Rudder counter balance

[Cow Cocky]

What would the steering characteristics of a sail boat mono hull that had too much counter balance on a blade rudder?

sailing and/or motoring

 

[skaraborgcraft]

The wheel or tiller would be pulling itself over very hard when given any input.

 

[Cow Cocky]

The wheel or tiller would be pulling itself over very hard when given any input.

This is exactly what it does. But apparently (not yet verified) it has 18% counterbalance which I thought would be correct.
When motoring, If I turn the wheel 90 degree it is relatively easy to return to centre. If I turn the wheel 180, it is hard and 270 it is extremely hard. ? Very light helm when tracking straight.

 

[skaraborgcraft]

Should not be a problem with that amount of balance. Maybe the gearing side of your wheel is the issue?

 

[jehardiman]

This is exactly what it does. But apparently (not yet verified) it has 18% counterbalance which I thought would be correct.
When motoring, If I turn the wheel 90 degree it is relatively easy to return to centre. If I turn the wheel 180, it is hard and 270 it is extremely hard. ? Very light helm when tracking straight.

Should not be a problem with that amount of balance. Maybe the gearing side of your wheel is the issue?

So what is the method for the wheel to rudder connection? Hydraulic? Push-pull cable? A shaft quadrant? Also, what is the steering ratio? You turn the wheel 90, but how much does the rudder deflect.

 

[Cow Cocky]

Wheel, cable, quadrant, spade all working fine. 3 turns lock to lock. Sorry, I am not armed with all the specs. Maybe all spade rudders get progressively harder to return to centre. I never noticed it on my previous boats. One was superbly balanced and the other hydraulic steering. This one has almost a barn door shape, not elliptical. It’s nothing to do with sail trim as I have tested it at say 3 to 4 knots under motor. As I said, maybe it is normal.

 

[Skyak]

Wheel, cable, quadrant, spade all working fine. 3 turns lock to lock. Sorry, I am not armed with all the specs. Maybe all spade rudders get progressively harder to return to centre. I never noticed it on my previous boats. One was superbly balanced and the other hydraulic steering. This one has almost a barn door shape, not elliptical. It’s nothing to do with sail trim as I have tested it at say 3 to 4 knots under motor. As I said, maybe it is normal.

If you think about the counterbalance in terms of how much of the prop wash is ahead of the rudder pivot it does make sense. I also think that the prop wash flow separation from the suction side at higher angles contributes to the imbalance. You need to keep the flow attached to keep the moment consistent.

 

[Cow Cocky]

I don't think it has anything to do with the prop wash. It is the same under sail. I just mentioned that it does it under motor to take out "sail trim" from the conversation. Maybe it is normal

 

[Cow Cocky]

Would excessive cord cause this problem?

I have been advised that 18% is about right for counterbalance and another advised no more than 10%.

go figure?

 

[skaraborgcraft]

Is it a spade rudder or skeg mounted? Up to 20% balance has been normally used. I dont see chord being an issue, high speed rudders can be widest at the trailing edge, apparently.

 

[Cow Cocky]

It's a spade but very square, not elliptical

 

[jehardiman]

Since it is sailing and motoring, I'd start by looking at the geometry of the quadrant. Poor geometry can cause binding as the rudder shaft angles increase.