Randonneur aerodynamics

On 3/15/2021 9:12 PM, wrote:
On Monday, March 15, 2021 at 8:00:28 PM UTC-5, jbeattie wrote:
https://www.renehersecycles.com/aero...ando-vs-racer/

And when is a handlebar bag a fairing?

-- Jay Beattie.

I think its fairly obvious the handlebar bag is a fairing in the very specific scenario Jan Heine states in the article. Speeding 50 mph downhill in a very tucked in position where you are able to get your whole body and arms and head behind the flat fronted handlebar bag. Its a fairing in this one situation because it smooths out the whole shape of your body better. But 99.99% of the rest of the time you are riding the bike, its a wind block because it adds lots of extra frontal area besides all the frontal area your body already adds because it is not tucked in behind the handlebar bag.

About the "rest of the time": I don't think the bag really adds to
frontal area. ISTM that in the front view, its profile is contained
within the outline of the rider's body.

And this next bit is speculation that I haven't thought about deeply,
but: What if we look at aero drag in terms of detailed energy losses?
That is, energy put into stirring air to turbulence?

The work or energy the bag puts into the air stirs the air only for two
feet or so - the distance from the bag to the rider's body. Compared to
the much greater stirring action of the bike+rider as a whole, that's
probably negligible. And if the bag's presence does anything at all to
deflect air around any part of the body+bike, it may be a net gain in
efficiency.

Again, vague speculation. But I've never perceived any aero cost from my
bag. My impression has been the opposite.

--
- Frank Krygowski

And when is a handlebar bag a fairing? I'd like to see the wind tunnel experiments on that one. Jan comes up with a whole lot of untested, intuitive truths that conveniently fit his product offerings. 45mm tires are super fast, and 1950s steel frames "plane" and a pre-WW II design crank are the best, particularly when they cost almost $500 in current dollars Okey-dokey. The bag-fairing is $300 f****** bucks. I got a pair of Orlieb panniers on sale at Westernbikeworks for half that. https://www.westernbikeworks.com/pro...ier-set?sg=507 This is bizarre fashion stuff worthy of a Frank Krygowski shout-down.

And those $300 bags are designed to be used with a front rack ($170 to $185)
and a separate decaleur (another $180).

On Monday, March 15, 2021 at 10:10:06 p.m. UTC-4, Frank Krygowski wrote:
On 3/15/2021 8:39 PM, wrote:
On Monday, March 15, 2021 at 11:22:07 AM UTC-5, AMuzi wrote:
https://www.renehersecycles.com/journal/

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971


https://www.renehersecycles.com/aero...ando-vs-racer/

Here is the article you are referencing. What he says makes sense. But it is not a surprise or a mystery or unknown by everyone else. Smaller frontal area makes you more aerodynamic. Which makes you faster. Adding a handlebar bag on front acts as a fairing. And despite the un-aero flat face of the bag, it actually makes you overall more aero because it forms a better shape with your body behind it than if the flat fronted bag was not there at all.
This is just a detail, but I've never understood why handlebar bags have
flat fronts. The ones I've mad do not.

I do think the bag aids coasting speed, based on my experience riding
with others.

--
- Frank Krygowski

Coasting speed can be increased too by simply keeping the legs on close to the bicycle frame and the arms tucked in close to the body. A dew years ago on a Tour (not a race) I was out coasting many riders on fancy high end aluminium or carbon fibre bicycles even though my 1980s era Miel had 30mm Schwalbe CX-Pro knobby cyclo-cross tires on it.

Or, perhaps those knobby tires didn't bounce as much a s the high-pressure narrow racing tires did? ;)

Cheers

On Tue, 16 Mar 2021 00:12:52 -0700 (PDT), Sir Ridesalot
wrote:

On Monday, March 15, 2021 at 10:10:06 p.m. UTC-4, Frank Krygowski wrote:
On 3/15/2021 8:39 PM, wrote:
On Monday, March 15, 2021 at 11:22:07 AM UTC-5, AMuzi wrote:
https://www.renehersecycles.com/journal/

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971


https://www.renehersecycles.com/aero...ando-vs-racer/

Here is the article you are referencing. What he says makes sense. But it is not a surprise or a mystery or unknown by everyone else. Smaller frontal area makes you more aerodynamic. Which makes you faster. Adding a handlebar bag on front acts as a fairing. And despite the un-aero flat face of the bag, it actually makes you overall more aero because it forms a better shape with your body behind it than if the flat fronted bag was not there at all.
This is just a detail, but I've never understood why handlebar bags have
flat fronts. The ones I've mad do not.

I do think the bag aids coasting speed, based on my experience riding
with others.

--
- Frank Krygowski

Coasting speed can be increased too by simply keeping the legs on close to the bicycle frame and the arms tucked in close to the body. A dew years ago on a Tour (not a race) I was out coasting many riders on fancy high end aluminium or carbon fibre bicycles even though my 1980s era Miel had 30mm Schwalbe CX-Pro knobby cyclo-cross tires on it.

Or, perhaps those knobby tires didn't bounce as much a s the high-pressure narrow racing tires did? ;)

Cheers

When we lived in Phuket I had a "morning ride" that had a long fairly
flat "hill" on the way home. Roughly a kilometer of flat, straight,
pavement with a very even slope all the way. I used to come over the
top of the hill and then coast all the way down. I found that, with
drop handle bars, sitting up with my hands on the top of the bars I
might coast at say, 30 kph, and simply by moving to the drops and
leaning forward a bit, not a real crouch, the speed increased 1 kph.
The hill was long enough that I could sit up and slow down and then
back on the drops and speed up several times on the same hill and it
was a very constant phenomena.

A real crouch, chin on the bars, elbows in, both feet together on the
top of the BB and knees squeezed together and the speed increased to
almost 33 kph :-)
--
Cheers,

John B.

On 3/16/2021 3:12 AM, Sir Ridesalot wrote:
On Monday, March 15, 2021 at 10:10:06 p.m. UTC-4, Frank Krygowski wrote:
On 3/15/2021 8:39 PM, wrote:
On Monday, March 15, 2021 at 11:22:07 AM UTC-5, AMuzi wrote:
https://www.renehersecycles.com/journal/

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971


https://www.renehersecycles.com/aero...ando-vs-racer/

Here is the article you are referencing. What he says makes sense. But it is not a surprise or a mystery or unknown by everyone else. Smaller frontal area makes you more aerodynamic. Which makes you faster. Adding a handlebar bag on front acts as a fairing. And despite the un-aero flat face of the bag, it actually makes you overall more aero because it forms a better shape with your body behind it than if the flat fronted bag was not there at all.
This is just a detail, but I've never understood why handlebar bags have
flat fronts. The ones I've mad do not.

I do think the bag aids coasting speed, based on my experience riding
with others.

--
- Frank Krygowski

Coasting speed can be increased too by simply keeping the legs on close to the bicycle frame and the arms tucked in close to the body. A dew years ago on a Tour (not a race) I was out coasting many riders on fancy high end aluminium or carbon fibre bicycles even though my 1980s era Miel had 30mm Schwalbe CX-Pro knobby cyclo-cross tires on it.

Or, perhaps those knobby tires didn't bounce as much a s the high-pressure narrow racing tires did? ;)

Our roads tend to be pretty rough due to potholes and patches. I think
my coasting is helped by my diligence in choosing the smoothest path,
and in taking a bit of my weight off the saddle - i.e. using my legs to
provide some suspension. I don't know if others I ride with do that.

I also pay attention to keeping elbows and knees tucked in as much as
possible.


--
- Frank Krygowski

On 3/15/2021 10:21 PM, Frank Krygowski wrote:


About the wind tunnel: In one issue long ago, [Jan Heine] did pay for wind tunnel
time. I should dig it out (assuming the guy I loaned it to has returned
it), but the points I remember are that drag coefficient is barely
changeable, so frontal area is the most important thing; and that
(surprisingly) fenders don't impose a significant aero penalty.

But I remember in that issue he attached a bit of cardboard to the top
of a handlebar bag hoping it would send air over the rider in a touring
position - which, of course it didn't. I thought the idea was ludicrous,
and showed that his aero instincts are not very sharp.

However, I agree with Russell that the handlebar bag can be an aid in a
full tuck. My homemade bag is larger than most and less boxy. I've long
suspected it's part of the reason I outcoast so many of my friends.

I recognize that this is in conflict with "drag coefficient barely
changes." More on that in another post.

OK, I found the old 2007 issue of _Bicycle Quarterly_ with the extensive
wind tunnel article. There are lots of measurements to evaluate
different sources of drag. I'll concentrate on just one chart.

Page 21, chart #6 has drag measurements for 22 mph (= 9.83 m/s = 35.4
kph) with and without a handlebar bag. Drag is in Newtons in the table,
but I'll convert to aero drag Watts at 22 mph, since we're more used to
thinking in those terms.

Rider on hoods, no bag: 256 W with bag: 262 W
Rider on drops, no bag: 238 W with bag: 249 W
Rider in aero tuck, no bag: 160 W with bag: 163 W

(Those Watt figures ignore rolling resistance and climbing power. And of
course, a rider can't pedal in an aero tuck. The rider was pedaling in
other positions.)

The handlebar bag he used is one of the large, sharp-edged boxy ones. I
have vaguely similar bags on a couple bikes, but the two bags I made
myself are more smooth, curved and tapered at the front. I suspect it
produces less drag, perhaps even a net benefit.

BTW, I mis-remembered one point: Drag coefficient dropped by 7% in the
aero tuck position; I had thought it stayed closer to constant. This is
in addition to the major benefit of the tuck, which was the reduction in
frontal area.

--
- Frank Krygowski

On Tuesday, March 16, 2021 at 9:03:17 AM UTC-7, Frank Krygowski wrote:
On 3/15/2021 10:21 PM, Frank Krygowski wrote:


About the wind tunnel: In one issue long ago, [Jan Heine] did pay for wind tunnel
time. I should dig it out (assuming the guy I loaned it to has returned
it), but the points I remember are that drag coefficient is barely
changeable, so frontal area is the most important thing; and that
(surprisingly) fenders don't impose a significant aero penalty.

But I remember in that issue he attached a bit of cardboard to the top
of a handlebar bag hoping it would send air over the rider in a touring
position - which, of course it didn't. I thought the idea was ludicrous,
and showed that his aero instincts are not very sharp.

However, I agree with Russell that the handlebar bag can be an aid in a
full tuck. My homemade bag is larger than most and less boxy. I've long
suspected it's part of the reason I outcoast so many of my friends.

I recognize that this is in conflict with "drag coefficient barely
changes." More on that in another post.
OK, I found the old 2007 issue of _Bicycle Quarterly_ with the extensive
wind tunnel article. There are lots of measurements to evaluate
different sources of drag. I'll concentrate on just one chart.

Page 21, chart #6 has drag measurements for 22 mph (= 9.83 m/s = 35.4
kph) with and without a handlebar bag. Drag is in Newtons in the table,
but I'll convert to aero drag Watts at 22 mph, since we're more used to
thinking in those terms.

Rider on hoods, no bag: 256 W with bag: 262 W
Rider on drops, no bag: 238 W with bag: 249 W
Rider in aero tuck, no bag: 160 W with bag: 163 W

(Those Watt figures ignore rolling resistance and climbing power. And of
course, a rider can't pedal in an aero tuck. The rider was pedaling in
other positions.)

The handlebar bag he used is one of the large, sharp-edged boxy ones. I
have vaguely similar bags on a couple bikes, but the two bags I made
myself are more smooth, curved and tapered at the front. I suspect it
produces less drag, perhaps even a net benefit.

BTW, I mis-remembered one point: Drag coefficient dropped by 7% in the
aero tuck position; I had thought it stayed closer to constant. This is
in addition to the major benefit of the tuck, which was the reduction in
frontal area.
I don't have much faith in wind tunnel data except for comparison purposes.

On Tuesday, March 16, 2021 at 9:03:17 AM UTC-7, Frank Krygowski wrote:
On 3/15/2021 10:21 PM, Frank Krygowski wrote:


About the wind tunnel: In one issue long ago, [Jan Heine] did pay for wind tunnel
time. I should dig it out (assuming the guy I loaned it to has returned
it), but the points I remember are that drag coefficient is barely
changeable, so frontal area is the most important thing; and that
(surprisingly) fenders don't impose a significant aero penalty.

But I remember in that issue he attached a bit of cardboard to the top
of a handlebar bag hoping it would send air over the rider in a touring
position - which, of course it didn't. I thought the idea was ludicrous,
and showed that his aero instincts are not very sharp.

However, I agree with Russell that the handlebar bag can be an aid in a
full tuck. My homemade bag is larger than most and less boxy. I've long
suspected it's part of the reason I outcoast so many of my friends.

I recognize that this is in conflict with "drag coefficient barely
changes." More on that in another post.
OK, I found the old 2007 issue of _Bicycle Quarterly_ with the extensive
wind tunnel article. There are lots of measurements to evaluate
different sources of drag. I'll concentrate on just one chart.

Page 21, chart #6 has drag measurements for 22 mph (= 9.83 m/s = 35.4
kph) with and without a handlebar bag. Drag is in Newtons in the table,
but I'll convert to aero drag Watts at 22 mph, since we're more used to
thinking in those terms.

Rider on hoods, no bag: 256 W with bag: 262 W
Rider on drops, no bag: 238 W with bag: 249 W
Rider in aero tuck, no bag: 160 W with bag: 163 W

(Those Watt figures ignore rolling resistance and climbing power. And of
course, a rider can't pedal in an aero tuck. The rider was pedaling in
other positions.)

The handlebar bag he used is one of the large, sharp-edged boxy ones. I
have vaguely similar bags on a couple bikes, but the two bags I made
myself are more smooth, curved and tapered at the front. I suspect it
produces less drag, perhaps even a net benefit.

BTW, I mis-remembered one point: Drag coefficient dropped by 7% in the
aero tuck position; I had thought it stayed closer to constant. This is
in addition to the major benefit of the tuck, which was the reduction in
frontal area.

So unless I'm missing something, the testing shows that no bag is more aerodynamic and that there is more drag with a bag, viz., exactly opposite of Jan's claim.

I was going to swap my 16lb Emonda for a steel Renee Herse with 45mm tires and bags to see if I could increase my speed.

-- Jay Beattie.

On Tuesday, March 16, 2021 at 10:17:12 AM UTC-7, jbeattie wrote:
On Tuesday, March 16, 2021 at 9:03:17 AM UTC-7, Frank Krygowski wrote:
On 3/15/2021 10:21 PM, Frank Krygowski wrote:


About the wind tunnel: In one issue long ago, [Jan Heine] did pay for wind tunnel
time. I should dig it out (assuming the guy I loaned it to has returned
it), but the points I remember are that drag coefficient is barely
changeable, so frontal area is the most important thing; and that
(surprisingly) fenders don't impose a significant aero penalty.

But I remember in that issue he attached a bit of cardboard to the top
of a handlebar bag hoping it would send air over the rider in a touring
position - which, of course it didn't. I thought the idea was ludicrous,
and showed that his aero instincts are not very sharp.

However, I agree with Russell that the handlebar bag can be an aid in a
full tuck. My homemade bag is larger than most and less boxy. I've long
suspected it's part of the reason I outcoast so many of my friends.

I recognize that this is in conflict with "drag coefficient barely
changes." More on that in another post.
OK, I found the old 2007 issue of _Bicycle Quarterly_ with the extensive
wind tunnel article. There are lots of measurements to evaluate
different sources of drag. I'll concentrate on just one chart.

Page 21, chart #6 has drag measurements for 22 mph (= 9.83 m/s = 35.4
kph) with and without a handlebar bag. Drag is in Newtons in the table,
but I'll convert to aero drag Watts at 22 mph, since we're more used to
thinking in those terms.

Rider on hoods, no bag: 256 W with bag: 262 W
Rider on drops, no bag: 238 W with bag: 249 W
Rider in aero tuck, no bag: 160 W with bag: 163 W

(Those Watt figures ignore rolling resistance and climbing power. And of
course, a rider can't pedal in an aero tuck. The rider was pedaling in
other positions.)

The handlebar bag he used is one of the large, sharp-edged boxy ones. I
have vaguely similar bags on a couple bikes, but the two bags I made
myself are more smooth, curved and tapered at the front. I suspect it
produces less drag, perhaps even a net benefit.

BTW, I mis-remembered one point: Drag coefficient dropped by 7% in the
aero tuck position; I had thought it stayed closer to constant. This is
in addition to the major benefit of the tuck, which was the reduction in
frontal area.
So unless I'm missing something, the testing shows that no bag is more aerodynamic and that there is more drag with a bag, viz., exactly opposite of Jan's claim.

I was going to swap my 16lb Emonda for a steel Renee Herse with 45mm tires and bags to see if I could increase my speed.

-- Jay Beattie.
Is this one of your "mostly peaceful demonstrations"?

On 3/16/2021 12:17 PM, jbeattie wrote:
On Tuesday, March 16, 2021 at 9:03:17 AM UTC-7, Frank Krygowski wrote:
On 3/15/2021 10:21 PM, Frank Krygowski wrote:


About the wind tunnel: In one issue long ago, [Jan Heine] did pay for wind tunnel
time. I should dig it out (assuming the guy I loaned it to has returned
it), but the points I remember are that drag coefficient is barely
changeable, so frontal area is the most important thing; and that
(surprisingly) fenders don't impose a significant aero penalty.

But I remember in that issue he attached a bit of cardboard to the top
of a handlebar bag hoping it would send air over the rider in a touring
position - which, of course it didn't. I thought the idea was ludicrous,
and showed that his aero instincts are not very sharp.

However, I agree with Russell that the handlebar bag can be an aid in a
full tuck. My homemade bag is larger than most and less boxy. I've long
suspected it's part of the reason I outcoast so many of my friends.

I recognize that this is in conflict with "drag coefficient barely
changes." More on that in another post.
OK, I found the old 2007 issue of _Bicycle Quarterly_ with the extensive
wind tunnel article. There are lots of measurements to evaluate
different sources of drag. I'll concentrate on just one chart.

Page 21, chart #6 has drag measurements for 22 mph (= 9.83 m/s = 35.4
kph) with and without a handlebar bag. Drag is in Newtons in the table,
but I'll convert to aero drag Watts at 22 mph, since we're more used to
thinking in those terms.

Rider on hoods, no bag: 256 W with bag: 262 W
Rider on drops, no bag: 238 W with bag: 249 W
Rider in aero tuck, no bag: 160 W with bag: 163 W

(Those Watt figures ignore rolling resistance and climbing power. And of
course, a rider can't pedal in an aero tuck. The rider was pedaling in
other positions.)

The handlebar bag he used is one of the large, sharp-edged boxy ones. I
have vaguely similar bags on a couple bikes, but the two bags I made
myself are more smooth, curved and tapered at the front. I suspect it
produces less drag, perhaps even a net benefit.

BTW, I mis-remembered one point: Drag coefficient dropped by 7% in the
aero tuck position; I had thought it stayed closer to constant. This is
in addition to the major benefit of the tuck, which was the reduction in
frontal area.

So unless I'm missing something, the testing shows that no bag is more aerodynamic and that there is more drag with a bag, viz., exactly opposite of Jan's claim.

I was going to swap my 16lb Emonda for a steel Renee Herse with 45mm tires and bags to see if I could increase my speed.

-- Jay Beattie.


If that doesn't work, try steel pinned cranks with 3 bolts.
Because France.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971