When it comes to spares and backups we are all informed by our experiences, prejudices and fears. It's hard to approach with total logic because we really don't have much reliable data about failure rates and causes.
One of the downsides to the NMEA2000 network is that it is all "of one piece." Although it is designed to be robust and fault tolerant, I have seen one corroded connector bring down a big piece of a boat's network. It's probably a good idea to have a couple spare connectors, and a spare terminating resistor for a NMEA2000 network just in cast you need to bypass part of the circuit.
I do not have any bad experiences with rudder angle sensors, but all of the ones I have used were "dumb" ones hard wired to the course computer. They are simple circuits, and as long as they are kept dry, with good connections, they SHOULD work. On the other hand, without a working sensor, the AP is not usable...
Adding the complexity to have the rudder angle sensor connect through the network makes things...more complicated. Our two independent AP computers have separate rudder angle sensors so I haven't really felt the need to think hard about backups for that part. I do carry a complete, drop-in spare, linear drive. So we have three drives, two computers, two rudder sensors, and two fluxgate compasses. Short of getting struck by lightening, we should be in good shape.
The only part of the system that we have deliberately kept independent of the NMEA2000 network is the backup AP. If the network totally died, we would still have the ability to steer to a compass course with the older course computer.
We travel with enough hand held devices that include GPS receivers, and paper charts that even serious network problems would be an very annoying inconvenience, not a disaster.
I know some people love their forward scanning sonars, and for good reasons. If I spent a lot of time cruising in rocky areas like New England I'd likely be more interested. For us, all of our "ground contact events" have been in gradual shoaling areas where we were well aware of the depth. When the forward scanning units get to the point they can help me find a 2.05 meter channel surrounded by 1.95 meter shoals I'll be all in!
Theoretically, the forward scanning units would allow us to move through coral head infested waters without needing to be as attentive to time of day and visibility, but I am not ready to turn over that task to electronics. If we are doing the eyeball navigation thing anyway, the added value of the electronic version doesn't push it high enough on my wish list. Don't get me wrong, these things are on my wish list, they just haven't quite gotten to the top of the priority list in the competition for available resources!
When my sailing students asked me some version of the question, "Do I need "X" on my boat to go cruising?" I asked them to do a thought experiment. Imagine you are at anchor in the lagoon of an isolated tropical atoll. Device "X" has just irreparably failed. Can you get home? If the answer is "Yes" then device "X" is a luxury. One you might very much want to have, but in the harshest of analyses--a luxury. If the answer is "No" and you would be stuck in this remote location until device "X" is working again, then you need two of them!
Annapolis, MD, USA
, wrote :
I like your concept of having some stand alone instruments and would like to learn of a good way to have some of the benefits of the network without being reliant too on it . I will be buying most everything new for my boat so have lots of options so long as I don’t blow the budget. (grin) If you have any thoughts or suggestions on achieving a good balance between the standalone and networked items please share. I am using a Zeus 3-9 as my plotter and was thinking of adding the B&G 4G radar. My instrumentation is the original B&G Analog style which mostly still work. The wind was replaced by an Advansea unit that still works fine but I think is being phased out. I really like the idea of the forward looking sonar but wonder if the range and accuracy might improve if I wait a while on that one. I have two backup chart plotters that are standalone plus a handheld. I only have the original rotary autopilot which works fine so far. Would you recommend carrying a spare rudder sensor? Beginning to get the boat ready for the trip from the Med. back to Florida.
Maramu #220, about to begin another season in the Med!