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S&S Swan Maintenance - Rudder construction
07 March 2015 - 16:52
#1
Join Date: 01 March 2007
Posts: 147

Rudder construction
If you ever wondered how the rudders are constructed, I attach some pictures showing the stock and how the tangs are attached. I have been aware of a bit of sloppiness in the steering, but I hadn't really worried given the many links between the wheel and the rudder - e.g. wheel bearings, chain links, slack in the cable etc but it appears that we may have had some movement within the structure of the rudder itself, which in extremis could have caused massive problems offshore.
The tangs have slipped on the shaft. It is unlikely that they could slide all the way off because of the bronze shoe and the quadrant gripping the shaft at the top, but if it had gone far enough to leave a small proportion of key, a bit further and we would have no steering. I am not trying to be a scaremonger, but following conversations with Lars I thought it would be informative to share the pictures with the forum.
Rob
Sarabande 47/029

09 March 2015 - 10:40
#2
Join Date: 30 January 2007
Posts: 461

Interesting indeed but I would like to know better. Was it the shaft that slid downward inside the keyed tang bushings due to its own weight or was it the rudder blade that slid downward? It appears to be the second case but then I do not understand why the lower tang bushing (along with the rudder blade) was not supported by the rudder shoe which, hopefully, was well fixed to the skeg and the hull.
Daniel, 411/004

09 March 2015 - 11:57
#3
Join Date: 02 January 2008
Posts: 1547

Dear Daniele
According to Rob the rudder blade was in the normal position, this means the stock worked itself upwards, which is very surprising. There must be a reason for this, but I can only guess. Something forcing the quadrant upwards?
The only place where this stock movement can be seen without removal of the rudder fairing pieces is at the upper end of the stock under the emergency tiller cap. The cap has to be unscrewed for this, and it is suggested that owners of 47's inspect this detail, and report the distance from the stock upper end to cockpit floor level. Other owners could well do this also, good to check that the cap has not frozen.
Kind regards
Lars

09 March 2015 - 19:47
#4
Join Date: 30 January 2007
Posts: 461

Dear Lars,
thank you for your kind reply. I agree that the stock working its way upward is pretty strange and unlikely but it is indeed possible. Apart from something pulling the stock up, it may depend on the combined action of vibrations and friction: in particular it may depend on the phase difference between an oscillating frictional force holding the stock inside the tang bushings and the vertical accelerations of the stock itself. If this is the case either the stock must be always kept free to find its position under its own weight inside the keyed bushings or else perfectly fixed to the latter (fixing screw, cotter pin, or else).
It is indeed an interesting mechanical problem!

09 March 2015 - 20:49
#5
Join Date: 02 January 2008
Posts: 1547

Dear Daniele
The bushings holding the rudder blade were hot shrunk onto the stock, and the intention was that they should never move. It is known however, that the long-term fluctuating loads on the rudder has caused some of them to work loose.
Kind regards
Lars

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