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Simrad Nac-2. Problems dialing in settings

Old 11-08-2020, 06:46 PM
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Default Simrad Nac-2. Problems dialing in settings

Have a Simrad GO-9/GO-5, hs60 Headings sensor, Nac-2, and simrad Pump-1.

I seem to be having trouble dialing in my auto pilot. I'm starting to think it has something to do with communication between heading sensor and Nac-2... Seems like there is no consistency, It will occasionally stay within 1-2 degrees of the set heading. Other times it will veer off course by 10 degrees. Some times it will start to correct it self, then continue turning in that direction without turning back to straighten itself out. . I would say it has something to do with counter rudder but this is not consistent. With all that being said, If I use the screen to make turns by pressing +10 in either direction, it seems to react perfectly which I think tells me everything mechanically is working as it should.

This has me wondering if the AP looks at COG or heading when it is keeping you on course? My COG compared to heading seems to be fairly close, within a few degrees of each other. What or where else should I be looking at to fix this?
Old 11-08-2020, 07:39 PM
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The autopilot is steering based on heading. Set the GO heading to True, I recall a post regarding issues when using HS60 and heading set to magnetic, but I don't remember if it was the radar or autopilot which got problems. I have only used True heading with my satellite compasses.

I suspect the problems are caused by rudder and counter rudder settings.
Old 11-08-2020, 07:45 PM
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Originally Posted by abbor View Post
The autopilot is steering based on heading. Set the GO heading to True, I recall a post regarding issues when using HS60 and heading set to magnetic, but I don't remember if it was the radar or autopilot which got problems. I have only used True heading with my satellite compasses.

I suspect the problems are caused by rudder and counter rudder settings.
I have played around with them and still can't seem to get it right, granted I don't have any experience tuning an autopilot so there could be a fair amount of user error involved. Shouldnt the auto tune get me closer then what I am seeing now?
Old 11-09-2020, 06:07 AM
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The auto tuning will for most boats give acceptable performance and I've never heard about anything as bad as your results.

If you take a couple of GO9 screen shots of the autopilot settings and post here it will be much easier to assist.
Old 11-09-2020, 05:22 PM
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I'll try to get some screen shots next time I get down to the boat. Will update then
Old 11-11-2020, 12:18 PM
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Here is what my low and hi speed settings look like after auto tune. I had a chance to talk to simrad while I was on the boat and we changed some settings. Mainly rudder gain. Didn't really solve my problem. The guy with simrad seemed to think the problem was having a single outboard with prop torque. He said it might be the best I'm going to get it. But it will run 10 degrees and only attempt to correct itself when it wants to. At times I would look back and the engine would be steering in the opposite direction of correcting itself. I have a couple thousand bucks into the auto pilot now, and if this is the best it can get, that's not a good look for simrad. Simrads product description says nothing about struggling with a single outboard. I'll post a couple videos when I can showing how bad it's off.


Old 11-11-2020, 12:35 PM
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The Low speed settings are messed up. If the High speed settings are OK a rudder gain of 0.45 and a counter rudder of 1.35 is a good starting point for Low speed.

Last edited by abbor; 11-11-2020 at 12:41 PM.
Old 11-11-2020, 02:20 PM
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Originally Posted by abbor View Post
The Low speed settings are messed up. If the High speed settings are OK a rudder gain of 0.45 and a counter rudder of 1.35 is a good starting point for Low speed.
Neither is really OK. We messed around a good bit with the rudder gains, i believe we set low to .3 or .4. Unfortunately I did not take a picture of the newest settings.

Here are a couple videos. First one shows it turning to starboard more and more, instead of trying to correct the heading to port. Believe it or not, the current was coming from the starboard side, so if anything you would expect the opposite affect:

I set a route on the way back just to see how it would do. As you can see from this video, not very well.:

I appreciate your help, I probably will not get back to the boat until the weekend now. But any input is greatly appreciated. My question is, am I expecting too much from the auto pilot? How tight should I expect it to hold a heading? What do you think about the Simrad techs comment about it being a single engine outboard?
Old 11-12-2020, 08:07 AM
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Forgot to mention.. The Simrad tech mentioned a Smart Stick rudder feedback might help. Anyone have any experience with these? Unfortunately Sea Star says it may not work with a Yamaha engine and a HC5345 cyclinder, which of course is what I have. Debating if its worth giving it a shot, and possible making a bracket to make it fit, or returning it if it does not.
Old 11-12-2020, 08:45 AM
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I don't think your problem is VRF, you need to get the autopilot dialed in. We installed a SmartStick on a friends boat where I wasn't able to get the performance I expected. SmartStick didn't fix the problem, replacing the helm pump later did.

It's challenging to give remote support over internet when it comes to tuning an autopilot, it's so much simpler when you are in the boat. I have one boat with NAC-2/AP44, but it's AC12/AP24 which I'm most experienced with so I don't remember all NAC-2 settings off the top of my head.
Old 11-12-2020, 09:07 AM
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Originally Posted by abbor View Post
I don't think your problem is VRF, you need to get the autopilot dialed in. We installed a SmartStick on a friends boat where I wasn't able to get the performance I expected. SmartStick didn't fix the problem, replacing the helm pump later did.

It's challenging to give remote support over internet when it comes to tuning an autopilot, it's so much simpler when you are in the boat. I have one boat with NAC-2/AP44, but it's AC12/AP24 which I'm most experienced with so I don't remember all NAC-2 settings off the top of my head.
Ok good to know. Curious how the helm pump affects the auto pilot. Isn't it bypassing the helm pump in a sense? But now that you mention that, maybe it is worth noting that I removed some disgusting fluid from the steering lines when I installed the new pump. Wonder if this was the sign of a problem within the system? Hard to say if it was an old problem that may have been fixed by the previous owner, or if the problem is still lingering. With that said, it does seem to make turns fine when I tell it to using the auto pilot commands, just seems to have trouble when it has to do the thinking to hold a heading. Hopefully you are correct and it is something in the settings.
Old 11-12-2020, 10:31 AM
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I Have the exact same problem with my NAC-2, hard to turn left and autopilot tracks off. There is a thread where someone replied that power assist solved his problem. I just installed it and used the boat for the first time with it Tuesday. I didnít have a chance to use the auto pilot but the hard steering to the left is completely gone so Iím hopeful this is going to solve my issue.
Old 11-12-2020, 10:39 AM
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Originally Posted by alex88 View Post
I Have the exact same problem with my NAC-2, hard to turn left and autopilot tracks off. There is a thread where someone replied that power assist solved his problem. I just installed it and used the boat for the first time with it Tuesday. I didnít have a chance to use the auto pilot but the hard steering to the left is completely gone so Iím hopeful this is going to solve my issue.
​​​​​​
I actually remember seeing that post. Considered this being the problem, even bought a torque tab just incase I need it. (Did not install it) but the auto pilot turns left no problem when I hit +10 to port or starboard. Only seems to struggle when it has to think for itself. On that note, the boat does have a decent list to port due to prop torque, but definitely not DIFFICULT to turn left. Does have a different feel when turning left due to prop rotation. It's definitely on my list of possible causes.
Old 11-12-2020, 11:32 AM
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Before I switched to a LFS4 4 blade prop it was just noticeable but after the switch the torque increased a lot. The power assist was definitely more for me than for the auto pilot. But same with me, hitting <10 it responds perfectly, I think the minor corrections for course use much lower voltage than the rough 10 degree manual corrections and why it gets off course when engaged.

now that itís in And I spent a ton of time bleeding and rebleeding the system after the power assist instal, Iím going to recommission the thing all over again and see if Iíve made any progress at all

Old 11-12-2020, 11:38 AM
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Originally Posted by alex88 View Post
Before I switched to a LFS4 4 blade prop it was just noticeable but after the switch the torque increased a lot. The power assist was definitely more for me than for the auto pilot. But same with me, hitting <10 it responds perfectly, I think the minor corrections for course use much lower voltage than the rough 10 degree manual corrections and why it gets off course when engaged.

now that itís in And I spent a ton of time bleeding and rebleeding the system after the power assist instal, Iím going to recommission the thing all over again and see if Iíve made any progress at all
Keep us updated, would like to hear how that works out. Thanks
Old 11-12-2020, 01:38 PM
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Abbor, this may be irrelevant, but I just remembered something that is alittle odd. When setting up the auto pilot it never gave me an option to select "commissioning", nor prompted me to press the standby button while setting it up. I simply went into installation > dockside commissioning. I noticed the difference when watching simrads install video, and the level 1 simrad tech mentioned it to me. Then he transferred me to a level 2 tech, and we kind of forgot about it. Did something change with the newer software or can this indicate an issue with my nac-2 software? Seems like a stupid thing to look into, but you never know
Old 11-22-2020, 05:04 PM
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UPDATE - Installed a torque tamer (beveled shim on the starboard side of the skeg). Made steering much easier to the port, which obviously made it easier for the pump to turn the motor. I guess this accomplished the same thing as installing power steering as mentioned above, but a much cheaper alternative. ( about 30 bucks)

I'm by no means an expert on auto pilot systems, but I am assuming that the computer calculates the amount of time the pump is applied in either direction to keep track of the rudder. Every time it tried to turn to port when on plane, the pump would run, making the computer think that the engine is turned to left even though it didn't have the power to move it. Once that happened, it had no idea where the motor/rudder was positioned. This is what made it a little more complicated then just saying it won't turn to port. It would apply counter rudder after trying to turn to port, and would actually make me turn to startboard.

Thanks for all that helped. Made an update so some one who searches for the same problem may be able to use this info. Too many un answered posts around here.
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