autopilot installation

[tomainsley]

hi there,
i'm re-installing a linear drive autohelm on my new second-hand legend 376. 2 problems.
1. the drive end was previously bolted to the quadrant. Raymarine and others recommend using a tiller bolted to the rudder stock. What's the advantage of doing that and should i bother.
2. i am concerned that the max rudder angle exceeds that of the rudder angle transducer/feedback. I don't want to exceed that and knacker the indicator. Is it ok to remove the quadrant to install chocking onto the rudder stops to stop this. It won't make the rudder drop into the sea will it (sorry, i've been powerboats before)?

 

[Boat44]

Not sure about 1).

2) I wouldn't recommend this personaly as it will reduce possible maximum rudder angle and hence the manouverability of the boat. The closer the linear drive arm is to the rudder stock the less travel there will be, but bigger forces. The linear drive should come with basic mounting instructions with regards to optimal distance from rudder stock etc.

(I'm not familiar with the setup of a Legend so couldn't say if removing the quadrant would drop the rudder in the pond!)

 

[hightech]

Ok,

1. If your quadrant is man enough, then yes, you caould bolt it down to that, unfortunately, the distance out that most drives need to bolt to is often on a weak bit or in fresh air, so a tiller bar is the only way. It really boils down to how your boat was made in the first place. It is possible to make clamp plates togoeach side of the quadrant and lock the whole thing together as a lump then mount the drive to that. Some times there is no space to add a tiller bar.

2. Feedback units will pivot over a far greater arc than your steering will, unless you have a really weird set up. +/- 90 degrees actual movement is quite normal for a feedback unit, where as most steering systems tend never togo beyond 45 degrees with most in the mid 30's.

While we are on the subject, make sure that your steering stops act before the drive unit runs out of travel, even if you have to add or modify existing stops,I have seen too many drives broken this way,also make sure that the drive cannot be fouled or caught on anything during its stroke, if the arm tries to go cound a corner it will snap like a carrot. Both of these are expensive repairs.

Make sure that at mid stroke the drive is at 90 degrees to your tiller bar or quadrant pivot point.

Also remember that the drive unit will put out 250kg or more of thrust, so make sure you bolt everything down securely and that the outboard end is substantially mounted.

 

[tomainsley]

many thanks for the advice, i'll put it to use