Autopilots

[Hunter34]

I need to buy an autopilot for a full keeled 11.5 tonne cutter that has mechanical wheel steering and a centre cockpit.
According to all the advice I have read what is needed is a below deck unit which attaches directly on to the rudder quadrant which is linked to a computer unit and finally to a control head all of which is 4 times the cost of the biggest wheel pilot.
I use an ST4000+ on my boat which copes fine whatever the weather and has managed over 9000 miles over the last 3 years.

The cutter weighs twice as much as my boat but the steering is no heavier and is still 2.5 turns lock to lock.
From what I hear full keeled boats as supposed to hold a steadier course than us narrow fin keelers so the wheel pilot should have less work to do.
Also with having a centre cockpit surley a wheelpilot will keep drier than in my aft cockpit.
I know the ST4000+ is only rated to boats of around 7 or 8 tonnes but if its operating conditions are better than that on a lighter less stable boat I cant understand why on shouldnt be used on something bigger.
Also as far as I can make out the reaction times and speed of the below deck unit and the wheel pilot is the same.
True the thrust power of a below deck unit is more but it would have to be if it is attached directly onto the quadrant.
Or am I wrong.Do full keeled boats need more work to hold a steady course, tear the wheel from your hands when the weather turns nasty and constantly have cockpits full of briney.
I dont mind spending the extra money on a below deck unit if I know that its necessary and worth the extra.
If its just a case of the wheelpilot is only expected to last half as long as a below deck unit I would just buy 2.

Any thoughs much appreciated.

Andrew

 

[Robin]

Re: Autopilots & wishful thinking

Sorry Andrew but you need to bite the bullet and buy a below deck pilot. 11.5 tons of boat sliding sideways puts a huge load on the rudder and whilst a human steering will sense this and simply wait a moment or two (subconciously maybe) the pilot still tries to move it and something will give! The ST4000 wheel pilots are very good but not for bigger boats, if they were capable of handling bigger boats the makers would be only too pleased to be able to claim that. If anything the reverse is the case and in some intances the wheel pilots are sold for boats 'on the limit' of their capabilities - believe me I broke 5 in a row on a Westerly 33 before they admitted it!

Robin

 

[LadyInBed]

The advice has always been to buy the biggest ( and best) you can afford, so consult the holder of the purse strings /forums/images/graemlins/wink.gif

 

[charles_reed]

Re: Autopilots & wishful thinking

Haven't come across anyone who is entirely satisfied with wheel/drum autopilots.

The only real workmanlike way is to have a quadrant-operated ram.

Mind you I'm talking about long-distance single handers.

Drum/wheel ones are great for when you want to relax with your guests for a drink and eminently suitable for your average 800nm/year marina-berthed, yachtie.
They're not for serious use though.

 

[Shanta]

Re: Autopilots & wishful thinking

If I am correct you have been recommended /worked out to fit a linear drive unit(electric) to fit straight onto the quadrant. Yes they are hellish expensive HOWEVER...If part of your mechanical steering is chain you can use a chain drive unit. These units can be still be bought new, BUT more importantly they can be found at boat jumbles ect..(used to be used on Sharp,NEC ect autopilots) These can be connected to the course computer (yes you still need to buy the core pack and control head). This can save a lot of money. Be careful of the amp draw of the motor. /forums/images/graemlins/cool.gif

 

[LadyInBed]

Re: Autopilots & wishful thinking

One of the bigger benefits of a ram drive on the quadrant (or on a tiller) is that it is very positive. A wheel / drum system has to cope with slack in the wheel linkage.

 

[Ships_Cat]

Re: Autopilots & wishful thinking

And another important benefit of the drive direct to the quadrant is that if anything in the steering pedestal or linkage from it breaks or otherwise fails (especially if wire which commonly fails through breakage or sheave problems) is that one can still easily steer using the pilot.

John