Hydra Heading Input

Ian Shepherd <g4ljf@...>

Well, it works! Just as B & G said it would. I now get the boats magnetic
heading when 'Nav' is pushed on the Hydra display, and the true (not
apparent) magnetic wind direction on the third push of the 'Wind' page.

As I know that several Amel owners have tried unsuccessfully to achieve this
this is how it's done.

1/ Remove the cover off the bottom of the autopilot computer which is
located in the cupboard above the sink. You should find a NMEA out
connection on the terminal strip. My 400G computer has 2 identical NMEA
outputs. The output is indicated by a down arrow and the terminals are
labeled + and -. Connect a two core cable (preferably shielded) to these
cables and run it through the roof duct to the back of the Hydra panel to
the right of the Nav desk.

2/ Slide out the navigation panel and look for a junction box (386-00-023)
which is connected to the black cable of the Hydra instrument. Also check
that there is label on the back of the instrument says that it is a 'NMEA
FFD' model.

In the junction box, you will see red and blue wires that are on the NMEA
side of the junction box. Connect the wire from the + of your autopilot NMEA
out to the red wire, and the other (-) to the blue.

NOTE: My boat is different to most that I have seen in that it does not have
the junction box at all, presumable because it does not have a Fastnet bus.
Not to worry. Maybe fitting the Furuno GP-80 with 4 data outputs remove the
need for Fastnet?

In this case, remove the cover off the back of the B & G processor which is
mounted in the pull out panel where the display unit is located. Follow the
black lead from the FFD display unit to the terminal strip. You will find
that several wires from the black cable are not in use and are folded back
along the cable.

Look for the brown and blue wires. Connect the NMEA + from the autopilot to
the brown cable and the other (-) to the blue.

Put the panel back and power up the autopilot with the circuit breaker.

3/ Follow the instructions on page 3-13 of your B & G handbook (para 3.4.2
Heading Node Selection) and set the Node number to 96, which is the NMEA
heading input select.

Et Voila, heading will appear when Nav is pushed and the wind direction will
be correct. There is a way to get true heading and true wind as opposed to
magnetic wind, by setting one of the values from 1 to 0, but I have
misplaced my notes and need to go out shortly. If anyone does not have the B
& G handbook and wants the instructions on how to set the Node value to 96,
I will type then out.

If its' so easy, I have to ask why the heck the boat is not wired up this
way in the first place? All it needs is a couple of more cores to the cables
that already run from the autopilot processor to the Hydra.

How satisfying it is to make things better on the boat. Nearly as satisfying
as as trouncing 10 other yachts in a race yesterday. Who says cruising boats
are slow!


Ian Shepherd SM 414 Crusader

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