Raymarine Autopilot

bcassal · Posted: Tue Dec 18, 2012 12:03 am Post subject: Raymarine Autopilot

I'm hoping the collective wisdom here will help me resurrect my autopilot.
I have a 2001 ST8001 control unit with a M81188 Linear Rudder Positioning Sensor. The thing has been wonderful when its working. I use it mostly crossing big water and the auto steeris great to relax a bit at the helm. For sometime now it has been suddenly veering off course and recently so often that I have quit using it. I've been on the horn to Raymarine and the rudder sensor is not up to specs and needs to be replaced ($300).
The fluxgate compass ($200) is boarderline. It has always been a bit dodgy. It varies from the GPS by varying degrees, sometimes a lot. Calibration has gotten it within a few degrees of it's allowable deviation, no better. I suspect its location may be the problem. It is mounted on the aft starboard bulkhead under the Wallace and within a foot of a washdown pump and set of Magma nesting pots. I'm thinking of moving it under the aft port seat, over the water tank. Has anyone had success with this. I don't see too many options. Any suggestions would be helpful.
Judging from comments on this site these things seem to be troublesome and I'm wondering about about pouring more $$ into it.
Any suggestions would be helpful.
Thanks in advance.

Carpy
Bruce Cassal

SeaSpray · Posted: Tue Dec 18, 2012 12:48 am Post subject:

Hi Bruce,
I have a similar unit but 2004 St9001. I have the same problem with the linear transducer.There is an after market transducer that is less money. Don't remember the name right now. My fluxgate is in the same place as yours but I keep my pans and other metal things out of that area.

I plan to replace the transducer for next summer.

Steve

starcrafttom · Posted: Tue Dec 18, 2012 2:06 am Post subject:

I had the same problem with the same unit mounted the same way. After a lot of work and re calibrating many times I broke down and sent it to raymarine. It was a bad board in the unit. A on going problem that they had knowledge of. I sent it into them and had it back with in a week with no problems since. I hate that I cant fix things my self some times but hey I did not have a new board just sitting around. Just send in the black box and get back on the water/

Sea Angel · Posted: Tue Dec 18, 2012 8:09 pm Post subject:

Sea Angel has the same units and had to send my SMARTPILOT back for repair. It was some of the caps on the board that had dried out prematurely. It, too, would not hold the calebration setup.

As to the Fluxgate unit, I had mine mounted on the bulkhead under the helm footrest/floor. I make sure there aren't any metal items within the storeage, only plastic containers.

If you are sitting at the dock and running only on thebattery, turn the helm slowly from one limit to the other and watch the rudder position display on the controller. It should follow smoothly as the helmm moves throught its range. If the disply "jumps" to a maximum or minimum reading, then it either has adirty or worn spot on the positiing sensor.

Good luck and may you have a healthy, prosperious and happy new year.
Merry Christmas and a belated Happy Hanukka.

Art

hardee · Posted: Wed Dec 19, 2012 1:48 am Post subject:

Not sure of all the problems, but the fluxgate compass is a metal seeking device. I had some issues with mine at first. Didn't even kow the thing was there for a while. Then, realizing I was have strange responses, I went looking. Had a whole bag of tools right in the drawer under the compass. Moved all that, and it is working fine now.

I would move it to the forward edge of the aft wall, above the water tank, and keep the steel tools out of that drawer. It will work much better. Mine sure did.

Harvey
SleepyC Moon

rogerbum · Posted: Wed Dec 19, 2012 6:44 am Post subject:

Sea Wolf · Posted: Wed Dec 19, 2012 11:09 am Post subject:

ROGER-

Regarding your few degrees of compass error:

Is the magnetic compass sensor gimballed?

I know it has a fluxgate type sensor, sensing the magnetic pole(s) (fields, really) through the difference in field detected between two coils set at 90 degrees to each other.

If it's not gimballed, would the difference in angle sensed be off by a few degrees when the boat is on plane vs. at displacement speeds or at rest?

Remember that the magnetic poles are not on or at the North Geographic poles but deep under the Earth's surface up towards Northern Canada. (It's really a three dimensional magnetic field, with the axis centered about 10 degrees south of geographic north.)

Might be worth a call to the technical rep from the company that made the compass. If it isn't this , they could suggest others! Laughing

Joe.

Sea Wolf · Posted: Wed Dec 19, 2012 12:57 pm Post subject:

Roger-

Upon further thinking, the coils may be 3 instead of two, all set at 90 degrees to each other. Therefore, gimballing may not be necessary, or could be generated for/created electronically.

I'm also sure there is some electronic dampening taking place to allow for wave action.

Still, there might be some shift in the relative position due to the boats difference pitch on and off plane, but ……{how much)…..?

Curious problem!

Joe. Teeth

tpbrady · Posted: Wed Dec 19, 2012 1:28 pm Post subject:

Joe,

You are always thinking, good on ya. Magnetic anomalies in boats are tough to diagnose. Just putting the Iphone under the front window changes my compass. Mounting the fluxgate higher would seem to help since it is further away from most magnetic influences in the cabin. The only thing to watch for there is that you are also closer to the VHF antennas and radar scanners on many boats. The one test I do to check on the effects of various devices on a compass is to take a hand held compass and check for changes in the compass as I move it around the cabin.

Tom

rogerbum · Posted: Wed Dec 19, 2012 1:29 pm Post subject:

Joe,

I'll have to look into how the device is made. From the outside, it doesn't appear to be gimbaled. It's just plastic box attached to a flat surface (whose pitch changes depending on speed of the boat). You could be correct in that the compensation is angle dependent due to the design and angle relative to the earth's magnetic field. I hadn't thought about that. Regardless, I still plan to move it from the current location to someplace up high and away from both other metal and potential changes due to people moving cargo around. I think the ceiling is a good location.

Sea Wolf · Posted: Wed Dec 19, 2012 1:48 pm Post subject:

Tom, Roger-

Yes, you're probably right in that all that s needed is a better location on the boat, and finding that will be the key.

I had a KVH Sailcomp electronic compass that I mounted on two different dinghy sailboats I raced. It had a few compensatory adjustments for where and how it was to be used, but I don't remember exactly. Other than a couple of adjustment screws and two power input wires, however, it was completely sealed.

Still and all, it's fun to speculate into the workings of the "black box" and imagine how it works. Would be fun to really engineer one in real life and time! CoolSmile

Joe.

Sea Angel · Posted: Wed Dec 19, 2012 3:25 pm Post subject:

A few other items I overlooked. Embarassed

1. The Fluxgate Unit has a note on it saying basically 'this side up'.
2. Locate the unit as close to the Center of Gravity as possible to minimize errors.
3. When I suggested the testing of the Rudder Position Sensor, I neglected to suggest that you could engage the AP and use the course correction "+/_" buttons to drive the hydraulic pump as a means to 'test' the system.
4. By all means keep any items that contain any ferrous/iron material at least 3' away from the FluxGate Sensor Unit, much like you would your Secondary Magnetic Compass.

Art

Sea Wolf · Posted: Thu Dec 20, 2012 12:25 pm Post subject:

BrentB · Posted: Thu Dec 20, 2012 2:34 pm Post subject:

thanks, Joe

fascinating

bcassal · Posted: Fri Dec 21, 2012 11:31 am Post subject:

I have run specs on the rudder sensor and the compass and according to Raymarine they are acceptable. I have also removed the compass from the boat and attached it to a wall in the shop with no metal nearby and get the same resistance readings. The next step is to send the computer to Raymarine and get it checked out. I'll see what they find.
Interesting information on electronic compasses. I appreciate all of your input.
Thanks,
Carpy.