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Catalina/Capri 25/250 Sailor's Forums

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Auto Tiller Compass problem

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Tray
Navigator

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Namibia
224 Posts

Initially Posted - 10/24/2002 : 18:28:58

I'm ashamed to say that I didn't use the ST1000+ auto tiller I installed months ago until last Sunday. But I finally did, and the fluxgate compass in the auto tiller does not come close to my boat's compass. I followed the calibration instructions and set it to match, then after my first course change, the two drifted apart considerably. I reset the tiller again with the same result. I'm not sure if the trouble is in the auto tiller or the boat's compass. I've never used the boat's compass before, so I can't say for sure that it works properly, but I bought it new in January 01.

Has anyone else had trouble with the fluxgate compass?

Tray
C-250WB #554
"Weeny Bean"

Edited by - on

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 10/25/2002 : 02:12:41

Tray,

Do you have any magnetic field issues(metal, engines, radio, speakers, compass...etc) interfering with either the autopilot or compass?

After you've done the calibration for deviation and you've performed the heading alignment to match the compass, are are you holding the "Standby" button until it beeps to save the data?

Furthermore, the manual states that after calibration,

<b>"If the heading requires further adjustment, enter Compass Deviation Correction again by pressing standby for 1 second.

1. Press "auto" to skip Deviation Correction and proceed to Heading Alignment."</b>

Once here you would use the -1/+1 buttons to match the autopilot to the compass then press the standby button until it beeps to save.

Don Lucier, 'North Star'
Catalina

Edited by - on

Brooke Willson
Admiral

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USA
983 Posts

Response Posted - 10/25/2002 : 08:26:58

Tray, I have had this problem with my ST 1000+, and more so since I dropped it, broke the fluxgate, and had it repaired last year. I'm going to try recalibrating the whole thing the next time there's a calm day. The manual calibration, I find, will adjust it for a particular heading, but then if I change tack the heading is wildly at variance with the bulkhead compass.

Basically, I'm learning to ignore the fluxgate readouts. I manually bring the boat to the desired heading, and then punch "Auto." This is especially important when tacking -- the auto tack never was very satisfactory.

As long as the tillerpilot holds a given heading so I can relax, use the head, go forward or below or whatever, I'm satisfied.

In retrospect, this might be an argument for people to buy the Navico tillerpilot, which doesn't offer a fluxgate readout.

Brooke

Edited by - on

Tray
Navigator

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Namibia
224 Posts

Response Posted - 10/25/2002 : 09:12:50

Don,

I did all the things you suggested. No joy. I also verified there was nothing that would interfere with the compass before I installed it.

Brooke,

It sounds like you and I have the same problem. Once steady on a course, I set the tiller pilot's compass to match the boat's, and it matches until I make a course change.

Like you, I'll be content to have it maintain a course, regardless of what the pilot thinks that course is, but I'd hoped for it to perform as promised. The auto-tack function helped sell my wife on letting me spend the boat units for it originally. We haven't tried it, yet, but I sense disappointment looming.

However, if it turns out to be only useful for maintaining course, that would still free us up in the cockpit to do other things.

Tray
C-250WB #554
"Weeny Bean"

Edited by - on

Arlyn Stewart
Master Marine Consultant

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USA
2984 Posts

Response Posted - 10/25/2002 : 11:04:34

I have the St4000 wheel pilot with a remote fluxgate and control head and compass differences occur...though they are not widely seperated, they are also seldom together.

This frustration goes away in part when and if the pilot is linked to a GPS as then track mode is used very often and only the data on the gps is relevant.

However, even when manually helming, when going to a waypoint the course is set to satisfy a non cross track error (straight line) course to the waypoint with the boat usually pointing something different to satisfy leeway. Its then that the compass comes back into play because its much easier to helm the boat to the compass than the gps. In doing that, its not important what heading the compass says....simply note whatever it is when the gps bearing and track agree, and steer it even though it may be different by 20-60 degs (deviation +- leeway)

If you start to use a GPS, you will soon care little about the differences in the fluxgate and your compass. If sticking with compass navigation and if your compass is accurate...pay no attention to the fluxgate....punch set when the compass bearing is what you want... and then adjust for expected leeway.

Arlyn C-250 W/B #224

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Douglas
Master Marine Consultant

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1595 Posts

Response Posted - 10/25/2002 : 12:27:44

When you instaled the new compass did you swing it. I.E. did you run it through a known compass heading set up. New compass instalation is often tricky and they dont come pree set. Do you have a hand held or GPS that you can verify you new compas with ?

Doug&Ruth
Boatless in Seattle
Tacoma Wa.

Edited by - on

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 10/25/2002 : 13:42:38

<b>"...the auto tack never was very satisfactory..." - Brooke Wilson

"...The auto-tack function helped sell my wife on letting me spend the boat units for it originally..." - Tray</b>

I, too, think the auto-tack function is useless. Instead of using the 'Auto-tack' feature, I use two manual techniques when tacking.

The first is quite basic. Just before a tack I put the autopilot in 'Standby', lift it off the pin, turn the boat quickly to new heading, put the autopilot back on and press 'Auto', and then trim the jib.

The other technique is, I make note of my desired after-tack heading. Next, right before I tack, I put the autopilot on 'Standby' and change the rudder angle using the controls on the autopilot. Since it is in standby, it will hold the tiller however many degrees I want. As the bow swings through the wind, I trim the jib while keeping an eye on my heading. When I'm on my desired new heading, I reach back and press 'Auto' and continue trimming the jib. You can somewhat control the speed of the tack by increasing/decreasing the amount of rudder angle induced at the beginning of the tack.

Don Lucier, 'North Star'
Catalina

Edited by - on

Mike Vaccaro
1st Mate

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77 Posts

Response Posted - 10/26/2002 : 11:14:48

Couple of thoughts:

1. Compass Error. "Deviation" is the amount of compass error induced by installation. Not all error can be "dialed out" (there should be two small brass adjustment screws on your compass one for N-S error and one for E-W error). The ship's compass should be "swung," i.e., adjusted for your particular installation. This requires aligning the centerline of the boat on a magnetic (not true!)N-S, then adjusting the N-S to eliminate as much error as practical, then aligning the boat to magnetic E-W. This normally requires several "spins" (i.e., multiple iterations on each axis) to minimize average error. It's generally impossible to eliminate all error, so a "deviation" card is made up. If you can acurately determine magnetic heading from an appropriately scaled chart, it's even better if you can stop the boat every 30-45 degrees during a compass "swing."
So the bottom line, is are you 100% confident that your ship's compass is accurate?

2. Flux gate error. Flux gate (or remote sensing) compasses tend to work well. They require a simple calibration, generally a turn in excess of about 450 degrees or so at relatively low speed. The amount of compass "deviation" will always change with mounting location. Thus the deviation apparent to the flux gate will not be the same as that at the ship's compass (unless the units are co-located). Thus the readout of the two will probably never match exactly, although if you correct for deviation, they should be pretty close.

3. GPS read-out. If you have a GPS on board, it will generally provide magnetic heading (it actually computes true heading and then adds or subtracts magnetic "variation" [the angular difference between true and magnetic north]). This is only as accurate as the variation programmed into the unit. Magnetic variation changes (albeit at a slow rate) from one chart publication cycle to the next.

4. No read-out! We use a Simrad/Navico tiller pilot--it has no flux gate read-out (unless you install an expensive hand-controller/programmer). Don't have a clue what magnetic heading the pilot thinks it's holding, but it works just fine. In other words, if your pilot holds a heading, and you're confident that your ship's compass has been properly mounted and calibrated, then just ignore the read-out of the tiller pilot.

5. Port/Starboard autopilot installation. This might be obvious, but the tiller pilots come out of the box set for a starboard side mounting, they must be manually set for a port side mount. Failure to tell the pilot what side of the boat it's mounted on will induce a 180 degree compass error, as well as screwed up steering and course correction!

6. Auto-tack. Don't know for sure about the Ramarine units, but the Simrad/Navico units have an adjustable auto-tack angle. The factory pre-set is 100 degrees, which we've found to be insufficent for the Catalina 25. The Simrad is adjustable from 40-140 degrees. We've re-adjusted ours to 130 degrees and simple tweek the heading as the boat speeds up after a tack (i.e., we allow it to "shift gears" as she accelerates, trimming the sails and heading up a bit as speed builds). The pre-set angle just didn't work well. I suspect that it is set at 100 degrees because that's the 50% point. The downside with the Simrad unit is that it is only reprogrammable with that expensive remote! So you'll have to either borrow one or send the unit back to the service center. Perhaps with the more detailed user interface, the Raymarine pilots are easier to reprogram?

Hope this is useful,

Mike Vaccaro on the "Swoose"
84TR/SK #4707

Edited by - on

Douglas
Master Marine Consultant

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1595 Posts

Response Posted - 10/26/2002 : 13:15:17

WOW thanks Mike. I just learned a lot from that post. Its sure good to have all this great knoledge available.

Doug&Ruth
Boatless in Seattle
Tacoma Wa.

Edited by - on

Tray
Navigator

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Namibia
224 Posts

Response Posted - 10/26/2002 : 17:42:05

Apparently my trouble is the bulkhead compass. I checked the fluxgate with my GPS set to Magnetic, and they matched after every course change. I even found that my auto tack function worked really well, not perfect, but well enough that I only had to "dial it in" a little after tacking.

At first, I thought the admiral would appreciate not having to be on the helm all the time, but she seems to feel threatened.
<img src="http://im1.shutterfly.com/procserv/47b2ce07b3127cce9139b642167c0000001410" border=0>
My bulkhead compass seems to be off a steady 40 degrees west. I'll have to get out the owner's manual and adjust it.

Tray
C-250WB #554
"Weeny Bean"

Edited by - on

ronrryan
Admiral

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USA
561 Posts

Response Posted - 10/27/2002 : 15:00:04

I once had a bulkhead compass on a new (old) boat off by 30 or so. Took out compass and went to a very respected repair guy. Sez he: you have a speaker nearby. Sez I: Not to my knowledge. He sent me to my room, or to look for a speaker. Lo and behold, when I looked real careful like, there was a lil bugger hiding behind a shelf. Removed speaker, compass became perfect instantly. A forty degree error means there is something magnetic messing with your bulkhead compass, IMHO. Fair winds, ron C25 srsk#2343 SW FL Orion

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Tray
Navigator

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Namibia
224 Posts

Response Posted - 10/27/2002 : 16:15:38

Ron,

I agree with you that a speaker would cause an error, but I didn't think I had that problem. But if you look in this picture you'll see an external VHF speaker I mounted in order to hear the radio in the cockpit with the outboard running. <img src=icon_smile_blush.gif border=0 align=middle> It might be too close. Luckily, it can be move easily.
<img src="http://im1.shutterfly.com/procserv/47b2ce06b3127cce91266260ef630000001410" border=0>

Tray
C-250WB #554
"Weeny Bean"

Edited by - Tray on 10/27/2002 16:27:02

Edited by - on

ronrryan
Admiral

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USA
561 Posts

Response Posted - 10/28/2002 : 10:37:26

Mine was a little bit further away than that, and when I removed the compasscard spun around like a top and settled right where it was sposed to be. All these years that had never occurred to me, one learns every day. Hope it works, fair winds, ron Orion #2343 srsk

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