Bluetooth LE 6
Nordic nRF54LM20A. The wind head broadcasts at 4 Hz with no connection to drop. It will also offer the standard Bluetooth Environmental Sensing service, so phones can read the wind planned.
Technology
Engineered like IoT. Built for salt water.
SailNav borrows from a decade of low-power wireless sensor design: energy harvesting, sealed electronics and radios that sip microwatts. Here is how it works, and what we still have to prove.
01 · Wind-powered sensor
A wind instrument that powers itself.
A masthead is the worst place for a battery you have to change and the hardest place to run a cable. So the SailNav wireless head turns a small part of the wind it measures into electricity.
Rotor
Propeller (dinghy) or cups (keelboat) spin with the wind.
Generator
Magnets in the hub pass air-core coils sealed behind a thin wall.
Harvester
An energy-harvesting chip with maximum-power-point tracking works from a few tenths of a volt.
Hermetic cell
A sealed Tadiran cell stores the energy and can be potted safely.
Radio
A Nordic nRF54 broadcasts wind speed and angle 4 times a second.
No cogging, no seals, no connectors
An ordinary motor used as a generator has an iron stator that "cogs": it wants to stop in fixed positions, which ruins light-air readings. Our coreless axial-flux generator has no stator iron, so there is no cogging and no magnetic pull on the bearings. Nothing passes through the sealed body: the magnets turn outside, the coils sit inside, and the electronics are fully potted.
Harvesting without spoiling the measurement
Every milliwatt taken from the rotor slows it slightly. The firmware controls how much energy it harvests, lets the rotor run free when the cell is full, and corrects the wind speed for the measured generator load. Each design is then calibrated over a grid of wind speeds and loads.
Direction without contact
A 3D Hall-effect sensor reads the angle of a magnet through the housing wall. No slip rings, no potentiometer to wear out, and it tolerates small gap changes.
0.3mW
while sailing at 4 Hz model
12µW
asleep, waiting for wind model
4–5kn
wind to start charging target
>1year
asleep on a full cell model
Figures from our Phase 1 design study (first-order models, ±30 %), to be verified on prototypes and in the wind tunnel.
Inside the dinghy head
One potted part that swivels.
On the dinghy head the whole body is the vane. The electronics turn with it and read their angle against a magnet fixed on the stalk, so generator, cell and radio share one sealed volume.
The head is balanced on its swivel axis so heel does not turn it, and it lifts off its quick-release socket in one pull.
- 1 Three-blade propeller, Ø 70 mm
- 2 Magnets in the hub: coreless axial-flux generator
- 3 Air-core coils sealed behind a thin wall
- 4 Fully potted electronics and Bluetooth LE radio
- 5 Hermetic rechargeable cell
- 6 Contactless magnetic angle sensor over a magnet fixed on the stalk
- 7 Vane: the whole head swivels into the wind
- 8 Stalk in a tool-free quick-release masthead socket
02 · From apparent to true wind
The numbers behind the numbers.
The sensor feels apparent wind. To tell you what the wind itself is doing, the display solves the wind triangle many times a second.
- Boat speed and course from the built-in GNSS, or from a speed log on NMEA 2000 (keelboats).
- Heading from the 9-axis motion sensor and magnetometer, for true wind direction and shifts.
- Heel and mast motion: a masthead swinging through a wave can add several knots of false wind. The display measures the roll and pitch rates and removes them.
03 · Sunlight display
The brighter the sun, the better it reads.
Phones and most screens fight the sun with a backlight. SailNav uses a reflective memory-in-pixel panel: sunlight is the light source.
- Reflective: 4.4", 320 × 240 pixels, high contrast in direct sunlight, readable at wide angles.
- Memory in every pixel: the image stays without refreshing, so the display draws very little power.
- Designed for glances: huge digits, pure black on light grey, one idea per screen.
Honest note: the panel has no usable backlight. Night-use options are under evaluation.
04 · Connectivity and sensors
Talks to your boat, and to your phone.
NMEA 2000 and 0183
SailNav Crew joins an NMEA 2000 backbone (M12, LEN 3), and listens and talks NMEA 0183 for older equipment. Certification is planned.
Updates over the air
Signed firmware updates with rollback. The potted wind head is updated over Bluetooth, so new features reach the masthead without a ladder.
GNSS
u-blox MAX-M10S with a built-in antenna and a filter that protects it from on-board VHF and AIS transmitters.
Motion and heading
CEVA BNO085 9-axis IMU with on-chip sensor fusion, plus a separate magnetometer: heel, pitch, heading and rotation rates.
Barometer
A precision pressure sensor records the trend and warns you of a falling barometer.
05 · How we compare
An honest comparison, by category.
We compare SailNav with the two kinds of product sailors use today. No brand names: individual products differ, and ours is still a prototype.
| Feature | SailNav Clip | SailNav Crew | Traditional wired masthead systems | Handheld meters and phone apps |
|---|---|---|---|---|
| Measures wind at the masthead, in clean air | Yes | Yes | Yes | No, at deck level |
| Cable down the mast | None | One NMEA 2000 cable, or none with the wireless head | Yes, a dedicated cable | n/a |
| Wind-sensor power | Wind-powered | Bus-powered, or wind-powered | Boat power via the cable | Own battery |
| Suited to dinghies | Floats, quick-release | Keelboat system | Rarely | Partly |
| True wind, VMG | Yes (GPS-based boat speed) | Yes (GPS or speed log) | Yes, usually with a speed log | Limited |
| Start line, tack angle, shift tracking | Built in | Built in | Often on higher-end displays | Varies by app |
| Screen in direct sun | Reflective memory-in-pixel | Reflective memory-in-pixel | Varies by model | Depends on the phone |
| NMEA 2000 / 0183 | No | Yes (certification planned) | Usually | No |
| Night backlight | Under evaluation | Under evaluation | Usually | Yes |
Generalised from typical products in each category; specific products may differ. SailNav figures are pre-production targets.
06 · Development status
What we still have to prove.
We would rather tell you now than surprise you later. These are the open engineering items between today's design and a shipping product.
Wind-tunnel calibration
Speed and angle accuracy over the full range of wind and harvesting loads.
Antenna in potting
Measure and tune the radio range of potted units, masthead to cockpit.
IP rating and flotation
Immersion, UV and thermal tests of the housings, including the IP68 floating case.
Harvesting in real conditions
Confirm charging wind speeds and calm reserve on the water.
NMEA 2000 certification
Required before we can use the NMEA 2000 name and logo on the product.
Night readability
Evaluate front-light options for the reflective display.
Kickstarter · coming soon
Be first on the water with SailNav.
We are preparing our Kickstarter campaign. Leave your e-mail and we will tell you the day it goes live, with all the details of the early-backer rewards.