self centering rudder/tiller?

[RussC]

In a totally unrelated post I was reading, the following bit caught my attention and made me go "huuummmm"
<snip> "All boats these days are built with unbalanced rudders as sailors, especially racers, like the "feel" of it and builders also like the safety thing of it swinging back to center when unmanned." <snip>
Now I've only owned 5-6 sailboats over the years, so I'm sure no expert, but I can't recall that any of them had anything resembling a "self centering" rudder. that being said.... it might be a good thing, and one worth considering working towards. I've always relied on a tiller tamer run with light tension to help hold the tiller in whatever position I leave it in, if I have to take my hands off for any reason. but the comment I mentioned got me thinking just what might have an effect on weather a rudder goes back to center.... or just swings off to one side, as mine generally does if left totally uncontrolled.
Envision a car running down the hi way. the caster built into the suspension brings the wheel back to the straight ahead position by itself. so what could be done to a tiller setup to do a similar thing? the angle of the rudder as it hangs on the transom perhaps? or maybe it's actually a better thing that it does go hard over when uncontrolled, as in the case of a MOB or whatever?
Thoughts?

 

[Joe]

Why would you want that built into the design of the boat? If you fell off. the boat would keep sailing... rather than rounding up. It shouldn't be like a video game controller,

 

[Cowpokee]

Well two of my boats have balanced rudders and they certainly aren't self centering. My other boat (Allied Seawind 30) has a keel hung rudder. I haven't had it in the water yet but I would think it would self center when I let go of it.

 

[kloudie1]

Self centering in the same way a car's steering wheels are.. All is good until there is a cross wind or a slant in the roadbed.. same with the rudder, it will stay straight except when some other force pushes it .. when sailing, the force is the sail force trying to scoot the stern over . when motoring, the torque of the propeller will do it..

 

[capta]

On a visit back to the US to visit family and friends, I borrowed my dad's Ford Probe. He lived in northern California, in the hills (read winding roads here) and on the first corner that damn self-centering wheel nearly killed me. I definitely did not like it in a motor vehicle and I wouldn't want it on a water vehicle either. When I turn the wheel to tack, for instance, I can let go of it and handle sheets or whatever, and it stays wherever I put it. A self-centering helm would be a really dangerous, IMO.

 

[RussC]

Why would you want that built into the design of the boat? If you fell off. the boat would keep sailing... rather than rounding up. It shouldn't be like a video game controller,

Just thinking out loud mostly.
Most of the days I sail I tend to prefer to stay on the boat , so I guess it boils down to priorities.
If I need to go forward, or below, for a moment, there is very real added safety in keeping the boat headed the way I pointed it, and especially that it not make any sudden moves off that line that might actually throw me off the deck. but then I do also appreciate what you're saying about if I did go off the side, the boat would then sail off into the sunset if there was no-one else aboard to bring it about to recover me.

 

[Davidasailor26]

From a performance perspective you don't really want the rudder to stay centered, at least not up-wind. A little bit of weather helm, requiring about 3 degrees of rudder angle to hold a straight course, enables the rudder to generate some lift. That lift adds to what the rudder does to reduce leeway. If your goal is to just be able to leave the tiller untouched the tiller tamer or an autopilot is probably the way to go.

 

[RussC]

From a performance perspective you don't really want the rudder to stay centered, at least not up-wind. A little bit of weather helm, requiring about 3 degrees of rudder angle to hold a straight course, enables the rudder to generate some lift. That lift adds to what the rudder does to reduce leeway. If your goal is to just be able to leave the tiller untouched the tiller tamer or an autopilot is probably the way to go.

Good point. straight ahead isn't the same as centered

 

[dlochner]

The original rudder for a Tanzer 22 was an unbalanced Scimitar shape. The good news was found in sculling, that rudder was almost more effective than a motor. It could also spin the boat around quickly. The bad news was the weather helm and pressure on the helm. After a long sail one arm was always longer than the other.

 

[Scott T-Bird]

I think you are thinking about balanced and un-balanced rudders in the wrong context. A transom hung rudder, based on it's geometry of pivoting at the inboard edge, is un-balanced. There is nothing that you can do to change that. The force that is required to steer the rudder is affected entirely by the flow across the rudder.

On larger boats, there needs to be some design of the pivot point of the rudder that incorporates "balancing" simply because the forces are increased when you turn the wheel or move the tiller. Moving the pivot point on the rudder forward is causing the rudder to be increasingly unbalanced. Moving the pivot point back increases the balance (until you move it behind the balance point). Weather helm or lee helm is related to the rudder pivoting under sail pressure. It is totally unrelated.

An un-balance rudder can theoretically stay "neutral" when the centered position is balanced against the forces from the sails. That's how a mechanical auto pilot works.

 

[dlochner]

A transom hung rudder, based on it's geometry of pivoting at the inboard edge, is un-balanced.

There are ways to design a rudder around this limitation. The easiest way is to have a reverse transom so that the rudder angles forward. A second way to have the section of the rudder below the water line be forward of the pintles. The J24 and the redesigned Tanzer 22 rudder took this approach. Here are some images of balanced transom hung rudders. http://www.tonymackillican.co.uk/index.htm

 

[Gunni]

A balanced rudder simply has enough of the foil forward the rudder axis center of rotation to provide some assistance with course holding. The portion forward the axis works to hold the rudder over against the effort of the aft rudder section to center. Critical on a big boat. Compare that to small boats with a vertical pintle-hung rudder - like driving an old truck. Yeah, an unbalanced rudder will center, but it won’t center the boat, you still have the keel and sail trim working to direct the boat. Balanced rudders just make the helmsman job easier, like power steering.

 

[Gunni]

A transom hung rudder, based on it's geometry of pivoting at the inboard edge, is un-balanced. There is nothing that you can do to change that.

Sure there is, you simply project a portion of a transom hung rudder forward of the pintles - now you are balanced.

 

[shemandr]

The rudder for the Hunter 707 is a beautiful shape. A classic Spitfire profile which should be a very efficient foil. Although it is backwards from what a wing or keel would look like. But is it balanced? I don't know. Does a small section of the rudder forward of the pintles make it balanced? How much forward constitutes balance? What is the definition of balanced?

 

[thinwater]

There are three types of balance and some are mixing them up.

1. Balanced rudder. This has to do with the location of the COE of the blade vs. the shaft. If there is a side force, can you feel it? And yes, transom hung rudders can be balanced if some of the area is under the transom or if blade is raked forward relative to the shaft. Some boats, like my first beach cat, had adjustable rake; that was a really neat feature.
2. Balance related to helm angle. This relates to the amount of leeway pressure that rests on the rudder. Rake the mast aft, for example, and pressure on the rudder increases (though if the rudder is balanced you won't feel it and the boat will not round up) and helm angle increases.
3. And what the OP is talking about. COG balance. If the rudder stock leans forward, the tiller tends to fall to the center and the helm is thus, self-centering at rest. However this force is tiny compared to the others and will have nothing to do with weather helm over a few knots.

Is it a worthwhile feature? Doesn't mean much to me, but I've been on boats set up that way. I guess it's nice on sport boats with wide cockpits.

 

[RussC]

Now that you mention it, I can certainly vouch for the steering effort conversation . When I first purchased our little boat (V-17) it came with the oem rudder assy as well as an aftermarket unit. the po told me the boat was "hard to control" with the oem unit and was the reason he only used the aftermarket piece after that. well the aftermarket unit weighed a ton, and I prefer wood, so I set about testing for myself. he was right!!... when hit by a strong gust it took both feet on the opposing side of the boat and both arms to pull the tiller back . when I returned home and did some investigating it became pretty obvious what the problem was. I found no obvious reason why it was this way, and no extra "non factory" holes, but the stop bolt for the rudder forced the lower portion to sit almost 11" out from the pivot axis.

I drilled a new hole for the stop which set the lower rudder perpendicular to the water line when installed on the boat, which obviously made a HUGE difference in steering effort.

Now I'm wondering how it would react to being angled forward to the limit of the transom angle... huum.. I gotta try that just for my own curiosity

 

[Gunni]

Axis for balance is the vertical through the pintle’s median, floating on the waterline, 20% forward the axis is a good start. Too much an she’ll lock over. Too little and you’ll be wrestling a bear.

 

[thinwater]

Just in case it's not obvious, a rudder that is actually raked forward (not just forward of the rudder post axis) will snag weeds and rope like there's no tomorrow. Even vertical is a problem. If the rudder can be tipped up it's less of a problem.

A rudder fence is also nice for snagging weeds. Good for stopping ventilation at high speed, but you need clean water.
(Re-cored anchor well cover and rebuilt rudder parts curing in the sun)

 

[dlochner]

Now that you mention it, I can certainly vouch for the steering effort conversation . When I first purchased our little boat (V-17) it came with the oem rudder assy as well as an aftermarket unit. the po told me the boat was "hard to control" with the oem unit and was the reason he only used the aftermarket piece after that. well the aftermarket unit weighed a ton, and I prefer wood, so I set about testing for myself. he was right!!... when hit by a strong gust it took both feet on the opposing side of the boat and both arms to pull the tiller back . when I returned home and did some investigating it became pretty obvious what the problem was. I found no obvious reason why it was this way, and no extra "non factory" holes, but the stop bolt for the rudder forced the lower portion to sit almost 11" out from the pivot axis.
View attachment 160166

I drilled a new hole for the stop which set the lower rudder perpendicular to the water line when installed on the boat, which obviously made a HUGE difference in steering effort.
View attachment 160167
Now I'm wondering how it would react to being angled forward to the limit of the transom angle... huum.. I gotta try that just for my own curiosity

View attachment 160168

The swept back rudder position may have been an attempt to reduce the boat's draft while maintaining the size of the rudder. That was the reasoning behind the Tanzer 22 scimitar rudder, lots of surface area, but kept the rudder draft lower than the keel/centerboard version of the boat. The new rudder for the T22 was deeper and exceeded the draft of the KCB version of the boat but not the fin keel version.

Check your rudder in the new position, is it deeper than the keel?

 

[jon hansen]

sailboats steer with their sails and trim with their rudder. yep, that's right.
so do not want to believe me, fine. then pay attention to the master, dennis conner. every time you move the rudder you are putting on the brakes, very slow. watch dennis, he is a master of the helm. he finds the sweet spot then holds the helm there and moves it sparingly. my observation is that 99% of sailors way over steer.