2017 America's Cup

AC35: Race 1 | Race 2 | Race 3 | Race 4 | Race 5 | Race 6 | Race 7 | Race 8 | Race 9 | Notes

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Notes on SOG/SOGR Plots:

1) Description of various data filters based on legs of race course:

Leg 1: Reaching Leg after start, Starboard tack to turning Mark (Mark 1)
Leg 2: Short downwind Leg to first Downwind Gate (Mark 2)
Leg 3: First full upwind leg to First Windward Gate (Mark 3)
Leg 4: Full downwind leg to Second Downwind Gate (Mark 4)
Leg 5: Final full upwind leg to Second (Final) Upwind Gate (Mark 5)
Leg 6: Final Downwind leg (sometimes shortened depending on finish placement) to turning mark (Mark 6)
Leg 7: Reaching Leg to Finish (length varies on finish placement)

Legs 3 & 5: Both upwind legs combined
Legs 4 & 6: Both downwind legs combined
Legs 1-7: Starting line to Finish line, without Pre-start
Pre-start: only the period from entry to start
All: All the recorded data for the race, including pre-entry and post-finish

2) Rudder data in the Match is available only in the first three races, and only for USA.

3) The SOG data is the same whether plotted with the rudder information, or not. The vertical scale has been adjusted to allow for negative rudder angles.

4) The timing of the data between the boats is not synchronized to each other. Each graph begins when the subject boat begins the leg of the course indicated. The data from the yachts is offset in time by the time difference (delta) at the mark that begins the leg.

5) Speed Over Ground is only one measure of yacht performance. Significantly, it is not the same as VMG (Velocity Made Good) which takes into account the direction a yacht is sailing.  Going faster (sailing with greater SOG) but away from the mark may not be as beneficial as going slower but more directly (sailing with greater VMG) to the next mark. 

However, there are still useful comparisons that can be made with the SOG data.  The comparison in a tack or gybe is one aspect of study in the SOG data. Speed lost in tacks or gybes is readily visualized. The difference in speed when tacking, multiplied over the length of time to execute the tack and return to a stabilized speed, equates to the distance lost in the maneuver.  The area between the two SOG plots is a visual display of distance lost. Compare USA relative to NZL in Races 1-4, sailed the first weekend) versus Races 5-9 (sailed the second weekend, after USA had five days to make adjustments), for example.