Danny Jo
Well-Known Member
Freestyle did pretty well on her most recent cruise, with head winds for only six of the fourteen days and insufficient wind for two. The highly implausible figure of six days of fair winds might at first glance appear to upset the well-established Scuttlebutt dogma that there are only three sorts of wind: too much, too little or from the wrong direction. (We cheated, of course, by choosing an itinerary to suit the forecast wind.)
But head wind days do tend to drag a bit, giving the opportunity for the crew to indulge in a bit of competitive, er, knowledge-broking, sometimes less politely referred to as bullshatting. One of our more vigorous discussions arose out of one of Freestyle's less endearing characteristics: she lacks a nice sharp cusp letting the helm know when she's nicely on the wind. I like to sail fast and free, but keen young crew members generally feel the need to pinch up and up until we start loosing way. We discussed the utililty of the VMG (velocity made good) displayed by Charlie Chartplotter. This VMG was actually the vector of the speed resolved in the direction of the (upwind) waypoint and therefore, however well you sailed, gradually declined from the potential maximum (dead downwind of the waypoint) to zero (when the waypoint was 90 degrees dead abeam). Freestyle's on-board mathematics graduate reckoned that using Charlie's VMG to optimize upwind sailing therefore made sense only when one was dead downwind of the waypoint - it makes you pinch progressively as the waypoint comes abeam.
Old Phil the ageing AP Navigator was much more canny, although to be fair he did have feeds, on wind direction and speed, to which Charlie was not party. Phil's VMG is the vector of the speed over ground resolved in the upwind direction. He even plots a curve showing how the VMG changes with angle on the wind, although you have to redraw it after every occasion on which the engine is used to go upwind. For real time optimization of upwind sailing, however, Phil is no more use to the helm than Charlie because his VMG is only visible at the chart table.
But head wind days do tend to drag a bit, giving the opportunity for the crew to indulge in a bit of competitive, er, knowledge-broking, sometimes less politely referred to as bullshatting. One of our more vigorous discussions arose out of one of Freestyle's less endearing characteristics: she lacks a nice sharp cusp letting the helm know when she's nicely on the wind. I like to sail fast and free, but keen young crew members generally feel the need to pinch up and up until we start loosing way. We discussed the utililty of the VMG (velocity made good) displayed by Charlie Chartplotter. This VMG was actually the vector of the speed resolved in the direction of the (upwind) waypoint and therefore, however well you sailed, gradually declined from the potential maximum (dead downwind of the waypoint) to zero (when the waypoint was 90 degrees dead abeam). Freestyle's on-board mathematics graduate reckoned that using Charlie's VMG to optimize upwind sailing therefore made sense only when one was dead downwind of the waypoint - it makes you pinch progressively as the waypoint comes abeam.
Old Phil the ageing AP Navigator was much more canny, although to be fair he did have feeds, on wind direction and speed, to which Charlie was not party. Phil's VMG is the vector of the speed over ground resolved in the upwind direction. He even plots a curve showing how the VMG changes with angle on the wind, although you have to redraw it after every occasion on which the engine is used to go upwind. For real time optimization of upwind sailing, however, Phil is no more use to the helm than Charlie because his VMG is only visible at the chart table.