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post #1 of 39 Old 10-23-2014 Thread Starter
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Rudder Failures

Over the past year or so I've seen many reports of rudder failures and/or loss in cruising boats. Apart from age and "cycles" like we've talked about in the past, I'm wondering what the cause is. And I'd love to get feedback on this from the great designers we have around here - as well as the salts.

I'll lay out my hunch to get things started, based on my own experience...

Last year the boys and I did a 150-mile offshore delivery of a friend's Pearson 365 in some relatively "rough" conditions. The seas were maybe 3-4 meters, and steep (left overs from a big storm in the Gulf) and winds were in the high 20s. We were, unfortunately, sailing with that stuff just forward of our starboard beam. So, though it was a gentle beating for the most part, it was pretty jumpy and rolly. We were steering with AP.

The next morning things were calming down and we suddenly lost steerage. I grabbed the wheel and confirmed we could still steer, while my friend's son reset the AP - thinking it had just been a glitch. It was fine for a minute or so, then we lost steerage again. I asked him to take the wheel and I opened up the lazarette.

The AP, a ram arm model, had ripped off its base, where it had been bolted, and was rolling around. At least we still had the rudder. We obviously shut down the AP and steered the rest of the trip by hand.

I remember thinking about the fact that there had been a lot of force applied there to rip that thing out. Then I started thinking about all the offhsore races I'd done - hand-steering only - and never recalled feeling that kind of force through the wheel - even in rough conditions.

So, my first question...is AP (especially ram arm versions) a liability in big seas? My hunch is that it is and that is one of the primary causes in these rudder losses we're seeing on cruising boats.

AP is almost continually used by sailors (especially short-handed cruisers) these days on long trips. And it especially used (I think) when things get tough because it seems to be safer than standing in the cockpit steering 24/7.

But when you look at the boat motion in these videos - you see that there is a tremendous amount of lateral force being applied to the rudder:



Now, that is an F10/11 in the second video. If I were unfortunate enough to be caught in that I'm pretty sure we'd already be on a drogue...not pushing the boat like that. I'd be way too scared.

But, you'll notice that in both of these cases, the boat is being hand-steered. It seems to me that this provides a great deal of "cushioning" (response time and give) for the rudder over a mechanical ram.

If your stern is swinging through 20-30 degrees at surfing speed on AP...what kind of force are we talking about on the rudder and stock? It seems astronomical.

I this a cause of the failures we're seeing?

Last edited by smackdaddy; 10-23-2014 at 01:31 PM.
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post #2 of 39 Old 10-23-2014
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Re: Rudder Failures

I think most rudder failures will be due to undetected fatigue on older boats, and aggressive weight-saving engineering/scantlings on 'new', esp dedicated race boats.

The undetected fatigue fails when suddenly subjected to unusually heavier loads, perhaps not even serious storm conditions, whereas the other is an engineering/design 'fail'.

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Re: Rudder Failures

I've always thought that an undersized, rather than over-sized, autopilot, had a lot going for it, as a self steering set up. Mainly because, if I am going to have a component break from being over stressed, I would rather have it be the AP than the rudder.
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Re: Rudder Failures

"I'm wondering what the cause is."
Falling standards and the rise of the hoi polloi, Smack.
First you let people play tennis in anything other than tennis whites. Then you let them use (horror) colored balls. Then they start checking out the yacht club, and buying those cheap plastic boats to avoid the mundane cost of having a proper crew maintain the brightwork. And sooner or later what happens? That's right, those plastic boats are now mass built "to a price" for those same rabble, who have no idea of what a proper rudder and rudder post should look like, much less what they will cost. And no, heaven forbid they have the yard crew inspect and replace the rudder from time to time, like everything else on a proper yacht.

Now, a proper rudder, a one-piece weldment of monel or marine bronze, carefully built up on a solid rudder post of the same material, or, a substantially similar one-piece composite rudder? Simply can't fail the same way, can it? There's always someone looking for a cheaper answer.

So you see, what you have been noticing is simply the fall of Western Civilization, brought on by a laxity in tennis, spreading to yachting, and wreaking havoc among all the proper folk.
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Re: Rudder Failures

What I've noticed in sailing a lot of miles, often when the winds have been strong (<25 knots) with good sized waves is how much load there is on the steering system. You really notice this with vane steering where you watch the vane steering the wheel. There is just a constant motion in the system. Even if the wheel is not turning the load on the lines from the wind vane is constantly changing from one side to the other. Loads on rudders and autopilots are the same with probably a couple thousand loadings and unloadings happening per hour. I agree that failures are just a result of fatigue. I think there are probably three reasons why most people sailing very long distances in moderate sized boats prefer vanes to electric pilots:
(in increasing importance)
1 Vanes are quieter - you don't get constant motor noises
2 Your electrical demands are much lower with a vane
3 Vanes are more reliable and generally easier to fix, i.e. wear factors are less and less critical. Our Monitor is pretty tired after 30,000 miles but it still works. I have a bag full of parts from Scanmar to replace all sorts of worn bits when we get back to Grenada.

After the refit we have decided to sell Ainia. We want something smaller that would be could for the light summer winds of Lake Ontario, although we plan to spend at least a couple of winters in the Caribbean before heading north.
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Re: Rudder Failures

Quote:
Originally Posted by hellosailor View Post
"I'm wondering what the cause is."
Falling standards and the rise of the hoi polloi, Smack.
First you let people play tennis in anything other than tennis whites. Then you let them use (horror) colored balls. Then they start checking out the yacht club, and buying those cheap plastic boats to avoid the mundane cost of having a proper crew maintain the brightwork. And sooner or later what happens? That's right, those plastic boats are now mass built "to a price" for those same rabble, who have no idea of what a proper rudder and rudder post should look like, much less what they will cost. And no, heaven forbid they have the yard crew inspect and replace the rudder from time to time, like everything else on a proper yacht.

Now, a proper rudder, a one-piece weldment of monel or marine bronze, carefully built up on a solid rudder post of the same material, or, a substantially similar one-piece composite rudder? Simply can't fail the same way, can it? There's always someone looking for a cheaper answer.

So you see, what you have been noticing is simply the fall of Western Civilization, brought on by a laxity in tennis, spreading to yachting, and wreaking havoc among all the proper folk.
I thought it was just case of green furry balls.
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post #7 of 39 Old 10-23-2014
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Re: Rudder Failures

Quote:
Originally Posted by smackdaddy View Post
The AP, a ram arm model, had ripped off its base, where it had been bolted, and was rolling around. At least we still had the rudder. We obviously shut down the AP and steered the rest of the trip by hand.

I remember thinking about the fact that there had been a lot of force applied there to rip that thing out. Then I started thinking about all the offhsore races I'd done - hand-steering only - and never recalled feeling that kind of force through the wheel - even in rough conditions.


The bigger the wheel, the less force you feel. How long was arm on the AP? Not the piston mind you, the ARM. The arm on most APs that I've seen is 6" or less, give or take.



If you were to steer with a wheel that has a radius equal to the arm length, THEN you'd feel what the AP feels.

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Re: Rudder Failures

Or try steering just using the spokes 6" out from the hub. We got a chance to go on one of the America's Cup 90 footers in Auckland. Very big wheel and a boat set up well - even for tourists). With such a big wheel even on a huge boat the steering was incredibly precise and easy. Move the wheel an inch and the boat turned.

After the refit we have decided to sell Ainia. We want something smaller that would be could for the light summer winds of Lake Ontario, although we plan to spend at least a couple of winters in the Caribbean before heading north.
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Re: Rudder Failures

A bigger quadrant would require a bigger ram and a bigger pump to drive it and pretty soon you've gone beyond your design budget ..Maybe less restrictions on designers Or build it your self and do it right.
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Re: Rudder Failures

Quote:
Originally Posted by killarney_sailor View Post
What I've noticed in sailing a lot of miles, often when the winds have been strong (<25 knots) with good sized waves is how much load there is on the steering system. You really notice this with vane steering where you watch the vane steering the wheel. There is just a constant motion in the system. Even if the wheel is not turning the load on the lines from the wind vane is constantly changing from one side to the other. Loads on rudders and autopilots are the same with probably a couple thousand loadings and unloadings happening per hour. I agree that failures are just a result of fatigue. I think there are probably three reasons why most people sailing very long distances in moderate sized boats prefer vanes to electric pilots:
(in increasing importance)
1 Vanes are quieter - you don't get constant motor noises
2 Your electrical demands are much lower with a vane
3 Vanes are more reliable and generally easier to fix, i.e. wear factors are less and less critical. Our Monitor is pretty tired after 30,000 miles but it still works. I have a bag full of parts from Scanmar to replace all sorts of worn bits when we get back to Grenada.
The other part of wind vane steering is that it Will Not steer the boat if you have too much sail up. I wonder how many autopilot failures are the result of continued use in sporty conditions without reduction is sail area. The skippers have no idea of the forces being exerted on the rudder, quadrant, cable and wheels because the electric auto pilot is overcoming those forces....until it breaks.

Pretty common to see the broken arms, fittings and attachment devices on the electric, ram driven autopilots. It would be something I'd be taking a look at before every passage, tightening the brackets, looking for fatigue cracks, etc.


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