damon_rinard wrote:
Hi Mark, I think the presentation you're looking for might have been called "Col de la Tipping Point". We should probably put it back up on the web; even though the bike models are somewhat outdated now, the information is still a quite informative reference.
I started typing a really long post explaining tons of aero testing and stuff, but let me just directly answer your questions in brief and we can drill down as needed.
1. The 1.5% difference you quote is drag force (or CdA, they're linearly related), not time, not power, not speed. Percent difference in power isn't the same as percent difference in drag force; power and drag force are not linearly related (see the "Total" curve on Figure 4's chart in the white paper; it's not a straight line). So differences in power have different percent results than differences in drag force; the 5.2% (your calculation result) is a difference in power, not CdA.
Anyway, of course a lot of details are different between the 2009 and 2011 R3, they're made in different molds, so have slightly different shapes and thus different aero properties.
Hi Damon-
After a bit more reading and researching- I was able to locate the Col de la Tipping Point on Cervelo's website- here: http://www.cervelo.com/.../tech-presentations/ under Aero vs Weight "Col de la Tipping Point" It does indeed compare the R3 series versus the S3. Also the new whitepaper uses the S3 tests in 2009 to bridge the gap with some of your data in 2011- so Cervelo must feel that bike hasn't changed (aerodynamically speaking). I also see the 2011 whitepaper data of S3 rider is about 2400 grams of drag at zero yaw and then drops as yaw increases. Even if the set up was different in 2009 and the drag was hypotheically 2700 grams (with rider- which would make the 1.5% savings larger in terms of watts)- a 1.5% difference (or savings of a S3 over R series)- is still really, really small- or about 36 grams of drag (4 watts) in the 2400 gram test or 40 grams of drag (4.5 watts) in my hypothetical (not knowing your exact numbers- but need a good ballpark) 2700 grams. Gerard affirms this is a small amount- in my ST post- that you for some reason want to pick nits about his reply, not truly being his words in the reply.
He also- affirms the difference is small here (when comparing Cervelo Road frames versus Aero Road):
http://forums.cervelo.com/...p/383/3611.aspx#3611
and here:
http://weightweenies.starbike.com/...der=asc&start=34
and here:
http://forums.cervelo.com/forums/t/3192.aspx
and here:
http://forum.slowtwitch.com/...%201%205%25;#2226796
So, in all due respect to understanding this new whitepaper, I still find it hard to understand how the 2009 S3 (which is essentially the 2011 S3 aerodynamically) per your 2011 S5 whitepaper (using the 2009/2011 S3 wind tunnel data in the actual S5 whitepaper)- has gone from beating a R series by 4-5 watts to now beating the R Series by approximately 13 watts with rider on board. Your own Col de la Tipping Point shows that data from the 2007 Etape du Tour- has a S3 completing the distance 8 hrs 0 min 35 seconds and the R3sl completing it in 8 hrs 1 min 10 seconds- so a real world savings was only 35 seconds in an 8 hour period.
1. Has the R series been made substantially a lot less aerodynamic since 2009 with the new molds you site in a previous response?
2. Has your testing protocols changed in how you report 'data' yielding more time/wattage savings?
3. Feel free to pick nits with my logic- or just say the grams of drag the 2009 S3 tested- and we can easily affirm or deny the 2009 savings and then you can comment on how the 2011 savings between S3 and R series are now different?
I'm just a consumer, trying to understand the numbers and the numbers consistency over time, and I'm always in the market for a faster bike- because faster is indeed faster.
Thanks-
