Sail Buddy

Sail Buddy is a light-weight sailing app designed to display navigation data in an easy-to-read, easy-to-use format. It started out as a no-frills display for day sailing and short trips, but recent updates have added a lot more power and sophistication while keeping the focus on simplicity, elegance and ease of use.

Download Sail Buddy from the App Store

iPhone 13

Large, easy to read format

iPhone 13

Analog-style, multi-function displays

iPhone 13

Display recorded data via maps

iPhone 13

Dark mode support

iPhone 13

Monitor, filter, and export raw NMEA data

Apple Watch 1 Apple Watch 2

Full Apple Watch support

iPhone 13

Works great in split view on iPads; view instrument data alongside navigation charts

Sail Buddy is not a navigation app. There are many other apps that are better at navigation. Sail Buddy focuses on data display in a super-easy-to-read format. On iPads, Sail Buddy can run next to your favorite navigation app in split view.

What Sail Buddy does

New in Version 4

Version 4 is the biggest update yet! The entire app has been redesigned with great new features including:

Tell me what you think!

Sail Buddy is always evolving with lots of room for new ideas. I am very interested in making it more useful so long as I can keep it fast and light. If you have ideas or are experiencing issues, please contact me.

NMEA Operation

Sail Buddy can read and display instrument data transmitted in NMEA 0183 format over a TCP or UDP connection. Here are some typical setups:


WiFi-based hardware such as the Brookhouse iMux multiplexer, the SailTimer AirLink or the SailTimer wind vane (discontinued in 2013) create their own WiFi networks.

  1. Go to iPhone settings and choose the wifi network created by your hardware
  2. Launch Sail Buddy, go to Settings / Connection and enter the network settings for your hardware
  3. Also enable the appropriate options under Hardware Support for your hardware
  4. Tap the NMEA button in Sail Buddy’s Instruments tab
SailTimer Wind Instrument

The SailTimer wind instrument connects directly to your iPhone via Bluetooth using a custom app.

  1. Download the SailTimer API from the App Store
  2. Launch the SailTimer API, connect to the wind instrument, and confirm it is receiving data
  3. Launch Sail Buddy, go to Settings / Connection and enter these settings:
    • Connection Type: UDP
    • Port: 55554
    • Select SailTimer Wind Instrument
  4. In Settings / Display make sure Wind Speed & Direction is selected
  5. Tap the NMEA button in Sail Buddy’s Instruments tab

Sail Buddy supports the following NMEA sentences:

Category Identifier Definition
Location ??GGA GPS Location (if location source is set to “NMEA Data”)
Location ??RMA Recommended minimum navigation information (if location source is set to “NMEA Data”)
Location ??RMC Recommended minimum navigation information (if location source is set to “NMEA Data”)
Wind ??MWV Wind speed and angle
Wind ??MWD Wind direction and speed
Wind ??VWR Relative wind speed and angle
Wind PSTW Wind angle and speed. See SailTimer wind instrument
Wind WIBAT Battery level (for SailTimer wind vane)
Depth ??DBT Depth below transducer
Depth ??DBK Depth below keel
Depth ??DBS Depth below surface
Depth ??DPT Depth (below surface or keel)
Satellite ??GSA Active satellites (if location source is set to “NMEA Data”)
Satellite ??GSV Satellites in view (if location source is set to “NMEA Data”)

If your device is not supported, please contact me and I can try to add support in the next update.


  1. Sail Buddy can obtain your location either from your iPhone/iPad’s built-in GPS (i.e., Location Services) or from your NMEA devices. The switch is in Settings / Data.
  2. If you are reading NMEA data and run Sail Buddy in the background, you must turn on GPS even if you receive location and course/speed data from an NMEA device. This is because Sail Buddy uses your iPhone’s Location Manager as a means to reliably get background processing time so it can read data connections. Also make sure you allow Sail Buddy constant access to your location, as set in the Settings app (even though Sail Buddy isn’t actually using your location in this instance). None of this is necessary if Sail Buddy is always the active app, but most of us don’t use our iPhones in that manner.
  3. Previous versions of Sail Buddy gave you the option to display wind angle relative to either your current heading (default) or compass north. Version 4 eliminates that option and displays both. Wind angle(s) are relative to your current heading, while wind direction(s) are relative to compass north. Both apparent and true values are shown.

Analog Wind & Satellite Displays

You may choose to show wind and/or satellite data in an analog-style multi-function display above the data table. Go to Settings / Display and turn on “Use Analog Display.” This option is enabled when you choose either of the “Wind Speed & Direction” or “Satellites” options above it. Sail Buddy will move the corresponding indicators to a visual display above or alongside the data table. Course and speed will also move to the analog display.

If you choose to display analog wind data, the display will consist of instrument dials, one for apparent wind and the other for true wind. Swipe left or right on the dial to switch between them.

Current satellites “in view” are shown on a separate dial that provides satellite location (compass north is at the top), signal strength, and status. Satellites with a signal-to-noise ratio (SNR) above 40 are shown in a green circle while those with an SNR between 25 and 40 are shown in a yellow circle. Below 25 is shown in red. Active satellites, used to obtain a fix, are shown in boldface.

NMEA Data Monitoring

The Monitor tab shows a running display of all incoming NMEA messages, even those that Sail Buddy otherwise ignores. Use the button in the top left to turn the monitor on or off. In Settings / Monitor you can choose whether to include timestamps or filter in or out select messsages. The “Include Network Events” option can provide helpful information if you are having trouble connecting or maintaining a consistent connection.

The display is color-coded by message status. Invalid messages appear in red while messages that failed checksum confirmation appear in orange. (You can disable checksum verification in Settings / Data). The codes for NMEA sentences that Sail Buddy recognizes appear in green while those it doesn’t appear in blue.

You can export the NMEA monitor (the most recent 500 sentences) with the Share button in the upper right. Note the extra “Mail to Publisher” option, which lets you email the data directly to me in case you are having technical issues.

Apple Watch

Sail Buddy for Apple Watch displays most of the same information as the iOS app. Swipe left or right to switch between information types.

You can also control Sail Buddy via the watch, for instance, start/stop route tracking. Force-press the display to access the menu.


Sail Buddy doesn’t display NMEA data

Check the following:

I get a network error when I turn on NMEA data

I’m receiving some NMEA data, but not all wind indicators

In certain cases Sail Buddy calculates some wind indicators using your boat’s course and speed. These indicators will not appear if your boat isn’t moving, or Sail Buddy isn’t receiving course and speed data from the GPS or NMEA.

Nope, none of that solves my problem

Use the monitor described previously to send me your data, and I’ll try to help you out.

Privacy Policy

All personal information collected by Sail Buddy, including your location, data logs, and any metadata you enter yourself, is only stored on your iOS device. Sail Buddy does not interact with a data server (other than your own devices) and does not access or store information remotely.

Contact Information

Download Sail Buddy from the App Store