Drafting

frenchyge said:

After you finish your analysis, how about running that plan through the works to see how it matches up?

Well, I jury-rigged my pacing model to handle a TTT rotation power management strategy, with variable pushes and recoveries (power/duration). The first observation (no surprise) is that NP is sensitive to the rotation duration. For example, using a 300w/208w pace and a 2:1 push/recovery ratio, average NP increases from 270w at 30s:15s to 276w at 90s:45s and flattens from there out. It may not sound like a big difference (270w vs. 276w), but I actually think it is a pretty big difference. For your proposed pacing rotation strategy (durations only, not pace), using a 300w/208w pace for comparison purposes (which may be a bit high for the OP), I get an avg NP of 289w. So, clearly NP is sensitive to the rotation ratio, but it is also sensitive to the rotation duration due to the half-life phenomenon. So, all three parts are in play: (1) team pace, (2) rotation ratio and (3) rotation durations.

Remember that you have to balance the NP of both riders. Your NP for a 30:15s rotation is 270w, but what does the 15:30s guy have for an NP. My goal was not to minimize the NP of the strong rider, but rather to balance both riders NP's to their individual capabilities to produce the fastest team pace.

Also, your pacing model needs to be able to handle multiple rotations right? If you're using the model that clips the first 30-secs while the averaging catches up, then that's going to really affect your results. You still have to consider the side-by-side or catch up power, too, but that'll probably have to be a subjective adjustment applied after the final analyses.

frenchyge said:

Remember that you have to balance the NP of both riders. Your NP for a 30:15s rotation is 270w, but what does the 15:30s guy have for an NP. My goal was not to minimize the NP of the strong rider, but rather to balance both riders NP's to their individual capabilities to produce the fastest team pace.

At the moment, I'm not trying to minimize anything. I'm just trying to understand the implications of the rotation durations on NP as you move away from the 15sec half-life baseline.

frenchyge said:

Also, your pacing model needs to be able to handle multiple rotations right? If you're using the model that clips the first 30-secs while the averaging catches up, then that's going to really affect your results. You still have to consider the side-by-side or catch up power, too, but that'll probably have to be a subjective adjustment applied after the final analyses.

Not really, I just have to have a valid power timeline. What I haven't done yet is to account for the brief acceleration to get into the slipstream position when the other rider pulls through. But, at the same time I have not accounted for the backing off immediately after pulling off. My own pattern after a pull in a 2-man rotation seems to be a 5 sec pattern that goes something like this: 0, 0, 0, 400, 400. After the 5 secs, I am in the draft position and my power is ~90w less than when I was pulling. I am re-doing my model to account for this little jig. Fortunately, the way I have it set up now, it's no big deal.

RapDaddyo said:

Not really, I just have to have a valid power timeline.

If you're saying a valid timeline that is long enough to let the 30sec averaging stabilize out, then I agree.

frenchyge said:

If you're saying a valid timeline that is long enough to let the 30sec averaging stabilize out, then I agree.

I'm not sure I know what you're talking about. I run the timeline out to 100 minutes. If it hasn't stabilized by then, it won't matter because they will have crossed the finish line and will be getting a cup of coffee. The timeline I'm talking about is the entire rotation, push, change, draft.

frenchyge said:

If you're saying a valid timeline that is long enough to let the 30sec averaging stabilize out, then I agree.

Okay, I made the enhancement to my model to take into account the rotation change. So, my pacing timeline is push, change, draft. The change is just the first 5 secs of the recovery phase. So, in my 30s:15s example, the draft segment is only 10s in duration. The change actually drops NP in my earlier example. Specifically, using a 2:1 rotation duration strategy and 300w/208w for the push/recovery segments, I get NP=266w at 30s:15s, NP=272w at 60s:30s, NP=275w at 90s:45s and NP=276w at 120s:60s. NP flattens after 120s. Your proposed duration ratio of 150s:30s works out to 288w. This is due mostly to the ratio (5:1) and somewhat by the duration. For example, maintaining the ratio but shortening the pull duration to 100s (100s:20s) drops NP to 286w. As to the father, his NP would be 234w under my 30s:15s example and 226w under your 150s:30s example. So, my 30s:15s stalking horse example results in 266w/234w and your 150s:30s stalking horse results in 288w/226w. The $64K question is what are their respective FTs?

frenchyge said:

After you finish your analysis, how about running that plan through the works to see how it matches up?

I do agree with you about one thing. The FT delta between the OP and his father is probably closer to the ~62w in your proposal than it is to the ~32w in my stalking horse. I haven't cared much about the delta until now, because I was focused on the implication of the rotation strategy vis-a-vis the half-life phenomenon. My final proposal will have an FT delta of ~70w, at least for initial trials. Frenchyge rules!

After playing around with rotation strategies to attain a 70w delta between the OP and his father, it looks like it's going to take something like a 10:1 rotation duration ratio. At a 275w pace, even a 10:1 ratio (150s:15s) only gets to a 62w delta (268w/206w). Priority #1: get Dad on a diet and on his bike more. Close the FT gap and the pacing options increase.

I agree that you get the best synergy when the teammates are closely matched (and little to none if they aren't). It might be better to slow the team down a bit so that both members can contribute significantly, and just enjoy the ride. Depends on how competitive they're wanting to be.

frenchyge said:

I agree that you get the best synergy when the teammates are closely matched (and little to none if they aren't). It might be better to slow the team down a bit so that both members can contribute significantly, and just enjoy the ride. Depends on how competitive they're wanting to be.

Well, playing the half-life card is out the window for the OP because of the FT gap, and it may not matter for the Dad because he will spend so little time in front that he will more than recover from any length pull. But, I'm still trying to get my head around the rotation duration ratio it takes to close a 70w FT gap. It seems huge, as in ~10:1. I think the key to their speed is this number (rotation duration ratio) and that they'll need to do some tests. Because he will be spending so much time in front, I think the team speed will be only slightly above the OP's solo speed. But, I'm not quite done looking at the question. The power variations associated with short pulls was an interesting detour on this question, but it turns out to be a moot point due to the huge FT gap.

I learned during MS150's that I can sit in at ~4 mph over my solo speed, or work in at +2-3mph (depending on the number of riders). Typically I start out fairly easy as a warmup and wait for a big train to go flying past me so I can jump on. Then I wait for the people who've gotten in over their heads to fall out and see what the working pace and number of working riders settles down to.

It's actually kinda funny to see the people that will grab on to any wheel that passes them during the 15th mile of a century ride. 🙄

frenchyge said:

I learned during MS150's that I can sit in at ~4 mph over my solo speed, or work in at +2-3mph (depending on the number of riders). Typically I start out fairly easy as a warmup and wait for a big train to go flying past me so I can jump on. Then I wait for the people who've gotten in over their heads to fall out and see what the working pace and number of working riders settles down to.

The 4mph sounds a little high to me. Drafting at +4mph on the flat is about a 50% power delta draft advantage, from 115w for a 200w FT up to 150w for a 300w FT. I think the draft advantage is less than 100w. For example, on my club rides there are riders who I know pretty well whose FTs are ~225w and they invariably get dropped when I go alone or in a group at ~300w. On a recent ride, just before turning into a strong headwind for a several mile stretch, I told one of these riders that I was going to up the pace when we turned upwind but that I thought he could stay on my wheel. I rode at ~300w for ~7 minutes to a stoplight and when we re-grouped this rider told me he held on for as long as he could but that he dropped off about halfway. I think if there were a 100w drafting advantage there is no question that this rider could have held on. So, I think the drafting advantage is closer to 75w-80w. This is a very key assumption for the OP and the pacing strategy.

RapDaddyo said:

The 4mph sounds a little high to me. Drafting at +4mph on the flat is about a 50% power delta draft advantage, from 115w for a 200w FT up to 150w for a 300w FT.

You're right, it's definitely speed dependent (ie, 17 --> 21 is different than 21 -->25). That was a few years ago, too. Nobody's blown past me at +4 mph in a while on that ride. There was one point where one guy was really trying to push the pace, and it just got to the point where I said "I'm not working at this pace." I could tell the other riders were of the same mind, and eventually he got the point.

RapDaddyo said:

So, I think the drafting advantage is closer to 75w-80w. This is a very key assumption for the OP and the pacing strategy.

You're test the other day showed a 92w delta on the drops, right (300 v. 208)? You think 100w on the hoods is unreasonable?

frenchyge said:

You're test the other day showed a 92w delta on the drops, right (300 v. 208)? You think 100w on the hoods is unreasonable?

I'm still working on this. I'll tell you where I am now. At a pace of 20-25mph, a 100w delta is definitely too much and a 50w delta is definitely too little. I guess I'm homing in on a 25%-30% drafting advantage (e.g., at 300w, it's somewhere between 75w-90w).

Here's what Floyd Landis's coach has to say on the topic - some useful tips in here:

http://www.bicycling.com/tourdefrance/experts/columns/0,5976,s1-12388-527-expert,00.html

WINGNUTT said:

Here's what Floyd Landis's coach has to say on the topic - some useful tips in here:

bicycling.com0,5976,s1 12388 527 expert,00.htmlOpen ↗

Thanks for the link. Wow, what a huge drafting advantage -- 40%! I wonder how much that ratio is affected by the size of the paceline?

RapDaddyo said:

Thanks for the link. Wow, what a huge drafting advantage -- 40%! I wonder how much that ratio is affected by the size of the paceline?

I'm not sure exctly, but I can say speaking from my own experience, there is a big difference between being in second place in a group, and being in the middle of a big pack. My guess is that, on flat ground, you save 25% of your energy when you are behind one rider, and 50% of your energy when you are smack in the middle of a huge group. I'd like to get a power meter sometime in the next month or so - when I get one I'll try to confirm this theory with actual data and post the results (if this thread is still alive).

There's some nice data here.
http://www.midweekclub.com/articles/broker98.pdf
On a track, the relative power for 4 riders in line are 100%, 71%, 64.1%, and 64.0

asgelle said:

There's some nice data here.
midweekclub.combroker98.pdfOpen ↗
On a track, the relative power for 4 riders in line are 100%, 71%, 64.1%, and 64.0

That's great data. Thanks, asgelle. The 71% number is very consistent with my short test the other day (300w/209w). And, from personal experience I can relate to the other numbers as well. This is very helpful.