tiller Pilot

[calloo]

I have a new Raymarine tiller pilot ST 2000. The Installation instruction tells me to connect it to the tiller 18 inches from the rudder pintles. I am planning to connect it to a tab attached to the aft end of the main rudder. Can anyone advise me on the efficasey of doing this. Is there, for example, a formula for calculating how long the fulcrum arm should be?

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[johnsomerhausen]

If I undeerstand you well, you want to control the rudder via a trim tab instgead of via the tiller. Thjat poses a whole slew of problems since the tiller pilot should be perpendicular to the tiller (or in this case,, the trim tab arm) which means it would be outside the boat.... Methinks you´d better consult the techies at Raymarinme for a thing like that....
john

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[AndyL]

Re: tiller Pilot on a trim tab

It ought to be possible, but since the TP thinks it is moving the rudder, the first hurdle might be making it act in the opposite direction. Fit it on the 'wrong side' and don't tell it? Secondly assuming you are fixing the TP to a fixed piece of boat, you will need some complicated linkage to the tab'so that the tab can still be controlled after the rudder has moved from the neutral position.
I need a beer before I can work that out.

Best of luck.

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[charles_reed]

You'll have to mount it on the rudder-stock and it will have to operate in the reverse direction to when it's operating the tiller.

Many have added an electric pilot to a servo-pendulum of a vane gear but I've not heard of one being fitted direct to a trim tab, tho' effectively that's what you do when you fit one to a Navik.

Try speaking with Steve or one of the other techies at Raymarine - make your first contact thro' Ruth Willett on 02392 693611 x 1230, they'll have to advise you on the ratio of x & y legs of the fulcrum.

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[Guest]

If you have a tiller steered boat - I cannot for the life of me see why you would want to complicate such a simple device ? Plus you would probably increase dramatically the risk of water ingress into the tillerpilot casing etc.

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[tross]

IMHO this can't be done with a tiller pilot unless you have a remote compass. If you mount the pilot on the tiller then the compass heading will change with any rudder movement. If you try and mount it on the boat and use levers and bellcranks and mout these over the pintal bearings,you still have the problem of maintaining the corrrect correction angle once the tiller moves

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[bbilly]

Calloo,
Why?

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[tross]

Because even if you mount the control point exactly above the pivot point as soon as the pilot make a course correction it will have to make a movement to the link and therefore it will no longer be over the pivot point. However, I had one of these 3:00am flashes this morning and realised that the answer for this is so so simple.

Mount the tiller pilot to the boat so that the compass stay fixed releative to the boat and connect the trim tab to the tiller pilot via a cable - I reckon one of those teleflex cables would be just perfect. You will have to find a way to secure the ends of the outer cable but that could be a bracket on the tiller pilot or fixed to the hull in some way.



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[finns]

I think you have to do as AndyL said: "Fit it on the 'wrong side' and don't tell it".
But there may be some more to it.
I assume: (1) you have an outboard rudder, (2) the trim-tab axis is behind the rudder axis, (3) the 'tiller' for the tab is coming forward above the rudder.

When the tiller pilot (TP) makes a correction, say pushing the tab-tiller to Sb, the trailing end of the rudder will go to Sb as well and so will the boat. When the trailing end of the rudder goes to Sb, the angle between rudder and trim-tab should decrease in order to avoid over steering. This "feed-back" is obtained automatically if the connection between tab-tiller and TP is placed behind rudder axis. Also, if a wave hits the rudder, pushing the trailing end to Sb, the feed-back should be arranged to steer the rudder back towards the original angle.
A possible length for the tab-tiller could be about half the distance between rudder axis and trim-tab axis. The deflection of the trim-tab should not be much more than that for the normal rudder. As the tab-tiller will probably be much shorter than the 18 in specified for the TP to work on (with the normal tiller), you will need to device some reduction from the TP to the trim-tab. This can be done by using a lever between the TP and the tab-tiller. This is much easier to draw than to explain here with my limited English. If you need a drawing, please tell me.
FinnS


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