Rudder cavitation?

[puddlejockey]

Hideho, all!

Last season, I noticed a slight pulsation and cavitation in the rudder, under sail I. Some conditions.
Muskrat love is a wheel steered boat, so I'm assuming that if I can feel it clearly through the " insulation" of the gearing, she's really flapping her wing, so to speak.
It seems as though it's gotten worse, and is very prevalent under power at low speeds. I don't detect any appreciable play in the rudder while she's tied up.

I spent a fortune at the start of last season, to have the motor and shaft re aligned, the stuffing box re packed, etc while she was " on the dry". It could very well be experience and/ or my craziness, but I swear I never noticed it prior to that.

Any thoughts? And are there things that I can/ should do while she's in the water, in a DIY format, that may identify a problem if there is one? She just doesn't "feel right" to me. That said, I've probably got less than 100 hours at the wheel with her, and I may be paranoid. She also seems to want to fall off to port, no matter the point of sail. ..

 

[Bill Roosa]

probably going to have to take a look below. Could be as simple as a big barnical buildup on the rudder.
What does the wake look like when sailing? does it look more disturbed than before?

 

[puddlejockey]

Good thoughts, Bill.. The wake looks pretty clean to me, but it can be tough to tell.
I'm on a warm, inland lake with usually a bit of chop. Since Im in freshwater,barnacles an impossibility, but algae growth a very real possibility, even likely.. Would it take much buildup to cause what I'm seeing?

 

[kito]

I believe the first thing I would do is have someone jump and inspect the rudder for any crap on it. If you are on Lake Norman it could only be slime or debris. Then I would have them hold the rudder while someone turns the wheel back and forth to see how much play is there.

 

[kito]

Another post here made me think of something. If you have an emergency tiller, maybe try it and see if the cavitation goes away. I know on my H30, the emergency tiller mounts directly to the rudder shaft. This will take all the gears, pulley, cable etc out of the equation.

 

[bobbyfingers2001]

I'd do some investigating; starting with inspecting all of the steering cables and pulleys. You want to look for any loose pulleys or gears, check cables for slack, then work your way to the rudder shaft. Look for water in the shaft well and again look at the pulley or lever mounting to see if everything is tight.

As someone else mentioned you can have someone hold the emergency tiller in a fixed position while someone else slowly rocks the wheel from side to side and inspect for play.

If everything checks out then the issue is left to only two other possibilities neither is good. First, the rudder shaft / bushings are worn, but this should only cause a small flutter in the rudder (which may feel pretty severe at times) however this should not cause any major steering variances as you described earlier. Lastly, and unfortunately the most costly, and not unheard of is the core of the rudder has rotted, this typically happens on foam core rudders when they have either hit something or grounded the boat. The rudder in your boat has a stainless steel shaft and a steel "flag" structure sandwiched between structural foam and then glassed together encapsulating the entire piece together.

They make terrific rudders especially for small boats, and race boats looking to keep the weight down.

Bellow are some images of what the construction looks like and what a damaged rudder looks like.

http://www.epoxyworks.com/12/Rudder1.jpg


http://www.boatdesign.net/forums/at...replacing-foam-core-rudder-img_2906-copy-.jpg

They often can be repaired, however, you can contact the manufacturer directly and he will build you a brand new one often for less than a repair yard will charge to repair it, and there is no way of knowing how much rust damage there is on the old post inside the rudder.

The manufacturer is Foss Foam Products of Florida, Bob Walker is the owner and he is very helpful he can be reached at: 352-529-1104

I hope this was useful. Smooth sailing.