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Old 13-05-2013, 05:49   #16
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Re: Autopilot advice

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Originally Posted by s/v Jedi View Post
Navigating to a waypoint requires a chart plotter and somebody plotting a waypoint on that, activating a goto for it and then acknowledge it on the autopilot. This is also supported by the simrad and called Nav Mode. But it isn't what I mean. I mean AP only. Normally you point the bow to a heading and switch the pilot to Auto mode to maintain this heading. All AP's support that. With the Simrad and this magic mode, you point the bow not to a heading, but physically where you want to go, like in between the piers of a harbor entrance and then activate this mode. No plotter needed/used. But it does need positioning data on the N2K bus.
They call this "No Drift Course" mode.

I would say the preferred heading sensors are Maretron, Airmar, Simrad, in that order, although I understand it when you swap Airmar with Maretron I don't kniw whi all have rudder oosition sensors for N2K but Simrad have a nice one and Maretron has a converter for old sensors based on resistance value (which is not the older non-N2K Simrad which is based on frequency).
I can't quite imagine why "No Drift Course" would be very useful, but I'll give it a try. If you're going to force your pilot to stay on a rhumb line, I would think you would want to see exactly where that rhumb line goes on your plotter.

As to rudder sensors -- I am not using an N2K one. I bought the regular Simrad RF300. It was easier and much cheaper to pull a simple shielded twisted pair from the lazarette to the nav table, than to pull an N2K cable -- it's about 15 meters. When I was making this decision, I was advised by Navico that there is no functional difference.

As to heading sensors -- why do you prefer the Maretron ones? The specs are decidedly worse than then Airmar one, the difference being that the Airmar compensation is all three-dimensional, whereas the Maretron is not. Even the Simrad guy told me (off the record) to forget the Simrad heading sensors; that nothing competes with the Airmar other than a satellite compass. See: http://www.airmartechnology.com/uplo...res/h2183.pdf; Panbo: The Marine Electronics Hub: Airmar H2183 compass, best in class?.
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Old 13-05-2013, 06:22   #17
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Quote:
Originally Posted by Dockhead View Post

I can't quite imagine why "No Drift Course" would be very useful, but I'll give it a try. If you're going to force your pilot to stay on a rhumb line, I would think you would want to see exactly where that rhumb line goes on your plotter.

As to rudder sensors -- I am not using an N2K one. I bought the regular Simrad RF300. It was easier and much cheaper to pull a simple shielded twisted pair from the lazarette to the nav table, than to pull an N2K cable -- it's about 15 meters. When I was making this decision, I was advised by Navico that there is no functional difference.

As to heading sensors -- why do you prefer the Maretron ones? The specs are decidedly worse than then Airmar one, the difference being that the Airmar compensation is all three-dimensional, whereas the Maretron is not. Even the Simrad guy told me (off the record) to forget the Simrad heading sensors; that nothing competes with the Airmar other than a satellite compass. See: http://www.airmartechnology.com/uplo...res/h2183.pdf; Panbo: The Marine Electronics Hub: Airmar H2183 compass, best in class?.
It is so handy because I don't use the plotter all the time. Let's say I'm leaving the marina; I don't plot waypoints through the marina! But there is only two of us, so I do go and help Josie to get fenders and lines taken care of. So, I exit the slip, point the bow to the marina entrance, press the button and go forward to help with engine in dead slow fwd. People are looking like it's magic that Jedi does not turn into a dock or another boat and that she turnes into the wind a bit when a gust comes and tries to blow the bow away. They don't even realize that the Simrad is at the helm already!
There is more; when you have a bow thruster, you can also connect that to the Simrad pilot and it will start using it to maintain course in very slow speeds. It's freaky.

About the heading sensors:

SSC200 - NMEA 2000® / NMEA 0183 Solid State Compass
Maretron's SSC200 is a solid state, rate gyro electronic compass that provides better than 1° heading accuracy through ±45° of roll and pitch angle, and better than 1° roll and pitch accuracy in static conditions. Each SSC200 is factory calibrated for maximum accuracy. It delivers precise, reliable heading information ten times per second, plus vessel attitude including pitch and roll readings once per second. A micromachined rate gyro is used by advanced stabilization algorithms to provide accurate, stable readings during dynamically changing conditions such as hard turns or rough seas, making it an ideal heading sensor for autopilot applications.
Maretron's SSC200 is certified to the NMEA 2000® network standard and compatible with the NMEA 0183 digital interface standard. It connects directly with any NMEA 2000® network and/or NMEA 0183 listeners to share information with navigational software, chart plotters, autopilots, and dedicated instrument displays – including Maretron's N2KView® vessel monitoring system, or Maretron's DSM150/DSM250 color graphics displays.

The SSC200 can be automatically calibrated for deviation. Its dynamic accuracy is improved with advanced digital filtering of the 3-axis magnetometer, 2-axis accelerometer and rate gyro.
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Old 13-05-2013, 07:10   #18
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Nick your a bit of a fanboy really.

Having sailed in boats with Simrad, Garmin , and newer rate stabilised Raymarine. I'd say there's little to choose based on performance. I usually use stern quartering seas as a test and all modern APa handle this now quite well. Better the most HelmMens too.

It's really a bigger choice as to your preferred system rather then an AP.

I was quite impressed by garmins unit given its the cheapest

Dave
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Old 13-05-2013, 07:19   #19
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Re: Autopilot advice

Quote:
Originally Posted by s/v Jedi View Post
It is so handy because I don't use the plotter all the time. Let's say I'm leaving the marina; I don't plot waypoints through the marina! But there is only two of us, so I do go and help Josie to get fenders and lines taken care of. So, I exit the slip, point the bow to the marina entrance, press the button and go forward to help with engine in dead slow fwd. People are looking like it's magic that Jedi does not turn into a dock or another boat and that she turnes into the wind a bit when a gust comes and tries to blow the bow away. They don't even realize that the Simrad is at the helm already!
There is more; when you have a bow thruster, you can also connect that to the Simrad pilot and it will start using it to maintain course in very slow speeds. It's freaky.

About the heading sensors:

SSC200 - NMEA 2000® / NMEA 0183 Solid State Compass
Maretron's SSC200 is a solid state, rate gyro electronic compass that provides better than 1° heading accuracy through ±45° of roll and pitch angle, and better than 1° roll and pitch accuracy in static conditions. Each SSC200 is factory calibrated for maximum accuracy. It delivers precise, reliable heading information ten times per second, plus vessel attitude including pitch and roll readings once per second. A micromachined rate gyro is used by advanced stabilization algorithms to provide accurate, stable readings during dynamically changing conditions such as hard turns or rough seas, making it an ideal heading sensor for autopilot applications.
Maretron's SSC200 is certified to the NMEA 2000® network standard and compatible with the NMEA 0183 digital interface standard. It connects directly with any NMEA 2000® network and/or NMEA 0183 listeners to share information with navigational software, chart plotters, autopilots, and dedicated instrument displays – including Maretron's N2KView® vessel monitoring system, or Maretron's DSM150/DSM250 color graphics displays.

The SSC200 can be automatically calibrated for deviation. Its dynamic accuracy is improved with advanced digital filtering of the 3-axis magnetometer, 2-axis accelerometer and rate gyro.
About the No Drift Course mode: I see now -- that does sound cool. I will give it a try. I don't think I'll wire up my bowthruster to my pilot, however -- that would be just too strange.

About heading sensors: The H2183 does absolutely all of that, plus it has higher dynamic accuracy. Also refresh rate for both heading, and pitch & roll data is faster -- 20 hz -- which ought to be concretely useful for autopilot performance. I have still not heard anything which indicates that the Maretron heading sensor is better in any way other than being cheaper, and cables included (irritatingly, the Airmar is advertised as including cables, but it is delivered without them, and they are expensive).
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Old 13-05-2013, 07:28   #20
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Quote:
Originally Posted by goboatingnow View Post
Nick your a bit of a fanboy really.

Having sailed in boats with Simrad, Garmin , and newer rate stabilised Raymarine. I'd say there's little to choose based on performance. I usually use stern quartering seas as a test and all modern APa handle this now quite well. Better the most HelmMens too.

It's really a bigger choice as to your preferred system rather then an AP.

I was quite impressed by garmins unit given its the cheapest

Dave
I am passed testing stern quartering seas. It is well known which pilots do well like you write. So it's down to details. You sailed with a Simrad pilot but apparently didn't find those extra features that make the difference

I find Simrad cheap actually. I would want to go any cheaper.
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Old 13-05-2013, 07:28   #21
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Re: Autopilot advice

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Originally Posted by goboatingnow View Post
COG in a small boat is far too damped to be of any use whatsoever in an autopilot,

dave
Our GPS provides position and speed data 5 times per second. Surfing waves, the GPS SOG keeps up with the knotmeter. I have to turn up damping on the position displays so that the projected COG line isn't moving so quickly.

Mark
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Old 13-05-2013, 07:39   #22
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Re: Autopilot advice

Quote:
Originally Posted by Dockhead View Post
About the No Drift Course mode: I see now -- that does sound cool. I will give it a try. I don't think I'll wire up my bowthruster to my pilot, however -- that would be just too strange.

About heading sensors: The H2183 does absolutely all of that, plus it has higher dynamic accuracy. Also refresh rate for both heading, and pitch & roll data is faster -- 20 hz -- which ought to be concretely useful for autopilot performance. I have still not heard anything which indicates that the Maretron heading sensor is better in any way other than being cheaper, and cables included (irritatingly, the Airmar is advertised as including cables, but it is delivered without them, and they are expensive).
I don't use the No-Drift mode much, but love the Wind-Nav mode. This mode steers to a waypoint upwind taking the wind into account. It optimizes VMG and calculates laylines and steers the boat at the best course (and through any wind shifts, current or leeway), then notifies you when it is time tack to make the next layline. After tacking, it optimizes the VMG on the new tack and recalculates the laylines.

Yeah, I know I should be doing this all myself, but when sailing 3-4 days straight, one loses the urge to constantly be at the wheel adjusting course or sails for local wind shifts, and at the chartplotter trying to determine the best time to tack to be on the next layline.

I don't know if the Wind-Nav mode is Simrad-specific or if all others also have it. Our old 1998 B&G certainly did not.

The Airmar heading sensor requires special cables? Isn't it just straight N2K that can use the cabling in place?

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Old 13-05-2013, 07:39   #23
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Quote:
Originally Posted by Dockhead View Post

About the No Drift Course mode: I see now -- that does sound cool. I will give it a try. I don't think I'll wire up my bowthruster to my pilot, however -- that would be just too strange.

About heading sensors: The H2183 does absolutely all of that, plus it has higher dynamic accuracy. Also refresh rate for both heading, and pitch & roll data is faster -- 20 hz -- which ought to be concretely useful for autopilot performance. I have still not heard anything which indicates that the Maretron heading sensor is better in any way other than being cheaper, and cables included (irritatingly, the Airmar is advertised as including cables, but it is delivered without them, and they are expensive).
I have heard that the Airmar sensor is supposed to be better. But at an accuracy better than 1 degree, how does the Airmar beat that? Better than 0.5 degree? Or dynamically beyond 45 degrees roll and pitch? I don't need that.

I'm sure the sensors used in airplanes are better again, but I also don't need that. For heading update frequency; 20 Hz... I didn't know that and agree it would make a difference. But I am not sure if AP's and plotter/radars use anything beyond 10Hz. I think they state 10Hz but maybe a new Furuno Vision or what's it called may take (use) 20Hz. Then, when I see how little my AP ever moves the rudder, I don't think it can be improved.

BTW, Dave, did you ever compare rudder movement between AP's? The Simrad is unreal, never saw anything steer like it does with minimum rudder movements... Which means minimum power usage. Yes, fanboy may be, I am
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Old 13-05-2013, 07:48   #24
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Our GPS provides position and speed data 5 times per second. Surfing waves, the GPS SOG keeps up with the knotmeter. I have to turn up damping on the position displays so that the projected COG line isn't moving so quickly.

Mark
Yep, my Maretron GP200 is 32 channel 5Hz but I guess we have the same kit

A lot of people are still tuned into the old generation of electronics, where you get position once every second or 2 or worse. Times have changed, more sats in the sky. I recently had 18 sats in use (GPS and GLONASS) on my silly iPhone.

My old B&G compass did one heading update every 2 seconds I think. Sleep well
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Old 13-05-2013, 07:51   #25
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I don't use the No-Drift mode much, but love the Wind-Nav mode. This mode steers to a waypoint upwind taking the wind into account. It optimizes VMG and calculates laylines and steers the boat at the best course (and through any wind shifts, current or leeway), then notifies you when it is time tack to make the next layline. After tacking, it optimizes the VMG on the new tack and recalculates the laylines.

Yeah, I know I should be doing this all myself, but when sailing 3-4 days straight, one loses the urge to constantly be at the wheel adjusting course or sails for local wind shifts, and at the chartplotter trying to determine the best time to tack to be on the next layline.

I don't know if the Wind-Nav mode is Simrad-specific or if all others also have it. Our old 1998 B&G certainly did not.

The Airmar heading sensor requires special cables? Isn't it just straight N2K that can use the cabling in place?

Mark
Yes, Wind-Nav mode. Other pilots are proud of their Wind mode and don't even realize what Simrad put in with laylines math etc. It is completely freaked out and no way I do that myself anymore. When I did, I always tacked too early because I was afraid to tack too late and loose a couple of seconds.
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Old 13-05-2013, 08:23   #26
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Re: Autopilot advice

I installed a Garmin GHP 10 on my 28,000 lb displacement boat and could not be happier. To save money I used my old Ratheon type 1 drive unit with plans originally to replace with larger unit, I don't think I have too, it rides like I am on rails on the heading hold setting.

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Old 13-05-2013, 08:33   #27
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Re: Autopilot advice

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I'm sure the sensors used in airplanes are better again, but I also don't need that. For heading update frequency; 20 Hz... I didn't know that and agree it would make a difference. But I am not sure if AP's and plotter/radars use anything beyond 10Hz. I think they state 10Hz but maybe a new Furuno Vision or what's it called may take (use) 20Hz. Then, when I see how little my AP ever moves the rudder, I don't think it can be improved.
The standard Simrad rate compass has a 20Hz update frequency, so I assume the Simrad AP uses that.

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Old 13-05-2013, 10:14   #28
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Re: Autopilot advice

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I don't know if the Wind-Nav mode is Simrad-specific or if all others also have it. Our old 1998 B&G certainly did not.
To clarify this, the Simrad also does standard wind mode, where it steers to an apparent or true wind angle (user selectable) or an auto wind mode - where it automatically switches from using apparent wind ahead of the beam and true wind aft of the beam and automatically switches the response time to higher response downwind. In all wind modes there is a tack and jibe prevention function that can be used (and really works). I don't know if others can even do this beyond apparent wind - our old B&G would only steer to apparent wind and we would never use it in really deep wind angles for fear of jibing.

Wind-Nav mode is an separate upwind mode where the pilot optimizes VMG and calculates laylines. It tells you when you can tack to make the next layline and reoptimizes VMG on the new tack.

It would be nice to have the downwind version of this that calculates jibe angles and lines, but I guess that would require polars to really work.

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Old 13-05-2013, 10:30   #29
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Did we already touch the subject of the Simrad pilot being able to follow a depth contour? I think not. Let's say you have a long long coast line with shallowing waters, like the Atlantic coast of South America. You want to follow that coast line. Now you can just tell it which side of the boat is the shallow side and which the deep and it will follow that line. Switch to fishing profile for that one.
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Old 13-05-2013, 10:31   #30
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The standard Simrad rate compass has a 20Hz update frequency, so I assume the Simrad AP uses that.

Mark
Hmm.. I got old fashioned gear
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