Nexus RACE BOX, Инструкция по установке и эксплуатации

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English RaceBox
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4.4 Target & Polar Boat Speed
The Race Box can calculate and present either Target Boat Speed (TBS), Polar Boat
Speed (PBS) or both.
Whats the Difference?
When a boat is sailing upwind, it can sail higher (decreasing its true wind angle) and
shortening the distance it needs to sail, but this causes it to sail more slowly, increasing
its travel time. Conversely, it can sail lower (increasing its true wind angle) which will
increase the distance the boat needs to sail but increase its speed. For any given True
Wind Speed (TWS), somewhere between zero degrees True Wind Angle (TWA) and 90
degrees TWA there is a sweet spot; a perfect TWA which is the optimum balance of
boat speed and distance.
This is also true downwind. Of course, all sail boats can sail with the wind exactly
behind them, dead down wind. But for almost all boats, its faster to gybe back and forth,
since your boat can reach faster than it sails down wind, even though this increases the
distance you need to sail. When sailing downwind, somewhere between 90 degrees
TWA and 180 degrees TWA, there is a TWA that produces the optimum combination of
boat speed and distance.
For any given true wind speed (TWS), these optimum TWAs change. When sailing at
the optimum TWA, your boat is traveling at a particular boat speed. This boat speed is
known as the Target Boat Speed (TBS). If you're actual boat speed is faster than your
target, you may want to head up to slow down but shorten your distance. If its slower,
you may want to head down to increase your distance but speed up.
If you choose to have the Race Box send Target Boat Speed to the Nexus TBS field
(more on this later), the Race Box will send the optimum TBS for the current wind
velocity. This means that if your TWA is less than 90 degrees (that is, you're sailing
upwind), the Race Box will send the upwind target that corresponds with the current
wind velocity. If your TWA is lower than 90 degrees, the optimum down wind TBS is
sent to the Nexus server.
Polar Boat Speed (PBS) is a simple concept. It is the speed at which your boat should
be traveling through the water given the current wind velocity and TWA. If you chose to
have PBS sent to the TBS field, The Race Box will send the speed at which your polar
table predicts you will be traveling given the existing TWA and TWS, even if the TWA is
above or below the optimum angle for these conditions.
Which one is better to use is a always a matter of an opinion and usually depends on a
variety of factors. Many people prefer to use TBS when racing a windward / leeward
course, while other courses may command PBS. Some drivers prefer to just write the
targets out on to the deck and send PBS to the instruments. There is no right or wrong
way to do it. You'll have to choose based upon your preferences.