Autopilot and rudder stops, URGENT

Chalker said:
I'm confused by some of the responses.
1 If the ram will not reach the quadrant stops then it must act as the stop when hand steering.
2 If the ram will reach the stop then the ram is trying to push the stops out of the way. As said before, the force is enormous and also will run continuously in a stalled condition,

Option 2 must be correct, but I would like to see it get close to the stops, but not reach them.
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Yes, this is how Raymarine say it should be set up. Firstly, the rudder must be able to reach the rudder stops - the ram mustn't be the stop. Secondly, the autopilot should be programmed so that the ram doesn't push against the stops.
 
charles_reed said:
One has to suspect the surveyor's professional competence.
Perhaps it would be an idea to find out what he does mean (unless of course he's doing a favour for the purchaser).
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From what the OP has said, the surveyor has highlighted an incorrect installation which could wreck the ram. Isn't that what he was paid for? Or do you just distrust surveyors?
 
I don't think 20 degrees turn on the rudder blade is adequate. A figure of 17 degrees is sometimes quoted as the angle at which a rudder blade will stall, but on a fin and separate rudder hull the rudder will not be acting in centre-line-straight water once you start a turn. As a result once a boat starts turning you can use much more than 17 degrees rudder and not stall. I certainly quite often use 45 degrees rudder movement when manouevring, or when simply choosing to turn really fast. Also I have at times steered almost 45-0-45 quickly just to keep a boat on course offwind when driving really hard under sail. Limiting a rudder blade on a modern hull to 20 degrees is wrong.

On a near-new Moody 40 I once berthed the boat using the autopilot +10/-10 buttons after the wheel steering seized, and the rudder was immovable with the emergency tiller. Fortunately the AP still had the grunt to turn the rudder quadrant, so there are huge forces generated by rams. I believe there is a setup option to match the AP to the rudder stop angles - though the ram does have to be fitted at the right distance from the rudder post.
 
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I installed my 6000+ about 14 yrs ago to Raytheon`s instructions.
apart from a "sticky" clutch, in the first year it has been trouble free.
It is fitted to a fin & spade IOR One Tonner, see avatar

jwilson said:
I don't think 20 degrees turn on the rudder blade is adequate. A figure of 17 degrees is sometimes quoted as the angle at which a rudder blade will stall, but on a fin and separate rudder hull the rudder will not be acting in centre-line-straight water once you start a turn. As a result once a boat starts turning you can use much more than 17 degrees rudder and not stall. I certainly quite often use 45 degrees rudder movement when manouevring, or when simply choosing to turn really fast. Also I have at times steered almost 45-0-45 quickly just to keep a boat on course offwind when driving really hard under sail. Limiting a rudder blade on a modern hull to 20 degrees is wrong.

On a near-new Moody 40 I once berthed the boat using the autopilot +10/-10 buttons after the wheel steering seized, and the rudder was immovable with the emergency tiller. Fortunately the AP still had the grunt to turn the rudder quadrant, so there are huge forces generated by rams. I believe there is a setup option to match the AP to the rudder stop angles.
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Moodyjim said:
This is a comment from a survey on my Moody 425 and I'm not quite sure what the surveyor means.

"The autopilot has been installed in such a way as to not allow the rudder to come to its rudder stops. This means that the actuator is acting as the rudder stop and that is not acceptable. Either the stops have to be extended or the installation redone."

If the A/P is engaged then surely this is correctly installed but if it isn't engaged then are actuators adjustable? I think it's the original installation although the A/P is a Raymarine replacement 5 years old.

Jim
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You will find all you need here (Raymarine manual) http://www.raymarine.eu/WorkArea/DownloadAsset.aspx?id=1937
Page 7 specification for the different linear drives from Raymarine.
Page 11 2. Mounting the drive and Drive alignment
Page 14 Steering check

Seems that the rudder angle used (or designed) by Raymarine is 35°
The total rudder movement is limited to +/- 35 degrees by the steering system end stops
rather than the linear drive’s end limits (see Figure 7 )
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The surveyor spotted a possible problem - from the manual
CAUTION
Linear drive
Make sure rudder movement is limited by the steering system end stops
before the push rod reaches its end stop. Failure to do this could damage
the drive and will invalidate the warranty.
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Perfectly explained. No ambiguity whatsoever.

A Tiller pilot is usually removed when not in use but if the tiller system was big enough to have stops installed and it is operated with the tiller ram in place ( Are any of them ? ) then i would expect the tillerpilot ram to be mounted closer to the hinge point so that the throw of the tiller was less than the throw of the tillerpilot ram. Even with a 10 metre long tiller a tiller ram installed to act 1 centimeter from the pintle hinge line will have to move only about 3cm to steer through say 160 degrees of tiller angle ( impractical but serves to illustrate the point ).

On a quadrant actuated system you move the pivot closer to the rudder post so that when under manual control the physical system stops are hit before the limits of the ram are reached. Banging either type of ram up against its stops will do it no good at all.

As you move closer to the hinge point in either system you need more power in the ram, but that's another calculation.
 
The issue is
1/ a tiller pilot is removed from the tiller when manually steering
2/ a plumbed-in unit is always engaged, when the ram is steering no stops are required. they are required when manually steering as the helmsman can turn the helm more than the ram can extend, thereby forcing it to extend beyond the ram travel
 
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