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Re: Dimond has some A2 data! [trail] [ In reply to ]
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trail wrote:
Power13 wrote:

No, you believe the Dimond will be slower. Belief is not knowledge.

Sure, but that goes both ways. Rappstar, above, says, "Based on what I've seen, the Dimond is faster than the Shiv." But then doesn't explain what he's seen - just offers justifications for not explaining it. To his credit he did water down the claim in the same paragraph, "But for me, I believe the Dimond is faster." (emphasis mine).

Most consistently, it's been on my measured TT course. Speed on that course - which is a rolling course with a net ascent that is relatively sheltered from the wind - is higher for a given power output on the Dimond than on the Shiv. And that's reinforced by a lot of rides on a lot of the same roads over and over. As I said, there are a LOT of variables. I have not made an effort to isolate every one of them. For example, the Dimond MIGHT simply be faster because 1X is faster than RED22. Or because the Dimond does better at low yaw relative to the Shiv which was admittedly designed (rightly or wrongly) for high yaw, which I rarely see where I train.

Before I signed a five year contract with Dimond, I talked to David Morse - who I knew from Zipp and who largely designed the Dimond and who is now back at Zipp - and several other of the Zipp engineers who were a part of the Dimond project (many of them contributed their time/expertise to helping "revamp" the Zipp 3001/2001). And I've continued to talk to them since as many of them have put the bike into the tunnel.

In terms of "explaining what I've seen," I wouldn't say that it qualifies as highly empirical. I did not take out both frames and "Chung" them with identical (or as close as possible) set ups. I've just seen, consistently, that I go faster on a given power output on the Dimond than on the Shiv. This isn't from "testing." It's just from riding. I don't want to present riding as testing, but I also don't want to discount that things can be apparent when you spend enough time doing it... I promise I'm not trying to be deliberately obscure here.


"Non est ad astra mollis e terris via." - Seneca | rappstar.com | Facebook - Rappstar Racing | @rappstar

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Re: Dimond has some A2 data! [Titanflexr] [ In reply to ]
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Titanflexr wrote:
romulusmagnus wrote:
You're completely missing the point. The speed they calibrated to is an industry stand to quantify deltas in product on a consistent basis, even as that measure (grams of drag) is itself incredibly stupid and inaccurate for real world application


Yes, 30mph is a standard (a reasonable speed for TdF FOP TTers like Fabian and Tony). I was just pointing out what the watts savings is likely to be for a "typical" Diamond owner who's considering cost/benefit.

My pref. is reporting time saved over 40K....since that at least scales up a bit for slower riders. CdA is ideal....but not really usable for the non-engineers.

Late to this thread by 30 mph is speed of airflow over the bike and rider. Really easy for mid pack age groupers to hit riding at 18 mph into a 12 mph wind. 30 mph is not ground speed. Ground speed is irrelevant!
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Re: Dimond has some A2 data! [devashish_paul] [ In reply to ]
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devashish_paul wrote:
Titanflexr wrote:
romulusmagnus wrote:
You're completely missing the point. The speed they calibrated to is an industry stand to quantify deltas in product on a consistent basis, even as that measure (grams of drag) is itself incredibly stupid and inaccurate for real world application


Yes, 30mph is a standard (a reasonable speed for TdF FOP TTers like Fabian and Tony). I was just pointing out what the watts savings is likely to be for a "typical" Diamond owner who's considering cost/benefit.

My pref. is reporting time saved over 40K....since that at least scales up a bit for slower riders. CdA is ideal....but not really usable for the non-engineers.


Late to this thread by 30 mph is speed of airflow over the bike and rider. Really easy for mid pack age groupers to hit riding at 18 mph into a 12 mph wind. 30 mph is not ground speed. Ground speed is irrelevant!

You sure about that Dev? Unless they were drafting someone or riding downhill I'd be pretty impressed.

Hugh

Genetics load the gun, lifestyle pulls the trigger.
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Re: Dimond has some A2 data! [devashish_paul] [ In reply to ]
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Not so much. Ground speed is very relevant. The power to ride 18mph into a 12mph wind is pretty close to 30mph power with no wind. Slightly lower because of Crr but not massive.

The problem with your assumption is that "12mph wind" is rarely 12mph when measured at 1m off the ground. And of course the likelihood of zero(ish) yaw even when it is windy.

But really the biggest factor is that reported wind speed is measured quite high in the air. Not at ground level.


"Non est ad astra mollis e terris via." - Seneca | rappstar.com | Facebook - Rappstar Racing | @rappstar

Ask me about: DiamondBack Bikes | Zipp | 1st Endurance | Normatec - $100 off RAPP2017 | Quarq | SRAM | MatchRider | Kiwami | ROKA
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Re: Dimond has some A2 data! [Rappstar] [ In reply to ]
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Rappstar wrote:
Not so much. Ground speed is very relevant. The power to ride 18mph into a 12mph wind is pretty close to 30mph power with no wind. Slightly lower because of Crr but not massive.

The problem with your assumption is that "12mph wind" is rarely 12mph when measured at 1m off the ground. And of course the likelihood of zero(ish) yaw even when it is windy.

But really the biggest factor is that reported wind speed is measured quite high in the air. Not at ground level.

Sure, I realize the power is almost the same (only delta at 18+12 is Crr should be lower). It's not an irrelevant air speed for an age grouper. Age groupers can his 30 mph air speed on a flat with a decent amount of power or slight downhill with low power. It happens a fair amount on a rolling course. Agreed to some degree that 12 mph wind is harder to achieve at 1 m off the ground, but it's not uncommon either.
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Re: Dimond has some A2 data! [Rappstar] [ In reply to ]
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Rappstar wrote:
The power to ride 18mph into a 12mph wind is pretty close to 30mph power with no wind. Slightly lower because of Crr but not massive.

Power to overcome drag is v_air^2 * v_ground. Power to ride 18 mph into a 12 mph headwind is therefore not really that close to riding 30 mph in no wind.
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Re: Dimond has some A2 data! [BryanD] [ In reply to ]
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Having completed a TTT with someone riding one I was surprised by how much the rear wheel moved / flexed about. It was a bit disconcerting at 1st. Don't know how much this effects speed. Guessing slight pay off for enhanced comfort / fatigue resilience.
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Re: Dimond has some A2 data! [MTM] [ In reply to ]
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MTM wrote:
Rappstar wrote:
The power to ride 18mph into a 12mph wind is pretty close to 30mph power with no wind. Slightly lower because of Crr but not massive.


Power to overcome drag is v_air^2 * v_ground. Power to ride 18 mph into a 12 mph headwind is therefore not really that close to riding 30 mph in no wind.

Aside from ground speed affects Crr related Power requirements, there can't be any difference between 30 mph airflow over a rider and bike whether it comes from 30 mph rider speed vs ground + 0 air speed relative to ground or 18 mph rider speed vs ground and 12 mph air speed against rider direction vs ground. Help me on what I am missing. Your head, arm or shoulder going through the air does not feel how fast your bike is moving over ground, only how fast the air is moving over you.
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Re: Dimond has some A2 data! [devashish_paul] [ In reply to ]
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Enough with the nerd talk. Let's get back to arguing about why my super expensive new bike sucks.

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Re: Dimond has some A2 data! [devashish_paul] [ In reply to ]
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devashish_paul wrote:
MTM wrote:
Rappstar wrote:
The power to ride 18mph into a 12mph wind is pretty close to 30mph power with no wind. Slightly lower because of Crr but not massive.


Power to overcome drag is v_air^2 * v_ground. Power to ride 18 mph into a 12 mph headwind is therefore not really that close to riding 30 mph in no wind.


Aside from ground speed affects Crr related Power requirements, there can't be any difference between 30 mph airflow over a rider and bike whether it comes from 30 mph rider speed vs ground + 0 air speed relative to ground or 18 mph rider speed vs ground and 12 mph air speed against rider direction vs ground. Help me on what I am missing. Your head, arm or shoulder going through the air does not feel how fast your bike is moving over ground, only how fast the air is moving over you.

While I agree that there intuitively seems to be some sort of logical fallacy in this, the way to calculate power the way you describe can't be correct. By your definition going 0 mph (i.e. standing still) on the bike with a 30 mph headwind would require the same power (aero drag wise) as riding 30 mph with no wind. Going 0 mph obviously doesn't require any power. You will have the same drag force (v_air^2), but no power requirement.
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Re: Dimond has some A2 data! [MTM] [ In reply to ]
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MTM wrote:
devashish_paul wrote:
MTM wrote:
Rappstar wrote:
The power to ride 18mph into a 12mph wind is pretty close to 30mph power with no wind. Slightly lower because of Crr but not massive.


Power to overcome drag is v_air^2 * v_ground. Power to ride 18 mph into a 12 mph headwind is therefore not really that close to riding 30 mph in no wind.


Aside from ground speed affects Crr related Power requirements, there can't be any difference between 30 mph airflow over a rider and bike whether it comes from 30 mph rider speed vs ground + 0 air speed relative to ground or 18 mph rider speed vs ground and 12 mph air speed against rider direction vs ground. Help me on what I am missing. Your head, arm or shoulder going through the air does not feel how fast your bike is moving over ground, only how fast the air is moving over you.


While I agree that there intuitively seems to be some sort of logical fallacy in this, the way to calculate power the way you describe can't be correct. By your definition going 0 mph (i.e. standing still) on the bike with a 30 mph headwind would require the same power (aero drag wise) as riding 30 mph with no wind. Going 0 mph obviously doesn't require any power. You will have the same drag force (v_air^2), but no power requirement.

OK, now I remember...drag force is proportional to the cube of the velocity through the fluid, so b v^^^3 where v is actually split between V1 (speed through air), V2 (speed over ground) so V1^2 (air speed) x V2 (ground speed). I think I was thinking about aircraft flying through the air where there is no connection against the ground like a wheel has so you can use ground speeds to get to your final air speed, but all that counts is air speed. For the aircraft the thrust is relative to the air, whereas for a bike the thrust is against the ground....so I stand corrected. I see where you are coming from.
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Re: Dimond has some A2 data! [devashish_paul] [ In reply to ]
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devashish_paul wrote:
MTM wrote:
devashish_paul wrote:
MTM wrote:
Rappstar wrote:
The power to ride 18mph into a 12mph wind is pretty close to 30mph power with no wind. Slightly lower because of Crr but not massive.


Power to overcome drag is v_air^2 * v_ground. Power to ride 18 mph into a 12 mph headwind is therefore not really that close to riding 30 mph in no wind.


Aside from ground speed affects Crr related Power requirements, there can't be any difference between 30 mph airflow over a rider and bike whether it comes from 30 mph rider speed vs ground + 0 air speed relative to ground or 18 mph rider speed vs ground and 12 mph air speed against rider direction vs ground. Help me on what I am missing. Your head, arm or shoulder going through the air does not feel how fast your bike is moving over ground, only how fast the air is moving over you.


While I agree that there intuitively seems to be some sort of logical fallacy in this, the way to calculate power the way you describe can't be correct. By your definition going 0 mph (i.e. standing still) on the bike with a 30 mph headwind would require the same power (aero drag wise) as riding 30 mph with no wind. Going 0 mph obviously doesn't require any power. You will have the same drag force (v_air^2), but no power requirement.


OK, now I remember...drag force is proportional to the cube of the velocity through the fluid, so b v^^^3 where v is actually split between V1 (speed through air), V2 (speed over ground) so V1^2 (air speed) x V2 (ground speed). I think I was thinking about aircraft flying through the air where there is no connection against the ground like a wheel has so you can use ground speeds to get to your final air speed, but all that counts is air speed. For the aircraft the thrust is relative to the air, whereas for a bike the thrust is against the ground....so I stand corrected. I see where you are coming from.

Yes, you are correct. So 30 mph air speed still happens even if you are not necessarily going 30 mph, but the power requirement is still pretty dependent on the ground speed.
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Re: Dimond has some A2 data! [BryanD] [ In reply to ]
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I wish the UCI would allow this!
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Re: Dimond has some A2 data! [glennf] [ In reply to ]
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Why? UCI legality doesn't matter for triathlon.

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Re: Dimond has some A2 data! [MTM] [ In reply to ]
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MTM wrote:
devashish_paul wrote:
MTM wrote:
Rappstar wrote:
The power to ride 18mph into a 12mph wind is pretty close to 30mph power with no wind. Slightly lower because of Crr but not massive.


Power to overcome drag is v_air^2 * v_ground. Power to ride 18 mph into a 12 mph headwind is therefore not really that close to riding 30 mph in no wind.


Aside from ground speed affects Crr related Power requirements, there can't be any difference between 30 mph airflow over a rider and bike whether it comes from 30 mph rider speed vs ground + 0 air speed relative to ground or 18 mph rider speed vs ground and 12 mph air speed against rider direction vs ground. Help me on what I am missing. Your head, arm or shoulder going through the air does not feel how fast your bike is moving over ground, only how fast the air is moving over you.


While I agree that there intuitively seems to be some sort of logical fallacy in this, the way to calculate power the way you describe can't be correct. By your definition going 0 mph (i.e. standing still) on the bike with a 30 mph headwind would require the same power (aero drag wise) as riding 30 mph with no wind. Going 0 mph obviously doesn't require any power. You will have the same drag force (v_air^2), but no power requirement.

How about riding 2mph into a 28mph headwind or 4mph into a 26mph headwind? You're getting hung up on just sitting in one spot rather than considering the forces acting on the moving cyclist.

Hugh

Genetics load the gun, lifestyle pulls the trigger.
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Re: Dimond has some A2 data! [sciguy] [ In reply to ]
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sciguy wrote:

How about riding 2mph into a 28mph headwind or 4mph into a 26mph headwind? You're getting hung up on just sitting in one spot rather than considering the forces acting on the moving cyclist.

Looking at just aero drag alone, it takes twice as much power for the second scenario (i.e. 4 mph into a 26mph wind) than the first (2 mph into 28mph wind).

The drag force in each of these scenarios is equivalent (since the relative wind in each case is 30mph), but the rate of doing work (Force x distance/time) against that force, or power, is not.

In the case of being stationary in a 30mph wind, no work is being done (the force is not being moved through a distance)...and hence it takes zero power.



http://bikeblather.blogspot.com/
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Re: Dimond has some A2 data! [Tom A.] [ In reply to ]
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Tom A. wrote:
sciguy wrote:


How about riding 2mph into a 28mph headwind or 4mph into a 26mph headwind? You're getting hung up on just sitting in one spot rather than considering the forces acting on the moving cyclist.


Looking at just aero drag alone, it takes twice as much power for the second scenario (i.e. 4 mph into a 26mph wind) than the first (2 mph into 28mph wind).

The drag force in each of these scenarios is equivalent (since the relative wind in each case is 30mph), but the rate of doing work (Force x distance/time) against that force, or power, is not.

In the case of being stationary in a 30mph wind, no work is being done (the force is not being moved through a distance)...and hence it takes zero power.

I stand corrected but need to ponder this a bit more to solidify my ownership of the understanding;) Perhaps all those year flying airplanes has clouded my intuition. Both land and taking off a seaplane vertically into 60 knot winds during hurricane evacuation of oil rig workers seems to have somehow brought me to an incorrect solution.

Thanks,

Hugh

Genetics load the gun, lifestyle pulls the trigger.
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Re: Dimond has some A2 data! [sciguy] [ In reply to ]
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sciguy wrote:
Tom A. wrote:
sciguy wrote:


How about riding 2mph into a 28mph headwind or 4mph into a 26mph headwind? You're getting hung up on just sitting in one spot rather than considering the forces acting on the moving cyclist.


Looking at just aero drag alone, it takes twice as much power for the second scenario (i.e. 4 mph into a 26mph wind) than the first (2 mph into 28mph wind).

The drag force in each of these scenarios is equivalent (since the relative wind in each case is 30mph), but the rate of doing work (Force x distance/time) against that force, or power, is not.

In the case of being stationary in a 30mph wind, no work is being done (the force is not being moved through a distance)...and hence it takes zero power.


I stand corrected but need to ponder this a bit more to solidify my ownership of the understanding;) Perhaps all those year flying airplanes has clouded my intuition. Both land and taking off a seaplane vertically into 60 knot winds during hurricane evacuation of oil rig workers seems to have somehow brought me to an incorrect solution.

Thanks,

Hugh

I think you may be confused by frames of reference ;-)



http://bikeblather.blogspot.com/
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Re: Dimond has some A2 data! [romulusmagnus] [ In reply to ]
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romulusmagnus wrote:
Rappstar wrote:
There are a lot of great bikes out there. I do not believe that the Dimond is dramatically faster than any of the very good ones - P5 or Trek SC or Scott Plasma 5 or Specialized Shiv or... Nor do I believe it is measurably slower. Or, more specifically, that the variance between bikes largely will come down to fit, bars, other equipment (bottle placement), etc. And that ultimately it's likely nearly impossible to determine the "best" bike for you without significant time and expense. So just pick one of the very good ones and be happy.


This is one of your best points -- not just in this thread, but ever. People who obsess over the minutia of these frames need to entirely understand the above.

By the way, I'm not actually mad at you. Part of being an internet troll is exaggerating things. It's for effect rather than sincerity. Of course, the underlying sentiment rings true, but I'm glad you clarified with your post.

(Not sure I understand the Callum Millward retweet at the end? For someone who routinely quotes Nietzsche and extemporaneously integrates obscure latin phraseology into posts, this was one of your odder external references.)

The bike industry's head will explode if people realize that. Shh
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Re: Dimond has some A2 data! [sciguy] [ In reply to ]
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sciguy wrote:
Tom A. wrote:
sciguy wrote:


How about riding 2mph into a 28mph headwind or 4mph into a 26mph headwind? You're getting hung up on just sitting in one spot rather than considering the forces acting on the moving cyclist.


Looking at just aero drag alone, it takes twice as much power for the second scenario (i.e. 4 mph into a 26mph wind) than the first (2 mph into 28mph wind).

The drag force in each of these scenarios is equivalent (since the relative wind in each case is 30mph), but the rate of doing work (Force x distance/time) against that force, or power, is not.

In the case of being stationary in a 30mph wind, no work is being done (the force is not being moved through a distance)...and hence it takes zero power.


I stand corrected but need to ponder this a bit more to solidify my ownership of the understanding;) Perhaps all those year flying airplanes has clouded my intuition. Both land and taking off a seaplane vertically into 60 knot winds during hurricane evacuation of oil rig workers seems to have somehow brought me to an incorrect solution.

Thanks,

Hugh

Yeah, I had the same airplane analogy problem from the airforce days. Think about it this way from a purely practical sense. If you have to ride at 5 mph into a 25 mph headwind, your power requirements are going to be really low. The airplane does not have a solid connection to the ground so can technical move backwards when you blow on it hard enough (certainly an aircraft with a super low stall speed that is a high drag aircraft, so all that matters is air speed). The bike has a connection to the ground.
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Re: Dimond has some A2 data! [devashish_paul] [ In reply to ]
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I wonder if a plane could take off from a giant treadmill.
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Re: Dimond has some A2 data! [jet black] [ In reply to ]
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jet black wrote:
I wonder if a plane could take off from a giant treadmill.

With airflow over the treadmill going faster than aircraft stall speed, then indeed yes, the aircraft can take off and the treadmill can be going at zero mph too!
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Re: Dimond has some A2 data! [jet black] [ In reply to ]
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jet black wrote:
I wonder if a plane could take off from a giant treadmill.

LOL...I remember that...



http://bikeblather.blogspot.com/
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Re: Dimond has some A2 data! [devashish_paul] [ In reply to ]
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devashish_paul wrote:
jet black wrote:
I wonder if a plane could take off from a giant treadmill.


With airflow over the treadmill going faster than aircraft stall speed, then indeed yes, the aircraft can take off and the treadmill can be going at zero mph too!

Back in my younger years I spent many an hour up in the Maine bush debating in what situations was it better to takeoff upstream or down stream on a river with a float plane. One gets "up on the step" of the floats based on their velocity relative to the water but the plane flies off the water due to its air speed and you can't make decent airspeed without being "on the step". So often we would begin a take off headed upstream but down wind, get on the step and make a turn back around and takeoff upwind.

Hugh

Genetics load the gun, lifestyle pulls the trigger.
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Re: Dimond has some A2 data! [sciguy] [ In reply to ]
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sciguy wrote:
devashish_paul wrote:
jet black wrote:
I wonder if a plane could take off from a giant treadmill.


With airflow over the treadmill going faster than aircraft stall speed, then indeed yes, the aircraft can take off and the treadmill can be going at zero mph too!


Back in my younger years I spent many an hour up in the Maine bush debating in what situations was it better to takeoff upstream or down stream on a river with a float plane. One gets "up on the step" of the floats based on their velocity relative to the water but the plane flies off the water due to its air speed and you can't make decent airspeed without being "on the step". So often we would begin a take off headed upstream but down wind, get on the step and make a turn back around and takeoff upwind.

Hugh

I wonder if a float plane could take off from an Endless Pool?

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