Polardiagram för AC72

Catsailingnews har fått span på polarer för en generisk AC72. Dessa används ju av domarna för att utdöma straff som i vissa lägen är baserade på avstånd/tider till märke. I vilket fall är det lite intressant att titta på farter och vinklar.

v1 a1 v2 a2 v3 a3 v4 a4 v5 a5
5 14 45 20 80 19 110 14 140 7 180
12 18 45 28 80 34 110 28 143 14 180
16 22 45 34 80 40 110 35 150 17.5 180
20 23 45 37 80 43 110 38 152 19 180
26 24 46 39 80 46 110 44 154 22 180

Som txt-fil.

Notes on the AC72 Polar Files

The file AC72polar.txt describes the predicted speed of an AC72 catamaran as a function of True Wind Speed (TWS) and True Wind Angle (TWA).

This information is used to determine the speed at which the penalty line advances when a boat is assigned a Velocity-Made-Good (VMG) penalty, where a
boat must drop back a certain distance along its own course. This is in contrast to a Boat-on-Boat (BOB) penalty, where the penalized yacht must
drop back to a certain distance behind another boat.

The TWA is the angle between the bow of the boat and the direction the wind is coming over the boat, ignoring the effect of the apparent wind caused by
the boat’s motion through the water. In other words, it’s the difference between the boat’s Heading and the True Wind Direction (TWD). TWA ranges between 0 – head to wind – and 180 – dead downwind. The performance of the boats is assumed to be symmetric on port vs stbd tack or gybe.

The number in the 1st column is TWS in knots. The performance for other wind speeds is obtained by interpolating data in adjacent rows. We assume that at TWS 0, all boat speeds for all wind angles are 0. We also assume that the boat speed is 0 at TWA 0 for all wind speeds.

The remaining columns are labeled (not in this order):
a1: the optimum upwind sailing TWA in degrees
v1: the predicted boat speed in knots at angle a1
a2: an arbitrary close-reaching TWA, typically 80 degrees
v2: the predicted speed at wind angle a2
a3: an arbitrary broad-reaching TWA, typically 110 degrees
v3: the predicted speed at angle a3
a4: the optimum downwind sailing TWA
v4: the predicted speed at angle a4
a5: the dead downwind TWA, always 180
v5: the predicted dead downwind boat speed

At wind speeds above the highest row in the table, the numbers for the highest wind speed are used.

17 July 2013