Comparison of the 4 boats tested in 2018 at different wind speeds, with a downwash correction applied.  These curves give an idea of how these boats would compare if they were sailed against each other in exactly the same conditions. It is clear that upwind the Bermudan rigged "Calisto" would be fastest in all wind speeds up to 12 knots, but the split junk rigged "Poppy" would be a close second and not very far behind. However, "Poppy" would likely be faster on a reach and a run. The hinged batten rigged "Weaverbird would be the third fastest upwind and looks best in 14kts of wind. She was reefed one panel on the first day of trials, which may have helped in the higher wind strengths. The aerojunk rigged "Miranda" would be slowest up wind, but this was (IMHO) largely due to the rig not being set up very well, with the jiblets being set too open, and the mainsail a bit too flat, and the sheeting system not allowing her to point well.

The codes in the title of the chart indicate what filtering and adjustments have been applied.

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

A64 means that any data points where the wind direction (A=Angle) changes by more than +6 degrees or -4 degrees per second are omitted. This level of wind angle filtering seems to produce the best curves when the downwash correction is 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.

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

C70D10 means a correction has been made on these results for downwash affecting the wind sensor, which was placed on the quarter of each boat. This is an arbitrary 10 degree (D10) correction at 35 degrees, tapering off to 0 and 70 degrees (C70) using a sin curve. 

No adjustment has been made for the length and sail area/displacement ratios. These will be added at a later date. They will have the effect of reducing Poppy's performance by 6% and enhancing the other boats performance by up to 29% in Miranda's case.

No smoothing has been applied to these curves. The big dips and the gaps in the curves are caused by the limitations of the data recorded, and the effect of filtering. We may apply some smoothing at a later data to bridge the gaps and dips, although taking the average of the top three boat speeds at each angle does smooth the results a bit.









       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

                                                              Site contents © the Junk Rig Association and/or individual authors

Powered by Wild Apricot Membership Software