A Canadian Boffin: Tiller-Pilot for a Dinghy

Tiller-Pilot for a Dinghy · Aug 15, 2007

No, the glider (mk 2) isn’t flying yet. It has been making progress though, in pulses, and it’s almost there. One day…

In the mean time, it’s sailing season. With no access to a keelboat this year, I’ve been getting into Dinghy Cruising, which is just about what it sounds like. You upgrade a daysailing dinghy (a small sailboat launched from a beach, that has no lead keel) for rougher conditions than normal, and maybe add oars or a trolling motor, then go camping. Similar idea to sea kayaking. It’s very popular in the UK, somewhat on the east coast, not so much in BC.

In other words, most people around here think I’m a bit nuts to do this, excepting the rare physics geek who’s been known to go along for overnight trips.

(under spinnaker off Bowen Island. No, that’s NOT me, that’s an actual physicist)

So I’ll mostly end up going singlehanded, which is a fun challenge in itself. When singlehanding, you wind up being a “slave to the tiller” for many hours on end. Grabbing your water bottle or adjusting something at the mast can end in a minor emergency, not least because the skipper is also the ballast. And dinghy’s don’t hove-too (stop with the sails up) all that well, so taking a leak is an even bigger issue.

The traditional answer is to lash down the tiller with a line, hopefully easily adjustable, like this, but the heading tends to drift.

So, an autopilot! Keelboat size tiller-autopilots use a linear servo and magnetic compass, burning a fair amount of 12v power, and cost around $550. I figured I could make my own.

The idea is you replace the usual single line bracing the tiller with a clothesline arrangement, with the autopilot on one gunnel and a pulley on the other. You then have a jam cleat on the tiller to grab the top line, and just attach or detach it from the line at will.

It has about 12 lbs of maximum pull, which is plenty, and gets NMEA data from a Garmin GPSMAP 76 for compass heading, track, and waypoints. So far it’s seen one day of testing, and worked well in light to moderate wind conditions or under oars, but not so well in waves. About what I expected; the major limit to performance is the only 1/2 hz updates from the garmin handheld.

It’s also watertight, including the servo, and has a small solar panel that should keep it full charged. An buzzer sounds to warn about error states. The microcontroller code wound up being 700 lines or so, 90% of the ROM available (4kb); close.

Not bad for a < 40 hour project. Hopefully it’ll perform well on the next longer trip.

* * *

Hi Art, nice to see that you’re still active. Hang on with the MK2-glider, will’ya? :) All the best, Rolf

— Rolf Sep 5, 12:00 PM #
Like the glider project. live here in arizona. might be a good place to fly high altitude glider

regards

Chuck koerber

— chuck koerber Feb 8, 04:15 AM #
Your first glider project was absolutley amazing, and I am envious of your skills in electronics, programming and automated flight control.

I have been eagerly waiting for quite a while for the MKII, any news on when it will be ready?

I’m starting to wonder if the project will ever get off the ground (sorry bad punn :) )

— Andrew Apr 15, 03:08 AM #
That’s awesome!

Personally I’ve picked up a 51 channel i-blue 747 GPS receiver from ebay for only 40 euro’s or so including shipping. And it’s deliciously hackable. You can set it to use the WAAS/EGNOS satellites, and you can also adjust the baudrate and updaterate. Mine can be set to 5Hz, so maybe it will be useful for you?

It does not have a RS232 output, but it does have UART pins on the PCB. Or you could convert your control box to sport a bluetooth connection.

— mace Apr 20, 12:45 AM #
Great project! How about a parts list and programming details? It looks like you could produce these, but I just want to put one on my International Folkboat.

— eric Apr 21, 02:04 PM #

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A Canadian Boffin

It's not quite flying, closer to falling with style.

Tiller-Pilot for a Dinghy · Aug 15, 2007