The need for speed brings with it a need for information, whether relayed by tell tale or electronics that sense every nuance of wind several stories above the cockpit.

With spring launchings and the 2005 racing season right around the corner, many of you may be thinking about upgrading or adding to your boat's existing instruments. Here's some insight into what information is really important and how to use that information and win a race or two.

The most basic functions are the ability to measure wind angle, wind speed, and boat speed through the water. Sounds fairly simple doesn't it? Now, add the words "consistently" and "accurately" to these functions and the situation gets a little more complicated. We want to use these instruments to measure, and if they are not consistent we can't measure angle, wind speed, or boat speed very well. Instruments that read differently from tack-to-tack or jibe-to-jibe will defy the best attempts to calibrate them, or adjust to their assumed corrections. If this sounds like a description of your instruments, do what the great sailors have been doing for years and rely on your boatspeed, telltales, windex, and intuition. Relying on faulty instruments for tactical decisions will ensure bad decisions. There's a saying on the racecourse that the only thing worst than no data is bad data.

For starters, it's important that boatspeed is accurate. Take the time to run a measured distance, both upwind and downwind, allowing for any current. If you are in a significant current area try to schedule your calibration during slack tides. If it's too difficult to run a measured distance, match the boatspeed read out to the speed over ground using your GPS, but again in both upwind and downwind directions to negate any current effect. What we are looking for is any difference from tack-to-tack: the boat should be just as fast on a port tack as it is on a starboard tack, given consistent wind and sea conditions. Sometimes the boatspeed transducer is not exactly aligned and the change in the angle of attack between port and starboard can impact the flow over the paddlewheel of the transducer. Some companies have adjustable settings in their calibrations to allow for this, but if your existing instruments don't, another fix is to slightly rotate the transducer in the thru hull. It's also a good to idea to check you speed over ground (SOG) again just to make sure your sail trim or boat set up isn't impacting your speed. If you can't adjust to make the speed even from tack-to-tack so be it, as long as it's consistent; note and record the difference.

Next up, is wind angle. Most instrumentation systems have a means to calibrate wind angle, but if your instruments don't, a trip to the masthead to manually rotate the mount might be in order. Again, we're looking for a consistent wind angle from tack-to-tack. Measure the difference the same way you measured the boatspeed and split the difference between the two tacks. Take care to trim the sails the same way, and that the day of your calibration has an even breeze with no wind shear. Wind shear is prominent in many areas during early spring and can be easily recognized. The boat will sail very close to the apparent wind on one tack, but will have to sail a really wide apparent wind angle on the other. If you expect wind shear during your calibration, procedure it's best to save your wind calibration for another day.

The third piece to calibrate is windspeed. Windspeed calibration is usually good right out of the box, but as the masthead unit ages resistance builds and the cups become more difficult to turn. The real difficulty in calibrating windspeed is measuring it. The wind at the top of mast can be significantly higher than what.s felt on deck. You can always compare with a dock mate, or wait for a nice flat day with zero wind and then compare the windspeed to boatspeed. Set the calibrations to match, and that should be sufficient.

When these three functions are calibrated we can start recording our performance, recognizing when are boat is set up and trimmed properly and going fast, or when something is wrong and we are slow.

There is a pot of gold at the end of the calibration rainbow: the use of a velocity prediction program that optimizes our sailing angles upwind and downwind. Most boats today will have these velocity prediction programs available, and if you can't find your boat, check with US Sailing and see if a sister ship was ever been measured for IMS. If it was you can purchase a copy of the certificate that will a have complete velocity analysis, including tabular and polar graphs. Here is a sample of a simple but effective polar chart.

VTW is true wind speed, BTW is true wind angle, VAW is apparent wind speed, BAW is apparent wind angle, and V is your targeted boatspeed. This simple sheet allows a number of racecourse and sailtrim decisions. If your system calculates true wind angle and speed, use those functions, but stick to it. It is very easy to confuse the crew by switching between apparent and true speeds. I find it much easier to use true wind angle, not only is the resolution greater, but it's also much easier to calculate tacking and jibing angles. You will also find it much easier to manage your sail configurations if you start dealing in true wind speed. If your system isn't capable of calculating true wind speed and wind angle don't despair, the apparent information is listed as well.

The next important step is adding a fluxgate compass into the system. The compass will not only bring heading information to the cockpit, but on most systems adding a fluxgate compass will also bring a very important piece of information called magnetic wind direction. Magnetic wind direction has become a confusing term through the years. Some companies refer to it as wind direction, true wind direction, and so on. Basically, magnetic wind direction is the magnetic compass heading the wind is coming from. For example, if you went head to wind to get a bearing of the wind direction, the magnetic wind direction will be that same bearing. When sailing upwind, it's fairly obvious to us, but as soon as we start to reach or sail downwind it becomes easier to lose track of the real wind direction and miss out on acting on important wind shifts. Having the magnetic wind information added to the instrument display significantly enhances our tactical knowledge. It's the next big step in information making current leg tactics, and next leg strategies easier and is a worthwhile addition if your system will accommodate one.

While the tell tales are streaming back indicating a properly trimmed main, the wind is also traveling upwards, interfering with a mast head wind indicator, an interference that becomes more pronounced the further downwind a boat sails.

Magnetic wind direction becomes one of those prized pieces of information so advantageous that manufacturers and consumers will spend large sums of money in order to improve their instruments on the quest to realizing the most consistent and accurate resolution as possible. One of these upgrades is the vertical masthead unit, a vertical wand anywhere from 42-60" in height, made primarily from carbon fiber for stiffness and weight savings (not monetary savings). These greatly reduce any inaccuracies that the upwash of wind the sail plan creates, giving a reading in clean air unaffected by the sails. Masthead rigged boats will recognize this upwash effect when sailing downwind by seeing their windspeed change due the upwash from the spinnaker. Remember, any inaccuracy here will throw your magnetic wind direction calculation off as well as your polar and sailing angle information. A vertical wand is another worthwhile addition to a existing system or option to a new system.

Learn to use what you have, and if you're replacing a system consider your needs and the ability of the system to provide those needs consistently. Many systems are modular and allow you to grow your system as your budget allows. Instruments are long-term commitments, so choose wisely. If you are looking for additional information I recommend a text created by Ockam Instruments for their Ockam Universities. You can visit them on the web at http://www.ockam.com/ and order their Ockam U Text Book. You won't find anything about using Ockam Instruments but you will find some very helpful guides on using your instruments to win course and offshore races.