Useful information to know the thrust coefficient CT (also said axial force coefficient, and which is dependent on the combined lift and drag coefficients) of a parasail can be deduced from the two reports on a tragic accident, as well as on the parasail (or at least a similar model) that was tested for the reconstruction.
According to my calculations (which can be made with the elements below), if the area of 139 m² (the indicated value reported below is 139.3 m²), the thrust coefficient CT is approximately 1 (about 0.96 with air density of 1.2), for an airspeed of over 11 m/s. But if we take the diameter of 39 feet (11.8872 m) into account, the diametral area (which should be taken into account) is about 111 m², and the thrust coefficient becomes approximately 1.2.
If we take a look of previous publications, it looks that this value is likely constant when the Reynolds (scale and/or airspeed) number increases, after a significant initial decreasing then a short climb. The short climb of drag (here thrust) coefficient can be an explain for the following. Indeed the traction force of 1102.23 kgf at 11.62 m/s is proportionally higher than the traction force at lower air speeds (16.5 mph = 7.37 m/s, for 830 lbs = 376 kgf), probably because the traction force, including the CD and the CL, increases slightly before stabilizing while the Reynolds number continues to rise.
A thrust coefficient CT of 1 or 1.2 could be promising when fast high altitude winds are envisaged in low-level jets (LLJs) or jet streams.
Parasailing Safety
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A canopy, yoke, flight bar,
and tow line similar to those involved in the Tied High accident were supplied by Custom Chutes
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In the table, the maximum tension force (2430 lbs, so 1102.23 kgf) on the line occurs at 26 mph (and also 28 mph) combined vessel and wind speed, so 11.62 m/s.
Tiedhigh.pdf
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Parasail Canopies and Harness
74. The parasail involved in the casualty was designed and manufactured by Custom Chutes Inc., and is called an XXtreme 39-foot parasail. The XXtreme 39-foot parasail was developed over many years from the original United Kingdom (UK) 16 panel design into a high lift, low drag
parasail for commercial operators. A Custom Chutes Inc. label on the parasail included on the
right side, the serial number , “0207475”, the size, “39 ft”, and the date “02/2007”. On the right side of the label the wind speed “12 mph”, the minimum weight “150 lbs” and the maximum weight “560 lbs” were displayed.
Commercial Parasails Size Charts - Custom Chutes
39′ / 139.3 Galaxy 160-580lbs 0-12 mph Tandems/ Heavy Tandems/ Triples New 2014
These specifications are close to the specifications from the “Tiedhigh” document.