Slow drafting?

Hello Joseph:
To help riders avoid accidents, you might want to ask for greater
gaps on hills, both going up and going down.

Robert Leone [email hidden]

Quoted message said:

Hi All,

Below what speed does drafting become all but pointless? Figures or
calculations welcome! I am interested in this to help with some team
pacing strategies when we are on steep hills.

Joseph

Quoted message said:

Hello Joseph:
To help riders avoid accidents, you might want to ask for greater
gaps on hills, both going up and going down.

The idea is for the stronger climbers to pull uphill, but often the
weaker climbers have to tell them to cool it. Rather than have the
slower riders having to tell the others to constantly slow down, at
some point on steep hills the slower riders should take the lead and
set the pace. This way we don't have to keep yelling at each other to
slow down. But this only makes sense if we are going slow enough for
there to be no advantage to be had for the weaker riders drafting the
stonger ones. As for safety, we ride togther quite a bit so we know
each other and trust each other, but safety is certainly the highest
priority in all situations.

Joseph

Quoted message said:

Robert Leone [email hidden]

Quoted message said:

Hi All,

Below what speed does drafting become all but pointless? Figures or
calculations welcome! I am interested in this to help with some team
pacing strategies when we are on steep hills.

Joseph

Quoted message said:

Hi All,

Below what speed does drafting become all but pointless? Figures or
calculations welcome! I am interested in this to help with some team
pacing strategies when we are on steep hills.

Joseph

Dear Joseph,

For a crude ballpark notion, you might experiment with this speed
calculator:

http://www.kreuzotter.de/english/espeed.htm

Pick a wattage, stick in a slope percentage, and compare the results
for hands-on-tops to hands-on-drops and other aerodynamic differences.

At high speeds, drafting makes a huge difference, but speeds drop so
low on hills that local wind can blow even the illusion of a draft
away.

If you can't feel a difference when you swerve out from behind the
rider ahead of you, drafting is unlikely to much difference.

There's also the cost of trying to stay that close while grinding
uphill--at low speeds, speed fluctuates more with uneven surfaces and
tiny changes in grade.

For 150/200/300 watts on a 3% hill, the calculator predicts

150 200 300watts
--- --- ----
9.8 12.1 15.8 mph hands-on-tops
10.1 12.7 16.9 mph hands-on-drops
10.3 13.0 17.4 mph triathlon
10.7 13.6 18.4 mph superman position

For 150/200/300 watts on a 5% hill, the calculator predicts

150 200 300watts
--- --- ----
7.0 9.0 12.5 mph hands-on-tops
7.1 9.2 13.0 mph hands-on-drops
7.1 9.3 13.2 mph triathlon
7.3 9.5 13.7 mph superman position

For 150/200/300 watts on a 7% hill, the calculator predicts

150 200 300watts
--- --- ----
5.3 6.9 10.0 mph hands-on-tops
5.3 7.0 10.2 mph hands-on-drops
5.3 7.1 10.3 mph triathlon
5.5 7.2 10.6 mph superman position

Obviously, the gentler the hill and the higher the power, the more
likely you are to benefit from drafting.

Another approach would be to vary a tailwind on the calculator.

For 250 watts, hands-on-tops, and a 0/5 mph tailwind, the calculator
predicts:

0-mph 5-mph
grade wind twind
mph mph
----- ---- ----
0% 20.6 23.8
3% 14.1 15.8
5% 10.8 11.7
7% 8.5 8.9

It's the slope that kills the speed, not the aerodynamics.

Cheers,

Carl Fogel

Quoted message said:

Below what speed does drafting become all but pointless?

Power to overcome wind drag is proportional to the cube of velocity
(with no wind)... or the square of the "wind in your face" times your
road speed. So it is much lower at 10mph vs 20mph (a 1 to 8 ratio), but
you should still draft if possible... especially if there is a
headwind.

A more important concern is to make sure that the weakest riders are
*not* going "into the red" at the beginning of the climb. In other
words, start slowly and ease into the optimum pace rather than wait for
the weaker climbers to blow. If the strongest climbers have power
meters it will be a lot easier for them to pace properly.

Ron Ruff said:

Quoted message said:

Below what speed does drafting become all but pointless?

Power to overcome wind drag is proportional to the cube of velocity
(with no wind)... or the square of the "wind in your face" times your
road speed. So it is much lower at 10mph vs 20mph (a 1 to 8 ratio), but
you should still draft if possible... especially if there is a
headwind.

I figure that as long as it is perceptible, we will go for the drafting
solution, as long as the stronger riders can keep their cool. A nice
thing about a pre-agreed rule about pacing is it eliminates discussion
about it during the ride when everyone's brain is slightly
mis-adjusted. So I may just arbitrarily choose a speed beforhand, since
I am the Ride-King (and coincidentally the weakest climber...).

Quoted message said:

A more important concern is to make sure that the weakest riders are
*not* going "into the red" at the beginning of the climb. In other
words, start slowly and ease into the optimum pace rather than wait for
the weaker climbers to blow. If the strongest climbers have power
meters it will be a lot easier for them to pace properly.

This is the key issue. The ride is long enough that everyone has to
stay well below the red zone, so some climbs may seem super slow to the
stronger riders, as we will take them at a pace that seems relatively
easy for even the weak riders.

This weekend as a test (and for fun) we are doing a 250km ride with a
fair amount of climbing to test our strategy:

http://www.telemark-tours.no/arrangement/telemark-tours2005/images/TT_hoyde_m-km-50.jpg

One 400 meter climb at about 4% and a 300 meter climb that varies from
4-7%. The rest are shorter and not too much of a concern.

None of us have power meters, so we have to play it by ear. Our main
540km event is in 3 weeks and one guy may have one by then, but I'm not
counting on it.

Joseph

Quoted message said:

I am interested in this to help with some team
pacing strategies when we are on steep hills.

In a TTT, hills and tailwinds have similar effects: both exacerbate power
differentials between team members.
http://groups.google.com/group/rec.bicycles.racing/msg/659e4603ac3df724

Robert Chung said:

Quoted message said:

I am interested in this to help with some team
pacing strategies when we are on steep hills.

In a TTT, hills and tailwinds have similar effects: both exacerbate power
differentials between team members.
http://groups.google.com/group/rec.bicycles.racing/msg/659e4603ac3df724

There are some very informative graphs there. That is almost exactly
our problem. By chance all of us (6 people) have essentially the same
power output, but we have weights ranging from 75-105kg. So on the
flats we are reasonably well matched, but as soon as the road tilts, it
gets complicated.

Joseph

Quoted message said:

One 400 meter climb at about 4% and a 300 meter climb that varies from
4-7%. The rest are shorter and not too much of a concern.

On a very long ride I'd say that none of that is a concern... just take
it easy on the climbs. The best climbers can get a very good rest even
riding at the front then.

My strategy is to let the weaker riders go to the front on the hills.
There is little to no draft benefit, and if a stronger rider at the
front goes just a little bit too fast, the slower rider will go too far
into the red.

If you let the weaker riders pull up the hill, they can go at their own
pace, and the stronger riders don't have to worry about how to pace.
When the group crests the hill, the stronger riders can move to the
front as the speed and draft benefit increase. Even the guys who led up
the climb will feel fresh even though they just hammered up the hill --
because they were able to do it in their own rhythm.

Let the strong riders do their hard work on the flats and descents,
where the draft benefit is so huge. A strong rider can completely open
up to 40+mph on a straight descent, and the weaker rider in back will
be teasing the brakes -- well out of the red zone. The faster the
better.

I use this strategy with a lot of the riders I mentor, and I have
consistently demonstrated much improved times on known courses. I've
limped a couple of teammates around a 2-man TT course both before and
after learning this technique, and it goes much faster to put them up
front on the climbs.

Of course, this assumes that you DO NOT want to drop your weaker
riders. If dropping them is ok, then you should burn them up and spit
them out the back so they can add as much value as possible without
becoming a liability. Just make sure they are fried from being on the
front, not from clinging onto the back. Otherwise, no value added.

-Mike

Quoted message said:

Hi All,

Below what speed does drafting become all but pointless? Figures or
calculations welcome! I am interested in this to help with some team
pacing strategies when we are on steep hills.

Joseph

Mike Reed said:

My strategy is to let the weaker riders go to the front on the hills.
There is little to no draft benefit, and if a stronger rider at the
front goes just a little bit too fast, the slower rider will go too far
into the red.

If you let the weaker riders pull up the hill, they can go at their own
pace, and the stronger riders don't have to worry about how to pace.
When the group crests the hill, the stronger riders can move to the
front as the speed and draft benefit increase. Even the guys who led up
the climb will feel fresh even though they just hammered up the hill --
because they were able to do it in their own rhythm.

Let the strong riders do their hard work on the flats and descents,
where the draft benefit is so huge. A strong rider can completely open
up to 40+mph on a straight descent, and the weaker rider in back will
be teasing the brakes -- well out of the red zone. The faster the
better.

I use this strategy with a lot of the riders I mentor, and I have
consistently demonstrated much improved times on known courses. I've
limped a couple of teammates around a 2-man TT course both before and
after learning this technique, and it goes much faster to put them up
front on the climbs.

Of course, this assumes that you DO NOT want to drop your weaker
riders. If dropping them is ok, then you should burn them up and spit
them out the back so they can add as much value as possible without
becoming a liability. Just make sure they are fried from being on the
front, not from clinging onto the back. Otherwise, no value added.

-Mike

Sounds pretty much like our plan. Good to hear of positive experience
with it. The only difference is our weak riders are as strong or
stronger on the flats. It's more of a weight issue. We did a 120km test
today on a windy rolling loop. It worked out pretty good. (In other
words, I didn't get dropped!)

Joseph

Quoted message said:

The idea is for the stronger climbers to pull uphill, but often the
weaker climbers have to tell them to cool it. Rather than have the
slower riders having to tell the others to constantly slow down, at
some point on steep hills the slower riders should take the lead and
set the pace. This way we don't have to keep yelling at each other to
slow down. But this only makes sense if we are going slow enough for
there to be no advantage to be had for the weaker riders drafting the
stonger ones. As for safety, we ride togther quite a bit so we know
each other and trust each other, but safety is certainly the highest
priority in all situations.

Theoretically... make the climber types pull *just before* the hill.
They can recover somewhat on the climb, while the heavier guys set the
pace. The heavy guys can set the pace at very little cost, since
drafting saves little energy at climbing speeds.

Realistically... your heavy riders might be motivated to ride a little
harder with a climber type in front of them. Peer pressure works to keep
up the speed.

IMO, you have to find a balance, and that can be tough depending on the
mix of personalities in your club.

--
Dave
dvt at psu dot edu