Rudder Problem?

Discussion in 'Boat Design' started by mikefossl, Apr 9, 2012.

  1. mikefossl
    Joined: Apr 2012
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 26
    Location: Hong Kong

    mikefossl Junior Member

    I have a CS 40 built in 2000. It was a Tony Castro design from the 80's. I've noticed that the top of the rudder post moves as much as an inch (that I can tell). Is this normal or do I have a problem?
     

    Attached Files:

    1 person likes this.
  2. kenJ
    Joined: Jul 2005
    Posts: 349
    Likes: 5, Points: 0, Legacy Rep: 56
    Location: Williamsburg, VA

    kenJ Senior Member

    In what direction does it move? Up and Down along the shaft axis? side to side or front to back?
     
  3. mikefossl
    Joined: Apr 2012
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 26
    Location: Hong Kong

    mikefossl Junior Member

    Side to side.
     
  4. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 115, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    Measure OD of the rudder shaft....measure the ID of the plastic bearing.

    If the numbers arent correct Make new bearings.

    Use a stable plastic for the bearings

    Delrin will swell and needs to be machined oversize.

    Ask your machine shop for appropriate plastics.
     
  5. mikefossl
    Joined: Apr 2012
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 26
    Location: Hong Kong

    mikefossl Junior Member

    Lower bearing is bronze, just replaced. Upper bearing appears to be nylon with almost no play. The whole FRP rudder tube seems to flex. I'm guessing the semi-skeg is flexing the opposite way along with the rudder with the axis of rotation at the hull. Just not sure if this is by design...

    I've had the boat in big seas crossing the Pacific. There are no stress cracks of any kind that I can see.
     
  6. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 115, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    How many bearing Two or three with the third at the deck ?

    Looks like a ss rudder stock...it wont flex.

    Skeg looks robust...its not moving,

    This only leaves the bearings.

    Measure. Is the bottom of the stock round ? or has it worn egg shaped ?

    Dry fit then applie load...rudder hard against the stops or a couple big guys grunting and see what moves.

    Their should be no load on the grp rudder tube. This is only to make the stock watertight.

    All the load is on the bearings. deck, hull and skeg.
     
  7. Eric Sponberg
    Joined: Dec 2001
    Posts: 2,004
    Likes: 209, Points: 73, Legacy Rep: 2917
    Location: On board Corroboree

    Eric Sponberg Senior Member

    From your photos it looks as if the rudder tube and the skeg are two different structures. The tube may have broken away from the hull. Look for cracks around the base of the rudder tube and the gussets that are supporting it. No, there should be no play at all in this structure, so something definitely is wrong.

    Eric
     
  8. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 115, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    Gee...if the hull rudder bearing tube structure were breaking free of the hull ,you would have a water problem and fault would be obvious.

    Measure the bearings and rudder stock. Its almost always the lower bearing . Bronze wears fast.

    Vesconite is commonly used . http://www.vesco.com.au/marine/index.php
     
  9. viking north
    Joined: Dec 2010
    Posts: 1,865
    Likes: 88, Points: 48, Legacy Rep: 1146
    Location: Newfoundland & Nova Scotia

    viking north VINLAND

    When measuring your bearings- (lower bronz/upper plastic) be sure to measure the outer dia. also and compare with the seating dia. that they fit into. From my past automotive experience with bearing races on wheel to axil cases, there have been situations where if the bearing seizes/semi seizes to the shaft the whole bearing will rotate in it's seat wearing away and reducing the outer diameter. This in effect will create the same slop as normal bearing wear. This possibly is not the case but it is something to check.---

    A yacht is not defined by the vessel but by the care and love of her owner---
     
  10. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 479, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Not necessarily so Micheal, the upper portion of the tube could have broken out it's tabbing, and is flexing on the lower end's tabbing or hull shell laminate. This is a fairly common issue and some laminate reinforcement is the usual fix.

    The first thing to do is find the broken/delaminate area(s) and grind them back to solid mat. Then a jig will be necessary to insure alignment. Once aligned, the tabbing can be laminated onto the hull shell and tube.
     
  11. mikefossl
    Joined: Apr 2012
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 26
    Location: Hong Kong

    mikefossl Junior Member

    So I had a closer look and was able to see a small crack at the end of the starboard gusset. When flexing the rudder post (using the wheel against the autopilot) I also saw a tiny bit of water. I can't imagine what it looked like in a seaway at 8 knots with opposite lock on the wheel.

    Any suggestions on improvements while I'm fixing this?
     

    Attached Files:

  12. philSweet
    Joined: May 2008
    Posts: 2,402
    Likes: 229, Points: 63, Legacy Rep: 1082
    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    Nothing I see in those pics (very nice pics by the way) translates into 1" of freeplay at the deck. Keep looking. Is it possible that the deck/cockpit is working around a stable post? Does your cockpit tie in to the hull bottom or is it hanging freely? With the halfround in the skeg to take the leading edge of the rudder, it seems odd you wouldn't notice some binding or hear the autohelm loading up. Is there any rudder stop or helm actuator tied to the cockpit floor that would torque it out of place?

    Under what conditions does the rudder head drift around. Tell us a sea story:p
     
    1 person likes this.
  13. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 479, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    You need to climb in there while someone is working the helm. I agree with Phil, that looks to be a stress crack, but not an unexpected thing to see in this location. With you down in the hole "cave" I'll bet you see the issue right away.

    The usual fix is more laminate.
     
  14. mikefossl
    Joined: Apr 2012
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 26
    Location: Hong Kong

    mikefossl Junior Member

    The rudder has three bearings, at the skeg, hull and top of the tube. The rudder never really seems to bind that I can tell, even when opposite lock when overpowered and rounding up. The cockpit floor is a pretty robust affair. I can't see it moving around too much. The autopilot rams are mounted to a shelf glassed to the transom.

    The top of the rudder post (SS tubing by the way) moves slightly as the boat rocks at anchor.

    The boat is getting hauled. I'll get some guy's to rock the rudder back and forth and see what's happening inside and out. After that it's lots more laminate once I make sure nothing inside is rotting. Probably take the opportunity to replace all the bearings with vesconite if they can get stock here quickly enough.
     

  15. mikefossl
    Joined: Apr 2012
    Posts: 10
    Likes: 1, Points: 0, Legacy Rep: 26
    Location: Hong Kong

    mikefossl Junior Member

    Further investigation show that the rudderpost is indeed moving and the the hull seems to flex between the ruddertube structure and the semi skeg. I was lying against the hull while the wheel was torqued against the autopilot. I felt the hull flexing underneath. Essentially it seems as though the rudder post and skeg structures are rotating as a unit with the center of rotation fore and aft along the hull. the only stress crack that I noticed was indicated above.

    If this is indeed the problem, is the hull thickness massively understrength in this location?

    My thoughts on a fix would be to add laminate and possibly a couple of stringers across the bottom tying in the cored sides of the hull. Any thoughts?

    Thanks for your help.

    Mike
     

    Attached Files:

Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.