ST2000 mounting position

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dur

dur

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Raymarine are pretty clear that the ST 2000 has to be mounted exactly 18 inches ahead of the rudder stock centre line which is where I have a galv steel mainsheet horse. Something about the gain /forums/images/graemlins/confused.gif

I might be able to squeeze the thing ahead of the horse and behind the cockpit coaming. Can anyone tell me...

- If it is, say, 24" ahead of the rudder line will it still work (albeit with less throw)

- Will the steel horse upset the compass

- how far does it extend / retract (so I can work out if there is enough swinging room.

Thanks
 
I have exactly the same problem (substitute cleat for horse) and Raymarine reckoned the measurement was critical to within a few mm. So I still haven't mounted it. I plan to get a mounting made which will fit over the cleat. Could you do the same with your horse?
 
The fluxgate on my autohelm is at the actuating rod end, so you don't want magnetic items too near there. If your horse is austenitic ss however, (try with a magnet ), it may not have much, if any, effect. FWIIW, Raymarine recommend that the (separate) fluxgate position for the ST4000 should be within 20 deg of correct on all points when tested with a hand bearing compass, so it doesn't seem ultra critical. Regarding the 18", I cannot see how it can make that much difference, I'd be interested in the justification for Raymarine's advice, mine certainly isn't to within a few mm, though it's not greatly out. After all, the overall gain of the system includes the response of any particular boat which is a big variable. As for total stroke, can't really help, but I'd guess perhaps 300mm.
 
[ QUOTE ]
The fluxgate on my autohelm is at the actuating rod end

[/ QUOTE ] "In the case at the actuating rod end " is I think what you mean. IIRC in the ST2000 it's in the "bulge" in the bottom of the case.

It surprises me that the mounting position is as critical as within a few mm of that specified I thought the optimum position might vary from boat to boat. However we can do little but respect the manufacturers superior knowledge of their products.
24" is a long way from 18" (According to the installation instructions I'm looking at it should be 17.5"!)


I think the possible effects of a galvanised horse could be an issue.

I deduce from the dimensions that are given in the Operation and Installation instructions that the stroke is about 12"
 
Thanks everyone. Hopefully this will show the problem. I think the cleat, slightly aft of the horse, and the horse itself occupy the suggested mounting position. There is then a space then the coaming.
I did wonder if something with a lever and push rods would work but it would be a fiddle and would have to be done well to work properly and might be beyond my abilities. But, a long haul under engine is very tiring as the boat has a quarter prop and wants to drive in circles so a bit of assistance would be very welcome.

ws_aft_sm.jpg
 
The horse is only about 15mm thick. can it not go immediately astern of it on an underslung bracket, taking note that the 18" specified is supposed to be perpendicular to the shaft. The 15mm will make no difference

that said, the 18" puts the attachment where the throw is sufficient to reaach both port and starboard and gets as much leverage as it can. The gain is surely a red herring as others have said as a perpendicar rudder shaft will have adifferent gain to a sloping one as yours has.

Mock it up with a fencepost as a tiller and a clamped block for the fixed end. It will work fine. then you can commit to it.
My ST2000 is a good unit IMHO. Others have criticised its watertightness, but mine is good.
 
Thanks. I think a bit more offering-up etc would be a good idea. The cleat might be a problem for the aft-of-the-horse mounting as the counter hung rudder gives a vertical movement to the tiller as well as side to side. The other problem with going aft is that the lever is shortened and the load on the tiller is significant when motoring.
 
Sloping rudder is a red herring. The 18 inches is perpendicular from the axis of the rudder, which means that a sloping rudder may mean the actual attachment point is more than 18 inches away on the horizontal plane.

Or at least that is how I remembered the instructions when I last read them.
 
[ QUOTE ]
Regarding the 18", I cannot see how it can make that much difference, I'd be interested in the justification for Raymarine's advice,

[/ QUOTE ]
I think the reference to rudder gain is a bit of a red herring. The issue with the 18' measurement is due to the way the body of the autohelm changes angle as the ram traverses. By knowing the extension of the ram AND the length of the tiller it can correct the reading from the compass which is in the body.

However as far as I can see this is only an issue if you're interested in the reading on the display. The system uses feedback to return the compass reading to the value it was showing when you pressed "Auto". By moving the thing further down the tiller you're reducing the gain in the feedback loop. But boats vary in sensitivity to the helm and the software automatically adjusts the gain anyway. So I can't see the issue myself.

BTW the manual also says it should be fitted level. Which is fine until you put the sails up...
 
I have an ST 2000 on Jissel, which I carefully fitted as per the destructions. It's fine under motor, but doesn't have enough movement to control the boat under sail, as Jissel has always been a bit twitchy, especially when close hauled. I'm going to move it aft several inches to give more (and quicker) movement. In my case, the TP2000's well overspecced for my boat, and tiller forces are fairly light, so it could cope with being a LOT further aft.

In your position, Max, I'd check the steering load on the tiller at a convenient point aft of the horse and make sure they don't exceed the maximum the TP can cope with and go for it. Just make sure the tiller won't foul the case of the TP when the TP arm is fully retracted.
 
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