Comparison of the 4 boats tested in 2018 at different wind speeds with no downwash correction applied. The codes after the wind speed in the title indicate what filtering has been applied.

When a data point is omitted, all the subsequent data points are also omitted, until the boat speed changes. This is because the boat speed data was coming through quite slowly compared to the wind data, and because the boat speed reacts quite slowly to changes in wind speed and direction.

S7 means any data points where the wind speed drops by more than 0.7 knots per second are omitted

A64 means that any data points where the wind direction changes by more than +6 degrees or -4 degrees per second are omitted. When there is no downwash correction this level of wind angle filtering seems to produce the best curves, with the fewest gaps and no odd upwind data points.

Avg3 means that the speed shown is the average of the top three boat speed values recorded for each wind direction and wind speed

No correction has been made on these results for downwash affecting the wind sensor, which was placed on the quarter of each boat, which may be why the upwind performance of some of the boats is better than would normally be expected. Results which will have an arbitrary 10 degree correction at 35 degrees, tapering off to 0 and 70 degrees, will be added shortly. These will have a code C70D10 attached.

No adjustment has been made for the length and sail area/displacement ratios. These will be added at a later date.

No smoothing has been applied to these curves apart from the averaging of the top three boat speeds for each wind angle and speed. The big dips and the gaps in the curves are caused by the limitations of the data recorded. We may apply some smoothing at a later data to bridge the gaps and to bridge across the dips.






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                                                               - the Chinese Water Rat

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