Microtransat

By Dermot Tynan • March 16, 2013

So, as I mentioned, the virtual boat was too eager to tack. If you're dead downwind of the mark, and you set off on a starboard tack, within a metre of being on the left-hand side of the course, the other tack is favoured.

I added code that essentially stated "unless the other tack is at least five degrees better than the existing one, ignore it." So, if I'm at 44 degrees TWA and the other tack is better by a degree (-43 say), stay where you are. This works quite nicely. If you look at the plotted course, it shows the boat sailing nice upwind legs, to the waypoint. As Henry would say, "it's sailing up the ladder."

By Dermot Tynan • March 19, 2013

There will be at least two Vcc busses on board. Labeled, oddly enough, as Vcc1 and Vcc2. The difference between them is that Vcc1 is always on, at all times, and Vcc2 (through VccN) are selectable by Igor.

The main processor runs off Vcc2, but Igor (and Otto) both run off Vcc1. In situations where voltage levels are critical, Vcc2 will be switched off and the boat will continue on whatever course had previously been set, until either voltage levels are healthy, the specified "wake-up" time has elapsed, or there are critical issues which require Mother to get involved. A critical situation could be something like a dramatic wind shift, or an error such as a mis-reading from a sensor.

By Dermot Tynan • March 19, 2013

I've been asked recently, about the software platforms used on board Beoga Beag. This seems as good a time as any, to talk about the various layers. As mentioned previously, the lower layer is a custom board, running an ATmega8 Atmel processor. The software (Igor and Otto) is custom-written in C for the boat.

By Dermot Tynan • March 20, 2013

After much tweaking and hacking with configuration files and kernel build options, I finally have a FreeBSD 8.3-RELEASE kernel and install running on a Wrap board. Technically, it's NanoBSD, which is a scaled-down FreeBSD install, which boots from Compact Flash. The WRAP board is the PC Engines forerunner to the ALIX. When National Semiconductor and AMD stopped making Geode chips, the guys at PC Engines had to stop making their very popular WRAP board. I still have a few of them tucked away, for emergencies such as this.

By Dermot Tynan • March 21, 2013

This time, I set the simulation granularity a bit smaller, so the updates are more regular and there are more data points, which explains the curved route in some cases. You can click on the image for a slightly larger version. An Olympic course is known to sailors as a "triangle and sausage", because you sail upwind to the top mark, turn onto a broad reach to the gybe mark, gybe around, and broad reach down to the leeward mark. From there you beat back up to the windward mark, and then turn dead downwind to the finish line at the leeward mark. A true Olympic course would put the start and finish line about a third of the way up the beat, shortening the first leg somewhat, but also making for an upwind finish as you would have to sail around the leeward mark and beat to the finish. I skipped all that!