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Old 23-10-2014, 16:44   #16
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Re: Rudder Failures

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Originally Posted by robert sailor View Post
Come on Onno, you know these boats always suffer damage sometime prior to losing a rudder, it can't have been new from the factory!
The people onboard tell a different story - who are you to say they are lying? The rudder post casing (? terminology? sheath?) failed at the Cape Verdes about 1000 miles after delivery in Hamble. It was due to wear, the boat didn't hit anything. The leak was unrepairable and the boat went down. Fortunately no lives lost.


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Old 23-10-2014, 16:50   #17
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Re: Rudder Failures

I know that I am new to the sailboat arena, but I would think that the three areas that need to be over built are the keel, mast supports, and the rudder assembly. I know racers are built for a specific need, but cruisers should always be over built?

Dunno...... just makes sense to me.
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Old 23-10-2014, 16:56   #18
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Re: Rudder Failures

No.

Nothing has to be overbuilt. If it is built right, it is enough.

The problem is that today many boats are underbuilt. They are designed for marina and inshore use but sold with an 'Ocean Class' sticker. Ask EU regulators what they had in mind and who paid them for the regulations they wrote for the industry.

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Old 23-10-2014, 17:04   #19
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Re: Rudder Failures

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No.

Nothing has to be overbuilt. If it is built right, it is enough.

The problem is that today many boats are underbuilt. They are designed for marina and inshore use but sold with an 'Ocean Class' sticker. Ask EU regulators what they had in mind and who paid them for the regulations they wrote for the industry.

b.

My gist was meant as "built right"....... which today is rarely sought after.
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Old 23-10-2014, 17:06   #20
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Re: Rudder Failures

Most of these incidents seem to be autopilot failure and bad installation, not rudder failure. The owner of one beautiful schooner accused me of poor sail trim when the autopilot shredded a gear one time. He didn't say much when the new replacement failed on him a few months later.
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Old 23-10-2014, 17:13   #21
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Re: Rudder Failures

It is. It is. Just we must make an effort to learn at least as much as to tell the 'right' from the 'CE certified'.

Makes one wonder why the EC had resolved not to use already tried and tested standards like Lloyds A1.

But what else could we expect from a bunch of ignorants.

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Old 23-10-2014, 17:40   #22
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Re: Rudder Failures

Generally fatigue stress accumulates over time. How much stress is dependent on how the boat is sailed (severity). Corrosion is another factor that accumulates over time. The rudder itself can absorb water eventually and the structure where all the gear attaches can deteriorate.

With all the 30+ year old boats out there that have had basically zero maintenance I am surprised there are not more rudder failures.

On new boats, of course, there should be no structural failure and in that case one can presume bad construction or bad design.

If I were to purchse a new (to me) boat I would definitely pull the rudder as part of my initial refit. Transom hung rudders are much easier in this regard.
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Old 24-10-2014, 09:38   #23
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Re: Rudder Failures

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Originally Posted by a64pilot View Post
usually hydraulic auto pilots are mounted on a very short arm as they have short throws, this of course means with so little mechanical leverage that very large forces are in play.
Having a rudder essentially "locked" in place by these type of auto pilots, can I believe lead to fatigue of the rudder or it's post, I think all of us have from time to time felt a "kick" back through the wheel from something, that little kick even though it's not much travel could well significantly reduce forces the rudder is exposed to.
This is exactly what I mean.

In races I've done we've pushed the boat too hard on occasion. "Too much" sail up (at least for our abilities) - and, when surfing, getting overpowered and being near the edge of a broach. In that situation it's very easy (for many of us mortals anyway) to crank the rudder near hard-over and stall it...which obviously creates a great deal of force on that rudder. When this happens, we do something about it (reduce sail, change course, whatever) to avoid repeating it.

If you're on AP in a storm and you have too much sail up for the conditions, and your rudder is working through all that force over and over and over again...yet, to you, everything is fine because the boat recovers and stays on course...doesn't this greatly increase the cycles on your steering system?

I want to make it clear that I'm not at all anti-AP. I love those things - especially after hand-steering a race for 3 days straight. But you DEFINITELY can lose touch with what's going on with the boat ESPECIALLY in rough conditions (where most rudder losses happen) if you are only relying on AP.

Now whether this actually is a cause of rudder failure is a different issue and is the basis of this thread. I'm just saying I could certainly understand a correlation.
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Old 24-10-2014, 10:20   #24
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Re: Rudder Failures

I'm sure an ap can have a great effect on a rudders life. After all if you are always having to crank the rudder over due to sail trim and/or conditions you expect it to really put the rudder though hell

Maybe rudders should almost start to be thought of the same as standing rigging.


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Old 24-10-2014, 10:26   #25
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Re: Rudder Failures

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Originally Posted by sailorboy1 View Post
Maybe rudders should almost start to be thought of the same as standing rigging.
Exactly right.

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Old 24-10-2014, 11:35   #26
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Re: Rudder Failures

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I now keep a close eye on the wheel position marker when using the AP to make sure the helm has not crept round to balance poor sail trim.

Matt

I've only had an AP for a very short time, but I've learned to do this, I have a zip tie on a spoke that is up when the rudder is straight ahead.
An IP's rudder is almost overbalanced, they have little wheels and if they weren't so overbalanced, it would be real hard to turn the wheel. They are actually a spade rudder on a full keel boat, anyway I have an opinion that these type of "light" rudders can well mask the forces that are going on, but knowing how far the rudder is cranked over to keep the boat going in a straight line should tell the story. My rudder post is solid 2" stock and I've never heard of an IP's rudder failing, but it doesn't hurt.
Also seems at least on my boat that being out of trim slows the boat down, or is this my imagination?
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Old 24-10-2014, 15:45   #27
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Re: Rudder Failures

MOST rudders are woefully; under designed, AND under built. I've had plenty of engineering... including Naval, as well as about 4 decades on the water, working on & rebuilding boats etc., etc. And years ago I began to do a bit of studying on Multihulls. Well, one of the better designers flatly states that he designs his rudders with a 1.5-2 factor of safety for when the rudder were turned 45 degrees & the vessel is doing 25 knots.

Given all that I've learned about boat design, construction, & repair. I wouldn't call his design standards to be overbuilt at all. And yet most of his designs get HAMMERED on by their owners, some of whom race them mercilessly in places like the N. Atlantic. Regardless of time of year. But to the best of my knowledge, not one of his boats have suffered ANY kind of structural failure.

The forces on a rudder can FAR exceed the weight of the vessel, if it is being pushed hard, and or they're caught in a storm. Given that, frankly, it's a surprise that we haven't seen a lot more failures (in both vessels, & rudders) than we have. And realistically, the only reason we haven't is that when things begin to get truly nasty, it's the crew which folds first, for the most part.

If even a fraction of the vessels out there were pushed by crew with the tenacity of professional ocean racers, every time there was a storm, it make the '79 Fastnet look like a 4yr old's Birthday Party. The boats would fold up as if they were made of paper machie.
One should literally be able to pick up a mid-sized pleasure vessel by it's rudder & shake it around, with at worst, moderate damage to it or the vessel. And in the yachting realm, only the most serious of racing vessels might be able to pass this test. Witness the VOR or ORMA boats, & the literal hurricane force conditions which they sail through day in, day out, for literally years at a time (between practice, testing, & races).

When I toy with the idea of getting a new (to me) boat. After going through the fairly standard pre-purchase checklist in my head. The next items of business which run through my mind are what parts of the boat need replacing, & or beefing up structurally. And assuming that I plan to do more than just day sail, replacing steering components, beginning with the rudder, are pretty much at the top of the list.
Then there's standing rigging, & sails, which under most owners sees next to zero maintance. And if a boat's previous owners are too cheap to have shelled out $2.5k to replace a 25 yr old mainsail, you can only imagine the true condition of the standing rigging, or what lurks at the bottom of an engine's oil pan.

It's a sad truth, but the reality is that literally everything on a boat which the wind, sun, sea, & salt can touch on a boat are semi-disposable items. Meaning that they need replacing with regularity. Yet aside from those who race seriously, or are preparing a vessel for a long distance & term oceanic voyage, who out there takes the time, & spends the $ to properly look after a vessel's care & feeding?

As to autopilots & some of the questions posed. In particular, the surprise at belowdecks AP's tearing themselves off of their mountings. Most of us have steered a boat with some stiff weather helm using a tiller for a few hours. Well, the AP's have at best 2' long tillers, as compared to the 4-5'ers in the cockpit. And they're asked to drive in much more demanding conditions, without the ability to see a good path through the worst sets of waves. Or to see when & where a gust is coming from, & compensate in advance. So it's kina of unsurprising that the result is akin to if we were to toss them into the ring with the terminator for a few days.

Much like wind vanes, boats need to be setup properly for conditions if we are to expect AP's to survive. However, unlike vanes, who's power input goes up as the wind rises, AP's max out at a certain level, mechanically. So again they're handicapped.
And as to ones of the hydraulic sort, yes, they can, or rather they could be setup to not beat themselves to death when conditions are bad. It's quite simple to do. However, when they did get to the point where their relief valves popped... and in the midst of heavy winds & seas, the boat subsequently crashed abruptly, not many folks would be happy. Despite the fact that all that's needed to monitor how hard they're working is a temperature gauge, & a hydraulic fluid pressure gauge mounted at the nav station. And that by viewing said gauges, the watch captain could make changes in sail combination, course steered, or decide it's time to kick out the drogue... prior to 5k worth of pilot self destructing, & leaving them to hand steer for the rest of the storm.

Sorry for the rant, but you guys asked why, & what was possible. And the thing is, is that in reality, a vessel to be seriously used needs a maintance schedule pretty much akin to one for light aircraft if it's to be reliable, & perform optimally.
The difference being that if you skip some, or a lot, of significant care items on a boat, it doesn't fall out of the sky.

I mean how often do you hear of a military vessel loosing their rudder, or steerage? And do you think that those components which make up said systems have a detailed maintaince & testing checklist which is adhered to?
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Old 24-10-2014, 16:36   #28
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Re: Rudder Failures

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MOST rudders are woefully; under designed, AND under built.
Pretty big statement. What engineering and design analysis for this do you have?
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Old 24-10-2014, 16:40   #29
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Re: Rudder Failures

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Originally Posted by UNCIVILIZED View Post
Well, the AP's have at best 2' long tillers, as compared to the 4-5'ers in the cockpit.
"At best" is being generous - most of the AP tillers are 8-10" long. From many AP mounts I have seen on many different boats, I'm surprised we aren't hearing more stories of AP's tearing off their mounts. That it is unusual probably speaks more to most boats never getting into truly testing conditions.

Even the manufacturers seem to grossly underestimate the strength and engineering needed in AP mounts. I've seen newer production boats that have the AP drive mounted on long wood shelves end-screwed to bulkheads, U-bolted to conduit tubes, bolted onto bulkheads without any backing plates or even washers - lots of bad mounting decisions.

But we don't hear of many mounting failures.

While it is a decent hypothesis, I don't think the majority of rudder failures are due to autopilot use. Particularly modern autopilots. I watch ours steer in trying conditions like it had a sixth sense - it applies counter rudder before the boat even starts to yaw down a wave and stops before the boat starts the other way. It steers better than me after an hour on the helm (heck, it probably steers better than me at all times in all conditions).

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Old 24-10-2014, 17:47   #30
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Re: Rudder Failures

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Originally Posted by UNCIVILIZED View Post
<snip>



As to autopilots & some of the questions posed. In particular, the surprise at belowdecks AP's tearing themselves off of their mountings. Most of us have steered a boat with some stiff weather helm using a tiller for a few hours. Well, the AP's have at best 2' long tillers, as compared to the 4-5'ers in the cockpit. And they're asked to drive in much more demanding conditions, without the ability to see a good path through the worst sets of waves. Or to see when & where a gust is coming from, & compensate in advance. So it's kina of unsurprising that the result is akin to if we were to toss them into the ring with the terminator for a few days.
Nice post but I thought I would comment on this part to make sure we are all on the same page here.

The structure that the rudder attaches to and the rudder itself will endure the same forces whether one uses a 5 inch lever or a 3 foot lever when overcoming the same forces. (Except of course the lever itself and the lever attach point) Archimedes proved this.

Now the structure that the AP attaches to is different. This makes sense as to why we see the AP structure/attach point failing and the ram coming loose or whatever.

I believe most pure rudder and rudder stock failures are more rare and have a lot to do with corrosion, wear and lack of maintenance. Certainly something within the owners control.

In regards to AP structure failing, I think we have seen some boats where this structure should probably be engineered, designed better for the sustained forces involved.

While it might be a good idea to "avoid" using the AP in stressful situations, I would prefer to evaulate the AP attach design and rebuild it.

When we first got our boat we were breaking a lot of old blocks and things on each sail. My partner said, "Maybe we shouldn't push things so hard." I replied that we should be able to pull as hard as we want/need to on anything on the boat and it shouldn't break.

When the crap hits the fan the last thing I want to be thinking about is will the boat hold together. My AP will need to steer in all conditions if I want the boat to "take care of me."

<edit> Here's an idea. If the AP stresses are correlated to hydraulic pressure or to amps (for an electric) I bet a simple idiot light near the helm could be installed and calibrated to light up when AP stresses are "high" - That would be an interesting clue that the AP and structure were taking a beating.
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