Minimum Autopilot

[dhmeissner]

I have an old Autohelm 4000, not fancy, but it works to give the pilot a break.

 

[TG]

I read this thread with some interest since I am engaged in a similar project currently.


My project involves automating a Benmar 16B by connecting it to a FURUNO NAVNET. I've already developed and prototyped the controller board that interfaces with the BENMAR and connects to an Arduino Mega2560 Processor that listens to NMEA from the FURUNO via RS232. With the hardware and communication code worked out I'm currently writing the navigation code for the Arduino.


I've read about several similar projects, some successful, and it seems the first idea that comes to mind is to use the XTE information provided by NMEA. The problem is the precision provided by XTE over NMEA in Nautical Miles is rounded to two decimal places or +- 30 feet so you'd be wandering a 60 foot path. My solution is to pass the position data to the Arduino and let it do all the math in order to gain precision of about +- 2 feet.


If anyone is interested in the math behind the GPS calculations, I've found the following site to be very informative: Calculate distance and bearing between two Latitude/Longitude points using haversine formula in JavaScript


I guess the point is that it's certainly do-able and for a fraction of the cost of a commercial unit, minus the time of course.

 

[Gdavid]

does anyone have personal experience with the raymarine ev-100? I believe it was referred to in a couple of posts based on the brand and price but not identified by model number. The unit is billed as ideal for a single outboard powerboat with hydraulic steering but the specs indicate that it would (just) handle the steering ram we have. The boat is a mainship 34III which has a small rudder for its size and the helm has never felt heavy. I understand there is a degree of risk when spec'ing a piece of gear that is just big enough. The next larger unit is three times as expensive so it would either be another brand or just not getting one. The mainship's helm offers no more effort than any outboard with hydraulic or I/O with power steering that I have ever driven so I don't see pressure as an issue but I can see where the rate of correction would be critical with a following or quartering sea.

 

[Wxx3]

ComNav with solid state compass.

My ComNav works better with the SS compass.

And the worse the seas, the more important that it works well.

Richard

 

[River Cruiser]

does anyone have personal experience with the raymarine ev-100? I believe it was referred to in a couple of posts based on the brand and price but not identified by model number. The unit is billed as ideal for a single outboard powerboat with hydraulic steering but the specs indicate that it would (just) handle the steering ram we have. The boat is a mainship 34III which has a small rudder for its size and the helm has never felt heavy. I understand there is a degree of risk when spec'ing a piece of gear that is just big enough. The next larger unit is three times as expensive so it would either be another brand or just not getting one. The mainship's helm offers no more effort than any outboard with hydraulic or I/O with power steering that I have ever driven so I don't see pressure as an issue but I can see where the rate of correction would be critical with a following or quartering sea.

There is a 38' Bayliner owner (same boat as mine) on the Bayliner owners forum who has the Raymarine evo 100 on his boat. He indicated that it works fine and it was on the edge of being suitable according to the specs. The 38s are twin engine, 18,500.00 lbs. have small rudders, Hynautic steering with a balanced ram. If I remember correctly he boats on the west coast. A place you might get some answers is on The Hull Truth forum, there are some electronic dealers on there who would answer you're questions and have the experience to be really helpful.


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[Gdavid]

There is a 38' Bayliner owner (same boat as mine) on the Bayliner owners forum who has the Raymarine evo 100 on his boat. He indicated that it works fine and it was on the edge of being suitable according to the specs. The 38s are twin engine, 18,500.00 lbs. have small rudders, Hynautic steering with a balanced ram. If I remember correctly he boats on the west coast. A place you might get some answers is on The Hull Truth forum, there are some electronic dealers on there who would answer you're questions and have the experience to be really helpful.


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Thank you, it is good to hear some real world experience. I haven't been on THT in forever but will drop in.

 

[bilge53]

Needs a remote forward looking camera and the hula bobble!

 

[refugio]

I replaced my auto pilot last year. I had a Cetrek system with hydraulic pump that worked great until the motherboard died. A complete Raymarine EV-400 (largest version, required by the electrical requirements for a large hydraulic pump) was $2500, and I got a $400 credit for the Cetrek take out parts. Utilizing the existing hydraulic pump and wiring it was a super easy install.

It was more than I wanted to invest to retain what was - for me - point and hold course control with rudder angle display. But I got a state of the art position controller, a NMEA 2000 network (though with RM connectors). So adding a small MFD was plug-and-play. And adding course control from my laptop with Coastal Explorer was as simple as adding a $100-ish adapter. And I think I'm set for as long as I'll own this vessel.

Edit: whoops, forgot the $300 RayMarine rebate! My net cost was $1800, but - again - I already had the pump.


Keith

 

[CaptTom]

Sorry to dredge this up again, but I have a question:

I like the looks of the ComNav, and the Raymarine EVO series.

How do I know how many cubic inches my hydraulic steering system is?

I have a Hynautic system with two pumps at the helms, a ram and a relief valve. I suspect the pumps are H25s, which according to one spec sheet I have are 2.75 cu in.

Does that mean I can use an EVO-100, good for up to 6.7 cu. in.?

Or do I have to add in the relieve valve, ram, and all the tubing?

 

[refugio]

It's all about the ram, or rams if there are two depending on configuration. You have to move that fluid in the ram to move the rudder(s).

The next variable is how fast you want to move the rudder, usually expressed from hard over to hard over.

The ram capacity is not that hard to calculate even if you do not know its specifications. You can measure the travel by going lock to lock and finding the delta of the extension. The you need the inside cylinder diameter which corresponds to the outside diameter minus cylinder wall thickness.

The helm doesn't move during AP use, but has similar considerations in terms of how many cubic inches it moves per turn of the wheel times the number of turns.


Keith

 

[River Cruiser]

I have the H-50 helm pumps and the K-18 cylinder, the ci of the cylinder is 8.3 if I remember correctly if this helps.


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[CaptTom]

It's all about the ram, or rams if there are two depending on configuration. You have to move that fluid in the ram to move the rudder(s).

Keith

Thanks, I think, based on photos, my ram is a K-22 or K-27, which specs out at 13.3 cu. in. Mapped to Raymarine gear, that requires at least a Type 1 pump (rated up to 14 cu. in.), or maybe a Type 2 at 14-21 cu. in.

In other words, triple the price of an EVO-100 (or more.)

So, I'm back to ComNav, which seems like a fine unit except I don't see any NMEA out options. If I'm going to spend $$ on a heading sensor, it would be nice to have that on my N2K bus, or at the very least, feed it over NMEA 0183 to my chartplotter.

The joys of boat ownership.

PS: Thanks to Ron, too, even though I think my cylinder is a different model. Plus, I just love your signature line. I use it all the time. I was leaning toward one of the Bayliners myself before this Prairie came up.

 

[refugio]

Thanks, I think, based on photos, my ram is a K-22 or K-27, which specs out at 13.3 cu. in. Mapped to Raymarine gear, that requires at least a Type 1 pump (rated up to 14 cu. in.), or maybe a Type 2 at 14-21 cu. in.

In other words, triple the price of an EVO-100 (or more.)

Let me see if I have this right. The smallest Raymarine pump is a Type 0.5 (3.1 to 9 ci) with a street price of about $550. The Type 1 (4.9 to 14 ci) has a street price of $650. But it corresponds to the ACU-200 over the ACU-100, which have street prices of $700 over $350. So a Type 1 / ACU-200 combo is $450 more than the entry level combination. Not sure where the "triple" is coming from.

You don't need to use the Raymarine pump, but if you want a hydraulic autopilot you are going to have to use something equivalent no matter which AP manufacturer you choose. Yes, it's a bummer that the higher "capacity" control units cost more money when the only significant difference is ampacity of the pump circuit, but that's one of the ways the manufacturers segment their markets.

So, I'm back to ComNav, which seems like a fine unit except I don't see any NMEA out options. If I'm going to spend $$ on a heading sensor, it would be nice to have that on my N2K bus, or at the very least, feed it over NMEA 0183 to my chartplotter.

I didn't really look at ComNav, but I'm pretty sure their APs are also NMEA 2000 and should integrate with other NMEA 2000 components like your chartplotter. NMEA 2000 doesn't have an "out" like NMEA 0183, but if you want to network NMEA 0183 devices I think you are better off adding an Actisense NGW-1 (true, it costs $170ish) and getting total control of the sentences.

 

[psneeld]

If trying to stay economical...not sure what heading sensor you want to connect to a chartplotter.

The typical Fluxgate compass is not a precision instrument from my point of view. To use it as a compass backup is only fine if you calibrate it accurately and ensure it doesnt get altered.

Certainly would never use it over GPS heading.

There are better heading sensors...but jump correspondingly in cost.

 

[refugio]

If trying to stay economical...not sure what heading sensor you want to connect to a chartplotter.

The typical Fluxgate compass is not a precision instrument from my point of view. To use it as a compass backup is only fine if you calibrate it accurately and ensure it doesnt get altered.

Certainly would never use it over GPS heading.

There are better heading sensors...but jump correspondingly in cost.

Agreed. The information from the EVO sensor is interesting to the AP - rate of turn and 3-axis positioning - but it's not going to be useful to the plotter. What might be useful is initiating a course from the plotter and having the AP receive steering directions.

The ACU, however, can make use of GPS data (if present) and, more important, rudder position data (again, if present). Rudder angle display on the AP control head (if separate gauge not fitted) is very useful.


Keith

 

[CaptTom]

Great discussion, thanks!!

Not sure where the "triple" is coming from.

In rough numbers, the price went from 1.5 BU to 4 BU, or about 2.6 times more, for a complete kit. I rounded up.

Yes, it's a bummer that the higher "capacity" control units cost more money when the only significant difference is ampacity of the pump circuit, but that's one of the ways the manufacturers segment their markets.[\QUOTE]

Agree on both counts; (1) it is a bummer and (2) these seem to be priced based on what the market will bear, rather than any consideration of cost to produce. I've never bought anything from Raymarine. I've used lots of their equipment, and it's good stuff. I always consider them, but when it comes time to buy, so far I've always ended up with something as good or better, for a lot less.

I didn't really look at ComNav, but I'm pretty sure their APs are also NMEA 2000 and should integrate with other NMEA 2000 components like your chartplotter.

The manual was pretty clear that it's only NMEA 0183. I thought that was odd too. My MFD has an 0183 "out" that I'm not using anyway. But N2K would make it a whole lot easier to swap things around if necessary.

To the rest who pointed out that there's really not much the MFD needs from the fluxgate, I see your point. I know nothing about their latency or accuracy. I know the GPS heading is always a second or two behind, and thought maybe the fluxgate would be better. I wasn't thinking about the rate of turn and multiple axes.

So, it's looking more and more like a ComNav unit in my future.

 

[refugio]

The EV-200 Power (P70R) with Type 1 pump is $2,400 online. You literally would need nothing more except a circuit breaker.


Keith

 

[twistedtree]

I actually think there is great value in a heading sensor fed into a chart plotter.

1) It will allow the plotter (most of them) to display both heading and GOG. A GPS will only ever display COG. The difference of course is set and drift from environmental factors. But if you frequent areas with significant current, being able to see both helps you better understand what's going on, and not wonder why you need to steer for the rocks in order to safely pass clear of them...

2) A GPS will only give you COG when you are moving, and it's accuracy is poorer the slower you are going. In contrast, a heading sensor can always show your heading whether you are moving or not. Without a heading sensor, when your boat is not moving your boat icon (if you are in north up display) or the whole chart (if you are in heads up display) will be spinning all over the place. It's not dangerous, but annoying, and makes things like route plotting impossible if you normally have the display in heads up mode.

3) As previously mentioned, a heading sensor will provide a much more stable and up to date heading than a GPS.

4) Another place where an at-rest heading comes into play is with an anchor alarm. Most plotters have them, and several are available for ipads etc.. I really like being able to see where the boat is within my swing circle, as well as what direction it's pointing, especially as it relates to the wind direction.

5) Oh, and there is another use. If you have a wind sensor, with a good heading sensor you can then display ground wind which, on a trawler, I think is more relevant than apparent wind.

But there is no reason why you can't connect the AP heading sensor to both the AP and the plotter. Unless it's a really old heading sensor that uses AT10 or some other sine/cosine output, it will emit heading in 0183 or N2K, and can be wired to both the AP and plotter. Worst case, an 0183 to N2K converter may be needed.

 

[psneeld]

I agree a digital heading sensor is nice for many reasons.

Just the cheapest ones may or may not hook up and work so nicely.

 

[johnrupp]

The EV-200 Power (P70R) with Type 1 pump is $2,400 online. You literally would need nothing more except a circuit breaker.


Keith

Raymarine has a $300 rebate on the EV-200 system through the end of April.

 

[refugio]

Raymarine has a $300 rebate on the EV-200 system through the end of April.

Yes, I forgot - I got $300 rebate on mine too. I don't see a lower cost option being possible.


Keith

 

[refugio]

Fair enough on heading stabilizing plotter in Course Up. I get apparent (and true) wind from my Airmar 200WX and hadn't considered that a plotter might do those calcs - is that common?


Keith

 

[FF]

All this high amp hyd/electric stuff is great fun, BUT


Do you carry an easy to mount emergency tiller in any boat that does NOT have a mechanical steering?

Why not?

 

[CaptTom]

FF makes a good point. Normally, I'd say my twin throttles and clutches are my backup steering. But I admit to being a little nervous about cutting into a 35-year-old hydraulic system to add a pump.

You guys are killing me. I thought I had this figured out. But I have to admit the Raymarine EVO-200 looks like a nice package, and "only" a few hundred ($700-800 to be exact) more than the ComNav, after rebate.

I like the N2K interface, and the ability (for another .5 BU) to add a remote some day.

I don't like the fact that a type 1 pump is rated for "up to" 14 cu. in., and my cylinder is 13.3. Seems to be cutting it close. Then again, I'm likely to be at the helm and throttles myself in rough weather, not using an autopilot, which can't work the throttles.

The other thing I notice is the package doesn't come with a rudder position indicator. The literature implies that's not needed with the fancy multi-axis sensor and computer. But it also contains diagrams which show one. The price of that one component alone would put the whole package so far above the ComNav that I'd have to rule it out.

 

[kulas44]

I consider the rudder indicator to be a very usefull item. It allows me to set my rudders amidship for low speed manuvers with the props/engines. Indespensible.

 

[what_barnacles]

All this high amp hyd/electric stuff is great fun, BUT


Do you carry an easy to mount emergency tiller in any boat that does NOT have a mechanical steering?

Why not?

I do, well I should say the PO did. I havent carried anything out past the slip yet.

 

[refugio]

But I have to admit the Raymarine EVO-200 looks like a nice package, and "only" a few hundred ($700-800 to be exact) more than the ComNav, after rebate.

After rebate and minus the pump (which of course could be any 12vdc reversing pump of an appropriate capacity and would be the same no matter what the AP manufacturer) the Raymarine EV-200 is $1,450 for the EVO sensor, ACU-200, and P70R.

I cannot figure out what equivalent ComNav package you are considering that would cost only $750 total ($1,450 minus your $700).

The RayMarine can function without a rudder position, but this would be a poor optimization. So let's add a rudder reference (the RM unit is $230).

So...an EV-200 with Type 1 pump and rudder ref are net (after rebate) $2,330. And that compares to the ComNav 1500 with 5-14 ci pump and rudder feedback for...$3,579 online. True, you get your legacy NM0183 with the ComNav, but that's because (and this surprised me) it does not support NMEA 2000.

What ComNav package are YOU looking at?

 

[twistedtree]

I assume you have looked at the Furuno NavPilot and ruled it out, probably because of cost? It's a good pilot and has both N2K and 0183 interfaces. But I'm not sure how the pricing compares. Probably more than you are looking for.

 

[CaptTom]

I'd love to see better pricing. Here are the best prices I've been able to find for each system (the GPS Store dot com and Defender):

Not counting shipping, that's a difference of $718.96.

I haven't found a huge difference in the pump costs, they all seem to be in the $500-700 range. The problem is, the Type 1 that Raymarine says works with the EVO-200 just barely meets the specs. Their documentation seems to suggest that if you use a Type 2, you need to go up to the EVO-400 (or whatever is the next size up), which is significantly more expensive. The ComNav pump specs puts my cylinder well within their pump's recommended range.

I'll go look at Furuno again, too. I usually like their stuff even better than Raymarine, but again I usually have trouble justifying the premium based on functionality.

 

[FF]

"justifying the premium based on functionality."

There is always reliability to consider.