ST4000 MKII help! PLUS - Rudder Sensor - Help!

[scottb34300]

Hi, I have just bought and installed a Raymarine St4000 MKII wheel autopilot. I have a 27ft Legend ('05) and am having a few problems.

First of all, the autopilot keeps overshooting its heading, and does not go on a straight line but snakes around it. I have adjusted the rudder gain down to '1' but it still does the same. I have also adjusted the rudder damping etc, but still no luck. So i thought I had better fit the rudder sensor. When I look at the manual it shows a tiller arm, which would be great, but with my wheel steering and many others I have the Lewmar Constelation system:
"A typical aft cockpit radial wire system incorporating 260° radial quadrant crosswire idler. "

So basically I have a circle quadrant attached to the top of the rudder. So how to i connect up the rudder sensor? PS. There is only room for mounting the sensor in front of the quadrant, not behind or to either side!

Hope someone can help - either with setting adjustments or position of the sensor.

Many thanks,

 

[scottb34300]

If you want to see the quadrant:
http://www.lewmar.com/webcat/html/steer_prod_view/steer_260quad_view.asp

Thank you!

 

[branko]

Maybe stupid answer, but looks to me as a calibration problem. Do you made three rotations on open sea to calibrate Autopilot instrument. Everything is explained in Manual.

 

[oldvarnish]

From experience, I think the sensor is a good idea especially if your steering is smooth and effortless. I had similar problems which the sensor solved. I think they now recommend fitting them to all wheel steered yachts. But I agree - they're a [--word removed--] to fit. Mine was easier than yours looks, but much blood was lost in achieving it.
Interestingly, the one I fitted replaced an earlier black box Autohelm which had done over fifteen thousand miles without any kind of sensor. At the time of fitting the new one I thought that it was too bloody sophisticated for its own good, and so it proved.

 

[sjohn_gibson]

Re attaching the rudder sensor. When I was faced with this problem, I manufactured a suitable arm that fitted over the stub of the rudder post protruding through the quadrant and then attached the arm to the quadrant. I had to play around with the length to get the geometry correct but it works fine. I used a piece of clear perspex as the force to drive the sensor is small. The clear perspex was easy to work and enabled me to see where to drill the attachment hole with ease. I made a spare at the same time but don't know where it is now!!!

 

[scottb34300]

Thank you for your help. I did something similar today, I actually used the end of a S/S ruler and connected it to the quadrant using self-tappers and put the sensor horizontaly on. Have only tested it slightly in the marina, but seems to be woking much much better. Hopefully I have solved it. I will be testing further on Monday.

Many thanks for your help.