This topic is a spin off from Mike Floutier's previous thread on installing a tiller-style autopilot below decks on a Mac 26.
The following is a copy of Mike's last comment in the other thread to kick off some context:
Looking at the other (much more expensive) autopilots, they all seem to have "ram travel limiting" covered in some way, e.g. Rudder position sensor etc.
I'm not sure what percentage of the Mac fleet have autopilots but my guess is it's fairly low and then mainly wheel pilots with their annoying bagel plus associated noise.
Given that the Mac, however good, is a "budget" boat, it makes sense that support for installation of a commensurate autopilot is available.
I guess what I'm thinking is that, since the "ram travel limiting" is a make or break issue on a below-deck st1000/2000 AP system attractive to Mac owners, a separate thread would be good as we may be able to brainstorm a simple mod that's easy to install.
Then, having done so, the "approved" mod can be incorporated into the overall AP mod.
(My Mac 19 benefits from tiller steering, enabling me to use a very simple, ancient Seafarer tiller pilot that I was given for nothing. Just needed the string replacing - I kid you not! Sometimes simplicity is king ... )
Rick Jones (Treasurer), former 26X & 19 owner, Isle of Wight
Was googling last night and came across this site - http://www.mouser.co.uk/new/Hamlin-Electronics/hamlin-littelfuse-59025-f...
The nice idea with these magnetic sensors is that there is no actual contact to go awry (over time & hard to set up) and the sensing distances are often in our range, eg 8mm.
Although they offer NC switching which we need, the working current ratings are far too small. I guess we could add a relay:)
What do you think?
MacGregor 26M 2009 - Sky's the Limit - Suzuki DF50
I've been giving this side issue (to my autopilot install) a bit of lateral thought.
Just to reiterate, the issue is that the ram bangs away at it's stop until either the motor burns out or the fuse blows.
The solution that most folk try, in various ingenious ways, to effect is one that cuts off power when the Issue occurs; in some cases with only power in the offending direction being cut off (the diode solution).
The CAUSE of the problem issue is typically a poorly balanced boat. You know that situation where you find yourself over-powered, the balance goes to pot and the helm gets heavier and heavier until the boat wins the battle and rounds up.
Bear in mind that, on the wheel, you have the benefit of gearing. Now imagine yourself in this situation BUT from a position down below in the aft berth, trying to steer by pulling on one of the tiller arms directly, without any gearing to assist.
Now, you'll find you can pull the tiller over a little but as you do the pressure against the rudder increases dramatically. You pull as hard as you can but you just can't hold the boat on course.
Ok, in practice you might settle for the little you can manage BUT the autopilot isnt that smart (well the st2000 isn't anyway:)) and so it just busts it's guts trying to obey YOU.
My feeling is that what I will do is to keep tinkering with different fuse ratings until I find one that's as sensitive as I want; ie it will keep the motor safe but will also cut me the most slack before it blows. Having done that I'll install a circuit breaker of similar rating on the binnacle near to my hard-wired remote buttons.
The logic behind this is that I WANT to make the system enough of a nuisance so that, rather than coming to rely on it (although in practice I don't see it being much more help that a breaker) it will force me to learn to sail and in the end it will stop tripping the breaker. I think psychologists call this aversion therapy.
MacGregor 26M 2009 - Sky's the Limit - Suzuki DF50
Ok, having actually used the autopilot on the boat both motoring and under full sail this is looking like a non-issue.
Balancing the helm is obviously key but again a non-issue having learnt how to do it. Also the M seems very well designed in this respect (one of many).
The only time I got caught out was when the wind disappeared. The AP was trying to follow my instructions but, with no wind, it just kept trying to no avail and the problem issue surfaced.
Its easy to spot though by simply observing the wheel position and knowing how this relates to the "stops". In this situation I either physically disconnect the AP or revert to Standby mode and "steer" with the buttons.
No problem, saves a lot of tinkering!
MacGregor 26M 2009 - Sky's the Limit - Suzuki DF50