Wind Gauge, Racing and Chartplotter Apps Tere are a a variety of choices of sailboat navigation apps on iOS and Android for chartplotting, marine weather, perfor- mance analysis and wind gauges. The following can connect to a wireless anemometer or receive data over wifi from marine electronics: Aqua Map, iRegatta, MID Wifi, NMEA Sail, Sail Buddy, SailRacer, SailTimer, SeaNav, AFTrack, Mariner GPS Dashboard, OpenCPN, and SailGrib WR.
Audio Feedback: A smartphone/tablet has certain disadvan-
tages out on the water; it is hard to see in bright sunlight, you don’t want it to get wet, and most sailing dinghies don’t have a good place to put it for easy viewing. If you wear polarized sunglasses to see into the water with less glare, you will also find that the LCD screen is visible in one orientation, but goes nearly black when rotated 90 degrees. Fortunately, several apps give you the option of audio feedback. No screen required. Put your phone away safe and dry, and use a Bluetooth speaker to hear wind conditions or boat speed when they change by more than a set amount. Tis keeps your hands and eyes free for sailing. You can also turn the screen off to reduce heat and save battery power. Polar Plots: In 1925, Dr. Manfred Curry published one of
the classic texts on sailboat navigation: Yacht Racing and the Aerodynamics of Sails and Racing Tactics (originally in German, with first translation to English in 1928). Te original book and later editions up to 1948 do not mention polar plots—graphs of boat speed on all wind angles around the boat. However, Frank Bethwaite (a WWII aviator) was using polar plots when designing racing dinghies in the early 1970s, as shown in the three books he published beginning in 1992. (Tere is a great summary of Bethwaite’s development of the Tasar in SCA #26, 2004.) So before computers and GPS, the use of a polar graph to show boat speeds and the fastest heading upwind (Velocity Made Good) is probably another technology that came out of WWII aviation. Another limitation before computers and GPS is that ane-
mometers traditionally did not provide tactical information; they only showed wind angle on a gauge, and leſt you to guessti- mate your optimal tack headings and tacking route. (Ten you wonder why you arrived much later than expected.) No-one can do trigonometry in their head, and it is not possible to work out the calculations on paper in a heeling sailing dinghy with the spray flying. Plus you can’t redo the calculations on paper every second. Fortunately, several apps can learn your boat’s polar plots. Te “polars” are a table or graph of your boat speed on all wind angles and wind speeds. Tat is one component that is needed for doing the correct calculations to find your optimal tack headings. Racers traditionally used polars as theoretical “targets” for
finding the optimal tacks on the upwind leg of a race. That was a way to avoid the trigonometry calculations, but it only worked within the artificial constraint of a race with the first leg precisely upwind. But now any smartphone can find the optimal tack headings in any direction, using tacking distances and boat speeds from polars. So now, whether in a daysailer or racing dinghy, it is quick and easy to display your optimal tacking route and solve Te Sailor’s Dilemma. •SCA•
Craig Summers, Ph.D., is founder and CTO of SailTimer, Inc., St. Margaret’s Bay, Nova Scotia, Canada.
www.SailTimer.co
SMALL CRAFT ADVISOR
Flying along under sail in a Paceship 17 on the Nicolas River, a side-arm of the Richibucto River in New Brunswick, Canada. Photo courtesy of Kurt Kleinmann
Bluetooth Wind Instrument
To get wind data into smartphone apps, in 2012 Sail- Timer came out with the first-ever masthead anemom- eter that could transmit to smartphones. Te wireless, solar-powered Wind Instrument RB™ with a Removable Battery is the 6th generation (
www.SailTimer.co). It is submersible, and suitable for boats of all sizes. No 12- volt battery required. It is about the size of a handheld wind meter, as you can see in the photo. If you are a sailor who looks up automatically to
check the wind angle and your sails, the SailTimer provides a visual indicator for wind direction. With a quick-release wing-nut, you can put it on/off your masthead in seconds on the boat ramp. No calibration is required when putting on your
mast, because there is a digital compass built into the wind direction arrow to determine wind direction or wind angle. An innovative blade shape is used for the wind cups, so that they remain equally accurate for wind speed whether upright or sailing along heeled over. Te SailTimer Wind Instrument connects on Blue-
tooth to your smartphone/tablet. Transmission range of 280 feet. If you are using the SailTimer chartplotter app, whenever the wind changes, the app updates your optimal tacks automatically. Many of the apps also have versions for smartwatches, which are easy to see in bright sun, oſten waterproof, and perfect in small boats.
A fee-shipping coupon is available for SCA readers by emailing
SCAcoupon@SailTimerinc.com
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