Hunter 380 Linear or Sprocket Drive Autopilot

smokey73 · Sep 25, 2017

Tucsonsailor said:
I have just purchased a Hunter 380 and have had three electronics folks seem to come up short with the best way to an autopilot.

All agree that the EV200 would be the best choice. Where the disagreement comes is with the drive unit.. Linear or Sprocket.

Perhaps I can draw on the experience of others here. There does not seem to be enough room for a linear drive underneath the access plate behind the binnacle. I am leaning towards a sprocket and chain drive.

Does anybody know what sprocket works, how many teeth, the size of the chain or cable connection and the best place to purchase that? That is where everyone seems to fall short.
Any idea of how much labor is involved would also be helpful because I am really getting a range from these folks. Thanks for your advice

I installed a Raymarine Type II Rotary (sprocket) drive on my 1994 Hunter 40.5 with the EV200 and P70 head. I love it!. So much better than the wheel ring drive. For my boat, the mounting bracket was already installed in the binnacle and could be accessed by taking out the "cup holders). It was actually built by Hunter for the use of the Rotary Drive. No modifications necessary.Rich Stidger has pictures on this on his owners modifications section for the Hunter 40.5. The size of the spockets needed are included in the instructions and it depends on the lock to lock number of turns for your particular boat. I believe Raymarine sells one of the sprockets (for the drive itself) but you will have to source the larger sprocket that goes on the wheel shaft that extends into the binnacle. I had one custom made I believe. You will want Stainless Steel for sure for the sprockets and the chain so as not to interfere with your magnetic compass. I have some stainless steel chain available that was left over from my installation as it was just as cheap to buy a "length" of it than a smaller amount. Let me know if you are interested and I'll sell it to you at cost for the chain plus shipping. You'll need to know the size and pitch for the chain before you source the sprockets. I'll try to dig up my purchasing info. I love the rotary drive. I am sure there are many who love the linear drive. A lot will depend on if the bracket is already installed. That made installation a snap. If I can find my records I can give you an exact cost that I paid less labor (I installed it into the binnacle myself) They had run the wires for the power etc. already.

Sailgunner · Sep 25, 2017

I think the Edson rep help be sizing the sprockets.

jviss · Sep 25, 2017

smokey73 said:
I believe Raymarine sells one of the sprockets (for the drive itself) but you will have to source the larger sprocket that goes on the wheel shaft that extends into the binnacle.

I'm not familiar wit these, or your boat, but I gather that the rotary drive is driving the shaft for the wheel? This means that if you have a cable steering fault, your rotary drive can't steer the boat, either.

One of the great advantages of a drive connected directly to the rubber post, as with a linear drive and tiller arm, is that if there's a steering system failure, one can steer the boat with the autopilot.

smokey73 · Sep 25, 2017

jviss said:
I'm not familiar wit these, or your boat, but I gather that the rotary drive is driving the shaft for the wheel? This means that if you have a cable steering fault, your rotary drive can't steer the boat, either.

One of the great advantages of a drive connected directly to the rubber post, as with a linear drive and tiller arm, is that if there's a steering system failure, one can steer the boat with the autopilot.

That is true for the rotary drive. That is also true for the thousands if not hundreds of thousand wheel autopilots in use today. If there is a steering system fault in the wheel itself or the steering cables, the autopilot won't work. Guess I can live with that possibility and make sure I know how to use my emergency steering bar.

jviss · Sep 26, 2017

smokey73 said:
That is true for the rotary drive. That is also true for the thousands if not hundreds of thousand wheel autopilots in use today. If there is a steering system fault in the wheel itself or the steering cables, the autopilot won't work. Guess I can live with that possibility and make sure I know how to use my emergency steering bar.

I doubt there are hundreds of thousands of wheel pilots in use. Be that as it may, it doesn't mean it's not an issue, just because there are lots out there. Most "emergency steering bars" are difficult, or near impossible to use. I like the idea of this hierarchy: primary steering, autopilot steering, and then e-tiller.

Couldn't you use a rotary drive connect to the rudder post, or would there not be sufficient mechanical advantage?

smokey73 · Sep 26, 2017

jviss, I don't disagree at all. I like the idea of the Hierachy you note. It has a lot to do with application, space, ease of installation, and intended sailing grounds. If you are going offshore for extended bluewater cruising I'd opt for the one that takes the least power as my primary steering and that would be the wheel followed closely by windvane style steering as the secondary with the electric autopilot (be it rotary or linear) as the backup then the steering bars as a last steering choice (followed by sails balance and drogues). If you sailing grounds are primarily bays, and coastal cruising where there is "help" not too far away or you can anchor and wait for a tow then other things influence the decision, including cost.

If my boat didn't already have the bracket for the rotary drive and the wires already run for the power and all the connections close by where the drive would be installed I would probably have opted for the linear drive and am sure I'd be just as happy with it too. If the Hunter 380 is anything like the 40.5 there is not enough room to install the rotary drive to the rudder post and you've lost all the advantage of using the rotary drive even if you could install it there. I think there is also the question of how "robust" the connection of the linear drive is to the rudder post. The way I'd have to install it didn't look all that robust. In my case I think the rotary drive is an order of magnitude more robust. Look at how the linear drive will have to attach and then decide. Good maintenance on the steering system including lubrication, maintenance, etc goes a long way to mitigating the potential for loss of the wheel steering capability. There are a lot of trade offs. YMYBYC (Your Money, Your Boat Your Choice)

jviss · Sep 26, 2017

Hi Smokey73, thanks for the thoughtful rely, and analysis. Steering and autopilots are one of my favorite topics, or I should say, topics that induce the most obsessive response in me.

Please don't take my questions and comments as criticism of your approach. I think that's a brilliant solution, to be able to so simply and easily install the rotary drive. It is far superior to an external wheel drive, in my opinion.

smokey73 said:
I think there is also the question of how "robust" the connection of the linear drive is to the rudder post.

It must be robust, of course, to work well. There should be a separate, strong, bronze tiller arm connected directly to the rudder post, as Edson makes. And, the linear drive must be robustly connected to the hull. A good installation in a fiberglass boat is a fiberglass shelf or pedestal securely tabbed and glassed into the hull. This is the part that costs a lot of money. I paid about $1,000, mostly in labor, just for a pedestal mount in my C36. The weak link is definitely the linear drive itself, and inside that, the belt, some plastic gears (I think they are still plastic), and so forth. The bad news is that Raymarine doesn't support end-user repairs of these. The good news is that you can swap out the entire unit very quickly, if you are rich enough and paranoid enough to carry a spare.

Interesting, your comments about offshore versus inshore. I think of the inshore situation as requiring more immediate attention, since there are so many things to hit and run aground on, and current and surf and wind creating a dangerous situation. My harbor is a bit scary and I would much rather lose steering far offshore, where I'd have some time to work on it, and while I'm approaching the harbor, rocks on my left, a shoal with a wreck on it to the right, a strong current into or out of the river, and occasional breaking waves on the beach to the North - or across the entire harbor entrance as for the last couple of weeks!

At the end of the day, the answer is to service and maintain the steering. Inspect and properly lubricate cables, check sheaves and sheave bearings, points where they attach, the radial drive wheel on the rudder post (for cracks), and so on. At least annually. Best not to need the back up!

Cheers,

jv

smokey73 · Sep 26, 2017

jv, Again I totally agree. We aren't plagued here in the Southeast from probably around Wilmington NC all the way to at least St. Augustine FL with too may "rocky" places. There are a few jetty's and some oyster beds but not much else. Traffic can be a problem and a sudden failure approaching the dock would be a problem of course. With those exceptions, you are more likely to "run amuck" into the silty bottom or onto a sandbar than into rocks. Of course traffic is always a problem but I try to avoid any close encounters anyway (I realize you may not be able to do that). The driver for me was the essentially "plug and play" installation once the wires were run. I also just couldn't figure out what I considered a robust enough place to mount the linear drive to the radial drive.

I occasionally get involved in failure analysis and accident investigations. I don't have any statistics to back up my beliefs, but I'd bet good money that most steering failures (except grounding damage to the rudder itself) can be traced back to failure to do appropriate maintenance. If its damage to the rudder then no autopilot (except the independent wind vane) will help. Prevention is the key. Our discussion just reminded me to do my annual inspection and lubrication of the steering system.

jviss · Sep 26, 2017

smokey73 said:
Prevention is the key. Our discussion just reminded me to do my annual inspection and lubrication of the steering system.

Indeed. Many people forget or put it off, and two years turns into three, to five, and eventually it's ignored.

Besides running a Kleenex over the wires to detect broken strands, and a good, thorough, visual inspection, I mean like you are a crime scene analyst, you should grab stuff and shake it, see if it moves, or is otherwise loose, or out of whack. Then just a very light application of a very light oil to the cables, which is really for internal lubrication. And lube shave axles, etc. But based on your background, I'm sure you knew that!

charliegrau · Sep 27, 2017

I installed the rotary drive with EV200 on my 1999 389. Eddie Breeden at Hunter sent me the specs for the sprocket. Attached file has the info you need for sprockets and chain. The set up works great. Mounting the rudder position sensor under the cockpit sole next to the rudder post was the trickiest part.

smokey73 · Sep 27, 2017

charliegrau said:
I installed the rotary drive with EV200 on my 1999 389. Eddie Breeden at Hunter sent me the specs for the sprocket. Attached file has the info you need for sprockets and chain. The set up works great. Mounting the rudder position sensor under the cockpit sole next to the rudder post was the trickiest part.

Great info Charlie, Are those carbon steel sprockets and chain? Did that or does that cause any problems with your magnetic compass at the binnacle? I went with stainless steel sprockets and chain?

artboas · Sep 27, 2017

There is a very important thing to keep in mind when installing the rotary drive.
I had a 40.5, and well appreciated the 2 threaded studs that Hunter welded to the pedestal which accommodated mounting a platform for a rotary drive.
Firstly, the platform has to be mounted very rigidly. Even though the 2 studs are (to the best of my memory) 1/2" thread, there is a lot of torque at the end of the platform. I put a stainless leg into the end of the support shelf to stabilize it.
The more difficult problem is chain slack, which results in hysteresis in the motor driving the wheel shaft. Essentially, if the chain isn't tight, you will have several degrees of motor rotation before the wheel turns. And this causes what is referred to as "deadband" It can really mess up the tracking capability of the pilot.
There are 2 ways of dealing with this:
Install a chain tensioner
Or
When you install the shelf, use the threaded mounting studs as your adjustment.
To do this, you will need to install a set of jam nuts (they are thinner than standard) and large fender washers under the platform.
This will be a trial & error fitting process, where you fit everything together, add washers, adjust nuts, etc.
But, you really want to spend the time & take the slack out of the chain
Another really good idea is using a Fenner Trantorque bushing to mount the gear to the motor shaft. It makes chain alignment a breeze. If you do this, your gear hub ID must be sized for the OD of the trantorque.
I highly reccomend you consider this.
Good luck!

Hunter 380 Linear or Sprocket Drive Autopilot

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