A New Reason To Shave Your Legs - It's Faster?
07-02-14, 01:02 PM
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From the Specialized web site, their new Evade road helmet saves 46 seconds over 40Km versus a standard road helmet. Leg shaving is more.
Last edited by Hermes; 07-02-14 at 01:16 PM.
07-02-14, 01:16 PM
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So to save even more seconds during 40km I'll strap two Evade helmets to the knees of my gorgeous shaved legs... To the TUB!!!
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07-02-14, 01:41 PM
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Can shaving your legs offer any advantage for regular male cyclists? | Trevor Ward | Environment | theguardian.com
When it comes to the aerodynamic properties of depilation, Burrows recommends a Mohican for your legs.
"If you've got a little bit of hair on your legs it will turbulate [sic] the air so you get a better flow. Now this in itself creates friction, so you don't want all your leg hairy you just want two thin strips, each about 10mm wide, just before the sides of your legs – though you will look really stupid.
You need the turbulent boundary layer – provided by these strips of hair - to get the air around the corner, and you need a smooth layer for it to flow over. But the leg is such a rubbish shape that ideally you want an aerofoil on the back of it."
"If you've got a little bit of hair on your legs it will turbulate [sic] the air so you get a better flow. Now this in itself creates friction, so you don't want all your leg hairy you just want two thin strips, each about 10mm wide, just before the sides of your legs – though you will look really stupid.
You need the turbulent boundary layer – provided by these strips of hair - to get the air around the corner, and you need a smooth layer for it to flow over. But the leg is such a rubbish shape that ideally you want an aerofoil on the back of it."
07-02-14, 02:15 PM
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the reason i ask is that prior materials stated the evade has a 1-3W advantage over the prevail @ 30mph, which is about 4-12s over 40k. when it was launched they considered the prevail to take aerodynamics into account, so perhaps they are using something else as the "standard road helmet."
07-02-14, 02:18 PM
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07-02-14, 02:28 PM
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damn, so much for the hair working like dimples to manage laminar airflow.
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07-02-14, 03:47 PM
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yeah. that's inline with what i wrote above (1-3W savings...most of the time yaw <=15). hermes wrote he saw 46s over 40k, which is a 16w redux. was wondering where that was taken from.
07-02-14, 03:50 PM
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Where are you getting 1-3 watts? The last graph shows the power savings of the Evade vs. Prevail to be ~14-19w at 50km/h / 31mph. The Evade actually performs best at 0 degrees of yaw.
07-02-14, 04:07 PM
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I have heard that chin hair has the most drag.
07-02-14, 05:55 PM
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My calcs from April showed a 1-3 w difference when you scale it down a bit. Will have to check if I scaled it to 20 or 25...or lower. I did a comparison for a short hill climb tt.
Ok...enough mobile replies. Will report back to either reiterate or correct the calcs.
My data in the past has agreed with other helmet comparisons that Chris (spcialized) has done...incl prevail v evade v selector v bambino v mclaren tt and tt3.
07-02-14, 08:21 PM
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07-02-14, 09:31 PM
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07-03-14, 09:42 PM
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I think you mean this test where they compare the Prevail to the TT2. The savings was 7.5w-9.5w at 25mph. You wouldn't think the Evade was as aero as the TT2. The LG Course goes from about 4w savings at 25mph to a peak of 8-10w at 31-32mph according to the manufacturer data. I have a hard time believing the Evade saves you double that.
i don't recall that article you linked to but remember the white paper. it did have that weird data point in it. thanks for posting it. i think what it highlights is that the angle of the helmet is extremely influential on the test results; presumably the angle of the helmet or position relative to the back changes the aerodynamics greatly.
the 7w difference b/w prevail and tt2 made sense.
the evade is a pretty damn aero helmet...in some positions more than others. still doesn't quite add up to me. the mclaren TT helmet literature showed a 2-3W difference between it and the TT3 (TT3 was never approved for use in the US)--when the tail is down. the evade was within 5w of the mclaren on a specialized sponsored athlete. (that's really awesome.)
but to get to ~20W....still scratching my head a bit on that one. maybe, under the perfect set of circumstances. a really perfect TT helmet could be 25w over a really bad road helmet over 40k....so maybe.
on some riders (e.g. tony martin) the tt3 tests the same as the mclaren. you see that he has sometimes worn the tt3 instead of the newer helmet. i am told he likes the feeling of the point on his back. i've found with the short-tailed helmets there's no feedback and it can be easier to lose perfect helmet/neck positioning.
07-04-14, 09:42 AM
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07-06-14, 11:20 PM
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well....u23 nationals just happened and a good buddy who rides for cal giant (specialized) posted some pics. the riders TTed in their evades. the mclaren's not legal at that event, and spesh considers it more aero than the tt2 (tt3 was not available outside of europe).
obv there are sponsor considerations, but they do think enough of the evade at big events, esp for high speed/low yaw.
obv there are sponsor considerations, but they do think enough of the evade at big events, esp for high speed/low yaw.