rudder vibration

[joss]

We have just bought our Beneteau First 31.7. It is only 3 years old but has
a significant vibration/movement in the rudder/tiller under power. The
tiller is quite stiff under power, but under sail it is fine, well, superb
actually, very light and precise. Have lifted it out of the water and there
is some play in the lower bearing, though not as much as the vibration would
have suggested. Also, prop looks fine (saildrive with folding two blade).
Has anybody else had any similar experience with rudder bearings on the
First 31.7 (or any spade rudder for that matter)?

thanks,
Mark


<hr width=100% size=1>

 

[jimi]

The lower rudder bearing seems to be a common problem with Beneteau. There is a brass teflon coated sleeve which should be held in place with Sikaflex or similar. Drop the rudder, get the sleeve out, tighten with cable tie,hold together with electrical tape. cut the cable tie and put 3 or 4 rings of sikaflex round outside, replace sleeve,when Sikaflex dry, replace rudder.

<hr width=100% size=1>

 

[MainlySteam]

Cannot speak for the First 31.7 but even in our own boat, where we have hard coupled wheel steering through a solid link arm to our semi balanced spade rudder (and not on a light AWB), under power the turbulance from the prop can be felt quite distinctly at the wheel as a low frequency vibration (actually more of a shake). It is also quite "firm" when under power, probably just as you describe, but no shake or firmness when under sail. We have no slack whatsoever in our rudder stock bearings.

With a tiller it is, of course, much more obvious.

John

<hr width=100% size=1>

 

[MainlySteam]

If Joss can feel/hear it shaking in the bottom bearing then deja vu perhaps /forums/images/icons/frown.gif.

Regards

John

<hr width=100% size=1>

 

[jimi]

erm .. must admit I've got a bit of form here!!! Also would recommend that when boat is lifted that the tiller is tied off securely and the rudder itself is checked for play. My rudder problem first started to show itself when under power.

<hr width=100% size=1>

 

[joss]

Interesting. The bearing is set in something like Sikaflex and it appears as though there are remnanats of something 'pvc tape-like' poking out of the bottom - well done that man!

Spoke with someone yesterday that suggested holding the bearing tight around the rudder then brazing a small strip along the split to make it permanet. Then, after cutting a small keyway into the hull, set ity in epoxy. For me that sounded pretty secure (assuming no plans in the near future to remove it again). Do you have any comment on this idea?


<hr width=100% size=1>

 

[jimi]

My concern here would be that the arrangement would be too secure and too rigid.
1)If the sleeve needed replacing, it would then be a nightmare.
2)I think there needs to be a slight give so that the sleeve can open slightly to receive the rudder and then close when it is in place.
3)Intuitively I feel the sikaflex would provide some small amount of shock absorbtion thus dampening vibration due to cavitation whereas epoxy resin would not.

All in all I'd replace with Sikaflex using the higher spec 292 rather than 291 .. but then I might be talking absolute bollocks as per normal!!

<hr width=100% size=1>

 

[MainlySteam]

Yes I remembered your problem. Sounds a troublesome little critter. I wonder why they don't just have a plastic/composite bearing in the rudder stock log?

John

<hr width=100% size=1>

 

[joss]

Found this in another thread:

...For example a loose rudder vibrates wildly.
Simply tightening the tiller, hinge, etc can stop the vibration. The
dimensional change "reduces" the apparent degrees of freedom of the syste

I'm going ahead and getting it tightened and see what happens.

Thanks for the input/responses.


<hr width=100% size=1>