Sunday, June 13, 2010

You can't always get what you want, and yes we have no autopilots today.


Like the headline says, sometimes you can't easily have what you want. That being said, I say, "that there is aways a way", if you want it bad enough. So here is the problem. 

The boat in question is a Freedom 35'. It's a nice looking, and sturdy vessel, but at the preliminary "design the boat meetings", no one apparently asked the question "Would anyone want to use an autopilot on this boat?"  Or maybe during the meeting, the question was asked, and some curmudgeon at the table said, "Real sailors aren't sissy's like those power boat guys are, they love the feel of the helm for hours on end, and the cold wet ocean spray on their face". In either case, the boat was not designed to have an autopilot installed.

The boat has a Raymarine wheel pilot, but its size, and displacement, exceeds the design specifications of the Raymarine autopilot. It's fine while motoring, or sailing in light winds, but in following seas, or blustery conditions, it does not have the horsepower to keep up. I was called to look at the problem, and see what kind of autopilot options were available. 
















In most cases, when a wheel pilot can't do the job, a inside installed hydraulic, or linear drive autopilot will do the trick. These types of autopilots are both stronger, and faster. This boat has a Edson radial drive steering system. In the picture above, as the helm turns, cables pull the flying saucer pulley thingy you see above left, or right, turning the rudder. It's a good system, especially if the rudder is raked back, as is this one.

















The large pulley sits on top off the rudder post, and passes through a collar mounted on a fiberglass table. So now we will open the proverbial "Can of Worms". Since this is a cable drive system, the hydraulic autopilot drive system is now a moot point, and we are left with the linear drive approach. All we have to do is to mount a tiller arm on the rudder shaft, and use a linear drive motor to push and pull it. Hmmm, no place up near the pulley thing to attach an arm to the rudder, how about below?


Nope, not below, the rudder shaft is encased in a fiberglass shaft. I call  Edson, and ask if they thought I could maybe attach a post to the outside edge the pulley, and attach he linear drive to it. Edson's reply was absolutely not, and the Edson manual says the same thing. I'm quickly running out of options, when I have a small idea. See the little post with the bolt in it, just under the hole in the deck in the picture below? That is the attachment point for an emergency tiller. The emergency tiller is a pipe section, with a slot in the bottom of it, that fits around the bolt you see in the picture. 

Now, if I did some very careful measurements, I could pull the bolt, and have a tiller arm fabricated, attached to a short pipe section that would fit into the emergency tiller pipe pulley mount. It could be drilled out to allow the original bolt to fit through both pipe sections. Take the original emergency tiller to the machine shop, and weld on a smaller section of pipe that would fit into the now smaller pipe. 

Oh crap, none of this would work, the moment would be lifted, Edson wouldn't approve, it would be a mechanically sloppy fit if it wasn't welded, and if it broke, it would most likely take out all of the steering with it.

















As I said there is always a way, but it might not be easy, or cheap, or both. So here are a couple more options, sell the boat, and buy one that you can install an autopilot on, or tear out the existing steering system, and install a hydraulic steering system, or don't be one of those power boat sissies, and enjoy the endless hours at the helm, and the cold wet sea water spray,  Got any idea's?, because I am fresh out of them. Thanks Bill Bishop

4 comments:

  1. Jim Maynard from Salem, OregonJune 13, 2010 at 11:49 PM

    Consider that bolt over which the slot emergency tiller's pipe fits. What if that bolt were longer, so as to form a long rod which could serve as a lever to which you attach the autopilot arm? It would have to be made, I suppose, of something stronger than the original bolt, to stand the increased stress because of the long lever arm.

    Continuing this train of thought, how about fabricating something shaped like an enormous socket wrench (including handle), but with a circular hole in the middle of its end rather than a hexagonal hole? The inside diameter of this circular hole would match the outside diameter of the rudder shaft, through which the bolt shown in your last picture passes. Drill and tap the end of the "socket wrench" so that the emergency-tiller-bolt can pass through both the emergency tiller shaft and the end of this "socket wrench". The original emergency tiller bolt would then serve its original function, independent of the sheave for the Edson steering mechanism.

    Then drill and tap an additional two (or four) holes, so that additional machine bolts can fasten the "socket wrench" doo-dad to the rudder shaft. The additional two or four bolts, unlike the original bolt for the slotted emergency tiller pipe, would not pass through the middle of the rudder shaft (which must be free to accept the emergency tiller). The additional two or four bolts just serve as additional fasteners to spread the load.

    I hope this helps...

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  2. Assuming the tiller arm for the autopilot is a "clamp on" for the rudder post, and is of aluminum or bronze... assuming there is enough flange, how about having the clamp on flange of tiller arm machined such that the emergency tiller bolt would fit through the clamp, and the rudder post. You would need a longer bolt but it would not require any more height for the rudder post.

    In the end, you would have the tiller arm "double" clamped (thru bolt), and no loss of emergency tiller function.

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  3. replace the edson radial drive with a Jefa Quadrant from PYI Inc or Lewmar/ Whitlock one that has a drive attachment pin built in, designed for an 8 or 10" autopilot drive link.
    JEFA also has a cool autopilot drive. Rob Bright Ex Simrad autopilot person.
    http://www.jefa.com/steering/steering.htm

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  4. I'm not impressed by the current emergency tiller design either. How does it attach to the rudder post?

    Sounds like Rob's idea is best.

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