click on the bmc tt link...
impressed with the test dummy with rotating legs. looking at the results the canyon/cannondale/cervelo have nearly identical aero.. spanish brands still lacking bh/orbea.


damon_rinard wrote:Tour Magazin have really improved their wind tunnel testing. Robert Kuehnen and I talked a bit at Eurobike and via email, and I'm glad to see they've adopted many of our suggestions. And - to their credit - they declined to allow us (or any bike company) attend their tunnel test.
However, when comparing data, please remember the P5 has a drag increase on the frame, which is there to reduce drag on the rider's back - and Tour magazine's set up has no back. We haven't tested legs-only, so sorry, I don't have an estimate as to the magnitude.
You can see the effect on the air flow (and drag reduction) starting on page 10 in the P5 white paper:http://www.cervelo.com/media/docs/P5-Technical-White-Paper-cd55ee37-81a3-4d19-8b4f-39946cd71205-0.pdf
Quote:
Seat tube aero zone
As part of our aero zone research, we’ve isolated areas where slightly unconventional airfoil shapes can work well, again taking into account the local airflow. Specifically, it’s rare that a truncated airfoil works well in typical flows, since the aft low pressure recirculation zone “sucks” on the back of the object, adding drag by “pulling” backward on the frame or component’s rear-facing surfaces.
Figure 13 Air flow characteristics over a semi-aerodynamic body. Stalled flow in aft wake indicates a low-pressure zone that adds drag by “sucking” on aft-facing surfaces. This drag can be reduced by completing the sharp trailing edge shape of the body, tapering the surfaces to follow the lines of the natural air flow.
However, in particular locations a well-designed truncated foil can help in both expected and in unexpected ways. For example, it generally works well to truncate an airfoil to allow the following components to draft. For example, Cervélo pioneered the seat tube cutout that allows the rear tire to draft in the truncated space behind the seat tube.
On the other hand, it’s counterintuitive that the P5’s truncated seat post and seat tube foils reduce drag, since truncated airfoils without a following body normally increase drag. In fact, the P5 uses the low pressure zone created by these truncated foils to redirect the air coming off the rider’s legs & back, delaying separation and reducing aerodynamic drag on the rider and bike system, despite slightly increasing drag on the bike itself.
Figure 14 CFD image showing air velocity contours. Low speed air behind the seat post and seat tube (blue) indicates a low pressure zone, which normally increases drag but in this case pulls the air down the rider’s back to delay separation (arrow), thus decreasing drag.
This is an unusual exception, and only proves the rule that it’s best to use truncation only where it makes sense. This breakthrough was possible because Cervélo has been testing and designing bikes with riders for many years now. One effect is that a P5 tested without a rider shows a slight increase in drag; the rider must be present to gain this aero benefit.
End quote.
Cheers,
cyclenutnz wrote:I was impressed by the Canyon until I looked at the geometry - pointless to have a UCI legal frame with reach of 457. And short F-C with long chainstays is also not an example of brilliance. Which is a pity as they appear to have put a lot of thought into the aero aspects. If anyone has dimensional data for the bars that would be useful.
cyclenutnz wrote:Comparison of the fastest config for each bike
cyclenutnz wrote:
So I think the winner from the test is the Slice RS - decent size range (not as expansive as the P5), UCI legal and has lower pricing for the base model.
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