panic switch for autopilot

[Daniel]

I recently witnessed a possible accident with the autopilot in my boat.
While going under autopilot a guest accidentally put her arm into the
wheel among the spokes and was caught at a wheel turn between a spoke
and the tiller post. The servo is quite powerful so that she was able
to withdraw the arm only after switching off the unit which took few
seconds - still too much. Fortunately only few bruises and some panic
but I fear that it could have gone worse. Any experience? Wouldn't it
be safer to put a panic shut-off switch somewhere? I mean the little red
mushroom to push in case of problems. I have never seen such things
mentioned in autopilot manuals.

Daniel

 

[Jack Erbes]

I recently witnessed a possible accident with the autopilot in my boat.

<snip>

Is that a cable steering system? I'm trying to remember if I've ever
been on a boat where the autopilot movements feed back to the wheel.
Must be that I have not been around an autopilot on anything but
hydraulic steering systems.

I like being able to rest my forearms on the wheel while the autopilot
is engaged. And if you need to grasp something to steady or brace
yourself, you can grab the wheel because it ain't doing nothing.

Jack

 

[Dennis Gibbons]

Raytheon actually recommends this. Occasionally their units will freeze and
you would be unable to turn the wheel (not a good idea with a freighter
bearing down). they recommended a cutoff switch ( has to cut the main power
to the unit that controls the rudder). I opted not to do it, but I have
practice diving below to hit the switch on the electrical panel

 

[Daniel]

Is that a cable steering system? I'm trying to remember if I've ever
been on a boat where the autopilot movements feed back to the wheel.
Must be that I have not been around an autopilot on anything but
hydraulic steering systems.

yes, there is an electrical servo-motor under the pedestal linked
through a chain directly to the shaft of the helm wheel (there are two
parallel chains inside the pedestal). The servo includes an electric
clutch that engages/disengages the motor shaft to its sprocket wheel.
When the clutch is powered the helm wheel is locked to the autopilot
movement and its torque is quite high, believe me.

Daniel

 

[Jack Erbes]

yes, there is an electrical servo-motor under the pedestal linked
through a chain directly to the shaft of the helm wheel (there are two
parallel chains inside the pedestal). The servo includes an electric
clutch that engages/disengages the motor shaft to its sprocket wheel.
When the clutch is powered the helm wheel is locked to the autopilot
movement and its torque is quite high, believe me.

Oh yeah, chain and a servo motor. No slippage there. The panic button
sounds like a good idea if the autopilot's off or standby button is not
prominent or obvious.

And it might be a good idea that engaging the autopilot disengages the
servo motor clutch. If you can't use the wheel for "dodge steering"
when the autopilot is on, there is really no good reason to have the
servo motor clutch engaged. For quick dodge steering I'd like a
prominent switch (momentary contact?) that disengaged either the
autopilot or the autopilot drive.

As you add more pieces it gets to be more complicated and more to
remember but it seems some safety override would be good on that.

I like if a spin of the wheel induces a dodge. Up here in Maine they
have magnetic lobster pot bouys that cause autopilots to home in on
them. A spin of the wheel at the last second will fool them on some
boats.

Jack

 

[Doug Dotson]

Might not be a bad idea, but there are many ways to get hurt on a sailboat.
Sticking one's arm through the wheel is definately a risky move even when
not using an autopilot.

Doug
s/v Callista

 

[Doug Dotson]

That will work in some of the wheel mounted autopilots but not
necessarily on a below deck system. Ours doesn't lend itself to
any such solution. Our remote control for the autopilot has an
instant shutdown button. Turning off the autopilot doesn;t release
the wheel though. Just freezes it where it is. Must activate the
hydraulic release to return to cable steering.

Doug
s/v Callista

 

[JGS]

<snip>

Is that a cable steering system? I'm trying to remember if I've ever
been on a boat where the autopilot movements feed back to the wheel.
Must be that I have not been around an autopilot on anything but
hydraulic steering systems.

I like being able to rest my forearms on the wheel while the autopilot
is engaged. And if you need to grasp something to steady or brace
yourself, you can grab the wheel because it ain't doing nothing.

Jack

Like Jack, I have only used a hydraulic autopilot. However, when I installed
it, I did hardwire the control power to the main computer unit through
Guarded Large Normally Closed Maintained Pushbuttons mounted at both the
upper and lower helms. They can be hit quickly with the palm of the hand.

Never had to use them but I have tried them and they work. I installed them
because I was not experienced with Autopilots at the time and wanted to make
sure I had a quick way of getting out of trouble should the computer go
haywire. (I still don't have full faith in computers)

I work in the steel industry and we always put in an E-Stop Pushbutton
Circuit to absolutely stop a process when life or equipment is in danger. In
our case, it is the law. In these cases we positively break the circuit to
the motors, not just the control.



Regards
JGS

 

[Doug Dotson]

Those can be disengaged quickly. In addition, I don't think they are
powerful enough to seriously hurt someone. My hydraulic one can swing the
rudder from stop to stop
in 3-5 seconds and probably wouldn't know if you arm was there or not.

Doug
s/v Callista

 

[BrianR]

Raytheon actually recommends this. Occasionally their units will freeze
and
you would be unable to turn the wheel (not a good idea with a freighter
bearing down). they recommended a cutoff switch ( has to cut the main
power
to the unit that controls the rudder). I opted not to do it, but I have
practice diving below to hit the switch on the electrical panel

Surely it's dangerous not to be able to disengage or override the autopilot
from the helm position.
What do you do if you have to dodge something in the water, if you can't
disengage or override the autopilot?