N4N1 the Autonomous Sailboat

I built N4N1 to learn the details of the ardupilot sailboat firmware. I have had a few student groups building similar vessels at work, and thought it would be worthwhile to go through the exercise myself. Plus I had a boat gathering dust that needed a job.

N4N1 uses the ardupilot sailboat firmware on a Matek flight controller, with external GPS, compass, and wind vane.

N4N1’s hull was designed and built by me in the previous century, and with the rig from an RC Laser, she sails autonomously on San Francisco Bay.

Videos

Early sail trim and wind vane testing
Testing at RYC
A windy day!

The name

N4N1 (pronounced “Nani”) is named after Lilo’s big sister and guardian in the movie Lilo and Stitch. This follows numerically after the autonomous boat N3M0, and keeps the Disney character naming convention originating from the autonomous boat Dumbo.

Lilo & Stitch (2002) - IMDb
Image from https://www.imdb.com/title/tt0275847/

The hull design

I designed the hull in the late 1990s to take advantage of a computer controlled hotwire foam cutter that was built for a project at the Stanford Aircraft Design Group where I was a graduate student at the time. I used the cutter to make a male mold (plug), then layed up the fiberglass hull by hand. Originally designed with a sloop rig, the current version of the boat uses the cat rig from an RC laser.

My sail plan design from 1997 was drawn on green engineering paper

Electronics

The autopilot is a Matek F405-CTR flight controller. I’m using a Radiomaster Tx16s RC transmitter, and a jumper R8 receiver. The RC link is for manual control and also sends telemetry data to the transmitter display. A standard ardupilot RF telemetry link sends data to my Amazon Fire kids tablet running mission planner. The wind vane is my own design, and the GPS/compass is a matek M9N-5883 under a 3D printed dome.

My genius idea was to attach the telemetry module and windvane using gopro mounts. I 3D printed the male (buckle) end, and used standard adhesive gopro mounts on the boat. This makes setup and transport easy. See the photo below in the mechanical section, and the separate article on the windvane construction.

I documented my wiring using powerpoint, it’s not the best format for a blog but the full PDF is downloadable below. There are a lot of wiring connections, and each one must be configured in ardupilot using mission planner. The photos at the end of the presentation are scans of my notes from my project notebook. The details are all there but you will need to cross-reference with the ardupilot and flight controller documentation. Flight controllers come and go so I didn’t feel a step-by-step guide would be all that useful if trying to reproduce this system.

Mechanical

The rudder servo is just a “standard” size servo I had in my parts bin.

The sail winch servo is the very excellent Power HD WH-65KG (amazon link but I actually purchased from a local shop)

The rig (mast, sail, boom, mast step, etc) is from an RC Laser at infinity sails

Deck arrangement

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