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Old 07-01-2014, 16:32   #1
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The Rudder Shaft Twist Quiz Do-op

We are rebuilding (at this point looks like replacing is a better term since all materials will be new) our mahogany rudder as part of our refit. We were hoping to reuse the 1 1/2" di bronze rudder shaft but at this point it looks like it may be wiser if we replace it. I believe the boat grounded at some point and rudder took a substantial hit. Bolts that secured wood to rudder shaft were bent and wood split in some places.

Here's the quiz. As photos show key-way for tiller cap is offset from bolts that secured the wood to the bronze shaft. What nobody involved in this project can agree on is,

1) was this defect done by Pearson in 1965 when the shaft was made? I do not believe that Pearson could let this defect go without noticing. However since the boat was sold with the wheel option it could have gone un-noticed to the original buyer. The only way you would know is that rudder would travel more to starboard then to port due to the steering quadrant stops which were alined to the key-way .

2) shaft was twisted during the hit the rudder took? Shaft is still true when rolling it on flat surface. Would not the bolts that hold wood to shaft shear before 1 1/2" di shaft twisted.

Myself I believe #2. I would hope Pearson would not sell a high end boat knowing it had this defect. But do not understand why bolts would not have sheared.

The winner gets to bad mouth Pearson our the guy that grounded the boat.
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Old 08-01-2014, 00:44   #2
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Re: The Rudder Shaft Twist Quiz Do-op

If you can post a photograph of the damaged rudder, showing the splits, and how the timber was attached to the rudder that would help me a lot in trying to figure out what happened. If the boat now has a tiller, did it ever have a wheel on it? How important is an offset key way? (Beyond my knowledge level.)

Were the bent bolts bronze, as well as the shaft? The way they were bent might tell you something about how the forces on them were.

Since, presumably you know all this stuff, maybe you could play the game, "How else than how I've been thinking about this might it have happened?" I personally find that hard to do, hard to let go of my preconceived notion, but, if those cracks are horizontal, maybe they came from forces on the rudder it was not designed to withstand.....but from the forces of the sea, laterally, instead of vertically from the bottom.

Did the bolts go through pintles and bend up towards the head of the tiller" or are/were they deflected laterally?

I apologize for not being able to help here; i think it is an interesting problem. Good luck with it.
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Old 08-01-2014, 04:59   #3
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Re: The Rudder Shaft Twist Quiz Do-op

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Originally Posted by Noreastern View Post
However since the boat was sold with the wheel option it could have gone un-noticed to the original buyer. The only way you would know is that rudder would travel more to starboard then to port due to the steering quadrant stops which were alined to the key-way .
Damage to mahogany foil and bolts that attach foil to 1 1/2" bronze shaft are consistent with twisting (if in fact the shaft is twisted).

Really there is not a way to prove when the defect happened, either at production or when the rudder was hit. My thinking is that it happened when rudder was hit for two reasons;

1 What are the chances of this rudder being hit hard in the same direction as the way shaft is "twisted"
2 I have a hard time believing Pearson quality would by this off

The person making the new mahogany foil believes the shaft was manufactured with the defect for two reasons;

1 Damage to the rudder would be much more extreme in order to twist the 1 1/2" shaft. (even though I believe rudder was responsible for heavy starboard weather helm it was only after I converted it to tiller steering last summer that I knew I had a rudder problem. This after seven years of sailing this boat)
2 If shaft was twisted by that much the shaft would no longer be true which it is.
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Old 08-01-2014, 05:18   #4
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Re: The Rudder Shaft Twist Quiz Do-op

There are wheel steering systems where the keyway is intentionally/correctly "offset" like that . . . The drag link steering systems by both Edison and Whitlock (now lewmar) for instance both use offsets.

There is no way that is due to a twist . . . It was machined in that way. There would be many obvious signs if it had been twisted that much - for one, the key way itself would be distorted.
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Old 08-01-2014, 05:48   #5
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My old Pearson vanguard was machined just like that. It drove me bonkers but there was nothing wrong with it.
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Old 08-01-2014, 05:51   #6
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Re: The Rudder Shaft Twist Quiz Do-op

I vote twisted since the rudder was supported in a skeg at the bottom and the distance between the upper bolt and top of stock is long so that it wouldn't take huge amounts of force to twist it.
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Old 08-01-2014, 16:41   #7
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Re: The Rudder Shaft Twist Quiz Do-op

Cold in Connecticut has kept me away from working on boat again today. So had time to fiddle around in the garage for another day.

I installed the steering quadrant on the rudder shaft as it was before the rudder was removed. As I have stated, the quadrant is also the rudder stopper by means of a single bolt protruding down from center line inside forward section of quadrant bracket.

I did this just as way to check myself if tiller key-way was in the same line as the quadrant. As picture here shows it is. This also verifies why the rudder was able to swing further out to port then starboard.

Why would a boat builder build a boat whose rudder swung more to one side than the another? Why would no Invicta articular I have read mentions this? Bigger concern to me is that I had a buyers survey performed nine years ago and an insurance survey performed four years ago and neither picked up on this problem. Is checking for equal rudder swing not common for a survey? It will be mine from now on.
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Old 08-01-2014, 17:59   #8
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Re: The Rudder Shaft Twist Quiz Do-op

After reading sailmonkey's post which shoots my comment down about the stock being twisted it got me thinking. Maybe the stock is keyed that way to make room for the helmsman to sit near the centerline and not be pinched by the tiller. Pearson may not have differentiated between wheel or tiller steering when making the rudder components.
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Old 08-01-2014, 20:24   #9
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Re: The Rudder Shaft Twist Quiz Do-op

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Why would a boat builder build a boat whose rudder swung more to one side than the another?
Just because the quadrant is 'off center' does not necessarily mean the rudder swung more to one side. They might have mounted the steering wire blocks on an axis also angled off center (perhaps to clear some protrusion or equipment) which would allow it to swing equally. Or they might have just installed equal rudder stops on each side that limited (equally) the swing.
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Old 08-01-2014, 20:59   #10
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Re: The Rudder Shaft Twist Quiz Do-op

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As I have stated, the quadrant is also the rudder stopper by means of a single bolt protruding down from center line inside forward section of quadrant bracket.
The single stopping bolt is center lined to beam of the boat. Also when the boat was last hauled I swung the rudder port to starboard and found this problem with the swing radius.
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Old 16-01-2014, 05:26   #11
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Re: The Rudder Shaft Twist Quiz Do-op

Here is an interesting twist to this story. I brought the old shaft to a machine shop to have a new one made. He found that the shaft is made from two pieces and brazed together. Seems when the rudder took the hit the shaft broke. When it was brazed back together they did not line the key-way up properly.

I do have a question now that I hope somebody here can help me with. What type of bronze should I use for the new shaft? I am thinking silicon bronze for it's non-corrosive properties. But is that type of bronze strong enough for a high load application like a rudder shaft? I am staying away from stainless since all the other parts on rudder are bronze.
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Old 16-01-2014, 05:41   #12
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Interesting....I wonder if that's what happened to mine too?!
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