I can still remember installing our current Simrad AP25 autopilot very well so it's a bit sad that I'm at it again. The original pilot is a WH Pilot and that still works! What started with a failure of the LCD display on the AP25 control head has spiraled down into a nightmare :)
First our current system: we have the AC40 central unit, AP25 control head, RC36 rate compass, RF300 rudder angle sensor and R3000X remote control, all from Simrad, with the Robertson reputation as they became part of Simrad. And that is my problem now: it is still based on the old, obsolete, RobNet wiring. The AP25 control head has SimNet connectors next to the RobNet connectors, which make it NMEA2000 (calling it N2K from here on) compatible, but none of the other components do. As it is this control head that failed, it's all down the drain from there :)
And there is more... we used to have a Maretron SSC200 rate compass which failed as well. Since then, displays switched to data from the Simrad RC36 (bridged by the AP25) but these displays show "no data" every couple seconds. I first thought the AP25 was completely failing, instead of just it's LCD, but using some NMEA diagnostics software, I have now found that the compass info is only transmitted once every 2 seconds. WTF!? today's electronics need a 10-times-a-second update rate which is 20 times as fast as what I got! This is the reason the displays think they lost compass data! The question is if the RC36 only gives updates once every two seconds or is it the bridging to SimNet that is only done at that slow rate? The autopilot steered pretty good so I guess it is the latter. This still leaves me with a worrying feeling because I thought I had a good backup for heading in case my primary sensor fails. The shock sets in when I realize that I am removing all the old style steering compasses, leaving me with nothing but a hand compass and an app on my iPhone :)
This down spiral needs to be stopped, I have had enough of this. The old pilot has to go. Both of the old pilots will go. I will try to sell the good parts (which is everything except for a LCD that is hard to read) to take the financial burden away a bit. This time I will make sure that every part is NMEA compatible and that I get top rated sensors.
I discussed this with my good friend Mark Cole aboard Reach, who has the same ideas about yacht systems as me and after a week of research I finished the list of components:
1. The heading, rotation, pitch and roll sensor. Removing the Simrad (RobNet) RC36 sensor plus the WH Pilots Fluxgate which is NMEA0183 AFAIK. I don't want the current Simrad RC42 rate compass; they charge full price for a sensor that does not supply roll and pitch data and I am also not convinced of it's performance for heading and rotation. Two sensors that I am convinced of are the Airmar H2183 and the Maretron SSC300 and I am opting for the Airmar H2183, which will be installed close to the center of gravity under the sofa in the salon. I will send my Maretron SSC200 sensor in for repair this summer and will make that (or a SSC300 if they make me a good offer) the backup and install that 10 feet forward under the bed in the master cabin. A a nice video of the Airmar sensor shows how well it performs with a rough sea state:
2. The satellite positioning sensor. Used to call this the GPS sensor but they now support Russian, European and Asian satellites as well as the American GPS. The Maretron GPS200 is great, my Furuno GP33 is a good backup and the new Vesper AIS transponder also acts as a backup. As all these are present on the N2K network already, I am good for this item.
3. The rudder angle sensor. I have two: one for the Simrad pilot and another one for the old WH Pilot. Neither are N2K compatible, but the Simrad still works on the new pilot, but I am removing both and putting in a B&G RF25N sensor which is exactly the same as the Simrad I am removing except that it connects to the N2K network. The added value is that all my displays get the rudder angle data and can show that even when the autopilot is switched off. Simrad and B&G are, apart for some minor software differences, the same now and I will be buying mostly the B&G variant because they are geared towards sailboats while the Simrad seems to target powerboats.
4. The wind sensor. I have the Maretron WSO100 wind instrument which would be great but it is acting up... after replacing it already once before. I need to investigate this more but will either use this sensor or an Airmar sensor. Both are ultrasonic so without moving components and both are N2K. This sensor is used by the autopilot to steer a wind angle.
5. The autopilot computer. The Simrad AC40 that I have now is perfect except not N2K compatible. This will be fixed by swapping it for the B&G AC42N. I was surprised to find a smaller and lighter box than the old one and can only hope quality is the same ;)
6. The control head. This started with the AP25 display failing so I looked at todays replacement units which shows the AP28 as the current replacement. It is very similar to the AP25 but at $900 costly. While talking to Mark Cole, I learned that B&G sells multi-function displays, the Triton displays, that support the autopilot plus small keypads, the Triton Pilot Controller, to control it: both together are a replacement for the traditional control head. He has both an AP24 control head and the Triton duo and told me he would just buy the Triton if he had to do it again. This is cool, because I still needed to buy new displays anyway (I sold my B&G Hydra2000 system a couple of years ago when it's wind sensor failed). I had my eyes on these displays for a while already and they have since received software updates that solved some problems that had stopped me buying them. Also, this eliminates my need for a remote control as I will install a Triton set in the cockpit as well as in the pilot house.
7. The steering power pack. The original WH Pilot came with a hydraulics pack assembled from industrial components, with two electric 1/8hp motors, hydraulic pumps, reservoir and RAM that is attached to the rudder quadrant. We are still using that and just have to perform regular maintenance.
The biggest part of this project is removing all the old components and cabling. The new system is built around our N2K network so just a matter of insert a T-connector at the locations where components are installed and connecting to that T. The advantages of N2K really shine when you see how much cabling is removed and how little put back in. We are removing many old systems that are obsolete or unneeded and the closing of old openings and screw holes in fiberglass is a time consuming business.
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