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Old 27-10-2014, 16:22   #76
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Re: Rudder Failures

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Originally Posted by robert sailor View Post
There is certainly some truth in what you say but ocean racing has been going on for a lot of years and rudder failures have always been with us but not like they have been since the lightly built spade rudders produced these days. Years ago there were no such requirements but over time the rudder failures increased and so did the rules....
Speed increases all efforts in a sailboat, including rudder. In what regards racing the time of spade rudders goes with the time of planing sailboats. Today the max speed of a 40ft racing sailboat doubled the max speed of a racing sailboats from 40 years ago. It is a miracle that with such an increase in efforts modern racers are so trustworthy.

Look at this 33ft performance cruiser reaching 24k
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Old 27-10-2014, 18:24   #77
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Re: Rudder Failures

Why dont they make the rudder stocks out of titanium, no more corrosion problems and not much more expensive to do. make all through hulls from it too, then they will never fail!
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Old 27-10-2014, 19:08   #78
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Re: Rudder Failures

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Originally Posted by stevensuf View Post
Why dont they make the rudder stocks out of titanium, no more corrosion problems and not much more expensive to do. make all through hulls from it too, then they will never fail!
I would like to know the answer.

Why not make them?

Given the thickness and unidirectionality, I would guess stocks can be made of glass/resin too. With metal inserts where they go thru the bearings.

Perhaps glass takes fewer cycles or maybe sheer strength is not high enough. Resined longitudinal fibers would be in sheer I think. Not all that good with any composite.

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Old 27-10-2014, 20:33   #79
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Re: Rudder Failures

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Originally Posted by smackdaddy View Post
I don't think this has been posted here yet, but it should be. If you do lose your rudder - will you immediately hit the button? Or will you nut up and do everything you can to get the boat home like these guys? [edit links]

Yes - even Oysters lose their rudders.
The Oyster 48 is a 26 year old design with a spade rudder. Maybe the possibility of this sort of failure was the reason Oyster has used a full skeg mounted rudder for most of their cruising yacht designs in order to gain the added protection and support.
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Old 27-10-2014, 21:30   #80
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Re: Rudder Failures

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The Oyster 48 is a 26 year old design with a spade rudder. Maybe the possibility of this sort of failure was the reason Oyster has used a full skeg mounted rudder for most of their cruising yacht designs in order to gain the added protection and support.
Personally I kind of dig the dual spade rudder config on their brand new 825. Sexy.



Or how about this 100 with its killer spade rudder?



Skegs on these would be like NFL knee braces on a Victoria's Secret model.

Full circle?
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Old 27-10-2014, 22:05   #81
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Re: Rudder Failures

Why not titanium? Absolutely no reason to. Rudder stocks can corrode just beneath the fiberglass (lack of oxygen). A prudent sailor will drop the rudder every few years, dig down along the rudder post's neck and look for corrosion (same should be done for the propeller shaft where the packings continually strip away the protective oxide).

Next, IF the rudder has the proper balance, the post and internal structures holding it are never over stressed. IF the rudder is not balanced (i.e. an attached rudder to the keel or a skeg), and a wheel is there instead of a tiller, one must take time to drop the cables and steer with a tiller to feel the force at speeds >1.5(WL)^1/2.

It's all about knowing ones boat and not exceeding her strengths.
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Old 27-10-2014, 22:37   #82
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Exclamation Re: Rudder Failures

I mentioned this earlier. Making rudders this way isn't anything new at all, & it's quite simple to do. Relatively speaking.

The engineer/designer, figures out what foil shape & size etc. that he wants for the rudder. Decides what type of fibers & resin(s) he wants to use where. Runs it through FEA. Decides to tweak a few things, & runs everything through this design cycle several times.

Then they layup the prepregs in the order specified in the final design. Debulking things a few times, & adding more fiber layers until the stack is finished. After which, it's autoclave time.

From there, the monolithic laminate block goes into the CNC Mill. And once it's precisely aligned, someone hits the "GO" switch on the mill. Which turns it into monocoque rudder/shaft unit.

After a dimension check, & a few other fine tuning, pre-finish steps. It's sealed & coated, & off to the boat or shop it goes.

There's a little bit more to it than that, in terms of details along the way. However, when done properly, you wind up with a unit, where for all intents & purposes, you can't say where the shaft ends & the blade begins, or vice versa. And you're winding up with a product that's literally bulletproof.

Mind you, they're not inexpensive. But they're darned impressive.


Quote:
Originally Posted by barnakiel View Post
I would like to know the answer.

Why not make them?

Given the thickness and unidirectionality, I would guess stocks can be made of glass/resin too. With metal inserts where they go thru the bearings.

Perhaps glass takes fewer cycles or maybe sheer strength is not high enough. Resined longitudinal fibers would be in sheer I think. Not all that good with any composite.

b.
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Old 28-10-2014, 04:38   #83
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Re: Rudder Failures

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Originally Posted by smackdaddy View Post
Personally I kind of dig the dual spade rudder config on their brand new 825. Sexy.

Skegs on these would be like NFL knee braces on a Victoria's Secret model.

Full circle?
On their cruising models designed by Humphreys, Oyster has stuck with the skeg supported rudder. I think the purpose behind the dual spades is the need to keep a/the rudder in the water when a wide stern yacht is healed way over, like on that particular model (which is basically a custom built prototype). At around 85ft overall, I doubt the company will be manufacturing more than 1-2 per year. Then of course, if one spade rudder failed, the yacht can still use the other rudder to get home.

Regarding the second yacht pictured with the long spade rudder... yes, Oyster will build any configuration an owner desires for a price, since they are a custom and semi-custom builder. Some guys want to race, some of us don't. Is it a trend? Who knows? I suspect building yachts with a wider stern and moving away from the center cockpit design is probably the direction design is going.
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Old 28-10-2014, 09:52   #84
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Re: Rudder Failures

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Originally Posted by Kenomac View Post
The Oyster 48 is a 26 year old design with a spade rudder. Maybe the possibility of this sort of failure was the reason Oyster has used a full skeg mounted rudder for most of their cruising yacht designs in order to gain the added protection and support.
They don't use them anymore on new models. I believe the fact they had used old designed rudders for so long had to do with the conservatism of their clientele that as all conservatives think old stuff works better and is more resistant. They were lucky in managing to convince sooner their clients that a modern keel is not dangerous and way better than a full keel or a modified fin keel. It seems that finally they manage that also in what regards modern rudders versus skeg rudders. All the new models have a very nice set of spade twin rudders, except the 545 but that one is a MKII and use the same hull of the old 54.





The Oyster 48 lightwave belongs to the Oyster past when they made some very modern boats and had a clientele that wanted modern fast boats. The fact that that 26 years Oyster is still a very fast boat says at how well that boat was designed. Unfortunately they did not sell many of them and understood that their future passed by a more conservative design, not to say older, that sell better in UK.

Regarding that Oyster 48 and the rudder breakage it is good to remember that boat is used exclusively as a race boat and make an huge number of races every year including transats and have certainly made hundred of thousands of miles. It remains to know if the rudder was still the original rudder. They, like masts and other stressed parts of the boat have a long duration, but not forever, specially if they are used in hard racing for many years.

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Old 28-10-2014, 10:01   #85
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Re: Rudder Failures

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Originally Posted by stevensuf View Post
Why dont they make the rudder stocks out of titanium, no more corrosion problems and not much more expensive to do. make all through hulls from it too, then they will never fail!
In fact carbon is a better material for it and carbon is used extensively for that in racing boats. The reason it is not used in cruising boats is price even if some expensive cruising boats have them in carbon.

Titanium was used on a keel of an Open 60 and it proved to be a bad idea...it broke without any impact while the carbon ones resisted breaking only under a big impact. When it broke it had already some years of use. It seems it had something to do with stress metal fatigue. Off course it would be better than a stainless steel one but the cost would be hug, certainly bigger than carbon.
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Old 28-10-2014, 11:52   #86
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Re: Rudder Failures

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They don't use them anymore on new models. I believe the fact they had used old designed rudders for so long had to do with the conservatism of their clientele that as all conservatives think old stuff works better and is more resistant. They were lucky in managing to convince sooner their clients that a modern keel is not dangerous and way better than a full keel or a modified fin keel. It seems that finally they manage that also in what regards modern rudders versus skeg rudders. All the new models have a very nice set of spade twin rudders, except the 545 but that one is a MKII and use the same hull of the old 54.
Exactly Paulo. It's good to see progress toward improved performance - regardless of the brand.
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Old 28-10-2014, 12:37   #87
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Re: Rudder Failures

Titanium is not cheap, maybe the material cost isn't that bad, but talk to a machinist about machining the stuff.
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Old 29-10-2014, 00:55   #88
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Re: Rudder Failures

There is no debate as to what rudder system works best, the spade is the most effective rudder. The quality in building them is what should be discussed. It is actually not the high speed planing racers that continue to lose rudders, its the production boats that are racing/cruising that are most often losing rudders. Offshore racing boats past and present are not cheap boats and are built to a standard well above production boats. They may look similar but there is really no comparison between them. "Light" "Strong" "Cheap" pick any two, nothing on this front has changed.
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Old 29-10-2014, 01:42   #89
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Re: Rudder Failures

Smackdaddy,

I recall a fair bit of discussion on this forum of rudder failures with Hunters.
search the forum.

There is also the rudder failure that contributed to the abandonment of the brand new first Alpha 42 catamaran.
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Old 29-10-2014, 16:07   #90
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Re: Rudder Failures

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Originally Posted by robert sailor View Post
There is no debate as to what rudder system works best, the spade is the most effective rudder. The quality in building them is what should be discussed. It is actually not the high speed planing racers that continue to lose rudders, its the production boats that are racing/cruising that are most often losing rudders. Offshore racing boats past and present are not cheap boats and are built to a standard well above production boats. They may look similar but there is really no comparison between them. "Light" "Strong" "Cheap" pick any two, nothing on this front has changed.
That's true that serious racing boats normally lose only rudders over an impact (broken) and that occasionally we heard stories of cruising boats that lose the rudder without any apparent cause but to my recollection, except on that catamaran case, never on new boats.

I don't think that it has to do with quality problems on modern mass production boats but with the fact that serious racers do adequate maintenance to their rudders, some, due to the intensive effort even put it down and do a serious inspection each season, while cruisers think that a rudder does not need maintenance or to be inspected and rarely or never do that.
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