Tiller autopilot installation

[Robert England]

My boat is a C&C 27 MkV, with a tiller. The rudder is transom hung. I installed an Autohelm ST 2000+ autopilot last summer. I installed it exactly as per the instructions -- exactly 18" from rudder pivot to autopilot pin. My problem is that the autopilot arm has only a 10" travel; 5" to port of center and 5" to starboard. This travel is not sufficient to move the rudder through a large enough angle to control the boat. For example, the autotack function does not work. When I try to use autotack, the boat turns so slowly that the autopilot drives all the way against it's stop, tries to go further, and pops the circuit breaker. This leaves me with a boat that keeps turning until I can get back to the tiller and unhook the autopilot. Since I usually sail singlehanded, this makes for some awkward and dangerous manouvers! Before I drill more holes, has anyone had experience with shortening the rudder pivot to autopilot pin distance to less than the prescribed 18"? How short should I go?Thanks for any help.

 

[Larry Barnes]

shorten the lever

The obvious limitation to shortening the lever length would be the thrust capacity of your tiller pilot. As the lever gets shorter the amount of thrust needed to control the boat would increase. Check to see if you have the capacity. Has the recomended length of the boat, for the tiller pilot that you've chosen been fullfilled, or would it work on a larger boat? That would certainly tell you if you have power in reserve. I think that you would want to maintain reserve power or the auto pilot will be going off line more often, when you need it most. Maybe not such a good idea.

 

[Ed]

autotacking

I have the same installation on a 25. Mine doesn't pop the circuit, but I know what you mean about the rudder not going over enough.The few times I have used the feature, the boat would over tack to going downwind before the unit would respond and bring it back. I think it is wishfull thinking to assume a tiller trimming device can handle such a large swing on a short hull. It's not even effective keeping the hull on course on rolling seas.I don't know what you need to do during a tack. I take the tillerpilot off of the pin and work the tiller and jib sheets by hand. I use a Davis tiller tamer to help hold the tiller in position. Not totally locked down. More like a friction clutch, the same way the dutchman boom brake works. Just enough to keep the tiller from swinging around if I take my hands off for a moment while backing the jib and moving my butt to windward.The autohelm isn't intuitive enough to handle the job.

 

[Robert England]

Autopilot power

Thanks, guys for the reasonable replies. I posted this question on some other forums and got some really wacky answers! The ST2000+ is rated for a 10,000 lb. boat; mine is 4500 lbs. The rated thrust is 170 lbs - enough to injure me if I get stuck behind the tiller! The reason I bought an overspeced unit is the lock to lock time - 4.5 seconds vs. 8 seconds for the smaller ST1000+. I know from previous experience that fast hard over time is important going downwind in a large following sea to keep control of the boat. Also, the ST2000+ has a recirculating ball drive vs. lead screw drive on the smaller unit. I plan to relocate the unit so the 5" throw can move the rudder through most of its swing. I'll also check to see if the autopilot should have a limit switch to prevent it from stalling at the end of its range. Thanks again.