Under deck Autopilot drive mounting

[prv]

I guess the nightmare scenario is that it drives the rudder hard against one of the end stops

As FullCircle says, this should be prevented by the sensors and software of the pilot system (though of course best not to rely on that if you don't need to).

The load I have in mind is in a big sea, when the boat falls into a trough or a wave smacks into the rudder - or possibly even something solid hits it. If the pilot is driving at the time, all that shock load gets transferred to whatever the base of the drive is attached to. In that moment the drive can be considered as a rigid strut.

Pete

 

[prv]

Still think you would be better of buying the 1/4 hp rotary motor to fit under the pedestal then choice of controller. It's a very simple installation with no drag.

What I like about having a linear drive is that it provides a completely redundant steering system. Mine has a separate tiller, so the only parts shared by the two systems are the rudder itself and the rudder stock. Moving it further up the system towards the wheel adds more shared parts whose failure will result in steering loss.

Admittedly this probably matters less with a decent rod system, which should be far more reliable than my cables and quadrant.

Pete

 

[Baggywrinkle]

As FullCircle says, this should be prevented by the sensors and software of the pilot system (though of course best not to rely on that if you don't need to).

The load I have in mind is in a big sea, when the boat falls into a trough or a wave smacks into the rudder - or possibly even something solid hits it. If the pilot is driving at the time, all that shock load gets transferred to whatever the base of the drive is attached to. In that moment the drive can be considered as a rigid strut.

Pete

That's why I thought of attaching it to the rudder end-stops, they should be designed to cope with exactly that use-case.

 

[fisherman]

Saw one where the actuator was the whole width of the (very small) transom, he made a U shaped extension to the control rod to bring the business end back to the central tiller.

 

[pvb]

It's difficult to tell from the photo of your locker, but there could be space to mount a second tiller arm facing forwards, and then mount the base of the drive unit on the starboard side. Again, it's not clear from the photo, but does the forward bulkhead of that locker go right out to the hull each side? If so, you could use that as the basis for a mount, or create a bulkhead, glassed in to the hull, to hold the mount. The Raymarine linear drive on my old HR352 was mounted in this way, on a built-up ply block bolted to the ply bulkhead, see pic...

If you haven't already got it, the installation guide on the Jefa website is well worth reading, as it gives you precise tiller arm dimensions for different rudder stop settings.

View attachment 60085

 

[ex-Gladys]

It's difficult to tell from the photo of your locker, but there could be space to mount a second tiller arm facing forwards, and then mount the base of the drive unit on the starboard side. Again, it's not clear from the photo, but does the forward bulkhead of that locker go right out to the hull each side? If so, you could use that as the basis for a mount, or create a bulkhead, glassed in to the hull, to hold the mount. The Raymarine linear drive on my old HR352 was mounted in this way, on a built-up ply block bolted to the ply bulkhead, see pic...

If you haven't already got it, the installation guide on the Jefa website is well worth reading, as it gives you precise tiller arm dimensions for different rudder stop settings.

Yep, read the guide on the Jefa website, unfortunately there's no bulkhead in the locker, I think choice one is second tiller and fore & aft mounting (if it's possible with all the alignment points taken into account), I'm seriously going to talk to Cliff Mogridge at SBS, as he knows Whitlock inside out to see whether the Lewmar will mount as well.

 

[Fr J Hackett]

Yep, read the guide on the Jefa website, unfortunately there's no bulkhead in the locker, I think choice one is second tiller and fore & aft mounting (if it's possible with all the alignment points taken into account), I'm seriously going to talk to Cliff Mogridge at SBS, as he knows Whitlock inside out to see whether the Lewmar will mount as well.

I got all my info from Cliff very informative fellow then I had to deal with the snake pit of Lewmar, if for your sake you go down that route I hope they have improved.

 

[Tranona]

One word of warning if you are thinking of going down the pedestal motor route, I find the one on my boat very noisy if standing or seated at the wheel.

 

[Fr J Hackett]

One word of warning if you are thinking of going down the pedestal motor route, I find the one on my boat very noisy if standing or seated at the wheel.

What pedestal and motor? and what type of noise? I only ask because I was never aware of any noise as opposed to the atrocious wheel pilot that it replaced and earlier linear types on other boats that whirled away.

 

[Tranona]

Lewmar pedestal and motor. New Bavaria 33. The only one in the range that uses the motor as the pedestal is almost immediately on top of the rudder stock and no room for a linear drive. Just the noise of the motor running back and forth, much the same as a wheel pilot, but at least it works! However, the noise may be specific to this model boat because of the motor location under the cockpit floor in the central tunnel. Fortunately the boat is very directionally stable so the motor does not have to work very hard.

 

[pvb]

What pedestal and motor? and what type of noise? I only ask because I was never aware of any noise as opposed to the atrocious wheel pilot that it replaced and earlier linear types on other boats that whirled away.

The Jefa linear drive (also sold with the Garmin badge on it) which you're considering is very quiet and seems very well engineered.

 

[ex-Gladys]

Just back in hotel after visit to Southampton Boat Show, and interesting conversations with Aztec (Jefa's UK importer and Others. First of all, that mechanical drive is a beast. The size didn't come across in the diagrams, and that may put paid... Secondly, the guy on the Lewmar stand was sure they could help with the fit of a Mamba drive to my ancient Whitlock system.... All the input has really helped, thanks to all

 

[Fr J Hackett]

If you go down the mamba drive option you won't be disappointed.

 

[pyrojames]

I had similar issues fitting an AP into a timber hull. I went for twin hydraulic Rams and 12v motor. The twin Rams are coupled to a cross head bar on the rudder stock and bolted to a rectangular frame that is bolted to the hull structure fore and aft. The advantage of twin Rams is the significant reduction in thrust loads on the rudder stock, and into the hull. The rectangular frame into which the Rams bolt, only tries to exert a moment into the hull structure and loads are easily accommodated. I think the whole framework was about 250 X 700 mm. It's now done thousands of miles without a hiccup.