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tomainsley

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As I'm about to fit my raymarine linear drive(with st7000) to my rudder quadrant on my yacht, I've been well advised to make sure that rudder hits its rudder stops before the linear drive comes to the end of its travel.I have 3 Questions;
1.Is this done by attaching the linear drive and then fully extending it under power from the controls to see if it does hit the stops and if it doesn't then adding some more material to the stops to decrease the max rudder angle slightly?
2. During usage will the linear drive damage itself if it does repeatedly drive into the stops, ?
3. Having dealt with the qn 1, should I then reduce the travel of the linear drive unit on the st7000 settings so that it should NEVER hit the stops under autopilot control?
Cheers
Tom
 
Approaching the question from entirely the opposite end.

The linear drive travel should be clearly marked on Raymarine's literature.

Some very simple Euclidean geometry should allow calculation of the radius about which the linear drive will need to move the "tiller" to travel from one stop to the other.

That presupposes that the boat designers/builders know what they're doing and the stops prevent the rudder from exceeding about 45-60°.
 
Hi,

I went through this last year when I did the same thing. There are a couple of things that matter:
1. The reason the stops have to limit the travel is for situations such as driving hard astern and loosing control of the rudder causing it to slam across to the end stops - if the linear drive is the end stop it will try to over extend it, causing damage.
2. The end stops must be robust for reason above.

If it is a Lewmar quadrant, they should have the dimensions on the web site to calculate the permisable travel.

When I fitted the linear drive I had to fabricate an adaptor to bolt to my quadrant as it didn't have anywhere suitable to mount the pivot pin. I spent a few hours planning, measuring, fitting, remeasuring and then judicious over engineering resulted in something that worked flawlessly over the whole of last season.

Hope it works for you

Piddy
 
Quote:
That presupposes that the boat designers/builders know what they're doing and the stops prevent the rudder from exceeding about 45-60°.

I suspect that should read 30 to 40°. The most common would be close to 33°.

If the rudder gets to 45 when reversing you will need a very strong tiller arm, rudder and hefty helmsman to have any chance of controlling it. Tiny not included.


Avagoodweekend......
 
A cautionary word concerning the connection between the linear drive and the quadrant. Ours failed in its second year, 12 hours from the Shetlands and we were startled to find ourselves suddenly heading back to Norway! Examination showed shear failure of the vertical bolt caused by work hardening. It is important to bolt into an appropriate block on top of the quadrant and not have a length of bolt cantilevering. Alternatively use an over-size bolt.
 
When I fitted mine, I put some blocks in to reduce the end to end travel on the quadrant.
My linear drive was connected to a stub tiller on the stock, so the linear drive travel depending on the length of the stub to where the linear drive connects.
The book gives an optimum length of stub, if too short - more end to end travel but more torque / power required to move the rudder. Too long - less power required but slower rudder response and larger boat turning circle.
Note: DON'T under estimate the force put on the linear drive fixings, I did and had to fit another (extra) support bracket
 
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