Drafting/slipstream

Much less effect at slower speeds. Aerodynamic drag goes up exponentially
with an increase in speed. So, when they're doing 15-18 mph up a climb,
there is a small slipstream benefit, if any. But tactically, you stay behind
so the rider in front doesn't know when you're going to go off the front.
Element of surprise counts.

~ AB ~

"Krusty" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I know a rider can expend up to 40% less energy riding in another's
draft, but is that the same on climbs? It would seem that at lower
speeds that the aerodynamic benefit of this technique would be
significantly lessened. Is this true? Or does the slipstream have
the same effect regardless?

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"Krusty" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I know a rider can expend up to 40% less energy riding in another's
draft, but is that the same on climbs? It would seem that at lower
speeds that the aerodynamic benefit of this technique would be
significantly lessened. Is this true? Or does the slipstream have
the same effect regardless?

I was just reading a very good article on the science of cycling:
http://www.sportsci.org/encyc/cyclingupdown/cyclingupdown.html

"As gravity supersedes air resistance as the primary force that must be
overcome, drafting becomes a relatively less useful tool in the competition.
At very slow speeds (on the order of 16 km/h or less) air resistance is
negligible, and drafting becomes nearly meaningless."

--
Disclaimer: This post is solely an individual opinion and does not speak on
behalf of any organization.

Roger Moore said:

Much less effect at slower speeds. Aerodynamic drag goes up exponentially
with an increase in speed. So, when they're doing 15-18 mph up a climb,
there is a small slipstream benefit, if any. But tactically, you stay behind
so the rider in front doesn't know when you're going to go off the front.
Element of surprise counts.

~ AB ~

First of all thanks.

I figured as much, but then why do they (Liggett & Sherwin) make such
a big deal about Armstrong having several teammates setting the pace
for him on the final climb while other GC contenders do not?

Is seems that if only a tiny benefit is gained from the slipstream on
a climb that a rider could set his own pace on the final climb with
very little detriment to himself. I realize that having teammates at
this point is better than not having them, but over the years the OLN
guys have portrayed it as a godsend that Lance has his teammates there
for him.

Then again OLN kisses so much US Postal ass that I can count the
amount of criticisms I've heard towards that team in the last few
years on one hand. I'm pulling for Lance, but what ever happened to
commentators being impartial?

Quoted message said:

"Krusty" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I know a rider can expend up to 40% less energy riding in another's
draft, but is that the same on climbs? It would seem that at lower
speeds that the aerodynamic benefit of this technique would be
significantly lessened. Is this true? Or does the slipstream have
the same effect regardless?

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-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

"Krusty" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I know a rider can expend up to 40% less energy riding in another's
draft, but is that the same on climbs? It would seem that at lower
speeds that the aerodynamic benefit of this technique would be
significantly lessened. Is this true? Or does the slipstream have
the same effect regardless?

It's mostly psychological.

Jiyang Chen said:

"Krusty" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I know a rider can expend up to 40% less energy riding in another's
draft, but is that the same on climbs? It would seem that at lower
speeds that the aerodynamic benefit of this technique would be
significantly lessened. Is this true? Or does the slipstream have
the same effect regardless?

It's mostly psychological.

Incorrect.

First, you might save 40% in the middle of a large pack, but sitting
one one wheel is closer to 25%.

In any case, if you can maintain 45kph in a given position in the
absence of rolling resistance and/or grade, and you can climb
at 1700 m/sec on a 7% grade, then you're going 24.2 kph,
54% of your peak speed. This means you save approx
25% 0.54^3 = 3.9% of power by drafting, with 15.5% of
your power going into wind resistance sans drafting.

Since 84.5% of your power is going into wind resistance,
if you + bike mass around 85kg, this is like saving approx
0.039 * 85 / 0.845 = 3.9 kg from your bike.

The key "if" is if drafting still saves 25% of wind resistance
power @ 24.2 kph. It depends on how closely you
can draft, among other factors. Even so, it's clear the effective
weight savings from drafting are at least in the kilogram
range.

Dan

Krusty,
In the late '60s Chrysler did wind tunnel tests of their Plymouth
and Dodge NASCAR racers in wind tunnels in various drafting positions. I
have the SAE research paper buried somewhere. I seem to remember the
aero drag reduction on the second car inline was something like 23%. It
was nothing like the 40% for bicycles claimed on OLN. Maybe it was 33%,
but I am pretty sure it was 23%.
By the way, the same paper found that the drag reduction was the
same within the range of almost zero gap (the second place car touching
the first place car's rear bumper) to a gap of one car length. However
the first place car had no reduction in drag with a one car length gap,
but when there was almost no gap to about 1 foot, the lead car got a
reduction of about 11%.
In passing situations, the race car with a half length lead over the
car in the lane next to it has an INCREASE in drag over running alone.
So two NASCAR racers could hook up in a draft and the lead car would
have an 11% reduction in drag. If the second place car wanted to save
fuel, and not make the lead car go faster, he could hold a one car
length gap and not effect the lead car with himself getting all the
benefits of the draft.
The "slingshot" effect, of accelerating in the draft and then
pulling out to pass, is needed to over come the headwind that occurs
when you are a half car length ahead.
Much later, some journalists tried coasting Honda Civics at the
Honda Ohio test track. Coasting while drafting a lead car increased the
distance to come to a stop, over coasting as a single car. The greatest
distance was achieved when the coasting car was the middle car of a 3
car sandwich. This shows that there is a benefit a slow speeds too.
However, I seriously question the claim of 40% reduction in drag. I
ride in pacelines often enough, and I have never detected any reduction
in effort (or measured anything like a drop in heart rate, or increase
in cadence).
Cheers,
Bruce Freeburger

Krusty said:

I know a rider can expend up to 40% less energy riding in another's
draft, but is that the same on climbs? It would seem that at lower
speeds that the aerodynamic benefit of this technique would be
significantly lessened. Is this true? Or does the slipstream have
the same effect regardless?

Quoted message said:

I figured as much, but then why do they (Liggett & Sherwin) make such
a big deal about Armstrong having several teammates setting the pace
for him on the final climb while other GC contenders do not?

Phil and Paul make a big deal about a lot of things that don't really
matter.

"Dan Connelly" <d_j_c_o_n_n_e_l@i_e_e_e.o_r_g> wrote in message
news:[email hidden]...

Quoted message said:

Jiyang Chen said:

"Krusty" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I know a rider can expend up to 40% less energy riding in another's
draft, but is that the same on climbs? It would seem that at lower
speeds that the aerodynamic benefit of this technique would be
significantly lessened. Is this true? Or does the slipstream have
the same effect regardless?

It's mostly psychological.

Incorrect.

Well, it's partly correct. Having someone in front of you to
worry about the lay of the road, the pace, perhaps carrying
supplies can really take a lot of stress off a rider. Also, the
teammate is here for support in case of a mechanical failure.
For instance, did you see Christophe Moreau's teammate
give him his real wheel when Moreau punctured? As you
point out, there is also some clear aerodymanic benefit as
well.

Perhaps more important, it's proven historically that for
whatever reason riders do better with their teammates, with
an occasional exception. That's enough when you consider
the stakes.

Mike

"Bruce Freeburger" <"Bruce Freeburger"> wrote in message

Quoted message said:

Krusty,
In the late '60s Chrysler did wind tunnel tests of their Plymouth
and Dodge NASCAR racers in wind tunnels in various drafting positions. I
have the SAE research paper buried somewhere. I seem to remember the
aero drag reduction on the second car inline was something like 23%. It
was nothing like the 40% for bicycles claimed on OLN. Maybe it was 33%,
but I am pretty sure it was 23%.

The 30% number is most commonly referenced, but if you've ever ridden in the
back third of a 120+ rider field going 30 mph and your heartrate is less
than 100, it would be easy to convince you that it's higher.

Dan Connelly d_j_c_o_n_n_e_l@i_e_e_e.o_r_g said:

Quoted message said:

It's mostly psychological.

Quoted message said:

Incorrect.
First, you might save 40% in the middle of a large pack, but sitting
one one wheel is closer to 25%.

Quoted message said:

In any case, if you can maintain 45kph in a given position in the
absence of rolling resistance and/or grade, and you can climb
at 1700 m/sec on a 7% grade, then you're going 24.2 kph,
54% of your peak speed. This means you save approx
25% 0.54^3 = 3.9% of power by drafting, with 15.5% of
your power going into wind resistance sans drafting.

Quoted message said:

Since 84.5% of your power is going into wind resistance,
if you + bike mass around 85kg, this is like saving approx
0.039 * 85 / 0.845 = 3.9 kg from your bike.

Quoted message said:

The key "if" is if drafting still saves 25% of wind resistance
power @ 24.2 kph. It depends on how closely you
can draft, among other factors. Even so, it's clear the effective
weight savings from drafting are at least in the kilogram
range.

Let's do the full problem. Suppose a 13 km Cat 1 climb at 7% and
a climbing rate of 1700 m/hr (top level) and rider+bike = 78 kg,
rider frontal area = 0.7 m^2 sitting up. Speed is 6.75 m/s,
24.3 km/hr, at which speed it takes 32:06 to do the climb.
Power is 439 watts from analyticcycling.com, very
high. Of this, 57 watts is wind resistance (I used the 1500m alt
air density value). If the rider saves 25% of that by drafting,
that's 14 watts, or 3.2% of total power, needing to expend
"only" 425 watts.

Seems small, but 3.2% is significant at this level. From
analyticcycling.com, the same rider putting out 425 watts goes
at 6.58 m/s and finishes in 32:56, losing 50 seconds. (Slightly
less than 3% slower.)

That is a pretty sizable gap. Of course, most of the riders are
in a group for part or all of the climb. But still, I think it
shows that drafting does make a difference for two reasons:
1. top riders go up climbs a lot faster than rbr geeks
2. differences between top riders are very small, so even small
percentages are important.

Hills are not uniformly sloped. That teammate might not do you any good
on the 10% section, but when it drops to 6%, or goes downhill...

Look at the back of a peloton sometime. The guys there are going as fast
as the ones in front, and a lot of them are barely pedaling at all. In a
large pack, I'd expect the drafting advantage to be in the 50+% range.
As one who spends a lot of time in the back, I know you can actually
feel "sucked" along by the slipstream.

--
--
Lynn Wallace http://www.xmission.com/~lawall
"We should not march into Baghdad. ... Assigning young soldiers to
a fruitless hunt for a securely entrenched dictator and condemning
them to fight in what would be an unwinnable urban guerilla war, it
could only plunge that part of the world into ever greater
instability." George Bush Sr. in his 1998 book "A World Transformed"

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

Then again OLN kisses so much US Postal ass that I can count the
amount of criticisms I've heard towards that team in the last few
years on one hand. I'm pulling for Lance, but what ever happened to
commentators being impartial?

OLN is a USPS sponsor, so what did you expect? Also, the TDF gave OLN
it's highest ratings ever, so they are going to play it up as much as
possible.
-------------
Alex

Well quite frankly, the USPS team is the best in the tour, esp. as far
as climbing goes. Lance has 2-3 teammates with him on the climbs, while
others are lucky to have 1. Maybe there is a bias, but a lot of it is
simply a fact that the team is the best.

Krusty said:

Roger Moore said:

Much less effect at slower speeds. Aerodynamic drag goes up exponentially
with an increase in speed. So, when they're doing 15-18 mph up a climb,
there is a small slipstream benefit, if any. But tactically, you stay behind
so the rider in front doesn't know when you're going to go off the front.
Element of surprise counts.

~ AB ~

First of all thanks.

I figured as much, but then why do they (Liggett & Sherwin) make such
a big deal about Armstrong having several teammates setting the pace
for him on the final climb while other GC contenders do not?

Is seems that if only a tiny benefit is gained from the slipstream on
a climb that a rider could set his own pace on the final climb with
very little detriment to himself. I realize that having teammates at
this point is better than not having them, but over the years the OLN
guys have portrayed it as a godsend that Lance has his teammates there
for him.

Then again OLN kisses so much US Postal ass that I can count the
amount of criticisms I've heard towards that team in the last few
years on one hand. I'm pulling for Lance, but what ever happened to
commentators being impartial?

Quoted message said:

"Krusty" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I know a rider can expend up to 40% less energy riding in another's
draft, but is that the same on climbs? It would seem that at lower
speeds that the aerodynamic benefit of this technique would be
significantly lessened. Is this true? Or does the slipstream have
the same effect regardless?

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Dan Connelly said:

The key "if" is if drafting still saves 25% of wind resistance
power @ 24.2 kph. It depends on how closely you
can draft, among other factors.

See
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=2318782

"Following another rider closely, i.e., drafting, at 32 km/h reduced VO2 by 18
+/- 11%; the benefit of drafting a single rider at 37 and 40 km/h was greater
(27 +/- 8%) than that at 32 km/h"

The difference is partly due to the higher effect of wind resistance (versus
rolling resistance) as speed grows, partly due to a reduction in drafting
benefit at lower speeds. I'm too lazy to calculate the wind resistance gained
from drafting at 32 km/h, but should be less than 25%

Jenko

On Wed, 21 Jul 2004 14:18:10 -0400, Alex Rodriguez <[email hidden]>

Quoted message said:

OLN is a USPS sponsor, so what did you expect? Also, the TDF gave OLN
it's highest ratings ever, so they are going to play it up as much as
possible.

Frankly, exactly what major criticism would they make about the USPS
team over the last few years? Lance supposedly weakening each year and
yet he wins. I didn't hear anyone argue that the team is why Lance had
a narrow victory last year. This year they are better.

You don't have to like them, but watching them reminds me of watching
any well coached team. I may not know exactly why they are doing what
they are doing at a given moment, but I'm betting Johan knows more
about it than I do. So I watch and wait and figure I may learn
something.

From team member selection to on-road tactics, USPS is the best team
over the last few years. Why look like an ass in front of
knowledgeable fans and criticize just to criticize? Especially when
there are plenty of bone-head directors that screw up in the selection
process and then continue the process until they run out of team
members.

Curtis L. Russell
Odenton, MD (USA)
Just someone on two wheels...