CD36 Rudder Angle

[John Danicic]

Cape Dory 36 Rudder angle.

Greetings fellow sailors.

I am in the midst of planning a below-decks autohelm install and was wondering if any one out there knew off hand the maximum rudder angle of a Cape Dory 36?

This would be the angle from helm in center to maximum port or center to maximum starboard in degrees…

Anyone got even an estimate for me?

[John Stone]

Hi John
I'll be going to the Far Reach in the next week and I will check. But, my recollection is my rudder will go about 47 degrees max either side of centerline. Though I have a tiller, I have a narrower sweep than a stock boat due to the improved faring at the back of the keel. However, I installed 35 degree rudder stops which is all you should ever have to turn the rudder.

Also, if I recall, there is a steel quadrant stop welded to the steel steering frame under the cockpit sole that supports the pedestal and steering cables. That should limit your maximum rudder angle.

[John Danicic]

Thanks John. That helps a lot. I am sure you more then likely removed the quadrant on yours so what do you use as stops?

I have the rubber coated metal stop in the quadrant that, when it was bent and not functioning gave me a much wider angle, that could be 47 degrees that you mentioned before your stops. I replaced it with this new one I had a shop make and had to get used to a much wider turning boat in close quarters as a result.

You can see it here with-in the quadrant on the left; the black bracket holding a silvery rubber coated pipe. I am estimating from this picture that the angle is about 40 degrees but that is hard to do from a picture taken at an angle.

For this new auto helm which is a lineal drive, I need to determine the maximum angle, i.e. where the rudder stops are so that I can locate the drive unit itself at the right distance from the rudder post in order to not to use the lineal drive as a rudder limiter which would damage it.

Ultimately, I will need to finalize this determination at the boat but that is 235 miles away and under a foot of snow. This info will help me figure out needs and think out solutions for when I am on site and installing. Besides of course, to chase away the winter sailing blues......

[Frenchy]

John, Is that small shaft leading to the quadrant at the bottom of the picture a rudder sensor? If it is, that would
take care of any worries about over-driving your new autohelm past the stops.
On my less desirable wheel pilot, I have a rudder sensor below and the control module on deck allows me to input
limits as to how far the rudder will be turned. I've heard of autopilots without a rudder sensor being ruined.
Another thing I like is that the topside control module indicates the rudder position - left, right and how far, (though
somewhat crudely). - Jean

[John Stone]

John,
The maximum angle on the Far Reach is determined by the fairing so her max angle will be different than on your boat. I'd think 40 degrees would be more than enough.

I have a pad eye bolted into the bottom of the cockpit sole (via tapped epoxy plugs) and to that I have some 1/4" dyneema loops shackled to anther pad eye on the old quadrant. I have it set for about 35 degrees. I tried to attach a photo but when I did I received an error message that says "Sorry, the attachment quota has been reached."

[John Danicic]

John, Is that small shaft leading to the quadrant at the bottom of the picture a rudder sensor? If it is, that would
take care of any worries about over-driving your new autohelm past the stops.

Jean:

It is but it will be removed as well as the wood base it is on. That sensor is for a venerable, over worked and noisy Raymarine Wheel pilot. On the new installation, an Edson tiller arm will be installed above the quadrant pointing down. The new Garmin Lineal Drive unit has a built in rudder sensor and will have all the bells and whistles you mentioned.
The drive has a limit of 11 inches port to starboard through its arc. It is like a big tiller pilot but with a little tiller. Finding the rudder angle will help me place the tiller to drive, connection point; which is the proper distance from the rudder shaft to keep the drive from over extending it's limits. These rudder stops are necessary to protect this drive as the original rudder stop was bent to useless by more then likely backing out of my slip and into a mud bank 40 feet behind me. Something I now try heartily to avoid. So electronic limiting of the drive is not an option here.

It will be a challenging installation what with the unit needing to go at a right angle to the tiller arm and into the port side cockpit locker where I intend to attach it to the bulkhead. And what do you know? Right where that big pancake drive motor needs to be is a solid 3/4 inch bulkhead. Boat work! It is never easy or simple. John Ring of CD36 #135 TIARA, has installed the same unit and has "shown me the way" so to speak. I love this board.




John. I can picture your stop loops. Did you removed the metal bracket for the Edson wheel that runs across the cockpit floor?

[John Stone]

Yes, I did remove it. Nothing remains of the wheel steering hardware other than the quadrant that I kept to connect to the Cape Horn windvane control lines.

[Frenchy]

John, as I understand it, your rudder's movement needs to be controlled by a stop 35 degrees either side of center,
so that the autohelm doesn't go beyond a certain limit. Sorry about that- I was a bit confused.
Measuring the movement doesn't sound easy. One possibility to get an idea would be to look at the
Edson installation and setup guide for pedestal steering. They have ratios listed for angles of movement.
For a common 5/8-11 sprocket and common 10" quadrant, it takes a bit over 2 turns lock to lock for 80 degrees
of rudder movement. Once you figure out the present movement of the rudder, you could possibly increase
the diameter of the stop in the picture to reduce the rudder movement. -Just an idea. - Jean

[John Danicic]

Jean:

That is correct. I need to have stops on the rudder that will keep the drive with-in its limits.

The Edson tiller arm has marks to drill holes for different rudder angles. By moving the drive connection down the tiller arm, I can get the drive to move the rudder to a larger angle but still stay within safe working distances. But the closer the connection to the rudder stem, the more force is needed to move the rudder and the harder the drive works. The trick is finding the right spot that allows the existing rudder stop to come into play before the the drive reaches its maximum. The drive shaft end can also be adjusted in and out a few inches to fine adjust.



I set up the tiller on this paper with the different angles that the drive manufacturer gave pin to rudder post distances for 36 40 and 46 degrees.

I could always add material to increase the diameter to the existing stop if the rudder angle turns out too great but that would further limit my turning radius in close quarters. I don't want to do that.

[Frenchy]

I think I understand, a little foggily maybe. The stops are there so that under manual input, you don't pull the
ram out too far or push it in too far. Under Autohelm control, the push-pull limits will be controlled by the
topside controller. If that's the case, you could mount the ram arm slightly closer than 250 mm to the rudder shaft
so that you would have more than 35 degree movement available, although you wouldn't use it. Possibly, you'd
set the maximum movement to say 32 degrees.
But if I'm thinking right, the rudder would have to be constrained by the stops to a maximum 35 degrees
under manual input, otherwise the autohelm would be kaput. So you would have to live with very slightly
less maneuverability. -Jean

[John Danicic]

Jean:

I think you got it. The rudder stop originally was to keep the rudder from turning in too wide an arch and damaging the wheel steering is what I figure.

Yes, but, ever the optimist, I think I can adjust the drive installation so that I can at least use the maximum rudder angle I currently have. I must have damaged the rudder stop early on in my ownership and was completely unaware of it for at least 6 or 7 seasons. I got very used to the much wider rudder angle and the sharp turns I could make as my dock requires a 90 degree port turn in a less then forty foot wide channel. It took the steering cable to break to find out that the rudder stop was bent to uselessness and had been for some time. Now, with a replacement stopper, docking requires a turn that starts much earlier and the rudder doesn't have the braking effect as the larger angle did. I am now used to it and don't want it any narrower if I can help it.

A good puzzle to work out this spring and think about now in front of the fire. I am strangely looking forward to crawling around under the cockpit, contorting and receiving the bruising that results from successful (as well as unsuccessful) boat work.

[tjr818]

. . . I am strangely looking forward to crawling around under the cockpit, contorting and receiving the bruising that results from successful (as well as unsuccessful) boat work.

This is a Family Forum, please refrain from such S&M suggestions.

[Frenchy]

I understand - you want to find a spot on the tiller arm that will limit the movement on the ram to its
prescribed limits when the quadrant hits the stops port and starboard. On my boat, the total rudder movement
is two turns on the wheel, about 80 degrees. If yours is the same, the distance from the rudder shaft hole
to the mounting point of the ram would be 228 mm, to allow a total ram movement of 294 mm. Here's how I
figured: Drawing a right triangle with a 40 deg. angle at the bottom and a side opposite the angle of 147 mm, we
have an unknown hypotneuse next to the 40 deg. angle. Sin 40=147/x, x=147/sin40, x=228MM
Hope this makes sense. At any rate, I've had a lot of fun figuring and someday, when I install my own below
deck autopilot, I'll remember all this. Good luck under there! - Jean

[John Danicic]

You hit it right on the nose Jean. Just what the chart says. Sometime it is nice to use those old skills, now do the calculation in your head!

Needless to say, the installation will get fine tuned on site and I am not drilling any holes into that lovely hunk of bronze from Edson until I know where the hole needs to be. As I said before, a complicated but fine boat project. One that exercises the mind and the body. I consider myself lucky.

[Sea Hunt Video]

Drawing a right triangle with a 40 deg. angle at the bottom and a side opposite the angle of 147 mm, we
have an unknown hypotneuse next to the 40 deg. angle. Sin 40=147/x, x=147/sin40, x=228MM
Hope this makes sense. At any rate, I've had a lot of fun figuring and someday, when I install my own below
deck autopilot, I'll remember all this. Good luck under there! - Jean

Not to brag or anything but I think the 5th time will be the charm for me. I have fingers crossed that I will pass the GED arithmetic test next month. Yea

Once I pass that test I am going to start working on what Frenchy just wrote.