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Instruments and Autopilots - current systems

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I said in a thread I'd write a bit about currently available AP's and instruments, and the good bits to look for. Here you go. 


Instruments first.

Pretty much all the instruments now available are NMEA2000 (yes, I know there are 1 or 2 exceptions). NMEA2000, for those who don't know, is the current industry standard for the data bus for your boat. It also carries power, and therefore there is a single cable connection to many of the instruments (ones that require lots of power have additional power connections). This makes installation and extension of systems much easier than it has been in the past. Basic NMEA 2000 rules (thin cable option, which is what virtually all yachts use) 100m max bus length, drop cables (to connect the devices from a T connector on the bus) max 6m. At each end of the bus, a terminator is required. Most boats use a masthead wind transducer that has a built in terminator as one end of the bus.

So, what has changed with instruments in the last few years?

I'll start with the B&G triton range as an example;


Firstly, Colour screens, bonded directly to the glass front. This obviously means colour, but more importantly there is no air gap between the display and the screen, so it is not possible for these screens to fog up. Ever.

2ndly the screens are now all multi's - no dedicated wind/depth/speed. All screens can display anything, including autopilot functions.

Resolution 320x240, giving clear, readable, bright displays for easy reading in sunlight.

Low power consumption (50mA with lights off, up to 150mA with the lights on).

So, that is the basic display units, how about the transducers?

Well, not much has changed here with the basic units. The most significant is that now you can get all your data from a single thru hull transducer - speed/depth/temp all in one. Another is required if you want fwd sonar, which is the same size thru hull, but needs a metal thru hull, not plastic. This is because it protrudes thru the hull and is potentially vulnerable to hitting something. It has a designed in fracture point, but the impact required to break it is too much for the plastic thru hulls.

Triton 1.jpg

AP's for the basic systems (like triton above) are quite advanced, and very reliable. They consist of a computer, control panel, and drive unit. Drive units are quite variable depending on your vessel type. The computers offer full integration (via nmea2000) to the instruments and plotters, and can steer compass courses, wind angles, to routes/waypoints, and No Drift mode. They can also auto tack (great for single handers), follow bottom contours, and have various other options too numerous to go into here. Well spec'd to suit the boat, they can reliably steer your boat in virtually all conditions if used sensibly. They have some intelligence - like if the wind is fwd of the beam they can steer to apparent wind, if aft, then to true wind. This prevents the AP thinking there is a wind shift if, for example, you suddenly accelerate and surf down a wave.

However, they have some limitations. They can use a LOT of electricity. You need to ensure your boat is well balanced with the correct sails for the conditions to minimise power use - if it is hard for you to manually steer, it's hard for the AP! Tune your boat properly, balance it well, and this should not be an issue. There is one further thing to mention, and that is that these AP's are almost entirely REACTIVE - ie they wait for the boat to go off course before they correct the issue.



This brings us to the high level instrument systems, like the h5000 B&G systems. These are aimed at serious race boats, and also long distance serious cruisers. This is the current state of the art. You can have multiple wind sensors, the calibration systems allow for things such as mast twist at various wind speeds, they (can) have a lot of sensors, including 3d motion sensors. The 3d motion sensor monitors the vessel position (roll, pitch & yaw) and, for example, configured with the known rig height, compensates the wind readings for boat movement. This means the instruments give steady, accurate information. They record any data to give trending and historical info. They interface with the boat's polars to give target speeds. 


The AP for the H5000 series was developed for the Vendee Globe boats, where the solo skipper has a gennaker on, and is doing 25 odd knots and wants to go to bed. This AP is as close to a human helmsman as it is currently possible to get with todays technology. As the system knows the attitude of the boat, it will, for example with a quartering wave, notice the change in attitude and apply counter rudder to keep course before the boat's course is effected by the wave. Steering is PROACTIVE with these AP's and a boat will keep a much better course than with the Triton series AP's.

As usual I'm happy to discuss this with anyone, and pricing as well as custom configuration for your boat is available - just give me a call 0221539176 or email matt@neptunes-gear.com

Thanks for reading!

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A path down which multiple electrical signals travel. Like a "Bus Bar" on a power distribution panel it is where multiple devices can be connected to gain access to common signals.

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As JK said, It's a distribution cable, that's all. If the BUS itself failed (fuse, power supply, broken cable) then all the instruments will cease to communicate. The ones powered from the bus will cease to function. If your plotter has a non NMEA2000 GPS, then it will continue to work as a plotter. Fortunately bus failures are pretty rare! Any other instrument or device can fail and the only issue is you will lose the function of that device. Here is a pic of an NMEA network showing the bus;

NMEA2000 Bus.png

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Having a full simrad/B&G suite we have actually installed a second bus block, so should the block fail, we would simply change all the terminations from one to the other. All our simnet cables run back to the same bus block. Changing over is very simple with the connector block used. 


As a bit of a redundant systems nut, I ran spare simnet cables to all vital "organs' of the system - there is a spare running to the AC42 computer, a spare AC42, 2 spares to the helm, 2 sets of wind gear etc. The depth/speed is not a vital, nor is the AIS connection. We also run a separate AP controller as well as the plotter - just in case the plotter spits the dummy, or, as has happened on a yacht I was once crewing on, the plotter got punched and smashed!.


It all adds cost, so many might choose not to have the redundancy, but for our piece of mind and the ability to not have to deal with getting units repaired in remote islands, it works very well for us.


The only failure which would stop our AP totally would be the ram or hydraulic pump. 


As IT says, rudder failure is rare. steering gear failure is not so rare - chains, blocks, etc can fail, even quadrants. Its nice to have a redundant system. Keeping the rudder well maintained and inspecting all parts which may fail is a must. Accidents will happen. Whales damaging the rudder are just one of the risks we take. 

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Hi eruptn, hmm, a power boat!!


It's also not a great example, although it shows the idea well.


The NMEA2000 rules are that dropper cables are no more than 6m long. That pic has one being shared by the radar, wind etc on the fly bridge. I like to have only one device on each dropper, and I'd bet that dropper cable would be more than 6 meters. It would probably work, but if you stay within the rules, you are MUCH less likely to have issues and weird problems with your system!! Weird, intermittent issues are a pain in the $%#@ and costly to diagnose and rectify. Best to avoid them to begin with where possible!

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I have all cables other than the speed/depth on less than 6 meter droppers. Effectively ours is created as a star network with a central hub being a simnet connector block - as noted before, this was done for a reason. It is more complicated than maybe required, but if you have a clear understanding of it, when problem solving it becomes very much easier. 


The 6 meter "rule" appears to be a little arbitrary - I have seen many simnet cables run to the top of a mast and still work. Unless Simnet has a relaxed timing protocol over standard NMEA2000, I would expect that most situations could get away with longer runs. Maybe the data volume could have an impact on this, although as the entire bus runs at 250kbps I would not expect this to be the case as timing is not the same as data flow. 


There are many ways to skin a cat, and the serial setup as pictured on wikipedia as linked to by eruptn is probably the most common way to do so - although as IT noted, that flybridge cable is very loaded with a radar and the wind, GPS and ( worst, in my opinion ) the radar.  The problem with that drawing is that whilst it looks nice and clear and logical, very rarely is this the case when you install a system in a vessel, and you end up with a loom snaking all over the show. This makes for more difficult problem solving.


Anyway, all in all, IT this thread is a very good idea - a lot of people have a very limited understanding of the electronics available, and many sailors don't understand how much easier life can become with a well sorted electronics package ( and how much lighter their wallets may also become! ). Just picking exactly what you want can be challenging enough without learning how to use it properly. The former is being addressed here well.

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Just one thing further TT, the masthead units from Navico (B&G/Simrad) are not droppers. They have a terminator built in, and are virtually allways one end of the bus, due to the length of the cable required.

Part of the real world issues, is that people say "this is ok, it works on my boat" but you can get away with stuff on some installs that wont work on others due to size of install, or exact configuration. Best to stay within the design guidelines.


Oh, and Simnet is, to all intents and purposes, NMEA2000 - it just uses different plugs, and has a few non standard extension PGNs.

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Indeed, its an issue. Much NMEA 2000 stuff is "compatible" not certified compliant. How "compatible" varies quite a bit!


All the new Navico  stuff is now standard Micro C connectors - the real "standard" for NMEA2000. There are adapters available for those with simnet connectors....

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After reading this thread I'm dam pleased to have a Raymarine Seatalk network running on my boat. Everything (wind, depth, speed, rudder, gyro, AP, compass, controller etc) plugs into the one bus on the course computer and instantly talks and interacts with everything else. The whole kit was a piece-of-cake to install and setup - Even I manged to get 90% of it running without reading the booklets titled Installation and Operating Manuel 


I'm sure there are better systems out there, but for your average cruiser/racer it'd be hard to beat.

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Actually TL, the Raymarine Seatalk ng IS NMEA2000! That is what I've been talking about here, just using the B&G stuff as an example.


Seatalk ng is just Raymarine's version of NMEA2000, like Simnet was Navico's version. Again, there is a cable adapter available to go to industry standard  micro C connectors.


In most instances, NMEA2000 systems do "just plug together and work" - it is way easier than it used to be, but the basic rules should be adhered to, so as to have a trouble free install, especially in a larger system.


Nothing wrong with a Raymarine system, back in May, when they released their lighthouse 11 software, they added Laylines, startline info and basic race management. The products look pretty good! However, IMO, at the top  end of the products especially, the B&G stuff has the edge. 


One thing you all may also like to consider though, is that Navico have a large presence here in Auckland. Quite a bit of R&D is done here, and they are as close as you'll get to proper local support, and help keep some Kiwis in work! I have no idea what Raymarine support is like.


As I said at the beginning, NMEA2000 IS THE CURRENT STANDARD. Most manufacturers are now using it, although they may call it something else....

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GS, the best ones have the brains below, and the muscle in the form of an electric worm drive, or a hydraulic ram to the tiller. Electric can have a plug, hydraulic is more robust but harder to remove.

There is, IMO, a void in the marketplace for a proper, robust tiller pilot. I have some ideas about using a stainless ram, possibly from a large outboard steering system, possibly with zero loss hydraulic couplings, and a standard ap system. This should work really well, and give all the advantages of the more common under deck pilots.

Anyone want to be the guinea pig?

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True zero loss hydraulic couplers are phenomenally expensive - and I have yet to see ones which don't start to weep after a while ( although I have not looked at the really expensive ones. I would seriously consider mounting the hydraulic pump on the ram somehow and having a high current power supply to the ram. The drive motor is not large at all, and you could use steel pipework then so it would look fairly tidy and be pretty compact. I am not sure if you could get SS housed pumps however. But where there is a will, there is a way!. 


The mounting points would have to be bloody strong!. 


In GS's case, If it could be made to work, a simple clevis type connection to the tiller, or, a quadrant mounted slightly below the tiller if possible, could be a workable solution, with the pump mounted semi remotely. Then only the ram would be exposed. It would be quite possible although potentially eyewateringly expensive to get a custom made 304 ram.

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That is good TimB, another source to stow away in my files. There are several suppliers of Stainless rams. I don't like the idea of the electrical parts (pump, solenoid etc) being exposed to the weather, so I'd be firmly in the Electronics below deck category...

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I have the electrics down below in the dust and the ram upstairs driving the tiller.




Proprietry system in my case , but I agree there's a gap in market.

Boy do people start talking gobbledegook as soon as you mention its a tiller steered boat!


and while we're at it, what does size of boat have to do with anything? Its the force required on the tiller that is of importance ,shirley.

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