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blackskydave 06-07-2013 10:22 AM

Sailboat Rudder (ROM) Range of Motion
 
(1974 Tartan 34) I am reinstalling my rudder, autopilot, and all associated hardware (quadrant, cables and pullies etc.) and am curious about the specified or typical range of the rudder movement in degrees. Here is what I have read so far (valid or not): Beyond 45 deg. the rudder will cavitate much like a boat aircraft propeller and be ineffective in controlling the direction of the vessel. Is this true? A further description is that it will "stall" like an aircraft wing. Certainly makes sense taken to it's logical extreme (a rudder turned to 90 deg. would be ineffective). Given the range of sailing velocities (say, 0-8kts). where is the "sweet spot area" on the range of movement and should rudder stops be placed at the point beyond which the rudder ceases to work? Should the effective control range be expected between 0 deg. (straight ahead) and say, 40 deg. starboard and port, or is that level of attempted control excessive for a small to mid size cruiser?

tommays 06-07-2013 10:34 AM

Re: Sailboat Rudder (ROM) Range of Motion
 
It depends on the boat my J24 is very happy turning around with in its own length in tight places with the rudder pretty close to 80 degrees

On my Cal 29 the rudder will hit the hull section it is faired into and requires stops so it will NOT be damaged

When doing actual sailing there both fastest when the sails are balanced in a way that the rudder is as close to ZERO movement as possible

Faster 06-07-2013 10:53 AM

Re: Sailboat Rudder (ROM) Range of Motion
 
45 degrees either side of center sounds reasonable.. beyond that it's acting more of a brake than anything. Hopefully the boat is responsive enough not to tempt one to hold it over that far very often or for very long. The limitation of restricted motion might be the ability to make a sharp turn at low speeds, eg entering a tight slip...

The best setup we've ever had was a tiller/rudder that could cleanly turn 360 degrees without stops or interference.. the beauty was we could spin the rudder around when backing up for ultimate control and no 'unbalanced' loads. But it was a very responsive boat and tacking rarely involved more rudder action than 15-20 degrees angle.

blackskydave 06-07-2013 11:13 AM

Re: Sailboat Rudder (ROM) Range of Motion
 
Thanks for the quick replies. I totally rebuilt (recored the foam) the rudder and it hits the hull at about 40 deg. I worry what I added a little too much material to the top of the rudder and have restricted its movement. However, the boat has bronze trim between the skeg and the rudder which also would limit its movement. Just wonder if I ought to trim a little more off the top end and get the rudder to move more. Is it the current consensus that more is better without stops? Makes sense. Especially at slow speeds with barely or no power when pulling into a slip turning the boat to the max even with a little rudder/breaking action would not be harmful. I'd post pics but I need to "html 'em" before posting.

Faster 06-07-2013 12:43 PM

Re: Sailboat Rudder (ROM) Range of Motion
 
You're better off posting pics by linking to them when they are hosted on a site like Photobucket.com.. free to join. Lurkers can see your pictures that way too - be sure to use the IMG CODE link option. (You may need more posts before links will work for you)

Alex W 06-07-2013 12:46 PM

Re: Sailboat Rudder (ROM) Range of Motion
 
My rudder turns way less than 40 degrees and it works well, steerage is not an issue. I think the locks are at about 30 degrees.

Going much harder over than that in most conditions just induces stalling anyway. My Catalina 25 rudder went over to 75 or 80 degrees and I only used it that way when motoring (with the motor also turned hard over) in slow circles while waiting for draw bridges.

mad_machine 06-07-2013 12:54 PM

Re: Sailboat Rudder (ROM) Range of Motion
 
stalling is also a factor of boat speed. Faster the boat is going, less rudder you need to turn.. and less rudder you need to stall.

blackskydave 06-07-2013 01:13 PM

Re: Sailboat Rudder (ROM) Range of Motion
 
Mad... hence my comment about velocity. Frequent radical rudder adjustments I see as a docking maneuver often coasting.


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