Rudder angle - included

[delmarrey]

I'm in the process of installing hydraulic steering to the ole' racer. At the present it has a tiller and I'm converting it over to wheel using a hyd. pump and cylinder.
The question is, what might be the best rudder angle from lock to lock?

Right now it doesn't have locks, and with the tiller I can swing it 180 degrees. Basiclly, spin it around on it's keel. But I'm sure that's not resasonable with a wheel, I think.

I was thinking at right around 120 to 140 degrees would be about right. Anyone happen to know the average angle or a formula that would work?

[Boracay]

When I was checking on self steering for a Flemming servo pendulum type wind vane it was recomended to have no more than 2 turns, lock to lock.
This could be a useful starting point.

[Alan Wheeler]

2 turns? that is one turn from centre to hardover? That is tight. Usually it is 3-3.5 turns lock to lock minimum. It can be greater. I have 7 turns lock to lock which is a bit on the too much side, but mine has a huge barn door of a rudder and it takes power to turn it and it doesn't require much movement to turn the boat.
However, I think Delmarrey is refering to how much the rudder should turn, Not the number of turns in the helm to make it turn.
Delmarrey, you want to be looking at 45 degress max from centre. Anymore than that and 1: you place too much strain on the blade and 2: the blade starts to stall and becomes more of a brake than a stearing device.
This travel is determined by the length of stroke of the ram and of course, the length of arm out from the shaft to the ram eye. You don't need stops for the rudder itself, the ram will be quite capable of stopping the rudder at it's positions.
Ensure you get a "balanced" cyclinder. This will make life easier for the day you fit an autopilot pump, other wise it becomes a hassle and is expensive.
The suppliers of the system should be able to help you with more info. Even if the system is second hand, search the makers website and you mayfind some engineering info on requirements and sizing.

[delmarrey]

Yeah, it is a balanced cylinder that I'll be getting. I'm getting a new setup from Surry, B.C. and on the Tech. Data Sheet it's asking for the degree of rudder angle so they can recommend which pump and cylinder.

45º doesn't seem to be very much? Getting into a slip might be a bit difficult. One of the things I use to like to do is when coming up slowly to an anchorage spot I would give the rudder a hard to port and spin around on my keel until she stop. I could put the anchor right where I wanted it. I guess I'll have to learn to back down and stop it into the wind.

I plan on tapping into the cylinder with an auto pilot. So, I'll be ordering a bypass switch and a sailboat lock valve which locks the hydraulics so you can release the wheel for a while, like a tiller tamer or wheel brake. And the whole system will be fitted with a PRV so It doesn't brake anything in case the rudder gets hit.

As for the turns, I'll leave that up to the designers. The hand wheel will be 54" (137cm).

[Talbot]

with the change from tiller to wheel, the ergonomics of movement within the cockpit will have changed. Suggest you re-visit the locations for winches and mainsheets.

You may also need to change the design of the seat aft of the wheel, from a flat seat to something more contoured so that sitting while healed over is still relatively comfortable.

[GordMay]

The most commonly referenced maximum ½ rudder angle, for naval ships, is 35 degrees (P&S), which allows a travel of 70 degrees “stop-to-stop”. Of course, large ships have different maneuvering characteristics than sailboats.

[Alan Wheeler]

As Gord said, 35 is about the norm, hence my comment of no more than 45. There are several issues to consider. (firstly, I am approaching this from an engineering point of view, I am NO rudder or hull design expert and stand to be corrected on any points of view)
Starting with the shaft as a centre point, from that shaft will be the new "tiller" that the ram connects to. The length of that device has the following affects. The longer it it, the less force required to move it = a smaller diameter ram = less dollars. However, the longer the rate of travel = longer ram = more room required to mount everything.
Shorter arm from shaft all amounts to the opposite of above. I would suggest you start with, how much room do you have = How long an arm can you get away with = swing (remembering you don't want to go any more than 45 degress or the rudder will stall and suffer undue forces AND the cyclinder will try to over centre the arm = undue force) Then to sum up, that will equate to the length of ram you can fit in there. You could also work from the point of view of length of ram you can fit and work backwards. A good excersise to double check all figures.

As for autopilot, make sure you get a helm pump with a valve block fitted. Once again it is cheaper to get one fitted than to fit one later in the system. This means you don't have to fit a lock valve etc etc for an electric pump system later. I presume your reference to bypass and lock valve are for bypassing the entire system so as you can emergency steer still using the old tiller arrangment? If not, ensure you have that capability and make sure any alterations you may make, take into account the old tiller arm swinging in the event of an emergency use.
That system is required as a must for our NZ Cat1 cruiser/racer rules by the way.

[patio]

don't know from nutin' about no injin earing.

but...


my pacific seacraft crealock 34 turns just over one full turn from center each way.

and when i had it out of the water last year to bottom paint, the rudder turned ( didn't put a protractor to it mind you and this is just best guess) 70 to 90 deesgrees. stop to stop.

edit: Edson btw.

[Rick]

I agree with Wheels. My own rudder (C&C 39) has the stops set for an 70 degree included angle. The boat urns fine.

[delmarrey]

Yur right Alan!

Now that I've given it some thought and with the responses, 45º/90º included is beginning to sound like the max I would want to give her.

When I first got the vessel, I remember backing out of a slip, when I lost my balance looking around. That tiller pinned me to the rail. The extreme angle I gave it was a little too much for me to handle. Fortunately the tiller lifts up and I was able to slide under and pull it back. But I was a little red in the face until I was out of sight of the dock.

Sooooo, backing with too much angle could be a little too much for a pump to overcome without going over-kill.

As for space in my steering room, I have enough to put a couple of kid’s bunks. I'd like to use it for storage but the need to have full access has its priorities. It seems I'm always crawling back in there to do some wiring or plumbing.

The pump does come with the lock valve already installed. And I do plan on keeping the tiller for a back up. I work with hydraulics almost on a daily basis and it is very dependable if set up properly.

And for the seat, I'm already sitting on the windward deck while she's a list. She has a shallow cockpit. The plan is to build up under the winches a sea wall to help keep it from a wash and mount the winches on top. Then I may put in an oriental bridge looking seat across the aft cockpit. And I'll be moving the gages and controls up to the pedestal.

I think I’ll give it a few more days and responses then decide, but 35º is sounding more desirable.

I thank y’all for the help!




Example #1


Example #2

[Alan Wheeler]

Love the photo's.
I guess because I look at problems from an "injin earing" point of view, I look at worst case scenarios. To me, the ability of swinging the keel to extreme angles can be of benifit when say docking. But what happens the day you just happen to get into something nasty and you have a rather big sea kicking you in the butt. If for some reason the rudder gets to an extreme angle, just like you mentioned about it pinning you before, imagine the damage that could be done to the boat and/or rudder and gear. I also have worked with Hydraulics, and as you know, the pressures developed are just plain mindblowingly scary. My installation called for hydraulic hose of 2000PSI rating. There is a reason for that.