Heaving-to with autopilot

[Alby1714]

Hi all,
Heaving-to in storm conditions puts a lot of stress on the wheel steering system when the wheel is lashed hard over. As I have an autopilot whose drive unit is directly connected to the quadrant I could in principle avoid wear and tear on the whole steering system if I could leave the wheel to turn freely and keep the rudder in the appropriate position by using the autopilot drive unit. Unfortunately in my system (Raymarine ST-6001) I can input a course but not a rudder angle.
I would like to ask if anybody has any suggestion on how to modify the circuit to by-pass the autopilot and input into the drive unit what I presume would be a DC voltage corresponding to the desired rudder angle. Ideally one would like to be able to vary manually the input voltage to be able to set the desired rudder angle.
Thanks a lot in advance for your suggestions.
Alberto

[Stu Jackson]

I think that using the ap would induce more stress, not less. An ap is always seeking a course, unless it is turned OFF, in which case it is locked in a position, similar to using the standby mode rather than the active mode.

All you're suggesting is using another means of keeping the quadrant in ONE position, so why wouldn't the basic steering system itself be able to do just fine?

Whenever I heave to, I always turn the ap off and simply lock the wheel.

Have you tried going to standby?

[Alby1714]

hi Stu Jackson and thanks for your reply. So far I have been doing exactly what you do: i.e. ap in stand-by and wheel locked. However it is one thing to do that in 15kn of wind and a rather different thing to do that when the wind blows above 40kn; in this latter case there is a lot more stress and if one lashes the wheel, the stress acts on the whole steering system i.e. the sprocket, the chain and the wires etc. I would like to be able to protect the steering system when in these conditions by acting directly on the quadrant and leave the wheel to run free. To achieve that I would put the ap on stand by and additionally I would like to be able to apply to the drive unit of the ap, please notice to the drive unit not the control unit of the ap, a voltage which would lock the rudder to a fixed angle. This obviously with the standard product, i.e. the Raymarine ap as is, is not feasible. I am therefore asking if anybody has any suggestions on how to modify the circuitry of the standard product to achieve that.
Cheers,

[Wrong]

Turn it off?

[Stu Jackson]

Alby, wrong & I seem to suggesting the same thing: once you have positioned yourself and the ap has the wheel where you want it, turn it off. That will seem to accomplish your stated goal. Standby is essentially turning it off, too, by simply locking it in whatever position you choose, i.e., my "standby" mode can change the rudder position by using any of the direction buttons.

Are we missing something?

[colemj]

I don't know about your specific AP, but all the AP's I have owned (non-Raymarine) have a direct drive feature where it steers by the person pushing the dodge buttons or turning a small wheel on the control head. If you set it to a specific rudder angle, it would simply hold that angle.

Perhaps buried in your manual is a similar feature?

Alternately, since you are heaving to, perhaps you could use the wind mode function?

Mark

[Pelagic]

Originally Posted by Alby1714

..... the stress acts on the whole steering system i.e. the sprocket, the chain and the wires etc. I would like to be able to protect the steering system when in these conditions by acting directly on the quadrant and leave the wheel to run free.

To clarify...
you have mechanical steering "sprocket, the chain and the wires etc." connected to the quadrant?
You are concerned that if you mechanically lock the wheel from turning.... (I have a slide out lever for that purpose)....it will put undue stress and wear on the cable connections

Since they won't move and cables are designed to counter higher forces underway... I would not be concerned.

If you still are...then consider mechanically locking the quadrant in the hove to position

[Alby1714]

Thank you all for the many suggestions.

Wrong and Stu Jackson: I do not know what make is your ap but is probably not like mine. When my ap is in stand-by the rudder is free and the helmsman can steer by hand. The rudder is also free if I turn the ap off, so those are options I cannot use for heaving-to.

Mark (Colemj): The function you mention is exactly what I would like to have but my ap does not have any "small wheel" on the control unit for that purpose. I am sure it can be modified and that is what I would like to do but as yet I do not know how. Can I ask you what make is your ap ?

As for the wind function I never use it ( I have a Scanmar selfsteering gear and when I wish to steer by the wind I use that rather than the ap) but will investigate if that can be of any help for what I want to do.

Pelagic: Yes, I have thought of mechanically locking the quadrant. The drawback with that option is that I would have to reach the quadrant when I want to heave to. In my boat the quadrant is located under the berth in the stern cabin. I would prefer to add a little electrical "black box" next to the control unit of the ap to have the function that Mark's (Colemj) ap seems to have as standard.

[Pelagic]

Originally Posted by Alby1714

Pelagic: Yes, I have thought of mechanically locking the quadrant. The drawback with that option is that I would have to reach the quadrant when I want to heave to. In my boat the quadrant is located under the berth in the stern cabin. I would prefer to add a little electrical "black box" next to the control unit of the ap to have the function that Mark's (Colemj) ap seems to have as standard.

What Mark is talking about on AP is called NFU or non follow up function.

On my boat I have 2 helm positions
Pilothouse is manual hydraulic steering with a bypass so that the AP pump can energize the rams for AP controlled power steering.

My Aft steering is mechanical... Chain/Cable to quadrant.
That means when Auto Pilot is engaged...Aft steering wheel turns when AP moves quadrant.

What happens to your hand wheel when AP is working?

[Albro359]

Originally Posted by Alby1714

Thank you all for the many suggestions.

Wrong and Stu Jackson: I do not know what make is your ap but is probably not like mine. When my ap is in stand-by the rudder is free and the helmsman can steer by hand. The rudder is also free if I turn the ap off, so those are options I cannot use for heaving-to.

Mark (Colemj): The function you mention is exactly what I would like to have but my ap does not have any "small wheel" on the control unit for that purpose. I am sure it can be modified and that is what I would like to do but as yet I do not know how. Can I ask you what make is your ap ?

As for the wind function I never use it ( I have a Scanmar selfsteering gear and when I wish to steer by the wind I use that rather than the ap) but will investigate if that can be of any help for what I want to do.

Pelagic: Yes, I have thought of mechanically locking the quadrant. The drawback with that option is that I would have to reach the quadrant when I want to heave to. In my boat the quadrant is located under the berth in the stern cabin. I would prefer to add a little electrical "black box" next to the control unit of the ap to have the function that Mark's (Colemj) ap seems to have as standard.

Why don't you use the Scanmar wind vane to hold you at a an angle to the wind...?
But if you think about it...the wind vane is connected to your wheel / tiller, so the stresses you talk about in the steering system are still there.

Just get the boat to sit still at a particular rudder angle and lash the wheel / tiller.

Even if you did use the autopilot in wind mode its hard to see what the benefit would be over the traditional approach

[colemj]

Originally Posted by Alby1714

Mark (Colemj): The function you mention is exactly what I would like to have but my ap does not have any "small wheel" on the control unit for that purpose. I am sure it can be modified and that is what I would like to do but as yet I do not know how. Can I ask you what make is your ap ?

On our old B&G (pre-Navico), it was called "power steer" mode, while on our current Simrad it is called "non follow-up" mode. I know Comnav also has this feature and suspect that it is not uncommon.

It doesn't require a small wheel - the dodge buttons work just as well. I only mentioned the wheel because some control heads have that instead of buttons as the input device.

One work-around if you don't have this mode is to add an external 12V supply through a switch to the clutch. Then just turn the wheel to where you want the rudder positioned and power up the clutch. Make sure the switch disconnects the computer when it powers the clutch.

Mark

[Albro359]

But if you can use the wind vane, why would you bother with all the electrical stuff ??

[colemj]

The OP's original concern was the stress on the steering system, which using the mechanical wind vane would not alleviate. He was wishing to put all the forces onto only the quadrant and AP drive/mount.

However, I think if the entire steering system can't handle the hove-to stresses, then it needs attention.

Mark

[Alby1714]

Originally Posted by Albro359

Why don't you use the Scanmar wind vane to hold you at a an angle to the wind...?
But if you think about it...the wind vane is connected to your wheel / tiller, so the stresses you talk about in the steering system are still there.

Just get the boat to sit still at a particular rudder angle and lash the wheel / tiller.

Even if you did use the autopilot in wind mode its hard to see what the benefit would be over the traditional approach

You are right: if I tried to heave to with the Scanmar wind vane I would not protect the steering system in any way, that's why I don't even think of doing it that way !
Thanks any way for the suggestion.

[Alby1714]

Originally Posted by colemj

On our old B&G (pre-Navico), it was called "power steer" mode, while on our current Simrad it is called "non follow-up" mode. I know Comnav also has this feature and suspect that it is not uncommon.

It doesn't require a small wheel - the dodge buttons work just as well. I only mentioned the wheel because some control heads have that instead of buttons as the input device.

One work-around if you don't have this mode is to add an external 12V supply through a switch to the clutch. Then just turn the wheel to where you want the rudder positioned and power up the clutch. Make sure the switch disconnects the computer when it powers the clutch.

Mark

Mark,
Thanks for the suggestion, this is the sort of modification I would like to apply to my drive unit. Presumably if I made the voltage of the external power supply manually variable, I could set the rudder to any desired angle within its range from hard over port to hard over starboard.