Raymarine autopilot setup help

[rob1699]

About a year ago I installed an new Raymarine SPX10 gyro computer with ST70 colour head unit, and I've never really found the sweet spot with it. Just wondered if anyone has any thoughts on this:

In Track mode when following a route, the boat either wanders about (slowly to about 50ft of XTE to port or starboard before correcting itself) or if the settings are "upped" (Response and/or Rudder Gain) the bow just hunts - violently if either of these are set beyond 5 - making 'er indoors feel sick!

Anyway, I've gone through the Auto learn process a couple of times. This has set the rudder damping set to 9, rudder gain at 3, autotrim at 4. I've played around with these settings one at a time but it seems like more rudder damping is needed to stop the bow from hunting - but this is already set to the max of 9.

My old S2 non-gyro course computer did much the same (although much worse) and this was the reason I changed it.

Boat is a Targa 40 on sterndrives.

Any thoughts much appreciated. The sooner I can get it sorted, the sooner my wife will stop saying "well that was a waste of money cos it still doesn't bl00dy well work"...grrr.. !

Cheers

Rob

 

[spannerman]

Have you got all of your initial settings right, i.e. drive type, cruise speed,vessel type.
I had big problems getting a Minor 31 with a D6 set up and have these settings written in the back of my Autopilot commissioning book if it helps.

Vessel type - S,drive
drive " - 4
Rudder limit - 20
Rudder gain - 9
Counter rud - 3
Rud damp - 5
Auto trim - 2
response Gyro -2
Turn rate - 5
Cruise speed - 25

This is for a single engine 38 knt boat but it has similar characteristics as the Targa, fast planing boat with high manouverability, and not much planted in the sea when up and running.
Another problem we found is that the hydraulic pump had too high a delivery rate when used with D4-D6 engines as these have a fast servo response already so the AP pump was overdriving the servo system on the boat, the cure is to use a smaller capacity pump from Raymarine.

 

[jimg]

In Track mode when following a route, the boat either wanders about (slowly to about 50ft of XTE to port or starboard before correcting itself)

I have to say what is wrong with 50 ft? Seems quite reasonable to me. I would much prefer a track that "feels" right, to one that is zig zagging all the time.
If it moves off track slowly and then corrects slowly I would say that was OK.

50 ft is only a boat length, but then maybe people expect more of todays modern electronics?

 

[peterb]

Compass correction?

Have you properly corrected your fluxgate compass?

A few years ago we were returning from the Baltic when we realised that the two compasses (binnacle and fluxgate) were giving different readings. We trusted the binnacle compass (recently swung), so decided to do the alignment check when we had a piece of calm, flat water.

We found it at Rendsburg, just off the Kiel canal. We did the usual two circles, but on completion the compass showed that an unusually high deviation (18°) had been corrected. Once we were on a steady heading down the canal we set the two compasses to agree with each other. We had no problems with the compass while we were in the canal or the Elbe, but once out we set up a route and put the autopilot on track. Immediately it started showing similar symptoms to those you've described (though in a sailing boat probably not as violently).

Again we compared the two compasses, and found that the deviation between the two of them did indeed go up to 18°. And it was almost all quadrantal error, so that the deviation curve gave two humps and two valleys. We reckoned that on the heading we were using, the effect of the change in deviation almost balanced any change of heading, and hence the fluxgate compass was not giving the proper course correction signals.

Fortunately the sea was almost calm, so we were able to repeat the alignment procedure. This time it told us that the corrected deviation was only 1°. From then on the system worked perfectly, with the XTE not exceeding a few feet.

I suspect that the area we had chosen for our first check had some magnetically active material (either iron or electric cables), and that our system had been trying to correct a 'local magnetic anomaly'. When and where did you do your compass alignment, and have you compared your fluxgate compass with your binnacle or bulkhead compass?

 

[rob1699]

Have you got all of your initial settings right, i.e. drive type, cruise speed,vessel type.
I had big problems getting a Minor 31 with a D6 set up and have these settings written in the back of my Autopilot commissioning book if it helps.

Vessel type - S,drive
drive " - 4
Rudder limit - 20
Rudder gain - 9
Counter rud - 3
Rud damp - 5
Auto trim - 2
response Gyro -2
Turn rate - 5
Cruise speed - 25

This is for a single engine 38 knt boat but it has similar characteristics as the Targa, fast planing boat with high manouverability, and not much planted in the sea when up and running.
Another problem we found is that the hydraulic pump had too high a delivery rate when used with D4-D6 engines as these have a fast servo response already so the AP pump was overdriving the servo system on the boat, the cure is to use a smaller capacity pump from Raymarine.

Have you properly corrected your fluxgate compass?

A few years ago we were returning from the Baltic when we realised that the two compasses (binnacle and fluxgate) were giving different readings. We trusted the binnacle compass (recently swung), so decided to do the alignment check when we had a piece of calm, flat water.

We found it at Rendsburg, just off the Kiel canal. We did the usual two circles, but on completion the compass showed that an unusually high deviation (18°) had been corrected. Once we were on a steady heading down the canal we set the two compasses to agree with each other. We had no problems with the compass while we were in the canal or the Elbe, but once out we set up a route and put the autopilot on track. Immediately it started showing similar symptoms to those you've described (though in a sailing boat probably not as violently).

Again we compared the two compasses, and found that the deviation between the two of them did indeed go up to 18°. And it was almost all quadrantal error, so that the deviation curve gave two humps and two valleys. We reckoned that on the heading we were using, the effect of the change in deviation almost balanced any change of heading, and hence the fluxgate compass was not giving the proper course correction signals.

Fortunately the sea was almost calm, so we were able to repeat the alignment procedure. This time it told us that the corrected deviation was only 1°. From then on the system worked perfectly, with the XTE not exceeding a few feet.

I suspect that the area we had chosen for our first check had some magnetically active material (either iron or electric cables), and that our system had been trying to correct a 'local magnetic anomaly'. When and where did you do your compass alignment, and have you compared your fluxgate compass with your binnacle or bulkhead compass?

Thanks guys so much for your thoughts - appreciated.

I have to admit not spending much time aligning the fluxgate compass so will give that a go.

Will report back!

Cheers

Rob