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Old 09-07-2014, 07:29   #1
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Full Tiller (rudder) Arc?

Is there a general range that most sailboat rudders operate within? (I've heard 60 degrees; 30 degrees side to side).

If it's not in the owner's manual, short of hauling a boat out of the water or putting on dive gear, how does one measure the full tiller arc?
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Old 09-07-2014, 09:06   #2
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Re: full tiller (rudder) arc?

I believe 45 deg. max either side from center.
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Old 09-07-2014, 09:23   #3
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Re: full tiller (rudder) arc?

I just installed twin steering cylinders from telestar. They reccomended 35 from center (70 lock to lock) for the the cylinders I bought.
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Old 09-07-2014, 09:34   #4
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Re: full tiller (rudder) arc?

Most quadrant systems have their stops set somewhere between 30-40*. Anything more than that generally stalls the rudder and is counterproductive. The actual number isn't very critical, except that steering cylinders and autopilot drives will often expect and specify an exact value.

Most tiller systems that I have used have not had rudder stops at all. Since a tiller is a direct connection to the rudder post, measuring the arc it swings through will tell you what arc the rudder is swinging through.

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Old 09-07-2014, 10:21   #5
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Re: Full Tiller (rudder) Arc?

How to measure in tight spaces:

Center the rudder, measure from the center of the quadrant or tiller to the bolt or cable. Mark where you measured with a grease pencil.

Tack a stick in place on centerline just ahead of the rudder or quadrant. Ideally it would be a plumb bob, but normally there isn't room for such nice things. Rotate the wheel to the lock. Measure from your mark on the tiller to the stick. Measure from the stick to the centerline.

Now go get a piece of cardboard and lay out your measurements and set a protractor over the top.

Draw a centerline, draw a perpendicular line. Pin a hacksaw blade to the intersecting point.

Measure out from the pin, the tiller or quadrant length. Draw a half circle. Measure along the centerline to put a mark where the stick or plumb bob was. Measure from the stick along the circle the distance you measured to the mark you made on the quadrant. Connect the mark to the spot where the hacksaw blade was pinned and you are done.

Set the protractor on the line you drew perpendicular the centerline and measure the angle.

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Old 09-07-2014, 10:48   #6
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Re: Full Tiller (rudder) Arc?

Easier to just measure the distance from the center of the rudder post to one of the rudder stops. Then measure the distance between the two rudder stops and divide by half. You now have a right triangle with the opposite and hypotenuse lengths. The inverse sine of that ratio gives you the rudder stop angle. Multiply by two and you have the entire swing angle.

Total rudder swing = 2 x invsine(1/2rudder stop length÷distance of stop to post)

I know the quadrant defines and arc, but unless you have a very small quadrant with widely spaced stops, the error will be less than a degree.

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Old 09-07-2014, 13:11   #7
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Re: Full Tiller (rudder) Arc?

I have a question related to this. The installation instructions with the cylinders I just installed said to be sure the cylinders reach their full range of motion BEFORE the rudder hits the stops. I take this to mean the rudder will not reach the stops when the helm is hard over. Does this sound reasonable?
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Old 09-07-2014, 16:36   #8
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Re: Full Tiller (rudder) Arc?

Cal 34 and Islander 26 swing 360 degrees. Marvelous for steering in reverse. Thought my Cal 40 would do the same, but it goes about 170 degrees before the rudder hits the hull. I was pissed. Doubly pissed when I figured out I couldn't just cutaway the aft top of the rudder a little to make it clear because it was the front of the rudder that didn't clear. (Tiller steered boats.)

Anyone have an idea how not to make a line/trap/weed catcher by cutting away a small part of the top of the front of the rudder?
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Old 09-07-2014, 17:12   #9
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Re: Full Tiller (rudder) Arc?

Quote:
Originally Posted by Matt sachs View Post
I have a question related to this. The installation instructions with the cylinders I just installed said to be sure the cylinders reach their full range of motion BEFORE the rudder hits the stops. I take this to mean the rudder will not reach the stops when the helm is hard over. Does this sound reasonable?
It does not to me. You would not want to have the rudder rip out the guts of the cylinder by traveling further than the cylinder can go. One time backing down and the rudder going full over and you would have a hyd leak.
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Old 09-07-2014, 17:54   #10
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Re: Full Tiller (rudder) Arc?

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It does not to me. You would not want to have the rudder rip out the guts of the cylinder by traveling further than the cylinder can go. One time backing down and the rudder going full over and you would have a hyd leak.
On the other hand, you don't want the hydraulics still trying to push the rudder when it is hard up against a stop.

I guess it depends on how the system is build. I'd trust the manufacturers instructions over someone's guess about the design of an unspecified hydraulic system.
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Old 09-07-2014, 19:30   #11
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Re: Full Tiller (rudder) Arc?

Well what about if the system is not operating/under pressure, the cylinder end cap is now the rudder stop?
Are these instructions a Chinese translation?
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Old 09-07-2014, 20:05   #12
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Re: Full Tiller (rudder) Arc?

My understanding is that you set the rudder stops so that the arc is within the travel length of the actuator and then set the autopilot so that the actuator doesn't reach the limit of its travel. Its been a while since I looked into this but I believe that is the way it is stated in autopilot installation and users setup manual.
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Old 10-07-2014, 07:45   #13
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Re: Full Tiller (rudder) Arc?

Yes, that is true for autopilots, but I think he was talking about hydraulic steering cylinders. I'm not sure how those are specifically setup, but it seems like one does not want them limiting out, nor providing great force against the stops.

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Old 10-07-2014, 08:38   #14
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Re: Full Tiller (rudder) Arc?

Edit: this was from a design engineer. It seems that different actuator manufacturers have different views on this so it appears that the boat structure has to be strong enough to withstand full on hydraulic pressure from the ram. Or the system needs pressure relief valves.

I don't like to do this but entry #24 on this thread at boat design forum seems to be the answer. It states that the limit stops should be built into the actuator itself. The thread is about a boat that tore up the steering because of the hydraulic pressure against the steering stops. The builder was asking for forum input.
Rudder stops with hydraulic cylinders - Page 2 - Boat Design Forums

Something I didn't mention is that cushioned cylinder stops inside the cylinder should be spec'd.
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Old 10-07-2014, 08:49   #15
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Re: Full Tiller (rudder) Arc?

Quote:
Originally Posted by Matt sachs View Post
I have a question related to this. The installation instructions with the cylinders I just installed said to be sure the cylinders reach their full range of motion BEFORE the rudder hits the stops. I take this to mean the rudder will not reach the stops when the helm is hard over. Does this sound reasonable?
Hey metal man from TN... Long time no talk... Sounds perfect to me... If the rams are at the end of travel, it would be impossible for over pressurized fluid to go past the piston seal... even with pressure regulation, this would save a lot of unnecessary wear and tear

Wonder what the heck oldfrogster was trying to accomplish? And even more importantly... why from under the boat?
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