Bluetooth sensors and the phone's own

A small boat often has no instrument network at all. Offwind can read a Bluetooth wind sensor or a Bluetooth NMEA bridge directly, and the phone itself measures position, heading, air pressure, and heel and trim.

Connect a Bluetooth sensor

Offwind connects to two kinds of Bluetooth device:

• Calypso wind sensor: the Calypso Ultrasonic portable wind sensors, for wind speed and angle.
• Bluetooth NMEA bridge: an adapter that carries NMEA 0183 sentences, or Yacht Devices RAW NMEA 2000 frames, over Bluetooth.

1. Wake the sensor. Turn it on and keep it within a few meters of the phone.
2. Search. Under Boat, press Connections, then Search this network. Offwind looks for Bluetooth sensors only when you press this.
3. Pick it. The sensor appears under Found on this network with Calypso wind sensor (Bluetooth) or Bluetooth NMEA bridge under its name. Press it.
4. Save. Check the name and press Save. The first time, iOS asks whether Offwind may use Bluetooth. Allow it.

Once saved, the phone reconnects to the sensor by itself whenever it is in range. While a track is recording, it keeps the sensor connected with the screen locked.

If the connection shows Needs attention, its line says why: Bluetooth is off (turn it on in Control Center), or Offwind is not allowed to use it (turn it on in the phone's Settings, under Offwind).

What the phone measures

The phone's own sensors fill in when the boat has nothing better. A value from the boat's instruments always wins while it is current, and the phone's values are never labeled as the boat's.

• Position, speed and course. The phone's GPS. With no instruments connected, this is what the Helm shows, and the chart takes the rest of the page.
• Heading. The phone's compass. The race tools use it once it agrees with your course over ground, and use course over ground until then.
• Air pressure. The phone's barometer runs all the time. Offwind keeps the trend, logs a reading once a minute while a track is recording, and raises an alarm when the pressure falls fast.
• Heel and trim. The phone's motion sensors, once you have zeroed the phone in its mount. They run while the race tools are open or a race is under way, and are logged once a second while a track is recording, unless the boat's instruments are sending heel and trim already.

Zero heel and trim

Heel and trim from the phone are only right once Offwind knows how the phone sits on the boat.

1. Mount the phone firmly. On a bulkhead or the mast with the screen facing aft, or flat with the top of the phone toward the bow.
2. Say how it sits. On Race, open Setup. Under Heel and trim, set Mount to Upright or Flat.
3. Zero it with the boat level. On the race heel page, press and hold Zero until it confirms. Do it at the dock or head to wind, not while heeled.

Move the phone in its mount and you need to zero it again.

Limits

• The phone's compass is affected by anything magnetic or electrical near the mount. Under Compass in Race Setup, Align to COG sets the mount offset from a straight course at 3 kn or more.
• A Vakaros Atlas cannot be read over Bluetooth. Import its .vkx log after the race instead.
• Offwind does not connect to other Bluetooth instruments than the two kinds above.