Tune my rudder?

Stu Jackson · Mar 24, 2015

Is this boat new to you?

It is called prop walk, and is NORMAL. I suggest you do a search on "prop walk" on this or any other boating forum and on Google.

Nothing to fix or change. It "comes with the territory."

Bill1565 · Mar 24, 2015

Richandhelen said:
My H44 has a pronounced pull to the left when cruising under power i.e. 2500 RPMs, 7+ knots. I have a Max Prop. If I were to release the wheel, the boat would rapidly turn to the left. I am frankly not sure if it does the same thing under sail. I just thought about it on the way back into the yard tonight. I'll I check that out next weekend. Is this something that can/should be tuned out? How is it done? Trial and error with the steering cable?

Dont usually disagree with Stu, but pull to the left in forward at 7 knots is not "prop walk". May be rudder, keel you need to look at boat out of the water.

capejt · Mar 24, 2015

My H33C did the same thing, though not as extreme as it sounds like its happening here. I agree, check the underbody next chance you get.

John T1594 · Mar 24, 2015

Perfectly Normal

Pulling to the left under power, especially at 2500 RPM and 7 knots is normal for sailboats under power. It's not called prop walk but rather a result of the spin/turn/wash effect of the prop on the rudder. Prop walk usually refers to the tendency of the stern of the boat to move to port when in reverse

Bill1565 · Mar 24, 2015

John T1594 said:
Pulling to the left under power, especially at 2500 RPM and 7 knots is normal for sailboats under power. It's not called prop walk but rather a result of the spin/turn/wash effect of the prop on the rudder. Prop walk usually refers to the tendency of the stern of the boat to move to port when in reverse

I have not been on nearly all of the sailboats out there, but I have driven a couple of dozen different inboard powered ones. Pulling either way at speed never occurred
. Must be a different "normal"

Jackdaw · Mar 24, 2015

Bill1565 said:
I have not been on nearly all of the sailboats out there, but I have driven a couple of dozen different inboard powered ones. Pulling either way at speed never occurred
. Must be a different "normal"

Happens mostly with modern 'balanced' spade rudders. Old school unbalanced rudders just weathervane in the prop-stream. The front edge of balanced rudders is pushed to the side by the slightly off-center pressure of the wash.

Richard Bryer · Mar 24, 2015

It is not unusual and happens with many sail boats. It is complicted because prop walk ( and yes you can have prop walk in forward as well as reverse- usually more pronounced in reverse) as well as prop WASH deflecting off the rudder which is not facing directly forward because of the position it is held in to correct for the prop WALK.

splax · Mar 24, 2015

I want to first congratulate you on your propulsion arrangement. 7+ kts @2500 RPM is pretty impressive as far as I am concerned.
I think shaft alignment may well be the issue here. Prop walk should not occur at this relatively high speed. Prop walk usually is noticed in reverse, i.e. low speed vs. relatively high RPM. Prop wash against the rudder is something accounted for in the shaft alignment. The higher the speed the less effect prop wash will have since the flow along the rudder tends to keep it straight.
Obviously something is not dragging you to PORT since you attain such speed at a cruise power setting. If the rudder were damaged the effect would be apparent at all speeds, just not as much at the lower.
A possibility, given that this is a new problem, is that your shaft bearings may have worn to failure and are not able to hold the shaft straight at the higher RPM. Check the alignment brackets for loose bolts, since the torque generated by the shaft may twist itself out of alignment.
I had a similar issue myself, but couldn't find the cause. I dove and examined things and could find nothing. It didn't occur again so I think I had something wrapped on the rudder that came off when I slowed to the dock.

Bill1565 · Mar 24, 2015

Jackdaw said:
Happens mostly with modern 'balanced' spade rudders. Old school unbalanced rudders just weathervane in the prop-stream. The front edge of balanced rudders is pushed to the side by the slightly off-center pressure of the wash.

Good I'm an old boat guy. Balanced spade like that would fail my sea trial.

Don Lucas · Mar 24, 2015

Mine doesn't turn noticeably when motoring at 2500 rpm. I don't think there is any "tuning" of a rudder, but it could be bent. Does it do the same when sailing in calm conditions and no current? You have a Maxprop and maybe there is something wrong with it.

Where were you at when you noticed the problem? What was the tide/current doing? What were the wave and wind conditions?

Where are you fuel/water/holding tanks located and how much was in each of them?

BTW - at low speed I get prop walk which is normal, but my RH prop turns the boat to the right.

Marc14857 · Mar 24, 2015

Tune MY Rudder

For what it is worth, my H44 also has a tendency to pull to the left when motoring at about 2200 RPM about 6 knots. It gets a little worse if I increase RPMs and Less pronounced if I reduce RPMs which leads me to believe it is associated with the prop. If the prop is turning clockwise when looking at it from the stern, I would think that there would be an equal and counter rotational force pushing the bow to port. I have experienced the same when taking off in a small single engine propeller driven plane. You need to hold in right rudder to counteract the planes tendency to want to go left ...opposite of the direction of the propeller. (Isaac Newton 3rd law for every action there is an equal and opposite reaction).

Benny17441 · Mar 24, 2015

Was it doing it before or did it just start? If it does not do it under sail you likely have a fouled prop.