Rudder Hardover when Motoring

[Steve H]

While motoring, my rudder has a tendency to hardover turn to the rudder stops. I suspect that since the prop wash hits the leading edge of the rudder first, the force of the prop wash pushes the rudder over. It is so pronounced that it easily overpowers the autopilot. This doesn't happen under sail and the rudder is balanced quite well. Does this happen on anyone else's 27' and if so, how do you manage it. This is my first season sailing "Molly Brown."

[BobK]

Under power my 27 tends to turn to port but no where's near hard over.  It also does not overpower the autohelm 3000 autopilot.
BobK

[wes]

You may have stumped the panel with this one. I've experienced nothing similar to this, at least in forward gear. It's common in reverse, because the axis of the rudder post is closer to the forward (leading) edge of the rudder. The natural tendency of the rudder when moving forward is to center itself, whereas in reverse it's to slam hard over as you're describing.

Something's amiss, but I can't say what it is.

Wes

[Whisper]

Hi Wes , if the autopilot is not connected and you just have a loose hold on the tiller or wheel  ,does it still have this tendency to go hard over.?
If so it?s prop wash over the rudder I think due to either incorrect alignment of the rudder or shaft  ,or maybe too much leading edge on the rudder .
But if it only happens with the autopilot connected then you may have the autopilot configured wrongly .
It happened on a boat I purchased the previous owner had configured the tiller pilot to a stboard setting but was mounted on the wrong side and it would do a hard over .
In your case it may even be the position of the compass in the boat that has interference  From some other source or not lined up correctly .. Maybe just go through the installation and set up procedures of the autopilot and see if it performs all other functions correctly .
Hope this is some help

[Steve H]

Under power she will turn hardover, I can manage it with the helm friction though. I guess I'll see if I can play with some power settings and speed.

[HJ51]

Wow, I literally logged on to the forum to post this same question.  I recently suffered two separate catastrophic rudder events (one from being towed off after running around, one from severe electrolysis due to loose ground wire) that required me to replace/rebuild my rudder twice within six months. 

The second (rebuilt) rudder was just installed this month and when I returned from my first sailing trip with it I told the shipyard that did the repair that the new rudder forces the boat hard to port when I remove my hands from the helm for just a couple of seconds.  I felt like it was dangerous and could easily send me into oncoming traffic in a channel.  Their reply was that the propeller is offset to allow the rudder to be dropped without removing the prop and thus it is prop wash that is causing it to go hard over.  Two problems with that:  (1) I feel confident it was not doing this previously and (2) I just confirmed with Com-Pac that the prop is not offset on the CP27.  Nevertheless, I still don't know what the range of normal is and have to decide whether and how hard to fight with the shipyard.  The fact that the original poster has the same issue also makes me wonder.

Here are links to a couple of videos of it occurring.

https://photos.app.goo.gl/1ZCv9HT8EoqQ39GP9

https://photos.app.goo.gl/tdzRzG15gZWkRKgX9

Would be very interested to get reactions from you guys.

[Renae]

Whoa...that's not right.

[Steve H]

HJ, please post if you figure out a solution and I'll do the same. I'm out of the water until April, but will try a couple of things once back in.

Steve

[Andre]

I have zero experience with 27s, but is there a chance of an asymmetry in the rudder after the rebuild? Either in the foil shape or the rudder shaft relative to the blade.  Maybe a slight mis-alignment compounded by prop wash might do it.

Hauling the boat or at least diving it might reveal something.

Andre

[wes]

Steve - I went out yesterday on my 27 determined to answer your question.

Here's what happens under power (speed about 3 knots) when I take my hand off the wheel. Look familiar?

https://vimeo.com/500570068

But here's what happens when I do the same with the engine in neutral (same forward speed):

https://vimeo.com/500580222

My boat is a 1988 with the Universal M12 engine and a two-bladed 12x9 prop. I'm pretty confident now that there's nothing wrong with your boat; it's just prop walk, which is milder in forward than reverse but still enough to push the stern around. Hope this helps -

Wes

[Steve H]

Wes, yep, that's pretty much it!

[Tim Gardner]

Well, the good news is if you fall overboard while under power, the boat will come back around to you.  The bad news is it could run you over .

[HJ51]

Hey guys, following up as promised.  Wes, thanks for posting those videos for something to compare to.  I feel like my issue was more severe than what I saw in your videos and I had a marine mechanic look at it.  After he was finished the problem was eliminated and my boat steers straight and stays straight, even with hands off the wheel.  So the following may not apply to the original poster (or anyone else) but here is what the mechanic reported to me verbatim. 

"Simply stated if the steering cables are loose, the rudder will start turning the boat to PORT until the cables tighten. By tightening the cables the movement of the rudder on its own is minimized.  The cables are tensioned by tightening the nuts at the steering quadrant. These nuts are prevented from loosening using jam nuts.  A jam nut was missing on one of the cables, which allowed it to loosen on its own. I tightened the cable and installed a new jam nut.

The following is a more detailed explanation:

The rudder is controlled by the helm using a chain and cables. The cables are attached to the rudder by means of a steering quadrant.  The tension of the cables is adjusted at the quadrant usung nuts. If the cables are loose the rudder can move on its own the extent of which depends on how loose the respective cable is.

The quadrant is attached to the rudder post which is attached to the rudder. The rudder post is not attached at the leading edge of the rudder, but is attached at a certain distance aft of the leading edge. This is done to balance the rudder and make it easier to turn.

Because of the direction of the propeller's rotation, the boat has a tendency to steer to PORT, which is normal. If the cables are loose the rudder will steer the boat to PORT on its own until the respective cable is tensioned. By that time the momentum of the boat along with the propeller's rotation and the offset of the rudder post on the rudder, the boat's turn to PORT becomes progressively worse."

Don't know if that will apply or be useful to others, but it fixed my problem completely. 

[Steve H]

Thanks HJ! Very useful, I'll check that.