Rudder angle

[TrentePieds]

Shane:

We are not really making progress with this thread, are we :-)

People still seem confused, and I confess I am. If you'll be kind enuff to answer the three questions I asked in post #6, we can begin to make headway.

Meanwhile, you say: "So I was thinking only of the angle required to steer the boat correctly."

What do you mean by that? "Steer[ing] the boat correctly" is far, far too loosey-goosey to be helpful. Do you mean that you would like the AP to hold the boat on a stated ("dialed in") course when sailing? And that in your particular boat the AP doesn't do that?

Forgive me if what I say below is something you already know. If that is so, it hasn't been obvious to me in what you've said so far.

You probably need to start with considering what your "point of sail" is when you hand over to the AP. You need to begin with this: On any point of sail above a beam reach, the boat should, when she is "balanced" hold her course unaided for several minutes at a time. The rudder(s), then, absent AP and if the helmsman lets go the tiller, should trail behind absolutely unloaded and having no influence on how the boat behaves. You achieve that blessed state by manipulating the relative areas of Mainsail and Foresail, and the tension of their particular sheets. Slight course corrections can then be achieved by varying the tension of the foresheet. No need to use rudder, and therefore no need for AP at all!

If, now, sailing along like that, you wish to come about, rudder is certainly required, but if you are "footing along", i.e. if you are not "pinching" (trying to point too high into the wind), 5º of rudder deflection is probably enough to make the boat turn far enough that the foresaii "back winds" and helps you complete the turn. As you shift the foresail to the new leeward side and trim it correctly, the boat should foot along on the new tack with the rudder(s) again trailing behind with no attention to the tiller being required.

I do not see why Mr. Ackerman's wonderful patent should have any relevance to that.

If this is the sort of answer you were looking for, then we can certainly continue the discussion, for use and effect of rudder depends in part on Point of Sail, but it also depends on fundamental design characteristics, including whether we are talking mono- or multihull. Summer Twins is, I believe, a forty or fifty year old design, and therefore, if there had been anything amiss with the basic design, the problems would have been well and truly written up by the aficionados.

The mechanics of leverage, moment arms and applied force I'm sure you already have under control.

TrentePieds

[silkie]

What does "losing 60% of rudder" mean?

[Shaneesprit]

60% was a guess,
But if I steer by hand I can turn the rudder 90’ or 45’ to port or 45’ starboard.
Yet the pilot has only 24’ or 12’ to port or starboard.

[Sailmonkey]

Originally Posted by Shaneesprit

60% was a guess,
But if I steer by hand I can turn the rudder 90’ or 45’ to port or 45’ starboard.
Yet the pilot has only 24’ or 12’ to port or starboard.

can the tiller pilot maintain a course?

under normal circumstances using much more than a few degrees of rudder while sailing isn't required.

[belizesailor]

Originally Posted by Shaneesprit

60% was a guess,

But if I steer by hand I can turn the rudder 90’ or 45’ to port or 45’ starboard.

Yet the pilot has only 24’ or 12’ to port or starboard.

You mean inches not feet right?

" = inches
' = feet

[belizesailor]

For maintaining course you should only need small rudder movements. If you need more than that then something else is wrong...like the sail plan is way out of balance.

To tack a catamaran you dont need big movements either. Unlike monos, cats tack much better with a relatively slow turn (more like carving a turn on skis than slamming the helm over to tack a peformance mono).

Take it out for a spin and see what it actually does.

[belizesailor]

Originally Posted by sv_pelagia

What a strange thread... no one has any idea what OP is asking. I certainly don't.

Perhaps he/she wants to know if a Rudder Angle Indicator is necessary (i.e., hydraulic steering)?

(Can't help it: spent 7 hrs yesterday installing a new rudder followup for new autopilot... nothing like being 6'3" and crammed into a stern locker.)

Well that's never stopped the CF crew before!

[Searles]

The more angle of attack on the tiller or rudder the more load ,the shallow angle advised for instillation may be to lessen the load on the pilot drive unit,on most sailing boats 35deg pt and stbd is about max if you don’t want too much drag,big sailing ships had less than 20deg rudder movement each way.⛵️⚓️

[Shaneesprit]

Originally Posted by belizesailor

You mean inches not feet right?

" = inches
' = feet

Degrees - I don’t know the best way to write, and although generally a metric guy, I do know the ‘ &”

[Shaneesprit]

[QUOTE=belizesailor;3379

Take it out for a spin and see what it actually does.[/QUOTE]

Yes it can hold a course, or at least it doesn’t loose control, problem is that the boat zigzags,
IN my opinion, due to the lack of angle available to the tiller, by the time the boat reacts to the pilot it’s too late and, hits the stop and then returns in the other direction.
It doesn’t matter if I am sailing upwind down wind. Flat calm on the engine or with rolling waves entering port under sail actually the only time I was impressed by the pilot is when in the waves it didn’t fault, it’s that bad that once a lifeboat that was in the waterway came across to have a look at what was going on.

Obviously I am looking at all options,
Today’s job is to work out the drive length of the old pilot and so the angles that used to steer

[Sailmonkey]

Try changing the rudder gain, let the pilot steer more slowly and wait longer for the boat to react. If that doesn’t cure the problem, it’ll help.

[belizesailor]

Originally Posted by Shaneesprit

Yes it can hold a course, or at least it doesn’t loose control, problem is that the boat zigzags,

IN my opinion, due to the lack of angle available to the tiller, by the time the boat reacts to the pilot it’s too late and, hits the stop and then returns in the other direction.

It doesn’t matter if I am sailing upwind down wind. Flat calm on the engine or with rolling waves entering port under sail actually the only time I was impressed by the pilot is when in the waves it didn’t fault, it’s that bad that once a lifeboat that was in the waterway came across to have a look at what was going on.



Obviously I am looking at all options,

Today’s job is to work out the drive length of the old pilot and so the angles that used to steer

Zig zagging is usually caused by calibration issues like rudder response. Also happens while the system is "learning".

I think youve got plenty of physical throw for steering (obviously, it generally holds a course). Review the calibration settings and test with different settings.

Case in point, I purchase a used Raymarine autohelm unit once that had been previously installed on a power boat. The unit was in excellent condition, but holy crap did it do wild things on a sailboat until I lowered the rudder response...like evasive maneuver swerving!

Try lowering the rudder response first.

[Shaneesprit]

Tried all of the settings, more aggressive, less aggressive, it’s been setup to play dumb, but only time it can hold a course is when it’s off.
I have just installed a MFD and updated the firmware.
I am more than cable of adjusting settings, in fact I could do with real access to the settings not just the ones they want you to use. that way it would work.
Not sure what the firmware update has done, as I didn’t get out this weekend, not sure when I get out this year, work gets in the way of a good sail.

The reason I asked about the rudder angle is that, I understand how computerised controls work and I am convinced, without access to a true dead band in the settings, my only option maybe to fit the tiller ram closer to the pivot in order to have the boat react faster, as the pilot is not capable of waiting for a response., my rudder sits behind a leg and as such has no leading edge. This IMO would make the response slower and the tiller heavier.
Boat is only 2500Kg and pilot can handle 6000Kg boat, although makes no mention of twin rudders.
( noting that the last pilot failed and was also rated well above weight ) could say failure was either a loading issue or poor quality manufacturing. Remember that the last pilot actually worked!

[Shaneesprit]

Although still not convinced about the lack of angle from the tiller pilot.
I have never tried to come about with the pilot connected.
Mainly because before I had no trust in it or control, now i have a little of both but no time left this season. ( Covid rules have devastated my sailing time )
I can be fairly sure the boat is difficult to tack into the wind at the best of times, well its a CAT but I found the best is just to turn and pretend the sails don’t exist until it’s gone around.

The main issue has been corrected by fitting an MFD and updating the firmware scary that the firmware could be that bad out of the box . I was hoping to decide if I should fit the pilot to my own instructions rather than the manufacturer’s instructions. - I still fully believe that I would be proven right, it’s just if I take the time to prove it.