Simrad MFD - course and heading do not align.

[mvweebles]

There is a bit more to the story. The change 25-degree variance coincided with an increase in throttle RPM by about 200 RPMs. Now, my engine is an older Perkins 4.236 that is 100% mechanical. But as I mentioned in a post yesterday, I had the rudder modified for a fishtail/Schilling that supposedly improves close-quarter maneuvering. Possible the adaptaions are asymmetric. Will check in 10-days when I haul for fresh bottom paint and some punch-list items. I may have the modification reversed as it doesn't really seem to assist much. Was not expensive to do, and hopefully not much to undo.

I have also noted a persistent 2-degree port-rudder on the rudder angle indicator, though that is opposite the cocked-angle of the boat. Definitely could be calibration.

Bottom line is I'll spend some time tomorrow in protected waters of San Diego and calibrate the system. I'll also likely order the SiTex Sat Compass listed a couple posts up.

Peter

 

[mvweebles]

Or just get the Furuno device and be done with it.

This one?

https://www.hodgesmarine.com/furscx20-furuno-scx20-satellite-compass.html

EDIT - here is one of the comments/reviews - thoughts?:

I have not installed it on my boat, yet. I did connected it in variable power supply at home, and tried to configure it. To my surprise I found out that configuring it with equipment other than Furuno, I have all B&G equipment, it requires a CAN BUS reader. I ended up purchasing the Actisense NGT-1 to get it done. Once the Actisense was configured, software updated, and port assigned, it was easy to access the SCX20 and see its functionality.
​

Peter

 

[Hippocampus]

May not be a fixed metallic object but rather a magnetic field that varies in strength and size as the boat is operated. Before blowing boat bucks maybe take another walkthrough with that in mind.

 

[Jc180]

There is a bit more to the story. The change 25-degree variance coincided with an increase in throttle RPM by about 200 RPMs. Now, my engine is an older Perkins 4.236 that is 100% mechanical. But as I mentioned in a post yesterday, I had the rudder modified for a fishtail/Schilling that supposedly improves close-quarter maneuvering. Possible the adaptaions are asymmetric. Will check in 10-days when I haul for fresh bottom paint and some punch-list items. I may have the modification reversed as it doesn't really seem to assist much. Was not expensive to do, and hopefully not much to undo.

I have also noted a persistent 2-degree port-rudder on the rudder angle indicator, though that is opposite the cocked-angle of the boat. Definitely could be

Bottom line is I'll spend some time tomorrow in protected waters of San Diego and calibrate the system. I'll also likely order the SiTex Sat Compass listed a couple posts up.

Peter

Am familiar with the Becker Shilling rudder. Essentially a sailboat rudder shape and is symmetrical. We have a motor sailer (essentially a trawler with sails) that has a sailboat rudder, powered by a Perkins 6.354. 200 rpm change has no effect on course.

The 2 degree port rudder position indication could be an adjustment of attachment rod, not software calibration. The Simrad set up routine does ask you for a center rudder position, but this does not affect the actual position indication.

Suspect your not up for another venture out into the ocean to check to see if caused by current. 25 degree delta COG to magnetic heading is a lot, but would be typical if set abeam by current. I experience a similar delta with 6 knot forward boat speed and an average 2 knot current on the beam.

 

[mvweebles]

Am familiar with the Becker Shilling rudder. Essentially a sailboat rudder shape and is symmetrical. We have a motor sailer (essentially a trawler with sails) that has a sailboat rudder, powered by a Perkins 6.354. 200 rpm change has no effect on course.

The 2 degree port rudder position indication could be an adjustment of attachment rod, not software calibration. The Simrad set up routine does ask you for a center rudder position, but this does not affect the actual position indication.

Suspect your not up for another venture out into the ocean to check to see if caused by current. 25 degree delta COG to magnetic heading is a lot, but would be typical if set abeam by current. I experience a similar delta with 6 knot forward boat speed and an average 2 knot current on the beam.

Will be headed back to Ensenada (70-nms) on Sunday so will have another chance to see. I am familiar with the Davidson Current - I was probably knocked by it by 0.5 kt or so headed north the other day. I do not believe it would affect steering to the extent shown in the picture I took. But right now, not ruling anything out.

BTW - I do not have a traditional hydraulic ram for steering, but an older style "T-Ram" from Wagner. It is used on commercial vessels - here is a schematic that shows the device. https://wagnerengineering.ca/category/model-t-actuators/legacy/t3

THanks for the good ideas - very helpful.

Peter

 

[Jc180]

Comment on the shilling rudder. As with any rudder needs boat speed through the water to be efficient. Doubt prop wash enough at slow speeds (such as docking maneuvers) to make a difference. So agree would be hard to notice much difference at slow speeds. As speed increases a little, should begin to notice.

 

[Jc180]

Will be headed back to Ensenada (70-nms) on Sunday so will have another chance to see. I am familiar with the Davidson Current - I was probably knocked by it by 0.5 kt or so headed north the other day. I do not believe it would affect steering to the extent shown in the picture I took. But right now, not ruling anything out.

BTW - I do not have a traditional hydraulic ram for steering, but an older style "T-Ram" from Wagner. It is used on commercial vessels - here is a schematic that shows the device. https://wagnerengineering.ca/category/model-t-actuators/legacy/t3

THanks for the good ideas - very helpful.

Peter

I have the older Simrad Rf300 rudder position instrument. It is mounted independent of the hydraulic ram and is connected to the rudder arm by an adjustable all thread rod. To adjust, must manually center the rudder and then adjust rod connection length to get zero indication on mfd or indicator.

Trip back to Ensenada will be an excellent opportunity to see what’s happening.

Again, not a Pacific Ocean guy. But a brief look at your currents, not the Davidson Current, but an eddy off of the California Current. Looks like Davidson starts a little north of that eddy. In any event, would be a current on the beam, think west to east, not a current due north or south. So your deviation should be to the opposite direction since now headed south (previous trip headed north).

Good luck in solving the mystery.

 

[twistedtree]

This one?

https://www.hodgesmarine.com/furscx20-furuno-scx20-satellite-compass.html

EDIT - here is one of the comments/reviews - thoughts?:

I have not installed it on my boat, yet. I did connected it in variable power supply at home, and tried to configure it. To my surprise I found out that configuring it with equipment other than Furuno, I have all B&G equipment, it requires a CAN BUS reader. I ended up purchasing the Actisense NGT-1 to get it done. Once the Actisense was configured, software updated, and port assigned, it was easy to access the SCX20 and see its functionality.
​

Peter

The unfortunately reality of N2K. But I'll bet the Sitex device is the same way. I'm pretty sure all of them are made by Hemisphere GNSS.

 

[twistedtree]

Again, not a Pacific Ocean guy. But a brief look at your currents, not the Davidson Current, but an eddy off of the California Current. Looks like Davidson starts a little north of that eddy. In any event, would be a current on the beam, think west to east, not a current due north or south. So your deviation should be to the opposite direction since now headed south (previous trip headed north).

Good luck in solving the mystery.

It would take a heck of a cross current to give you a 25 deg yaw.


When this happened, visually, was the boat pointing in the direction of the indicated COG, or was it pointing according to the indicated heading?

 

[klee wyck]

+1 on the satellite compass. Slam dunk. Libra is steel so I really have no choice, but also have the SC20 on DOMINO(frp) and it performs very well.

 

[mvweebles]

When this happened, visually, was the boat pointing in the direction of the indicated COG, or was it pointing according to the indicated heading?

Assume you're talking to me about the change with RPMs. Boat made a noticeable steering correction to port, then swung back to starboard to settle back into course. Boat remained pointed to waypoint, but bearing line showed the 25-degrees to port; and on chart plotter, boat was crabbing with stbd forward quarter pointed to waypoint target.

To be clear, boat pointed correctly. Icon on chart plotter and track line on radar was incorrect. Everything was correct until I increased RPMs, then went 25-degrees wonky. I power-cycled the system and never returned to normal. I could replicate the error by goosing RPMs - same steering correction happens. I plan to take a video of it tomorrow.

Sorry for the dribble of info. When I first posted, I had not correlated the events. I cannot fathom how they would be related - correlation but cannot figure out causation. Frustrating. POssible the RPMs and steering are unrelated.

Peter

 

[ofer]

Or just get the Furuno device and be done with it.

+1
the Furuno SCX 20 nema 2k version it the top unit for only a couple of hundred more than the sitex. it has quad GPS heads, comes with a cable that only needs to be connected to the nema 2k bus.

 

[Jc180]

It would take a heck of a cross current to give you a 25 deg yaw.


When this happened, visually, was the boat pointing in the direction of the indicated COG, or was it pointing according to the indicated heading?

So during my Gulf Stream crossings going almost due East from Florida to the Bahamas, I intentionally have autopilot steer to a course about 20 miles south of arrival way point. So the boat is pointed to the indicated heading, but actual Course Over Ground (COG) is at an angle to heading due to current on beam. My boat speed is 6 knots to heading with average 2 knot current taking me 90 degrees to heading. When you think about it, have a force 1/3 the speed of forward motion pushing the boat sideways, so 25 degree delta reasonable.

Alternatively, I could ask autopilot to steer to way point, in which case it would result in the same heading because it would be steering to COG. I’m just old school, want to be in control, not autopilot.

So this is really a slow trawler speed discussion. Those of you who travel double digit speeds, conversation irrelevant.

 

[Jeff F]

I think the early advice you got here was spot on. Check for objects and cables close to the compass, then go through the complete commissioning setup. That will include swinging and calibrating the compass and centering the rudder indicator, confirming rudder limits, etc.

I can appreciate the features of the sat compass, but in your case it's not clear yet that it's a necessary step.

 

[Hippocampus]

Remain concerned about what you said about rpm and the problem. Question in my mind is whether they’re related or not. If not related go get a sat compass and be done with it if you can’t fix it. You actually cruise. Having any unreliability in this system is unacceptable.
If they are related then something related to engine rpm is developing a large enough magnetic field to effect your readings.
You did a huge amount of work with your refit. Is there any possibility some thing was moved or added that could be causing this?
No question the sat compass is a better device. But we got by without them for generations. Also wonder if your flux gate can be removed from the boat and be bench tested.. either something is broken or something changed.

 

[FWT]

Assume you're talking to me about the change with RPMs. Boat made a noticeable steering correction to port, then swung back to starboard to settle back into course. Boat remained pointed to waypoint, but bearing line showed the 25-degrees to port; and on chart plotter, boat was crabbing with stbd forward quarter pointed to waypoint target.

To be clear, boat pointed correctly. Icon on chart plotter and track line on radar was incorrect. Everything was correct until I increased RPMs, then went 25-degrees wonky. I power-cycled the system and never returned to normal. I could replicate the error by goosing RPMs - same steering correction happens. I plan to take a video of it tomorrow.

Sorry for the dribble of info. When I first posted, I had not correlated the events. I cannot fathom how they would be related - correlation but cannot figure out causation. Frustrating. POssible the RPMs and steering are unrelated.

Peter

Not sure I really understand the crabbing issue you report, but I will mention something I saw.

I said my own system calibration got out of whack. One of the things that happened was within the system the helm center got shifted from 0 degrees to something way off. Hit the button to hold course heading and it would make a hard turn. Recalibrating the auto pilot fixed it.

Calibrating the compass and calibrating the auto pilot are two different routines. Do both. Before concluding you need new hardware.

 

[mvweebles]

Well, I had success today with the A/P heading issue. To enable radar/chartplotter overlay, Simrad requires a secondary compass (C-25 if I recall). I added this and for some reason, this compass was selected as the steering compass for the A/P. When I reverted to the Precision 9 fluxgate, the problem resolved (well, mostly - I 'fat-fingered' a couple items on rudder calibration that caused some issues). At least for now. I did some additional A/P setup and calibration - the rate of turn was way too fast for my boat and I still need to futz with it.

I still plan to add the sat compass. I was never really satisfied with the location of the Fluxgate - locating these is a problem on any boat and a 36-footer is especially troublesome. There just isn't room.

My wife and I are into the last run of getting ready. I'll start a new thread - sort of a diary. For those entering retirement, might be interesting. Especially those doing so as a couple.

I have to say, I am blown-away by the responses to this thread I started. Many, many thanks.

Peter (and Cheryll)

 

[Hippocampus]

Congrats. Always knew you’d figure it out.

 

[Bacchus]

Peter
Good work on resolving your course issue.
Hope that helps with steering the course into retirement
Congrats on both

 

[psneeld]

Can't speak to every autopilot or much newer ones, but even 20-25 years ago, any old fluxgate compass could operate an autopilot very well. They were just lousy compasses. As long as you didn't move metal objects while following a course or energize nearby untwisted wire pairs, fluxgates work just fine to run an autopilot.

An autopilot used to just need the "change" in magnetic field to run a straight heading and uses GPS if running a plotter course. The pilot may say anything for the "heading" but it would keep the bow of the boat pointed in the same direction when you pushed the button.

There are areas of large magnetic disturbances around the world.... did the chart mention one for that area? Aside from that, it's usually source inputs that drive one nuts as Peter discovered and others mentioned.

 

[twistedtree]

Can't speak to every autopilot or much newer ones, but even 20-25 years ago, any old fluxgate compass could operate an autopilot very well. They were just lousy compasses. As long as you didn't move metal objects while following a course or energize nearby untwisted wire pairs, fluxgates work just fine to run an autopilot.

An autopilot used to just need the "change" in magnetic field to run a straight heading and uses GPS if running a plotter course. The pilot may say anything for the "heading" but it would keep the bow of the boat pointed in the same direction when you pushed the button.

There are areas of large magnetic disturbances around the world.... did the chart mention one for that area? Aside from that, it's usually source inputs that drive one nuts as Peter discovered and others mentioned.

Very true, and begs the question of why they seem so much more problematic today.


I suspect the growth of higher power electrical systems is a big part of it. 20 years ago inverters were rare and/or small. Now they are much more common, higher power, and often retrofit. The result is a lot more high current wiring running around the boat, creating variable magnetic fields as electric loads change. It's harder and harder for a magnetic compass to hide from all that stuff.



Another contributor is that typical nav electronics now depend more on having an accurate heading reading, not just a consistent reading. Things like North up displays on chart plotters and radars require a good heading sensor, or even just a heading stabilized chart display vs COG. And (M)ARPA creates a whole new demand on heading sensors as well.

 

[Hippocampus]

TT totally agree. Would add all the little electric motors for conveniences. Simple things like fans, microwaves, small pumps and such.
We got most of our weather information and did a lot of social chatting on the SSB. Although after final outfitting didn’t add anything nor move anything. Still was putting ferrites in new places to ensure good voice and modem. Still needed to have the exhaust fan for the galley and small overhead fan at the nav station off. Also think it’s not only the compass device but also the cabling that needs to be free of expanding and contracting fields.
If I every got the opportunity to put in a system from scratch again the runs would be as short as possible and inputs dedicated to each device. We did that for AIS, VhF, MFD, and AP and think that helped.
Before passage would still swing the compass, look at deviations we expected to encounter and record expected magnetic courses. Thinking was if we had a power failure or a lightening strike could use the compass and the Hydrovane and not need any electronic device. Also used the computer to develop a great circle and printed that out on paper. Carried a cheap Davis and the books figuring local noon and lower limb of the moon would get us close enough. Fortunately never needed it.
We’re so dependent upon black boxes now and there’s a downside we often forget. Self included as I now no longer carry any paper except what’s in the few cruising guides that aren’t on the iPad.

 

[psneeld]

While true there are many reasons to have top notch sensors...not sure just heading hold on an autopilot demands much more than the trusty old fluxgate....assuming it is a trusty old fluxgate...

Even if the compass was much more accurate, especially on smaller vessels, I doubt the autopilot and steering system plus wind/wave action could come close to matching that precision.

As far as "all" the new systems on newer boats being problematic...not sure it's a big deal. Disturbance from minor magnetic fields isn't all that great especially depending on distance, twisting DC wire pairs help a lot, AC circuits I don't believe are a problem, some things are shielded and others usually not where to mount away from compasses..... having installed quite a few or got calls to investigate.... it was usually user or installer error that was the problem and was pretty easily fixed.

Not trying to make it a big deal, just letting owners with older boats or system know their fluxgate compass shouldn't kill them any quicker than the fancy stuff.... vigilant captain skills are the key to stressless cruising much more so than the older/less expensive equipment.

 

[Hippocampus]

Definitely true for us but not so much for racing sailboats. Look at some of the APs offered now. They have AI inside and can predict course changes caused by the environment. Not only wave actions but headers and lifts are compensated for. Boat steered by them is faster and with a better velocity made good than any human being. A sat compass is a required input. Look at the NKE product line as an example. Such APs integrate with the nav programs and are superhuman.
Some go so far as to include awa, accelerometers, heel angle and such. They’re predicting not reacting so rudder angle is changing before the wave has reached the boat. Just like a good helmsman. Amazing. Still agree for us blowing tens and tens of thousands of dollars for such a thing is foolish. A working fluxgate will serve. But agree with TT a sat compass is a better device.

 

[psneeld]

Again, I live in a different world. 20 yoa autopilots and fluxgate is still good enough for me/ my style cruising/ fishing/ etc.

 

[twistedtree]

Again, I live in a different world. 20 yoa autopilots and fluxgate is still good enough for me/ my style cruising/ fishing/ etc.

I don't mean to say that a fluxgate can't do the job for many. They can, and are used all over the place. It's more a caution that as boats have more stuff on them, especially high current DC devices, it gets harder and harder to find an immune location for a fluxgate.


People should also know that a sat compass will provide a more accurate heading which improves performance of an AP, chart stabilization, and ARPA. Plus you get a higher precision GPS.


Is it a must have? No, not at all. Will it work better? Almost certainly. Will it eliminate magnetic interference problems experienced by a rate compass? Yes.


Hopefully with this info people can make an informed decision about what's best for them.

 

[psneeld]

Agreed.

For me, cost vs benefit has always been an issue, plus with my commercial time the bosses were often frugal with some equipment.

Occasionally I used higher end stuff when I ran oher people's boats.

 

[mvweebles]

Again, I live in a different world. 20 yoa autopilots and fluxgate is still good enough for me/ my style cruising/ fishing/ etc.

This is a good world and I'm not sure it's wise to move past it. My prior Comnav was rock steady and easy to adjust. My Simrad system has a ton more adjustments but I'm not sure they provide much value to my approach to cruising.

I've thought a lot about the complexities I've introduced into Weebles. If I were to start over, there are many "shiney bauble" temptations I'd try harder to resist.

Although I did indeed order a Sat Compass and will have it installed, I am totally unsure of the value it will bring. Could be similar to improving hearing but only in inaudible ranges so net effect is inconsequential.

I will say that going with new nav gear requires a commitment to tinker with settings and layer-down into submenus. I'm okay with that and mildly interested in doing so. A good friend of mine has the attention span of a gnat in a furnace and has zero tolerance for frustration.

Peter

 

[Hippocampus]

This is a good world and I'm not sure it's wise to move past it. My prior Comnav was rock steady and easy to adjust. My Simrad system has a ton more adjustments but I'm not sure they provide much value to my approach to cruising.

I've thought a lot about the complexities I've introduced into Weebles. If I were to start over, there are many "shiney bauble" temptations I'd try harder to resist.

Although I did indeed order a Sat Compass and will have it installed, I am totally unsure of the value it will bring. Could be similar to improving hearing but only in inaudible ranges so net effect is inconsequential.

I will say that going with new nav gear requires a commitment to tinker with settings and layer-down into submenus. I'm okay with that and mildly interested in doing so. A good friend of mine has the attention span of a gnat in a furnace and has zero tolerance for frustration.

Peter

Spot on and also agree with PS it’s important to not conflate the importance of stuff for what you actually do. My main complaint with the big 4 (RM, G, S and F) is there’s an ongoing battle to offer more “features”. I don’t want or use the “features”. They make it more complicated for me to actually bring up the information I do want. It means more to learn and remember or I’ll need to search through documentation at a time I don’t have the time or inclination. So for now I’ll continue with the fluxgate I have. When there’s a malfunction I can’t sort out with go with a sat.

 

[SteveK]

I like and use autopilot just to keep a straight course while I go about looking at other things, talking to others while I look at them. I seldom care what the compass course is or if it is accurate. But then I can see land.
Enter a waypoint lat/long and I expect that it will get me there and not somewhere else.
Out of sight of land I expect gps to be accurate.
Accurate compass course/heading is needed for dead reckoning, (time, speed, course).