Autopilot installation issue

[Deefweef]

Okay, here is an interesting problem:
I'm busy figuring out how to install the mechanical linear drive on a Hunter 44 DS. It never had an autopilot installed yet.
Looks like the steering arm is mounted a bit twisted on the rudder shaft. In the first picture the rudder blade is in the center, but you can see the two tiller levers are a bit rotated towards one side. This makes the endpoints of the auxiliary arm be off quite a bit and there is no good place to mount the drive as it is supposed to.
I'm not sure but it looks like the hole in the rudder shaft is not at a 45 degrees angle to the rudder blade (as it is supposed to be?) Can it be that this part of production was not carried out according design?
The steering from the whitlock stand is working fine, but I would think that steering to one side is more progressive than to the other, but I can live with that.
The problem I'm having is that there is no good spot to mount the linear drive.
The second photo is from an instruction on how to mount the linear drive from Hunter, but for me the mount point of the linear drive would not end up in this spot at all, but would be far away from the bulkhead and it would be a bad spot from a constructional strength perspective.
What would be the best way / easiest way to address this?

 

[Gunni]

Are you noting that you don’t use the existing quardrant hole to mount your drive rod? The drive ram should have an acceptable angle to attach to once you line up to a new quadrant mounting point.
That should also remedy your confusion about how to mount the drive in the adjacent locker.

Make absolutely sure you have the rudder centered up. Remember, AP drive range is typically 25 degrees short of full stop - your AP doesn’t have the range of steering that your wheel does. So even if you have to go with the geometry you have here you should be fine.

 

[Deefweef]

Thanks for your quick reply. I should point out that there are two pictures I found on a Hunter instruction for mounting an autopilot. The one with the pencil markings of the radius and endpoints is the picture from our boat.
In the pictures of the Hunter instructions there is an additional hole for mounting the linear drive. Mine doesn't have that one and doesn't seem to need it because the existing hole is already under the recommended 10 inch (250 mm) arm length that is sugested by Raymarine.
I guess you're suggesting to drill a hole in my arm a bit closer to the rudder shaft and because I have some more room there I could offset it a bit to starboard side? My worry there would be to make the moment arm even shorter. But a good suggestion I hadn't thought about. I'll have to take some measurements on the boat.
I didn't know that AP drive range is always limited (I did see a setting in the raymarine evolution setup, think it was at 30 degrees). That does help, because the problem, of course, occurs at one extremity of the steering range, but what if you would power-up the drive from that rudder position? The forces on the actuator would be enormous. This is my main worry. On the extremity of steering towards starboard, the linear drive doesn't "actuate" by very much and mainly just turns.

 

[Rick486]

Okay, here is an interesting problem:
I'm busy figuring out how to install the mechanical linear drive on a Hunter 44 DS. It never had an autopilot installed yet.
Looks like the steering arm is mounted a bit twisted on the rudder shaft. In the first picture the rudder blade is in the center, but you can see the two tiller levers are a bit rotated towards one side. This makes the endpoints of the auxiliary arm be off quite a bit and there is no good place to mount the drive as it is supposed to.
I'm not sure but it looks like the hole in the rudder shaft is not at a 45 degrees angle to the rudder blade (as it is supposed to be?) Can it be that this part of production was not carried out according design?
The steering from the whitlock stand is working fine, but I would think that steering to one side is more progressive than to the other, but I can live with that.
The problem I'm having is that there is no good spot to mount the linear drive.
The second photo is from an instruction on how to mount the linear drive from Hunter, but for me the mount point of the linear drive would not end up in this spot at all, but would be far away from the bulkhead and it would be a bad spot from a constructional strength perspective.
What would be the best way / easiest way to address this?

Well Deef, I'd like to help but I'm not sure how. I have a 44DS vintage 2008 with the same autopilot. I haven't looked down there in a while, but probably should. Is there anything I can look at or measure or take pics for you? I imagine my setup is the same as yours.
Rick

 

[Deefweef]

Wow Rick, that would be really helpful. For pictures of the tiller arm you would have to unscrew the part of your cockpit floor behind the steering console.
Since yours is 2008 I would suspect it to also have the composite rudder shaft and I would be very curious how the alignment is when the rudder is amidships.
If your installation, as Gunni suggested also uses an additional hole I would be very much interested in the length of the moment arm for the raymarine drive (distance between rudder shaft center and bolt for the drive). maybe you could measure this by accessing the emergency tiller port.
I've double-checked the Raymarine manual for the mechanical linear drive and they advise on a tiller arm of 10" (no maximum or minimum mentioned). A 10" tiller arm would never fit in the area Hunter provided.

 

[Deefweef]

What I like about figuring out these challenges is that you figure out stuff more and more. I've just read the whitlock Cobra Steering manual. The forward offset for the main steering tiller, that has the cobra steering attached to it, is by design!
"...the pedestal output lever is shorter than the tiller lever by a ratio of 1.52:1. At midships therefore the tiller arm and output lever are not pointing athwartships, but instead are slightly angled forward..."
So this is one worry less. It still doesn't make sense to me though that the auxiliary arm for the drive is at a 90 degree angle with that offset arm. I believe "wide angle geometry" as the Whitlock manual mentions, doesn't work when you have a linear actuator.

 

[Rick486]

Wow Rick, that would be really helpful. For pictures of the tiller arm you would have to unscrew the part of your cockpit floor behind the steering console.
Since yours is 2008 I would suspect it to also have the composite rudder shaft and I would be very curious how the alignment is when the rudder is amidships.
If your installation, as Gunni suggested also uses an additional hole I would be very much interested in the length of the moment arm for the raymarine drive (distance between rudder shaft center and bolt for the drive). maybe you could measure this by accessing the emergency tiller port.
I've double-checked the Raymarine manual for the mechanical linear drive and they advise on a tiller arm of 10" (no maximum or minimum mentioned). A 10" tiller arm would never fit in the area Hunter provided.

Unfortunately, I will not be able to get at the AP installation until the shrink wrap comes off, and that won't be until Around April 15.
Maxine definitely does not have a composite rudder shaft. Stainless steel. I am certain of that. I suspect that the installation is as shown in the Hunter pics. I have inspected it in the past.
If you have not done so already, I would discuss this with Hunter tech support.

 

[Deefweef]

If it is exactely like the Hunter pictures, I don't get that they went for the much shorter moment tiller arm than is advised by Raymarine. If you take a guestimate from the picture you could conclude that the tiller arm is around 6 to 7 inches and not the recommended 10 inches. This will make ahuge difference on the rotational force that the mechanical drive is able to produce. A type 2 drive will deliver less than a type 1 with a 10 inch tiller arm in rotational force. and would probably be out of spec for the actual displacement. Luckily I have chosen a type 2. I will take it up with Hunter Tech support. I will report back with the reaction.

 

[seadaddler]

Try contacting Hunter for info for your install,they Hunter helped me a few years back with all the info for a below deck linear drive
and in the process of installing one for my 2007 H-36.
I am waiting for a shop to make a tiller arm for me as we speak but
my rudder post is solid stainless or aluminum and I thought that Hunter went with solid rudder post for all boat back in 2007.
Nick

 

[Deefweef]

Try contacting Hunter for info for your install,they Hunter helped me a few years back with all the info for a below deck linear drive
and in the process of installing one for my 2007 H-36.
I am waiting for a shop to make a tiller arm for me as we speak but
my rudder post is solid stainless or aluminum and I thought that Hunter went with solid rudder post for all boat back in 2007.
Nick

Thanks for sharing this I have contacted Hunter technical support.
What I notice in their instruction that you shared, is that Hunter describes the importance of obtaining a 90 degrees angle to the AP drive tiller arm and with the instructions I got for the 44 ds it describes a location for mounting the AP drive that with my rudder tiller setup I would never obtain this 90 degree angle.