 Newtons, which we found requires about 7.5 watts of effort at 30mph (48.3kph) to overcome. The airfoil developed in CFD that is used in the SL-70 Aero handlebar creates just 0.11N of drag, which means a savings of 6.4 watts over a round-tube section.

Language is a bit ambiguous. One interpretation is that the reported force is only the force on the bars. But rider drafts off handlebars. Round bars provide better draft. So question is what is the net force, rider + bars.

This language is open to other interpretations. Another interpretation would be the net force was 0.11N relative to bars with only drops, no top at all, but the force included the rider.

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 Post subject: Re: Zipp SL-70 Aero
PostPosted: Sat Aug 23, 2014 1:53 am 
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TBH I have the VukaSprints and as nice as they look there really is no substitute for a nice round bar. Found the quite flexy (not sure about how the new ones are) and the tops are uncomfortable as it is a sin to put tape on them!

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 Post subject: Re: Zipp SL-70 Aero
PostPosted: Sat Aug 23, 2014 3:37 am 
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djconnel wrote:
Round bars provide better draft.


When aero matters your hands are supposed to be in the drops. The tops of the bars don't really have anything behind them until your knees.

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