Balancing the Rudder
 

I get a vibration in the steering system of my old Owens 27. I've checked
and had checked all the steering linkages and the gearbox and there is no
play. Also I checked the boat (it is old) for hogging underway and none what
so ever. I've got the problem down to being that the rudder is not balanced.
I have called dozens of prop shops up and down the coast to see if they do
rudder balancing, none of them do. I can't even get them to point to someone
who does. Does anyone know of any shops that balance rudders? Otherwise, it
looks like I'm going to have to braze material on to the leading edge of the
rudder and grind it off in a trial and error fashion until the rudder
balance. One old guy said to try bending the rudder relative to the shaft so
the center of effort is moved forward but I don't think this is good advice.
It would give the rudder a forward canted leading edge which I don't think
is good. Thanks.

Randy

Balancing the Rudder
 

On Feb 18, 2:53*pm, "Randy Haupton" wrote:
I get a vibration in the steering system of my old Owens 27. I've checked
and had checked all the steering linkages and the gearbox and there is no
play. Also I checked the boat (it is old) for hogging underway and none what
so ever. I've got the problem down to being that the rudder is not balanced.
I have called dozens of prop shops up and down the coast to see if they do
rudder balancing, none of them do. I can't even get them to point to someone
who does. Does anyone know of any shops that balance rudders? Otherwise, it
looks like I'm going to have to braze material on to the leading edge of the
rudder and grind it off in a trial and error fashion until the rudder
balance. One old guy said to try bending the rudder relative to the shaft so
the center of effort is moved forward but I don't think this is good advice.
It would give the rudder a forward canted leading edge which I don't think
is good. Thanks.

Randy

In all probability, your vibrations are due to the shape of the
leading edge of the rudder. A knife edge shape to a leading edge will
often promote extreme vibrations in very thin sectioned and high
aspect ratio (depth to length) rudders, especially at high speeds
where they develop 'harmonic' (natural frequency) induced
vibrations.
The most often used keel/rudder shape on sailboats is the airfoil
"NACA 010" shape to promote 'stable' flow across the rudder at most
common speeds, there are other NACA shapes but the "010" will result
in the least hydrodynamic 'stability problems'. Overly thin rudder
sections are very difficult to change to a NACA010 shape profile.
Such NACA010 shapes were primarily developed for air foils but are
used equally as well for 'boat's' keels and rudders.

Do websearch for "NACA 010" and simply 'scale' those parabolic shapes
to your rudder if you want to 'experiment'.

'Buzzing' rudders can be remedied ... just takes time to change the
shapes, etc. by continued experiment to arrive at one that is
'stable'.

Balancing the Rudder
 

"Randy Haupton" wrote in message
...
I get a vibration in the steering system of my old Owens 27. I've checked
and had checked all the steering linkages and the gearbox and there is no
play. Also I checked the boat (it is old) for hogging underway and none
what so ever. I've got the problem down to being that the rudder is not
balanced. I have called dozens of prop shops up and down the coast to see
if they do rudder balancing, none of them do. I can't even get them to
point to someone who does. Does anyone know of any shops that balance
rudders? Otherwise, it looks like I'm going to have to braze material on to
the leading edge of the rudder and grind it off in a trial and error
fashion until the rudder balance. One old guy said to try bending the
rudder relative to the shaft so the center of effort is moved forward but I
don't think this is good advice. It would give the rudder a forward canted
leading edge which I don't think is good. Thanks.

Randy

You did say that it is an older boat.
Sounds as if there must be too much wear, giving excessive clearance in the
rudder hangings or bearings that support the rudder.
Get hold of it and see if you can shake it. If you can then renew bearings
etc. as required.
It is highly unlikely that you need to start redesigning the rudder on an
old established design.

Balancing the Rudder
 

"Randy Haupton" wrote in message
...
I get a vibration in the steering system of my old Owens 27. I've checked
and had checked all the steering linkages and the gearbox and there is no
play. Also I checked the boat (it is old) for hogging underway and none
what so ever. I've got the problem down to being that the rudder is not
balanced. I have called dozens of prop shops up and down the coast to see
if they do rudder balancing, none of them do. I can't even get them to
point to someone who does. Does anyone know of any shops that balance
rudders? Otherwise, it looks like I'm going to have to braze material on to
the leading edge of the rudder and grind it off in a trial and error
fashion until the rudder balance. One old guy said to try bending the
rudder relative to the shaft so the center of effort is moved forward but I
don't think this is good advice. It would give the rudder a forward canted
leading edge which I don't think is good. Thanks.

Randy


You might be experiencing prop-whirl-flutter. Have you changed the prop
recently? If you went from a 3 blade to a 4 blade you could see this type of
problem. Does the vibration get worse on a port or starboard turn?

Ron

Balancing the Rudder
 

On 2008-02-18 17:53:58 -0500, "Ron Fiengold" said:

"Randy Haupton" wrote in message
...
I get a vibration in the steering system of my old Owens 27. I've
checked and had checked all the steering linkages and the gearbox and
there is no play.

You might be experiencing prop-whirl-flutter. Have you changed the prop
recently? If you went from a 3 blade to a 4 blade you could see this
type of problem. Does the vibration get worse on a port or starboard
turn?

I'm thinking this may be closer to the situation. I built a balanced
rudder (NACA 0012 http://homepage.mac.com/jerelull/FileSharing.html)
and at certain speeds and heels, we get a slight flutter that seems to
be from water disturbed by the prop and/or keel. Since we're
transom-hung and have a tiller, there's no where else it could come
from.

--
Jere Lull
Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/

Balancing the Rudder
 

Oooooops, He has an Owens 27 .... a stinkpot.

Vibrations in high speed props can arise from various causes: bent
prop, prop out of balance, shaft-whip due to engine misalignment, bent
propshaft, missing or severely worn cutless bearing, etc. etc.
A flat-plate rudder on a powerboat 'can' develop vibrations
(excitation of natural frequency) but that is extremely rare on a
powerboat so check the above first, starting with the engine
alignment.