Tiller pilot - is 90 degrees critical?

[dolabriform]

Hi All

I'm preparing my new tiller, and about to drill holes for the bolts that mount the tiller pilot.

I've measured them from the old ( broken ) tiller, so they will be almost identical in position, maybe a few mm off. This would mean the TP would not be at exactly 90 degrees.

Will this be an issue? I'm not able to offer it up on the boat to check as I'm a long way away and I'd like to get the tiller finished so I can fit it this weekend!

Thanks

David

 

[bedouin]

The action of the tiller pilot moving the tiller changes the angle anyway as the tiller moves off the centre line so it has to tolerale a significant difference in angle so an erro of a few mm either way won't make any difference.

However if it were me it would annoy me immensely if the error were large enough that it was obviously not 90 degrees when the tiller is central!

 

[dolabriform]

However if it were me it would annoy me immensely if the error were large enough that it was obviously not 90 degrees when the tiller is central!

Thanks for your quick reply... if there is an error it will only be a few mm, so I suspect ( hope ) that won't be obvious !

 

[Daverw]

I would have thought as you are sailing to a heading the tiller will be centred anyway when on track, mine does not know rudder position

 

[AngusMcDoon]

My tiller pilot outputs compass heading to the rest of my system by its data connection. If your tiller pilot is not at 90° to the axis of the boat when the tiller is central the heading value will be wrong. It might not matter though if you don't use the data anywhere else or you don't set your tiller pilot to follow an absolute compass heading.

 

[LittleSister]

Note (as many apparently don't) that the specified distance from the rudder pivot (18" IIRC?) is measured perpendicular to that pivot, so if your rudder and tiller are not at 90 degrees to one another that distance is not measured along the tiller (Or to to look at it the other way around, the distance along the tiller is different from the specified distance.)

In my experience a little deviation from what's specified for the various lengths and angles is usually tolerable, but if you want to maximise the pilot's performance get as close as you can.

 

[Ruffles]

It's an interesting question.

I believe they work as a PID controller. Which means that from the moment you press auto it measures the compass bearing and from that point uses
1) The compass bearing error,
2) The rate at which the current bearing error is changing and
3) The bearing error * the time it has been in error.

It uses these three values to calculate movement of the rudder. The proportion of each is set by constants traditionally called Kp, Kd and Ki. But from memory I think this is actually the rate of movement of the rudder. Not that actual position which on tiller pilots at least it is blissfully unaware of.

Also it has no way of knowing how much movement of the rudder on any boat will affect the boat itself. For that reason in dynamically recalculates the constants anyway. Which is why you find the autohelm settling down over time.