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Old 19-02-2019, 10:04   #1
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Autopilot: Wheel based or quandrant servo?

I need to replace or repair my existing Raymarine ST4000 autopilot as the fluxgate compass is toast. The system works manually but it's pretty noisy and it would not be easy to interface with my new B&G electronics.

Is there a great benefit to using an autopilot that uses a servo attached to the rudder quadrant vs one that attaches to the wheel as my current ST4000 does?

The boat is a Tashiba-31 with a displacement of 13,700-lbs. I solo sail and use the autopilot in short periods to allow me to step away from the wheel from time to time. Eventually, I'll get a something like a Monitor windvane
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Old 19-02-2019, 11:01   #2
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Re: Autopilot: Wheel based or quandrant servo?

Your need for an autopilot seems to be short-term and light duty. Quadrant-mounted autopilots are often installed for long-haul, heavy duty use. They are frequently hydraulic-operated. Does your boat have any hydraulics already rigged up? If not, add that to the costs. Is there room down there in the lazaretto/rudderpost area to slip a quadrant and hydraulic piston and whatever else needs to get in there? Besides the cost of the equipment, the install would not be cheap, either. Workmen don't enjoy standing on their heads for long periods in contorted poses with their legs sticking out of lockers. (I've had a look at some of these, myself.) If the system you have now attaches to the wheel and (obviously) isn't too cumbersome, that would seem like the simplest route. The lighter-duty wheel attachment seems to suit your needs and is likely less expensive than the other setup.
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Old 19-02-2019, 22:30   #3
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Re: Autopilot: Wheel based or quandrant servo?

Those old Raymarine ST4000 heads are a pretty tough piece of equipment with pretty well everything electronic sealed in the head whereas the newer ones have them separated and the computer needs to be placed somewhere where neither splash or condensated water can get to them. Mine would accept signal from either Seatalk (never used) or NMEA 0183 which I used to connect it to numerous gadgets including hand held gps's, tablets and computers running OpenCPN through USB to RS422 converters.

If you are not going to use the autopilot for heavy duty service I'd hang onto it and look for a replacement wheel drive unit.
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Old 19-02-2019, 22:39   #4
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Re: Autopilot: Wheel based or quandrant servo?

You could use your existing autohelm drive unit and buy a tinypilot controller. This is a good solution that also gives more functionality. The controller is controllable by WiFi or infrared remote.
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Old 19-02-2019, 23:06   #5
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Re: Autopilot: Wheel based or quandrant servo?

Quote:
Originally Posted by dmksails View Post
I need to replace or repair my existing Raymarine ST4000 autopilot as the fluxgate compass is toast. The system works manually but it's pretty noisy and it would not be easy to interface with my new B&G electronics.

Is there a great benefit to using an autopilot that uses a servo attached to the rudder quadrant vs one that attaches to the wheel as my current ST4000 does?

The boat is a Tashiba-31 with a displacement of 13,700-lbs. I solo sail and use the autopilot in short periods to allow me to step away from the wheel from time to time. Eventually, I'll get a something like a Monitor windvane

The compass can be replaced separately, and is not expensive. Why do you think you need to replace the pilot?




Below decks pilots are completely different animals from wheel pilots. Those that have them typically don't steer by hand much except when docking. But if you only use the pilot to step away from the wheel from time to time, and you're happy with that, then I doubt the cost of a below decks pilot (thousands) would be worth it to you, but only you can decide.


For long passages under sail on a boat that size, wind vanes are awesome. If I were you, that's probably the direction I would be going.




You talk about interfacing the pilot with new electronics -- why would you need to? The only reason is to use nav or wind mode, or to control the pilot from an MFD. You don't need to do any of that if you are just stepping away from the wheel from time to time, and are otherwise happy to hand steer.



If, on the other hand, you would really like for the pilot to steer the boat most of the time, then a below decks pilot is the right tool for that job. If that's what you want, then here's a money-saving tip --


Don't buy the whole pilot from B&G. Buy just the pilot computer. Then buy the guts of the pilot -- the ram, the pump, the lines, and the bypass solenoid -- which are all made by Hypro in the UK -- directly. This guy is a good dealer of Hypro stuff: https://jgtech.com/Autopilots/Autopilot-drive-pumps


N.B. that Raymarine, Furuno, and Navico (B&G, Simrad, etc.) hyraulic pilots all use the same drive mechanisms -- all made by Hypro, which can be bought without the Ray, ** or B&G brand on them for about half the cost.


A whole set for your boat costs Ł900 from him (plus VAT if you live in the UK). Then all you need is the rudder sensor and the B&G pilot computer, another grand or so.


Then the pilot can steer your boat all the time, be controlled by a B&G MFD, will do nav mode, wind mode, etc. -- if you actually need all of that.


If not, then stick with the good old ST4000. I used one for about 15 years -- it gets the job done in calm weather.
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Old 20-02-2019, 00:28   #6
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Re: Autopilot: Wheel based or quandrant servo?

If you want to go quadrant, keep the 4000, connect a new compass and rudder sensor, connect output to a Simple H HV, and use a Type I drive to the Hycor Type 1 hydraulic equivalent.

The clutch is just a separate circuit with a switch on the binnacle.

You could also set the system up to drive the wheelpilot without the simple H, as a backup.
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Old 20-02-2019, 00:42   #7
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Re: Autopilot: Wheel based or quandrant servo?

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Originally Posted by Dockhead View Post
The compass can be replaced separately, and is not expensive. Why do you think you need to replace the pilot?




Below decks pilots are completely different animals from wheel pilots. Those that have them typically don't steer by hand much except when docking. But if you only use the pilot to step away from the wheel from time to time, and you're happy with that, then I doubt the cost of a below decks pilot (thousands) would be worth it to you, but only you can decide.


For long passages under sail on a boat that size, wind vanes are awesome. If I were you, that's probably the direction I would be going.




You talk about interfacing the pilot with new electronics -- why would you need to? The only reason is to use nav or wind mode, or to control the pilot from an MFD. You don't need to do any of that if you are just stepping away from the wheel from time to time, and are otherwise happy to hand steer.



If, on the other hand, you would really like for the pilot to steer the boat most of the time, then a below decks pilot is the right tool for that job. If that's what you want, then here's a money-saving tip --


Don't buy the whole pilot from B&G. Buy just the pilot computer. Then buy the guts of the pilot -- the ram, the pump, the lines, and the bypass solenoid -- which are all made by Hypro in the UK -- directly. This guy is a good dealer of Hypro stuff: https://jgtech.com/Autopilots/Autopilot-drive-pumps


N.B. that Raymarine, Furuno, and Navico (B&G, Simrad, etc.) hyraulic pilots all use the same drive mechanisms -- all made by Hypro, which can be bought without the Ray, ** or B&G brand on them for about half the cost.


A whole set for your boat costs Ł900 from him (plus VAT if you live in the UK). Then all you need is the rudder sensor and the B&G pilot computer, another grand or so.


Then the pilot can steer your boat all the time, be controlled by a B&G MFD, will do nav mode, wind mode, etc. -- if you actually need all of that.


If not, then stick with the good old ST4000. I used one for about 15 years -- it gets the job done in calm weather.
That's good information to have on the manufacturer and distributor of those hydraulic pumps Dockhead, thanks.
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Old 20-02-2019, 00:53   #8
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Re: Autopilot: Wheel based or quandrant servo?

But on a boat that size I would look at Raymarine's linear drive and not go the hydraulic route. The power savings alone make the Raymarine a great choice for a small boat, but reliability, low resistance when turned off (you can't feel it at the helm) lower noise and price are all a great bonus to think about.

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Old 20-02-2019, 00:56   #9
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Re: Autopilot: Wheel based or quandrant servo?

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But on a boat that size I would look at Raymarine's linear drive and not go the hydraulic route. The power savings alone make the Raymarine a great choice for a small boat, but reliability, low resistance when turned off (you can't feel it at the helm) lower noise and price are all a great bonus to think about.

Matt

That's good advice. Those of us with larger boats forget about those, but they are very good, and simple.




There are also rotary drives, like the Jefa.
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Old 20-02-2019, 01:48   #10
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Re: Autopilot: Wheel based or quandrant servo?

Someone may have mentioned it already but what about the CPT. Great for a small boat. Easy to install on the wheel. Simple and robust. . I have less and less faith in newer brand named electronic autopilots. These days theyre overly complex and cheaply built. Many have firmware issues or networking problems. Below deck hydraulics may be more powerful but have their own set of issues. On a smaller boat not necessary. Another good autopilot made in Washington state are Alpha Pilots.
www.alphamarinesystems.com/index.htm
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Old 20-02-2019, 03:14   #11
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Re: Autopilot: Wheel based or quandrant servo?

There is also Pelagic, they make a control unit now to run a linear drive.
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Old 20-02-2019, 03:27   #12
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Re: Autopilot: Wheel based or quandrant servo?

CPT is a great wheelpilot. Maybe overkill on this size of boat? But very reliable and well built. Powerful enough to handle much bigger boats. Like mine.

For drive units, Jefa in Denmark make a very good linear drive unit, with little power consumption. Hydraulic is not a good option on a smaller boat, as the power consumption is too high.

Also, you have to check if it is possible to install a linear drive unit on your boat without major modifications.
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Old 20-02-2019, 04:16   #13
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Autopilot: Wheel based or quandrant servo?

Only thing with a CPT is that your not interfacing it with anything, nor are you getting a remote.
It’s a heading hold only, I have one and for me heading hold is all I need.
Original plan was to get a below deck with the CPT as the back-up, but the CPT works so well I don’t think I actually need a below deck.
Power consumption is so low and intermittent, I haven’t been able to measure it.

They are actually quite strong, they can produce 86 ft lbs of torque, and if you have a smaller wheel that is an enormous amount of force.

Wheel size matters as the toothed pulley for the CPT is the same size regardless of your wheel size, and if you have a small wheel then your boat is set up so that excessive force isn’t required cause if it was you couldn’t turn the wheel, you don’t have enough mechanical advantage.
I don’t believe boat size is as relevant as the force required to turn the wheel at 1’ from center is, a properly balanced spade rudder can be quite large and still not require a whole lot of force to operate, where an unbalanced rudder may require quite a lot of force.
If however you have a big ole 6’ diameter wheel, then it’s likely that 86 Ft lbs of Force may not be enough, cause with a 6 ft wheel you can put enormous torque into the system.


The ideal autopilot drive for my boat is a rotary chain drive with the sprocket mounted on the aft end of the pinion shaft, that is way more energy efficient than hydraulic, hydraulic is in fact actually pretty inefficient, best in my opinion for motor yachts that always have an engine running and therefore an alternator.
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Old 20-02-2019, 05:14   #14
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Re: Autopilot: Wheel based or quandrant servo?

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. . . The ideal autopilot drive for my boat is a rotary chain drive with the sprocket mounted on the aft end of the pinion shaft, that is way more energy efficient than hydraulic, hydraulic is in fact actually pretty inefficient, best in my opinion for motor yachts that always have an engine running and therefore an alternator.

The bigger issue with autopilot efficiency is RUDDER design. A balanced spade or semi-balanced requires much less force to operate, than an unbalanced full skeg rudder or barn door rudder on a full keel boat.


With an unbalanced rudder, you are actually much better off with a wind vane of the type which has its own rudder. Otherwise, it takes a lot of power whatever the type of autopilot is, to steer the boat (and even more power if you don't trim the sails well).



Hydraulic does use more power than linear or rotary mechanical pilots, as A64 says, but the difference is not great if the rudder itself does not require a lot of force to operate. The hydraulic pilot on my boat ranks far below refrigeration in the list of power hogs on my boat, and so power consumption underway on a long passage is practically the same as power consumption at anchor. YMMV.



A64 has an Island Packet, which has an unusual combination on of a full keel with a fully balanced rudder, so he should be fine with whatever type of pilot he likes best.
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Old 20-02-2019, 05:27   #15
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Re: Autopilot: Wheel based or quandrant servo?

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Only thing with a CPT is that your not interfacing it with anything, nor are you getting a remote.
It’s a heading hold only.
I use a tinypilot as a secondary controller for my CPT. It is fully interfaced and steers heading, track, wind angle. Remote controlled by Wifi or a separate IR remote. A lot of functionality for 200$.
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