dom
Well-Known Member
That makes sense as the shaft tube can only survive if the shaft shears off below it. Cutting into the shaft - Jees!
Beneteau 43 rudder loss, er I mean Jeanneau
- Thread starter ChrisE
- Start date
PeteCooper
Well-Known Member
Well as the oft quoted forum limit is £200 I'll cheerfully take your death trap off your hands, and I'll provide my own spare rudders. Once you move up here we can complete the deal!!!!!!!!!!!!!!!!!!!
gandy
Well-Known Member
[ QUOTE ]
A brand new Westerly lost it's keel as the boat lifted on the tide ..... probably 30 years ago.
Relevant? No.
Interesting? Not really.
[/ QUOTE ]
That'll be the well-known Griffon of 1981. Interesting and relevant if you own the same model. It may also be relevant that Westerly put their hands up and recalled existing boats for modification as well as changing the design for future production.
A brand new Westerly lost it's keel as the boat lifted on the tide ..... probably 30 years ago.
Relevant? No.
Interesting? Not really.
[/ QUOTE ]
That'll be the well-known Griffon of 1981. Interesting and relevant if you own the same model. It may also be relevant that Westerly put their hands up and recalled existing boats for modification as well as changing the design for future production.
Ruffles
Well-Known Member
I understood that spade rudders were designed to fail at the blade rather than the shaft to avoid tearing a hole in the hull. Is that true? No relevance to the initial post - just interested in the truth of the matter...
FullCircle
Well-Known Member
Wow Pete, thats a really good offer considering the risks you are taking. Are you sure its worth that much?
clouty
Well-Known Member
I was racing on a boat called AWOL - Hurley 31 perhaps, newish, when the spade hung rudder fell off, and inspection showed later that it had sheared through the stock where it exitted the hull - it was a solid stainless bar as well, and also showed signs of crevice corrosion. No copper plating though. So this is not the only instance. /forums/images/graemlins/mad.gif
Roberto
Well-Known Member
a friend in my marina has a sun legende too, like Robin's (hello) and myself: last December she experienced a wind blow at night while at anchor, the wind turned onshore and she had to quickly lift anchor and go away
while doing this, the boat drifted with the stern against the rocks, and the rudder took a hell of a smashing, interminable crunch crunch as she said
she eventually managed to set free and go away: result
1.the lower third/one half of the rudder had been slowly ground away; she could still still steer as the blade area is impressive and could easily do with 1/2 rudder
2.no damage to the (partial) skeg, which ends at the upper third of the blade, no damage to the rudder shaft either
3.she bent the lower facing plates (those which are welded to the shaft and embrace the wooden blade), but again no damage to the shaft
if on one side it looks frightening, given the kind of smashing the rudder took, imho its structure coped quite well, or anyway with bearable damage, both in terms of steering and floatation
fwiw /forums/images/graemlins/smile.gif
while doing this, the boat drifted with the stern against the rocks, and the rudder took a hell of a smashing, interminable crunch crunch as she said
she eventually managed to set free and go away: result
1.the lower third/one half of the rudder had been slowly ground away; she could still still steer as the blade area is impressive and could easily do with 1/2 rudder
2.no damage to the (partial) skeg, which ends at the upper third of the blade, no damage to the rudder shaft either
3.she bent the lower facing plates (those which are welded to the shaft and embrace the wooden blade), but again no damage to the shaft
if on one side it looks frightening, given the kind of smashing the rudder took, imho its structure coped quite well, or anyway with bearable damage, both in terms of steering and floatation
fwiw /forums/images/graemlins/smile.gif
Sailfree
Well-Known Member
As the owner of a 2 yr old Jeanneau 43 DS thanks for bring this to my attention!!
I think Robin is correct in his judgement but hope that not just because I would like him to be correct!
From the photo it appears such a smooth break. Unfortunately I cannot see the edge but looking at what appears to be copper deposit indicated to me that its an old crack that has been "working" and rubbed the suface to remove any sharpness in addition allowing copper to deposite itself in the crack. The other edge out of the picture frame I suspect was the last of the section to fracture.
I confess I do wish I had been more attentive in my material science lecture but metal phase diagrams never turned me on! However I am aware that aluminium and copper are no no's but I was unaware that there was any real problem if a bit of copper antifoul got on SS. Can someone please enlighten me?
I think Robin is correct in his judgement but hope that not just because I would like him to be correct!
From the photo it appears such a smooth break. Unfortunately I cannot see the edge but looking at what appears to be copper deposit indicated to me that its an old crack that has been "working" and rubbed the suface to remove any sharpness in addition allowing copper to deposite itself in the crack. The other edge out of the picture frame I suspect was the last of the section to fracture.
I confess I do wish I had been more attentive in my material science lecture but metal phase diagrams never turned me on! However I am aware that aluminium and copper are no no's but I was unaware that there was any real problem if a bit of copper antifoul got on SS. Can someone please enlighten me?
Bav34
...
Tony, it is NOT relevant to BenJen rudder failure in the same way as a Bav keel so why do 'they' have to drag Bav keels into it? Think I'll just start random postings in the middle of other peoples if I think it's relevant.
ps my Audi Multitronic gearbox has just failed at a cost of 4.5k
sorry not relevant.
ps my Audi Multitronic gearbox has just failed at a cost of 4.5k
sorry not relevant.
Robin
Well-Known Member
Thanks Roberto, we will sleep much better next time at sea in a gale!
dulcibella
Well-Known Member
There's a lot to be said for a keel-hung wooden rudder.
vyv_cox
Well-Known Member
I suggest that people should not jump to conclusions regarding the 'copper'. It looks coppery in colour but, assuming a fatigue failure, which it most certainly looks like, then the colour may well be fretting debris. When fracture surfaces rub together for some time in air they produce a compound called 'jewellers' rouge, alpha Fe2O3. This is a brownish-red in colour and is readily identified by X-ray diffraction. I have no idea what compound would be generated if the rubbing surfaces were immersed in seawater but I assume some hydrated form of the above, which may well also be red in colour.
It is a characteristic of fatigue failures that they appear to fracture suddenly. In fact they have been fracturing for very many stress cycles but the crack is normally undetected until the stress in the component exceeds the strength of the remaining area. In well-designed components with a good factor of safety this is usually only about 10% of the total cross-sectional area. It appears to me, although the photograph is not great, that the final fracture area is quite small. It also seems that it may be a multiple origin fracture, which is highly characteristic of a change of section with inadequate fillet radius.
Fatigue fractures are almost always initiated by a stress raiser. This may be a change in section caused by, for example, manufacture, a wear step, a modification, or something else such as corrosion pits, damage, keyways and a host of others. This photo shows a fatigue fracture of a pump shaft. I don't have an example of one just like the rudder shaft one, although I have seen plenty. In this case the fatigue initiated at the line of corrosion pits, due to a sleeve of a dissimilar metal.
I would inspect your rudder shaft for any of the above possible defects. If you find any, do a dye-penetrant test to reveal any cracks. You can buy enough of the necessary materials to do a hundred tests fo £50, or you could get an inspection company to do it for you quite cheaply.
It is a characteristic of fatigue failures that they appear to fracture suddenly. In fact they have been fracturing for very many stress cycles but the crack is normally undetected until the stress in the component exceeds the strength of the remaining area. In well-designed components with a good factor of safety this is usually only about 10% of the total cross-sectional area. It appears to me, although the photograph is not great, that the final fracture area is quite small. It also seems that it may be a multiple origin fracture, which is highly characteristic of a change of section with inadequate fillet radius.
Fatigue fractures are almost always initiated by a stress raiser. This may be a change in section caused by, for example, manufacture, a wear step, a modification, or something else such as corrosion pits, damage, keyways and a host of others. This photo shows a fatigue fracture of a pump shaft. I don't have an example of one just like the rudder shaft one, although I have seen plenty. In this case the fatigue initiated at the line of corrosion pits, due to a sleeve of a dissimilar metal.
I would inspect your rudder shaft for any of the above possible defects. If you find any, do a dye-penetrant test to reveal any cracks. You can buy enough of the necessary materials to do a hundred tests fo £50, or you could get an inspection company to do it for you quite cheaply.
kcrane
Well-Known Member
[ QUOTE ]
ps my Audi Multitronic gearbox has just failed at a cost of 4.5k
[/ QUOTE ]
B**ger, just got a call from Audi saying our new A6 Multitronic was on schedule, shall we cancel?
ps my Audi Multitronic gearbox has just failed at a cost of 4.5k
[/ QUOTE ]
B**ger, just got a call from Audi saying our new A6 Multitronic was on schedule, shall we cancel?
Bav34
...
Not if it has the 7 plate internals. Mine had 6 plates which apparently failed often as it couldn't take the torque !!! Now replaced with a 7 plate system. Bavaria ... no...no...no... can't blame them ....just need to get their name in in a negative post /forums/images/graemlins/cool.gif /forums/images/graemlins/cool.gif ....Audi fully aware of the problem and if you went even 1000 miles over the 40000 oil change recommendation you were on your own. Guess that was a bit tricky for the high mileage guys. German engineering eh ???? Give me an Austin Allegro any day /forums/images/graemlins/tongue.gif
misterg
Well-Known Member
[ QUOTE ]
The problem that caused the failure with Megawatt, was, as far as I can remember, that some 'engineer' retrofitting an autopilot had drilled or cut the SS shaft in the wrong place! As the boat surfed down a wave the rudder shaft snapped, this in turn put pressure on the shaft tube which then tore away from the rest of the hull moulding.
[/ QUOTE ]
Lets not set any hares running here:
Megawatt's rudder shaft wasn't drilled or cut by the people that fitted the AP. The shaft wasn't SS, it as an aluminium alloy. The machined finish was rough, the 'temper' of the metal was a little hard, and there was pitting from corrosion present, however these were not thought to be a significant cause of the failure.
The most likely cause (IMHO) is that described in a letter in the appendix to the MCIB report: An additional tiller arm / rudder quadrant had been fitted for the AP which was fitted below the steering quadrant, near a change in section of the shaft. 'Normally' a modified steering quadrant is used to fit an AP to this type of yacht, which is fitted close to the top bearing. Steering forces through the second arm when the AP was in use would have generated bending loads in the shaft where it was fitted, which induced fatigue cracks, weakening the shaft.
Your last sentence is correct, though!!/forums/images/graemlins/grin.gif
Read it for yourself here.
Puzzled by the Jeneau failure, though. I agree with VicS, et all that it looks like a very old fracture that's been grinding away for a while.
Andy
The problem that caused the failure with Megawatt, was, as far as I can remember, that some 'engineer' retrofitting an autopilot had drilled or cut the SS shaft in the wrong place! As the boat surfed down a wave the rudder shaft snapped, this in turn put pressure on the shaft tube which then tore away from the rest of the hull moulding.
[/ QUOTE ]
Lets not set any hares running here:
Megawatt's rudder shaft wasn't drilled or cut by the people that fitted the AP. The shaft wasn't SS, it as an aluminium alloy. The machined finish was rough, the 'temper' of the metal was a little hard, and there was pitting from corrosion present, however these were not thought to be a significant cause of the failure.
The most likely cause (IMHO) is that described in a letter in the appendix to the MCIB report: An additional tiller arm / rudder quadrant had been fitted for the AP which was fitted below the steering quadrant, near a change in section of the shaft. 'Normally' a modified steering quadrant is used to fit an AP to this type of yacht, which is fitted close to the top bearing. Steering forces through the second arm when the AP was in use would have generated bending loads in the shaft where it was fitted, which induced fatigue cracks, weakening the shaft.
Your last sentence is correct, though!!/forums/images/graemlins/grin.gif
Read it for yourself here.
Puzzled by the Jeneau failure, though. I agree with VicS, et all that it looks like a very old fracture that's been grinding away for a while.
Andy
misterg
Well-Known Member
[ QUOTE ]
I agree with VicS...
Andy
[/ QUOTE ]
Err.. sorry, should be vyv_cox. Apologies to both.
I agree with VicS...
Andy
[/ QUOTE ]
Err.. sorry, should be vyv_cox. Apologies to both.
Birdseye
Well-Known Member
That coppery colour looks too coppery and shiny not to be copper.IMHO Cant imagine what could cause that, and only on the fracture surface.
Sans Bateau
Well-Known Member
Thanks, yes you are right, thanks for the link, I wasn't too sure that's why I covered what I said with the caveat 'as far as I remember'.
I knew the AP quadrant had some part to play in the failure.
I knew the AP quadrant had some part to play in the failure.
halcyon
Well-Known Member
Funny that, the multitronic box on my brother's A6 went as well, must say the Germans produce reliable failures. Bigger shock was when he went to trade in at Audi for another, £27K new, £10K trade in at 2 years.
Fatique's a funny thing, the wat time Liberty ships were sinking on there own, turned out to be fatique cracking from welder striking an arc to light there ciggy from the red hot welding rod tip. Also saw a demo of stailess plate being cut through by putting a elastic band around it, the cutting was due to electrlytic corossion. The band causing differant areas of water soltion contact, and differant voltages. Expanding this, was there a copper sleeve or similar in cotact with the rudder, the crack causing electrolytic depositing of the copper ?.
Brian
Fatique's a funny thing, the wat time Liberty ships were sinking on there own, turned out to be fatique cracking from welder striking an arc to light there ciggy from the red hot welding rod tip. Also saw a demo of stailess plate being cut through by putting a elastic band around it, the cutting was due to electrlytic corossion. The band causing differant areas of water soltion contact, and differant voltages. Expanding this, was there a copper sleeve or similar in cotact with the rudder, the crack causing electrolytic depositing of the copper ?.
Brian