Random data collection: Power over a half and aerodynamics
I know this can vary a lot based on your weight, the course, wind, etc but one of the back-of-the-envelope goals I have for the year is to be able to do 56 -flat- miles with a 20MPH average--so approx 2:47 or less. For those of you willing to share that are in the 5'9" range, 3 ?s:
1. what kind of AP did you have to have to hit that time or better?
2. (roughly) how many CM of drop in your position?
3. What kind of w/kg were you pushing @ ftp?
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I have a lot of data in my race reports in the forums...check out my reports Racine 2012 and Steelhead 2011 for some examples of bike times and power splits for a flat course. Ignore the reports from Kansas and Vegas becuase those ones are really hilly.
The long and the short of it is that my FTP is about 4.1w/kg and I rode a 2:20:xx at IF 0.89 at Steelhead '11 and a 2:24:xx at IF 0.83 at Racine 2012. I'm quoting these from memory so they may be a bit off. I think I rode a 2:26 at Racine 2011 at IF 0.83 on a lower FTP.
Truth is the time depends a lot on the course. More than on your weight (unless very hilly). I have done right around 2:45 every time I've done KS which is pretty hilly and can be windy. My last effort there at 2:45 was probably 'better" than previous ones because it was so darn hot, but I did 2:30 on Steelhead in a year that I wasn't in any better shape. Las Vegas was just under 3 hours for me in a year I did KS at 2:45ish.
For reasons that are not clear to me (maybe I haven't tapered well for this race at this time of year?) all three times I've done it I have underperformed wattage wise, compared to what I wanted to do. Last year was my lowest average (175, which should be closer to what I would do an IM at than a half IM!), with the others in the 180-190 range. However, I had re-fit myself last year, so the faster time was probably the fit. I have about a 15 cm drop on a P3.
I rode 2:44 at Racine.
1. AP 141, NP 150
2. drop ~8cm
3. 3.2w/kg. 5'7", 145#, hed 9, disc, powertap.
My numbers may help you get started. I'm 5'9, weighed 146 at the time (Nov 2011), had an FTP of 225, and w/kg of 3.4. @ IM AZ, I looked at the first 56 miles of the bike, which is pretty darn flat (800' total elevation gain) and found I did it in 2:49, @ 20.42 mph.
My Normalized Power (NP) was 152, for an IF of 0.675. My Average Power (AP) was 149, for a Variability Index (VI) of 1.02. My drop was 11 cm. But that's less important, I think, than how you hold your head and how well you stay on the aerobars. And remember, each person's drop will be unique for his body type, depedning on length of torso, arms, flexibility, etc. Like I said, tucking your head between your shoulders, keeping it there, and stay in the bars may all be more important factors in aerodynamics than simply the drop from saddle to arm rests.
Anyway, if you are trying to do this in an HIM, the back calculation for what your FTP needs to be assumes an IF of 0.8%, taken from the EN table for estimating IF in an IM based on bike time. 152/0.8 = 190 for the FTP. You can figure out your w/kg from there based on your own weight. Looking at your avatar, I estimate the w/kg you'll get @ an FTP of 200 to be, oh, about 0.95.
1st 56 miles of IMFL: 2:30:45
AP 147, NP 154, 22.3 mph
2nd half: 2:42:39
AP 127, NP 136, 20.9 mph
2:42 with NP 136 @ FL 2nd half
2:44 with NP 150 @ Racine
That said, eyeballing Al's and Carlo's numbers it would seem that an FTP of 3.5w/kg would be more than enough to hit your target. Probably you would be fine a few tenths lower but hey, the goal is as high an FTP as you can get in the OS!
56miles 2:46
NP168w
FTP 250w
Weight 172lbs
Drop 7cm
I'm on the upper edge of 5'10". 163 lbs race day. W/kg ~ 3.2
IMAZ 2013
Second Half Course (second half is faster, since first half has 1 hr easy riding in it) Riding with aero covers, aero helmet, race wheels, 12cm drop.
Time: 2:43
NP: 163
AP: 159
VI: 1.02
FTP: 235
IF: 69.6
Remember though if you're doing a 70.3 your IF is going to be higher 80-85% of FTP. If you dont have them: get youself aero covers, aero helmet, and race tires. Those combined give you lots of 'free' time in regards to your watts.
I'm 6'0" and about 165 lbs. on race day. My FTP peaked at 301 watts early in 2012. It was probably more like 290 watts come race day. Let's say my w/kg was 3.87 from a peak of 4.01.
My cm drop is somwhere between 13 and 14cm. I ride in a fairly aggressive position.
Here are the numbers from my two 70.3's this year which were Texas and Syracuse. Two very different courses as one is windy and flat as a board and the other is hilly:
Texas 70.3
Time: 2:27
Avg. Speed: 22.9 mph
Elevation Gain (per my Garmin 500): ~ 300 feet
NP: 240
AP: 236
VI: 1.017
IF: .828
TSS: 167.9
Syracuse 70.3
Time: 2:31
Avg. Speed: 22.2 mph
Elevation Gain (per my Garmin 500): ~2600 feet
NP: 245
AP: 238
VI: 1.03
IF: .844
TSS: 170.3
Here is another data point.
I'm 6'0" & 161 lbs on race day. My ftp last summer was 260W, 3.55 w/kg. I raced Racine 70.3 ( flat course but hot day @ 95F) bike leg in 2:37 and average watts of 199. 3rd fastest bike split in my AG. Avg speed of 21.3 mph. This was an IF of 76.5%. This a little lower IF than I normally would race a HIM at, but it was very hot and humid so I made an in-race decision to back off the bike a bit to make sure I had a solid run. Had a good run and finished in 5:15, 2nd in 55-59 AG.
Not sure what my drop is. Guess I should look that up from my bike fit. But I can tell you that my position isn't aggressive as could be since I have a pinched nerve in my neck so I have to be careful about how low I get or the nerve acts up on longer rides.