Yeah, there is no maybe about it. He never understood airspeed.
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Merged DDWFTTW in a “Real” Wind
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Yeah, there is no maybe about it. He never understood airspeed.
A Sky dance for those interested
This is too freaking cool! A minor interlude for Aero pleasure!
http://www.newscientist.com/blogs/n...on-air.html?DCMP=NLC-nletter&nsref=viraldance
For the TM disbelivers, this doesn't work because the earth and wind doesn't transform properly so they crash in your universe!
I think many of you will enjoy this especially if you've ever made a "jump"!
WindGrins
This is too freaking cool! A minor interlude for Aero pleasure!
http://www.newscientist.com/blogs/n...on-air.html?DCMP=NLC-nletter&nsref=viraldance
For the TM disbelivers, this doesn't work because the earth and wind doesn't transform properly so they crash in your universe!
I think many of you will enjoy this especially if you've ever made a "jump"!
WindGrins
My first tandem jump was pretty high at 13,000 ft* but the free fall time was still a heck of a lot shorter than that dance.
* Out of "Mr. Douglas", the same DC-3 that was in "Drop Zone" with Snipes and Busey. I actually got nervous because it looked like my instructor was out like a light on the climb up to altitude, and there was no way I wanted to land in that plane, especially with the pilot that looked 18 years old.
Subduction Zone
Muse
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Just a thought, there are quite a few magazines that support DDWFTTW and spork and JB's accomplishment. You would think you could find at least one saying it is not possible. Oh wait, there was one. The Make magazine article by Charles Platt. Of course the publisher of that article did something very rare in the magazine world. He admitted that his author was wrong and published a very thorough article debunking their original claim.
Surely humber with his vast web searches can find another article proving that DDWFTTW is not possible
Actually a good sign (probably!)
If your tandem jump instructor fell asleep, its usually a sign of experience. I had an old flight instructor that use to fall asleep in the back of the taildragger between touch and goes. You knew she was pretty confident in your landings when she would nod off back there. The first time I figured it out was when the aileron felt heavy. It turns out that in that old Taylorcraft L-2 that the control cable ran by our heads and her head was laying on the cable. As I wiggled the aileron, her head bobbled around! She slept through it.
ETA: She was Amelia Reid of Amelia Reid Aviation at Reid/Hillview Airport in San Jose. You may have known her years ago! She's passed now. She was a great instructor and use to do an aerobatic routine at about 50 feet in a C150 aerobat. It was a good show of stored energy. Her love was her Pitts however. She was a hot-dog!
My first tandem jump was pretty high at 13,000 ft* but the free fall time was still a heck of a lot shorter than that dance.
* Out of "Mr. Douglas", the same DC-3 that was in "Drop Zone" with Snipes and Busey. I actually got nervous because it looked like my instructor was out like a light on the climb up to altitude, and there was no way I wanted to land in that plane, especially with the pilot that looked 18 years old.
If your tandem jump instructor fell asleep, its usually a sign of experience. I had an old flight instructor that use to fall asleep in the back of the taildragger between touch and goes. You knew she was pretty confident in your landings when she would nod off back there. The first time I figured it out was when the aileron felt heavy. It turns out that in that old Taylorcraft L-2 that the control cable ran by our heads and her head was laying on the cable. As I wiggled the aileron, her head bobbled around! She slept through it.
ETA: She was Amelia Reid of Amelia Reid Aviation at Reid/Hillview Airport in San Jose. You may have known her years ago! She's passed now. She was a great instructor and use to do an aerobatic routine at about 50 feet in a C150 aerobat. It was a good show of stored energy. Her love was her Pitts however. She was a hot-dog!
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While you are looking at that report, LLyricist, take note of how the rolling resistance is calculated, then you may see the other reason I asked if it was .08
I know what number he used in the hypothetical situation that explained how the cart works. It has a couple numbers that may be the same as the actual cart, but they are all used for illustration purposes nonetheless, and aren't necessarily representative of the actual cart.
The propeller diameter I asked about above was not in that part of the report, but at the beginning, and was in fact, referring to the actual cart.
Now I know some people have a hard time separating reality from hypothetical (or fantasy for that matter), but I am not one of them.
I did change it because it was not what I intended to say. I did not say you had said the opposite.
But, factoring in the wind angle as the cosine (for, or against) is not what is written in the submission, and power of the wind is related to the cube of its velocity. Energy = KE =1/2mv^2, mass over time is related to V, so the power is related to V^3.
It is a cheap trick to unjustifiably worsen the cart's behavior when NOT ddw, in order to claim that it is then better when ddw. While you may say the headwind increases when the wind is not ddw, and that is correct, despite that, boats can exceed the speed of the wind by exploiting the lift force so generated. That was the point.
Moreover, there is no doubt the the tailwind drives the rotor as a turbine, and the power generated by a turbine is related to the cube of the cosine of that angle away from the axis. The opposing turbine force will fall when the wind is not ddw, so opposite to your contention. The cart works better when not ddw because if benefits from both of the above effects.
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Never mind.
This must be the "busted cart", that humber is talking about.
Yes, you did.
I know that, I said this before, and called it the AOA problem, and I have no way of quantifying it. But I can quantify the longitudinal component of the airspeed, which also, and more obviously affects the cart's performance.
This is just wrong in every imaginable way.
No, I changed the way I expressed the same point.
No you can't quantify that, and it still wouldn't deny that boats can gain from tacking, and so can the cart; and it is a fact that turbine force falls as the cube of the cosine away from the axis.
http://en.wikipedia.org/wiki/Wind_turbine_design
Yawing
Modern large wind turbines are typically actively controlled to face the wind direction measured by a wind vane situated on the back of the nacelle. By minimizing the yaw angle (the misalignment between wind and turbine pointing direction), the power output is maximized and non-symmetrical loads minimized. However, since the wind direction varies quickly the turbine will not strictly follow the direction and will have a small yaw angle on average. The power output losses can simply be approximated to fall with cos3(yaw angle).
You are claiming that the cart performs worse when not ddw, when the contrary is true.
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It is not difficult to fit data into a system where all major parameters are linearly related. Speed, prop AV, acceleration etc, are all coupled together.
What you have failed to do, is show that other influences are not.
The opposing turbine force is one such example.
The matter of the prop size, is the result of throwing about any numbers that come to mind. Neither the prop nor the cart have been weighed, nor any force actually measured.
"I get pretty much the same results as before with a Cd of .3 and a crr of .012"
Aero drag related to V^2
Frr related to V
.3^2 = .09
Give or take the relative velocity difference, it is not surprising the total remains the same.
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The opposing force from the propeller is accounted for.
Fnet = Thrust - (Prop Power Demand / Drivetrain Efficiency / Ground Speed) - Aerodynamic Drag Force - Rolling Resistance
Where the power demand is simply the load at the prop shaft, and "powered" by the wheel. That says nothing about the effect of the tailwind on the propeller, which will reduce the demand.
And you are mixing power and force from two different frames.
The aerodrag force is related to the difference of the cart and wind speeds, Vhead, so producing an opposing force, F, related to Vhead^2, and power related to F*Vhead^3. But, the power consumed from the ground frame is F*(V_cart)
F_Drag = K*Vhead^2
Power_Drag = K*Vhead^3
Pcart = K*Vhead^2*Vcart.
And airfoil section can gain lift from incident wind, and so can the remainder of the cart. The apparent area exposed to the wind increases when not ddw.
The prop also spends 50% of its time in above the hub where the wind is measured, and that wind will certainly be faster then seen the other blade which will be below the hub. The cart can exploit both vertical and horizontal wind gradients and angle changes.
The videos clearly show that the prop turns freely CCW, when not forced by the chain to turn the other way. That turbine force does not go away. The net force is the difference of that turbine force and the direct force driving the cart and wheels to turn it the other way. That is why it is so slow.
When raced, the small turbine cart was quick of the mark, while the prop cart limped along, because that same turbine force was opposing the cart.
It is exactly what you are doing.
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Wow, this almost to new humberism level, but not quite.
There is no turbine torque above wind speed. only the power demand of the prop.
That isn't the part that was wrong.
There is no tailwind at the propeller, unless you are actually using that term as a pilot would. In which case, absolutely right, and it is that tailwind and the reduced power requirement because of it, that enables the cart to work.
Forces are frame invariant, as is rotational power.
And the F is the same in all frames.
All irrelevant, Force is frame invariant.
Yep, it's just too bad that the drag the airfoil sections produce always leave them with a net force pointing to the rear. And I have done the polars for those airfoils, and I know this for a fact.
You can assert this all you want, but until you can actually explain it, it remains fantasy.
There is no turbine torque above wind speed. only the power demand of the prop.
That isn't the part that was wrong.
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