We’ve been using the WH Polar Pilot option now aboard our 78′ ketch Beowulf for the past year. To say that the features in this option improve the breed is a major understatement. We think the performance and comfort enhancements are nothing short of revolutionary.<\/p>\n
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This system allows you to tailor a simple computer program to select the optimum wind angles to steer downwind and when beating, so that you have the fastest, most comfortable ride. The racers have been doing this manually for years, steering to “target boat speeds” to weather and to “target wind angles” when sailing downwind. In each case data is accumulated over time about what wind angles or boat speeds are best for making the fastest way to the next waypoint.<\/p>\n
In a cruising context this takes a slightly different tack – as cruisers we are after boat speed of course, but the most important issue is usually comfort.<\/p>\n
So how does this system work in the real world? Within the program there is a simple table in file format for upwind and downwind optimums. You can have several of these files for different conditions. On Beowulf we have three – one for smooth water, one for normal (moderate) waves, and as third for bouncy sea states.<\/p>\n
In the upwind file data you enter two values: target boat speed and maximum apparent wind angle. This is done for a series of true wind speeds, and the computer then interpolates between these values. The pilot will try to steer the boat to target boat speed. If the boat is going too fast, the pilot will head her into the wind a few degrees to bleed off some speed and gain ground to weather. If she is going too slowly, the pilot will head the boat off to leeward until the boat hits the targeted speed, or until you come up against the max allowable apparent wind angle.<\/p>\n
What the Polar Pilot is doing is steering the boat on an “S” curve, the same way an experienced and alert sailor would do, if he or she was trying to work the boat to weather as quickly as possible. We find that when there are seas about, the Polar Pilot in conjunction with occasional use of the rudder gain boost button really helps working through waves – assuming we are paying attention and trying to get the best speed out of the boat.<\/p>\n
Compared to steering a compass course, or a fixed apparent wind angle course, this automatic steering to polars is a huge improvement!<\/p>\n
Off the wind the results are similar, but the approach is different. Here you have a target apparent wind angle for a series of given true wind speeds (again the computer interpolates between the values). The pilot varies course upwind slightly in the lighter winds, and further downwind in the puffs or stronger continuous winds. This keeps the boat moving at its most efficient speed relative to a given downwind mark. It also helps to maintain air flow over the boat for ventilation in the lighter wind ranges, and really settles the boat down in sloppy seas and light airs.<\/p>\n
Developing the “target” data can be done in a series of ways. If there is a sistership which has been measured for an IMS handicap, you can get the smooth water optimum data from her handicap sheet. This will give you a start, but real world performance will be less, and you will want to change the polar table values as you learn the boat.<\/p>\n
Perhaps the easiest way to get this data is to take some experienced racers out in a couple of different conditions (a racing sailmaker is ideal for this), and then establish targets for the boat for upwind and downwind performance.<\/p>\n
You can also do the same by yourself when you first install the system.<\/p>\n
Your initial set of targets will get you 85% to 90% of the way there, but to get those last few tenths of a knot will take a bit of time. And if you change sails, you will want to check the polar values being used against the new performance. Aboard Beowulf we’ve just gotten a new main and mizzen, of considerably different design than her original sails. So, between now and our next passage, we are going to spend some time checking the target values.<\/p>\n
How much difference does this system make in passage times? That is hard to quantify as it calls into question how attentive you are to the needs of the boat when she’s being steered by the pilot or vane. In our case, we tend to pay careful attention as we enjoy going fast. Even so, the Polar Pilot is good for a net gain in speed of at least three and sometimes as much as five to eight percent. And the less attention you pay to the situation, the bigger will be your net gains!<\/p>\n
To find out more about this system contact WH Autopilots at pilotwhale@worldnet.att.net.<\/p>\n","protected":false},"excerpt":{"rendered":"