Rudder a cause for vibration??

[gabosifat]

Hi All,

I recently posted regarding a cyclical vibration I'm getting.

"It cycles on and off on with a regular rhythm. It lasts maybe 3 seconds, goes away for 3 seconds and then comes back for another 3. I do notice it happens more when the boat rolls from side to side. I just pulled the boat, did the bottom & replaced the zincs thinking the zincs might have corroded in a way that would throw the shaft off balance. The cutlass bearing was tight with no play & the shaft spins easily by hand with the engine in neutral. I haven't checked the the engine alignment or the motor mounts yet - that's my next task."

When I hauled the boat this past week, I could take the rudder & move it back and forth a bit & I'm wondering if this could be the cause of this type of vibration. When I'm standing at the wheel, the vibration seems to come through the cockpit floor & especially when my foot is over the emergency tiller access port which makes me want to look at the rudder. I guess the first thing I'll try is the grease fittings on the rudder post bushings then go from there.

Any suggestions?

Thanks,
Steve Gabbott
E35/3 "Silent Dancer"
Vancouver

 

[Mark F]

I remember someone (maybe Seth) mentioning that nicks on the leading edge of the rudder or keel can cause a vibration. Did you try a site search?

 

[gabosifat]

Yes I did see that. I do think the rudder shaft is a bit loose in the tube but I'm not sure if this would make it vibrate.

Thanks,
Steve

 

[Art Mullinax]

Conditions?

Does this vibration occur when you are under power or sailing?

 

[gabosifat]

Only when powering.

Steve

 

[NateHanson]

It's probably just the turbulent prop wash against the rudder, and if the rudder stock has too much play it's able to wobble around in all that wash.

Does the vibration go away if you turn the wheel 10 degrees and hold it there (so the prop wash is consistently just pushing against one side of the rudder)?

 

[gabosifat]

It actually does go away when the wheel is turned one way or the other. I guess I should look into tightening up the rudder stock with shims of some sort. Has anyone done this before?

Steve

 

[NateHanson]

I'd say you've tracked it down.

 

[hodo]

I'm with Nate on this. we had the same issue on a Peterson 34 we raced. what we did was made sure the rudder shaft was true and smooth, no grooves, pre drilled holes in the rudder tube, cleaned it out, coated the rudder stockwith silicone grease, centered it as close as we couldin the tube, then mixed up a slurry of graphite rich epoxy, injejected it in the holes let it set, then checked for tight spots, cleaned upand we were done in a day. I thought it worked well, and after 5 years, it is still a snug rudder. Harold.

 

[Seth]

There you have it-mostly

As Nate says-You probably have it figured out. Make sure the shaft is straight, fit some bearings, and make sure the rudder is symmetrical (same shape on both sides). The fact that it happens only under power, and goes away (great catch, btw, Nate!) when the rudder is loaded up (one side or the other) confirms it has something to do with the rudder- likely looseness.

But-the pulsing aspect of this suggests also something in the drivetrain-maybe a prop blade slightly out of whack, or a possible alignment/mount issue.

There may be 2 things going on here....
S

 

[gabosifat]

Thanks everyone,

I think I have a bit more of a handle on it now & I'm fairly sure the rudder is the main culprit. Is there another fix for the rudder or is the epoxy with graphite the best way to go? How exactly did you inject the slurry into the holes?

Many thanks,
Steve

 

[NateHanson]

Does this boat have rudder shaft bearings?
The graphite epoxy idea is great, but only for boat's that have no bearings, just a rudder shaft inside a fiberglass rudder tube (my boat's constructed that way and I may well use this trick myself!).

But doesn't the E35 have a more sophisticated rudder bearing?

 

[Chris A.]

Rudder bearings

I just tightened up our 34's rudder and here's what I did for what it's worth. On our 34 there are 2 bronze sleeves that act as bearings- one at the bottom of the fiberglass rudder tube and the other at the cockpit sole, associated with the emergency tiller access plate. There is also a stuffing box at the top of the fiberglass tube. I had some slop- both side to side at the lower bearing and also about a quarter inch of vertical play. I was hearing noise under way- not what you're describing under power, but more of an intermittent "thunk". Anyway, I lowered the rudder post out of the boat and inspected it and the tube for damage (found none). I then took care of the vertical play with a plastic / Delrin spacer (I'm not sure of the material- my brother machined it for me though) positioned just beneath the quadrant and above the 3 inch spacer that was already there on top of the stuffing box. This had the effect of lifting the rudder a quarter inch closer to the hull. For the side to side motion, I considered epoxy injection but ended up shimming the post where it contacts the lower bearing. I used two wraps of special tape for the shim: utrahigh molecular weight polypropylene tape, with a 3 mil thickness and 2 inch width. Re-installed the post, added some grease at the two zerk fittings (one near each bearing), and it feels good. We're schedule to splash on Friday- so we'll see how she holds up!

Cheers,

 

[gabosifat]

The manual says there are rudder bushings both at the top at the cockpit sole as well as at the bottom of the fiberglass tube. Both of are supposed to have grease nipples.

Steve

 

[gabosifat]

Chris,

Where did you get the Polypropylene tape?


Steve

 

[Dan Callen]

I had this same problem on my Ericson32-3......same rudder as yours. Be sure you have greased both fittings on the rudder shaft. There are three bolts on the packing flange. One of mine came loose and damaged the threads. I purchased some longer bolts and put a nylock nut with some blue lock tite. I readjusted the flange using a coin for a guage so I was sure to have equal distance on all three bolts....... mine was so loose it was actually dripping. Since the repair I have had no problems. Dan Callen Ericson 32-3 Andiamo

 

[Chris A.]

Tape

Steve,

Sorry I've been away. The tape I used came from the CS Hyde Co (with which I have no affiliation) and I incorrectly called it polypropylene. It is polyETHYLENE. The exact product I used was part# 19-3A