The recent Wired article has opened up this topic, and with even more bizarre claims that earlier. See "Planet Oil Barrel" of the Wired article.
The original and long-standing claim was that the cart would travel
directly down wind, steady state. That claim included wind tunnel conditions, and that was the basis of the argument over the conservation of energy which such a cart would violate. Sleight of hand has allowed that claim to be dropped in favour of an ad-hoc trail, which does not support the original claim.
None of the former conditions have been met by the recent NALSA trail, and there is evidence of data tampering to disguise the changing wind, and so avoid the obvious rebuttal.
This thread concerns a
cart in the wind, and I hope the moderators will keep that in mind. Currently, on other forums, Spork and his posse derail the topic with imaginary carts and cotton reels, to avoid answering to the test itself. One does wonder why if the record is so solid, that Spork feels the need to convince the last men standing.
The question has always been one of thermodynamics, and not simply of speed over land. It has been long established that sail boats can exceed wind speed, but ddw is a
specific claim; that must be exclusively tested, and all other plausible explanations eliminated if the claim is to be valid.
The employed wind instruments are designed to meet NIST standards for stationary weather stations, and that poses some problems for the measurements from a moving vehicle, but the NALSA data is all the is available, so I will work with that.
This chart was produced by Spork and
not NALSA. TAD had free access to all the data, and that certainly is not acceptable.
The first thing to note is that the cart is about 8 degrees off the wind at the start, and is pushed to above the nominal wind speed of 10mph. As soon as the pushing ceases, acceleration rapidly falls until the wind changes at 588990, at which point the cart begins to accelerate. Note that the cart's acceleration is
least when close to ddw. That is contrary to NALSA's conclusion that it is
best when ddw.
The straight (black) line between 588990 and 588997, indicates a constant change in wind direction of 10/7 = 1.4 degrees/second. It is not just changing, but
turning.For the remainder of the trial, the wind is constantly changing and turning, so opening up opportunities for tacking, crosswinds and momentum storage to be responsible for the performance.
None have been eliminated by NALSA. In fact, the rules allow for at least one plausible mechanism involving the rotor and chassis:
"Comment on Rule S2:... Stored energy in the form of momentum of the yacht, its wheels or other normally moving or flexing parts of the yacht is allowed."
That alone disallows the trial for the purposes of the original claim.
The cart is pushed to 40% of the record speed, and gains 3500J ( in the 295kg chassis) and that is
energy external to the wind. That is another violation of the claim, unless the cart is shown later to be steady state, and it is not. Unless the cart reaches a constant speed, it
does indeed matter "how it gets to windspeed". The cart is allowed to start when it pleases, be pushed, or wait until short-term wind patterns allow for "success". That is why steady-state is a critical parameter. NASLA concerned themselves with only the top speed, and ignored all else.
There is more to be extracted on that topic, but the record itself, as defined by NALSA, is suspect due to data tampering and instrument limitations.
There are clear differences between NALSA's data and the orange chart.
( I have appended the windspeed data to this chart.)
The NALSA chart shows the wind turns South at 8.8 seconds into the measurement period, but about 4 seconds on Spork's chart. The measurement point at 589065.8, also shows different wind patterns at that time.
The NALSA chart shows the wind changes rapidly; 20 degrees in 0.2 seconds, if the data is correct.
That is not ddw, nor like a wind tunnel no matter how "averaged". With that level of energy input, the question of the Conservation of Energy becomes moot.
For the 10 second test period, NALSA use a "10 second average" which is simply the arithmetic mean of all the samples within that period, resulting in -4.1 degrees.
That is meaningless in any context.
NALSA's chart is the
difference of cart and wind.
Averaging, as NALSA have done, would allow a jibing cart to average to zero.
But, that is quite obviously not the method used to obtain the wind data in Spork's chart. A likely explanation for the delay, and the smoothed wind changes, is that the data has been low-pass filtered. That process has not been made explicit, and is a violation of NALSA's regulations.
It is claimed that the cart accelerates through the speed measurement period of 3 seconds. That will be hard to sustain. The GPS speed data, from which the acceleration is derived, is updated once a second (1Hz). NALSA took the extraordinary step of interpolating that to 5Hz.
The GT31's speed "accuracy" is given at 0.1m/s, but that is subject to many factors that are perhaps best explained later. But, it is too low to support the small change in speed, and so prove acceleration.
Spork may claim that he has "some sort of record" forged between he and NALSA, but has not met his original claim, yet he allows the names Prof Allain and Charles Platt to be sullied upon that basis. He can keep his "record" but should withdraw his remarks concerning proving anything,
that manages a peak of 2.8x average windspeed?