Freedom from the “Tyrrany of the Tiller”

I have an ST4000+ wheelpilot on my 33ft Dick Carter sail boat. IMHO it is an essential piece of safety equipment when you are sailing shorthanded, or even just with a smaller crew (i.e. less than 4 people).

I recently had a challenging night offshore after splitting the mainsail in a squall (just after putting the 3rd reef in). Even though I had two crew, they were both too sea-sick to be of much use, and the autopilot steered perfectly under motor while I lashed the main to the boom and set the storm tri-sail.

The benefits in freeing you from the “Tyrrany of the Tiller” is obvious.

It is vitally important though that you:

  • fit a rudder angle sensor, otherwise the Autohelm performance will be mediocre at best, but probably next to useless;

  • select the location for the fluxgate compass very carefully to avoid magnetic and RF interference.

  • Getting it as close as posible to the keel will also minimise unecessary movement of the fluxgate, making the Autohelm more stable;
  • make sure all wiring is done professionally, cable joins are avoided as far as possible and cables are routed in dry areas (keep them out of the bilge if possible).

The Autohelm on Sunny Spells was pretty useless when I bought her, but after fixing the problems listed above, she now helms perfectly downwind for hours on end. I’ve had an 11 hour run downwind with poled out genoa and main by the lee without touching the autopilot controls (on wind-vane mode) other than accepting wind shift alarms.

The best $1000 you can spend!

Navbus/NMEA and Displaying Wind Data

Mystery solved…

After a lot of correspondence, telephone calls and hours in the boat, in front of the laptop, decoding NMEA0183 sentences (did I really need to know all this stuff??), the mystery is finally solved…

It appears that the chartplotter firmware is the culprit. If Navbus is enabled on the chartplotter, it will only accept wind data from Navbus, not the NMEA0183 input. Disable Navbus, and the wind data is displayed!

It seems like a quick fix, but it comes at a price. The biggest issue is that DSC capability (i.e. automatic communication with the VHF to receive and transmit DSC messages) is lost. Also, the barometric pressure and air temperature data sensed by the VHF is now not available at the helm… Navman’s John Dusting said that he would request a firmware update to solve this issue, but it could be a while…

Connecting NMEA input to Navman 8084 Chartplotter

When I got around to installing the AIS receiver in Sunny Spells, I had a bit of a frustrating time working out how to connect to the NMEA input of the Navman 8084 (similar to Navman 8084, Northstar M84 and Northstar M120). The handbook was no help at all…

A quick call to Navman confirmed what I had found elsewhere on the internet:

  • The NMEA 0183 input is on the white “Fuel/Nav” input on the Navman/Northstar unit.
  • You need one of the Navman/Northstar extension cables with an LT8 plug on one end and bare wires on the other. AA002412 is one of the part numbers but there are several others that would work (different cable lengths have different part numbers…). Your friendly Navman/Northstar dealer can help you order the right cable.
  • The WHITE and BLACK wires on the extension cable are used for the NMEA 0183 input. Black (you guessed it…) is the NMEA negative (earth) and white is the NMEA positive.

Navman 8084/8120 and Northstar M84/M8120 rear connections

Remember that the chartplotter will look for some inputs on the NavBus input if that option has been activated. For example, if NavBus is turned on, the chartplotter will NOT look for wind data on the NMEA input even if there is no wind data on the NavBus input – very annoying! The NMEA input automatically selects the high speed option (38400 baud) if a high speed data stream (such as AIS or a multiplexer with a 38400 baud output) is connected.

Getting Navbus, Seatalk and NMEA to talk

Wout at Brookhouse replied to my e-mail today. (Thanks Wout for your prompt reply and the USB driver). Of course, I remembered this morning that I had printed out the user manual for the MUX and had bound it nicely, with a pocket for the CD, in the back…

The MUX is now connected to the PC via USB. All operating at 38,400 baud as the AIS is also connected. Digiboat’s Software-on-Board shows all wind data present and correct (see screenshot). So where’s the problem?

Looks like I’ll have to go to Navman for this one…

Wind data displayed on SoB