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Old 25-10-2014, 19:19   #46
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Re: Rudder Failures

Spade or hung rudders on mass production boats ... Don't want to go there..
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Old 25-10-2014, 19:39   #47
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Re: Rudder Failures

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Originally Posted by neilpride View Post
Teflón is not used anymore my friend, Delrin is the right stuff this days, define strong Pólux because if you mean a hollow shaft surrounded by foam and covered with matt and maybe a decent layer of glass this is not strong in my book, with out mention the structure inside suporting the whole thing in some boats, where is that funny post about Foss Foam rudders and the builder claiming they need sun cream protection factor 15 to avoid problems, LMAO.....
Yes I know I just did not remember the name of the dam material (Delrin) LOL. Last year I mounted a new one on my boat and they used Delrin).

Who talked about strong? Just talked about statistics. I used the word solid referring the perceptual few number of accidents given the overall lack of proper maintenance and used the word solid in a relative way. They are not strong and they need regular maintenance work that in most cases is not made. It is not enough to dismount the rudder when you have problems and that's what just most do.

Strong was the one on that Motiva 39...all steel, I mean the custom steel boat that lost the rudder on last year's ARC edition. Motiva is a well known and famous builder of steel custom strong boats.
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Old 25-10-2014, 19:56   #48
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Re: Rudder Failures

As I recall Dashew uses double the normal ABS/Loyd's standards for spade rudders but he also has much greater requirements for the design of the bearing areas.
We have had this discussion before and there is some suggestions that failure rate of production spade rudders is approaching 1% overall but if you consider that the % of production boats that are sailing offshore is very low then the failure rate of spades offshore could be much higher.
Whatever you want to believe losing your rudder in a fin keel/spade rudder boat offshore is not something you want to have happen so the idea of having a back up system is a good one and if you are racing in any major race (I don't include the ARC as it doesn't qualify as a race) a back up rudder is part of the requirements.
If you don't believe that spade rudders suffer a fairly high failure rate then ask yourself why all major ocean racers require a back up rudder system. While all designs of rudders can and do fail spade designs seem to top the poles.
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Old 25-10-2014, 21:02   #49
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Re: Rudder Failures

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Originally Posted by AdagioCal246 View Post
Is the A/P working too hard - can you move the wheel with 2 fingers on a spoke when you engage the A/P? If not, you've a problem with balance or friction; either way, the A/P takes the abuse.
Maybe I'm not understanding this statement correctly, but if you can move the wheel at all, with any amount of force, when you engage the AP, you have an AP problem.

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Old 25-10-2014, 21:06   #50
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Re: Rudder Failures

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Originally Posted by Polux View Post
How many do you know that makes a complete check up, dismounting the rudder and changing the Teflon piece each 4 or 5 years?
What is this Teflon/Delrin piece you speak of? We certainly do not have this in our spade rudder system.

Are you describing the bearings? If so, I don't think this is a major factor in rudder failures. And while changing bearings every 4-5 years may be SOP for some boats, I think that is a very weak design indeed. I don't know of any boats needing fresh bearings that often.

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Old 25-10-2014, 21:54   #51
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Re: Rudder Failures

Quote:
Originally Posted by robert sailor View Post
As I recall Dashew uses double the normal ABS/Loyd's standards for spade rudders but he also has much greater requirements for the design of the bearing areas.
We have had this discussion before and there is some suggestions that failure rate of production spade rudders is approaching 1% overall but if you consider that the % of production boats that are sailing offshore is very low then the failure rate of spades offshore could be much higher.
Whatever you want to believe losing your rudder in a fin keel/spade rudder boat offshore is not something you want to have happen so the idea of having a back up system is a good one and if you are racing in any major race (I don't include the ARC as it doesn't qualify as a race) a back up rudder is part of the requirements.
If you don't believe that spade rudders suffer a fairly high failure rate then ask yourself why all major ocean racers require a back up rudder system. While all designs of rudders can and do fail spade designs seem to top the poles.
As to losing appendages, we're in agreement on that. And I'm about as familiar with it as I'd like to be, given that a very close friend was on a boat which lost her rudder. And subsequently wound up self destructing in the surf, on a Mexican beach as a result.
- The owner was too cheap to have the boatbuilders doing the modifications, use all of the proper materials. Tried to save a few hundred $ on a half million dollar boat. But then that had always been his nature... still is.


On the Dashew's & ABS safety factors, I'm thinking that the 2x minimum ABS number is for keel floors structures. But my book's not here, so I can't check.
And while more spade rudders fail than say the type which are on pilot cutters, there are I think, a LOT more spade rudder equipped boats out there than any other type.

As to them failing, there's one or two things I didn't mention.
- While a lot of their stocks are undersized IMHO, more often than not, it's the connective bits, cores, & skins which are more problem prone.
- The failure problem is HUGELY exacerbated by cruising & racer/cruiser designers following the trend of racing boats in their never ending quest to get weight out of the ends of the boats. And this is VERY often done at the expense of sufficient strength in rudders.

And yeah, it results in offshore racers needing to have a safety net like this Kurt Hughes Multihull Design - Catamarans and Trimarans for Cruising and Charter - J46 Emergency Steering

Although, I, personally, am a big fan of the boats running 2, kick up rudders, & them carrying spare blades onboard as well. It's a good nod to having learned something from the multihull crowd (racing type, not cruising).

I can also say that I'm a fan of the monolithic, composite rudders. Wherein the blade & shaft are all one piece. They're milled out of a big pre-laminated block, which has more, & stronger fibers where the shaft on a standard rudder would be. And when they're done machining it, said fibers & location are the shaft.

Given the materials which they're made of, & how heavily they're autoclaved. Assuming that a designer puts in anything resembling sane safety factors, I'd think that they're tough to beat in terms of performance & long term reliability.

As always, the bottom line in terms of what's put onto boats, is those that write the checks. So the designers can draw up things as tough as they like, but if they want to keep their jobs, they'll do what needs doing to keep both the bean counters, & the public, happy.


EDIT: On this 1% thing. I know that if it were cars losing critical systems at even 1/10th of that rate, there'd be a lot of automakers out of business. And some REAL Fat lawyers.
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Old 26-10-2014, 13:56   #52
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Re: Rudder Failures

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Originally Posted by colemj View Post
What is this Teflon/Delrin piece you speak of? We certainly do not have this in our spade rudder system.

Are you describing the bearings? If so, I don't think this is a major factor in rudder failures. And while changing bearings every 4-5 years may be SOP for some boats, I think that is a very weak design indeed. I don't know of any boats needing fresh bearings that often.

Mark
It is a bearing ball. You see one at the end of the system and it allows the rudder to auto align and have more flexibility:



The drawing does not give an idea of the piece: it is a big rounded piece with a hole for the rudder shaft to pass. It works on an aluminium round enclosure.

Jefa use them as most production builders.
Here you have a better image:
ftp://ftp.jefa.com/rudder/Bearingbal...ball_55x34.pdf
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Old 26-10-2014, 14:48   #53
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Re: Rudder Failures

"...years between 1998 and 2006, considering that about 1500 boats (probably more) made the ARC, there was 5 boats that lost the rudder. That gives a percentage of 0.0034."

If my math skills haven't deteriorated with my other faculties, the above percentage would be .33%. (whistling emoticon here)
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Old 26-10-2014, 15:22   #54
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Re: Rudder Failures

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Originally Posted by jongleur View Post
"...years between 1998 and 2006, considering that about 1500 boats (probably more) made the ARC, there was 5 boats that lost the rudder. That gives a percentage of 0.0034."

If my math skills haven't deteriorated with my other faculties, the above percentage would be .33%. (whistling emoticon here)
Keep whistling it is good for your health
.33%=0.0033 you are talking about a difference of 0.0001...but in fact is less since the correct number is 0.003333..... so you are talking about a difference of 0.00007.
That makes a big difference!!!!!
Next time I will try to be more accurate...just for you
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Old 26-10-2014, 15:39   #55
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Re: Rudder Failures

a percentage of 0.0034 is not equal to .34%.

Just sayin'. (smiley face or some such here)
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Old 26-10-2014, 16:01   #56
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Re: Rudder Failures

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Originally Posted by jongleur View Post
a percentage of 0.0034 is not equal to .34%.

Just sayin'. (smiley face or some such here)
You are absolutely correct, it is equal to 0.034. I did not thought you had messed up with that percentage of yours. The correct percentage (if you want to present it in that weird way) is 0.033% and not 0.33% as you have posted. The correct number is still 0.00333333...

You seem to have some difficulty understanding this: that number says that during that period on the ARC about 3 in each 1000 boats have a rudder problem. The total of boats making the ARC on that period where about 1500, 5 have rudder problems.
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Old 26-10-2014, 16:03   #57
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Re: Rudder Failures

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Originally Posted by Polux View Post
It is a bearing ball. You see one at the end of the system and it allows the rudder to auto align and have more flexibility:



The drawing does not give an idea of the piece: it is a big rounded piece with a hole for the rudder shaft to pass. It works on an aluminium round enclosure.

Jefa use them as most production builders.
Here you have a better image:
ftp://ftp.jefa.com/rudder/Bearingbal...ball_55x34.pdf

This is drawing come from Nautitech catamarans? my 2 cents, is the only one using the delrin ball at the bottom, the vast majority use a metal bushing at the bottom and delrin at the top, in other words, only Nautitech use this stuff , the ball thing in their catamarans,,,, PS . ahh i see the link info, jefa rudders , ok, could be replacement balls for Nautitech? Cheers,
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Old 26-10-2014, 16:08   #58
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Re: Rudder Failures

Didn't say that at all.

5/1500 = .0033333 which is a percentage of .33, or .33%

Anybody else want to jump in here and help
him understand this. (out of emoticons at this point)
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Old 26-10-2014, 16:12   #59
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Re: Rudder Failures

Ahhh those math lovers with numbers and numbers, i guess that 1% is nothing for many, but hey ,,,a family of 5 in a gale with a rocky leeshore and that 1% is to much, no???
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Old 26-10-2014, 16:33   #60
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Re: Rudder Failures

Quote:
Originally Posted by Polux View Post
It is a bearing ball. You see one at the end of the system and it allows the rudder to auto align and have more flexibility:



The drawing does not give an idea of the piece: it is a big rounded piece with a hole for the rudder shaft to pass. It works on an aluminium round enclosure.

Jefa use them as most production builders.
Here you have a better image:
ftp://ftp.jefa.com/rudder/Bearingbal...ball_55x34.pdf
So there is only a single bearing in that system? I still don't see why it needs to be replaced every 4-5 years, or why it would cause rudder failures if it wasn't.

Again, I don't know of any boats replacing rudder bearings every 4-5 years, and if this is the case, I think it is a bad design.

Ours have UHMW (maybe Delrin, but they are black) bushings/bearings - one on the bottom of the rudder tube and one on the top. There is no need to ever replace these unless they actually become so worn as to cause rudder post movement.

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