Rudder Drop Off

[DannyB]

When considering rudder failures, don't forget that on some designs, the only thing holding the rudder in place is the tiller. Many years ago, when I was doing my day skipper course, the instructor handed the tiller to one of the students, and it literally came off, the rudder stock dropped down flush with the afterdeck, so there was no way of getting a hold of it. We ended up getting towed back into the marina, and when the boat was lifted the rudder dropped out completely, it appeared the only thing holding it in place was the water pressure against it, either that or it was naturally buoyant. I can't remember the type of yacht but it was a fairly common make. I remember at the time thinking it was a good opportunity to try sailing without a rudder as you would a dinghy, but that didn't work, presumably because the rudder was still having an effect, just an uncontrolled one.

 

[ELAiNe333]

Resigned to hope

Thank you all for interesting and informed comments. The result is however disappointing in that there seems no ready way to check the condition of the step in the rudder stock without destroying the blade.
I think that for peace of mind constructing a viable emergency rudder is the best bet, although carring such a bulky "spare wheel" is a long term irritation.
Pivoting the temporary rudder is an immediate first problem, but I do have an idea for that if I can find a source of the bits...

 

[r_h]

It may well be worth having a word with Ben Pierrepoint, who does ultrasound non-destructive testing:

http://www.pierrepontanalysis.com/crbst_2.html

 

[oldsaltoz]

Given the history of potential failure and not knowing when it might occur, I think very seriously about replacing it rather than carry a jury rig rudder.

Seems to me the cause of the problem is well documented and a taper rather than a step looks like the best option.

So rather than spend good money on something you have to carry, why not rebuild the rudder with a new shaft, you can probably use the existing blade as well.

Though I think I would also look at a long taper rather than a short one to relace the step.

Good luck and fair winds.

 

[William_H]

It may well be worth having a word with Ben Pierrepoint, who does ultrasound non-destructive testing:

http://www.pierrepontanalysis.com/crbst_2.html

Ultrasonic NDT is extremely hard to interpret as you get reflections of all the walls of the shaft. I imagine an ultrasonic beam from the top of the shaft straight down may work. However you would have to identify the reflections from the step in diameter and then look for any cracks if present in the same area. This type of testing is most successful where you have a known cracked shaft and a known good one to use as a bench mark. By all means discuss it with Ben or any other ultrasound specialist but I think you will be disappointed. good luck olewill

 

[ELAiNe333]

Cost has an influence

Given the history of potential failure and not knowing when it might occur, I think very seriously about replacing it rather than carry a jury rig rudder.

Seems to me the cause of the problem is well documented and a taper rather than a step looks like the best option.

So rather than spend good money on something you have to carry, why not rebuild the rudder with a new shaft, you can probably use the existing blade as well.

Though I think I would also look at a long taper rather than a short one to relace the step.

Good luck and fair winds.

I seem to remember that Elan wanted about £3000 for a new rudder. I cannot see that a specially macined rudder stock and one-off fibreglaas blade will be much less.
Established problem is another issue, these are the only two boats out of nearly 500 built that are known to have the issue. I must wonder if I am exaggerating the risk ?
Hence my original request for a non-destructive route to peace of mind.

 

[oldsaltoz]

I seem to remember that Elan wanted about £3000 for a new rudder. I cannot see that a specially machined rudder stock and one-off fibreglass blade will be much less.
Established problem is another issue, these are the only two boats out of nearly 500 built that are known to have the issue. I must wonder if I am exaggerating the risk ?
Hence my original request for a non-destructive route to peace of mind.

I would estimate that building said rudder from a drawing and shft supplied would be at least half that price or less.

Have a talk to a local fibreglass specialist. I have built and repaired more rudders here in Oz than I care to remember for a fraction of that figure.

It's also worth noting that very few boat building manufacturers build their own rudders, specialist rudder builders produce them faster and cheaper, not necessarily better or stronger, just cheaper.

I do sympathise with you though, there are enough things to think about when out in blue water and far from anywhere without having to worry about the loss of your rudder or cluttering the place up with a spare one.

If you ever have to, or plan to replace it, just make sure:
The machining of the stock is done by a competent machinist.
The tangs are welded with small gussets onto the stock and properly pickled after welding, to prevent corrosion.
The shaft is fitted with 'O' rings (glassed in) just below the entry point of the stock to spade, I started doing this a couple of decades ago and no problems.

Good luck and fair winds.

 

[ELAiNe333]

New view on rudder failures

This thread was based on the YM articles which blamed the step in the stock as the reason for the Elan rudder failures.
Hearing from another competitor in the Triangle he was pretty sure that the root cause had been water ingress and corrosion in the rudder blades. This gave catastrophic delamination of the fibreglass and huge stress therefore on the stock. I must admit one of the YM photos seems to show corrosion.
He also told us that another competitor, a Dehler, also suffered a similar delamination and "balooning" of the rudder although they made port in this state. Why no mention of this incident? I must check amount of advertising by various yacht builders in YM.
If the cause is water ingress then it is likely all spade rudders carry this risk.
His advice was to watch for any water seepage from the rudder on lift out as this would be a sure sign that repairs were due. Otherwise just keep sailing.

 

[doug748]

"If the cause is water ingress then it is likely all spade rudders carry this risk."


Not just spade rudders either.

Though, I must admit, I am not convinced with the water ingress / delamination/ huge stress idea. Lots of old boats tend to have soggy rudders

I seem to recall that there was some suggestion that a badly fitted autohelm crank was possibly part of the problem? I could be all wrong so ignore this if it is my faulty recollecton.

 

[oldsaltoz]

Perhaps I should have applied for a patent on my practice of installing '0' rings on rudder stock shafts that goes a long way to preventing water ingress in this area.

Good luck and fair winds.

 

[johnphilip]

Perhaps I should have applied for a patent on my practice of installing '0' rings on rudder stock shafts that goes a long way to preventing water ingress in this area.

Good luck and fair winds.

I had been assuming water entry was most likely around the stock so your design does sound to be a good one.

 

[Daydream believer]

Have you tried Jefra who make some of the rudders for the Hanse brands
It has been reported that they quote about £ 1500 for a rudder on the smaller boats
These rudders are also optimised for best shape & have been known to improve performance
I would suspect that Bearings etc are all pretty much standard diameters so i would have thought that the shaft would be non standard but the same initial diameter etc & no longer than a Hanse one. Non standard may not be that much " non standard"
Although thinking about it - if you have 2 rudders ( do you ? some Elans have I believe) then that would be the £3000 you have been quoted
Still if one dropped off you could still get to a point of refuge. Assuming you could plug the hole. Assuming you could reconfigure the steering. Assuming etc etc!!

 

[wotayottie]

During the summer YM featured two ELAN 333s that had lost their rudders having sheared the stainless stock (right word?) where it was step tapered within the rudder moulding.
I would apprecciate the old salts forgetting out their hobbyhorse about spade rudders and instead consider whether there is a practical method of non destructive testing to check for cracks or fatigue..

I dont believe you can test for fatigue before it manifests itself as cracks but you certainly can X ray for cracks.

Cant resist. Its nothing to do with spade rudders and everything to do with inadequate detailed build / design. Sure a spade rudder has less support than one with a skeg so you build it stronger to compensate. I suppose this problem on 333s is really Elans answer to Bav's keel problem. It will be interesting to see if the Poles win the race by having both fall off.

 

[Norman_E]

You say that the rudder is easily dropped to enable the stock to be inspected. I think this is a large part of the answer. Give the stock an annual inspection. Hidden in a bearing where it gets very little oxygen, crevice corrosion starts from the surface of the metal. I've seen several stainless stocks to which this has happened. Eventually the stock becomes wasted and will give way close to the point where it enters the bearing.

So, any surface indication of crevices - change at once. I bet the ones that failed hadn't been inspected in years.

Good general advice, but that was not where those two Elan rudders failed. The failures were due to the rudder stocks being stepped down to a smaller diameter inside the rudder blade rather than tapered as the designer intended. The sharp internal corner at the step is a stress raiser and the stocks failed from that

 

[Avocet]

Interesting thread. Although I haven't seen the failures, abrupt changes in section in shafts loaded in torsion and bending is a classic design no-no! I can't think of anything you could do from an inspection point of view (especially with the weak point being hidden inside the rudder). A few thoughts did cross my mind though:

1. Is it possible to "life" the component? These two failures, did they occur on "high mileage" yachts? Would it be possible to just resign yourself to buying a new rudder and replacing it as a matter of course every (say) 10 years or X,0000 nautical miles? They sometimes do that with fatigue-critical components when there's no other way round the problem.

2. Although it doesn't help you right now, if the designers are aware of the problem and the design flaw, newer rudders might be more long-lived anyway (assuming they've revised the design).

3. OK, quite a messy one, but would it be possible for you to take your rudder off, split it (or maybe cut a few big access holes in it), and try to build-in some kind of redundancy? For example, I don't know if the space inside and general design would make this impossible, but could you fit (say) a big split "collar" or tube round the shaft, spanning the area where the fracture occurs, such that if the original shaft DID fail, the collar would prevent total loss of steering (and, indeed, the rudder)? It would obviously be best to engineer some "slop" in this assembly so that you'd be able to feel some play if a failure of the original shaft occurred, otherwise you might never know it had happened.

4. Actually, after the kicking us "long-keel aficionados" have just had on the other thread, I won't say was 4 was)!

 

[doug748]

Good man Avocet....

......don't mention No 4..... I think wottayottie has spotted it though

 

[johnphilip]

mindless

I dont believe you can test for fatigue before it manifests itself as cracks but you certainly can X ray for cracks.

Cant resist. Its nothing to do with spade rudders and everything to do with inadequate detailed build / design. Sure a spade rudder has less support than one with a skeg so you build it stronger to compensate. I suppose this problem on 333s is really Elans answer to Bav's keel problem. It will be interesting to see if the Poles win the race by having both fall off.

Exactly the sort of useless wind up that spoils this forum. Humour I enjoy but this is so feeble. Anyway what have the Poles got to do with it.

 

[charles_reed]

No, not new here, but taken on a new persona.
During the summer YM featured two ELAN 333s that had lost their rudders having sheared the stainless stock (right word?) where it was step tapered within the rudder moulding.
I would apprecciate the old salts forgetting out their hobbyhorse about spade rudders and instead consider whether there is a practical method of non destructive testing to check for cracks or fatigue. I feel this might be a comfort not just for 333 sailors but for many with spade rudders.
Lowering the rudder on a 333 is relatively easily accomplished so taking it away for testing might well be worthwhile.
Is Xray or ultrasonic or anything going to be give an answer?
Particularly keen to hear from others with the same concern as a testing house might be more amenable to setting something up if there was a prospect of several customers.

You're quite correct in excluding the generalisations about spade rudders from your query about the two reported rudder shaft-breakages on the Elan.
The problem was down to fatigue fracture at the end of the machining for the bearings. Instead of being radiussed this was a right angle. The phenomenon is well documented, starting with the explosive decompression of the Mk 1 Comets and I've had personal and saddening experiences with a number of narrow-aisle trucks losing steering with their motor-in-wheel unit when a massive shaft fractured.

First, I'd suggest you drop the shaft out and check the machining ends with a radius - if it does put it all back together again and breathe a sigh of relief.
If, however, it is a right-angle try dye-penetrant testing, this will show if any cracks have started to propagate - ultrasound is less messy and quicker but does require specialist equipment. If there is no cracking put it together again and check on a regular basis - frequency dependent on how hard you use the boat.

 

[Daydream believer]

Exactly the sort of useless wind up that spoils this forum. Humour I enjoy but this is so feeble. Anyway what have the Poles got to do with it.

So who promoted you to web master?

 

[Yacht Yogi]

Well I've been thinking about buying an Elan 333 and for my day job I am a chartered aircraft structures engineer dealing with stress analysis and fatigue of components on a daily basis. I cannot see any way to determine that the rudder with a step in its shaft will not fail. It is just a case of when not if.

To determine a "safe life" one would need to know exact details of the stress concentration at the step, the material fatigue life properties and the loading cycles of the rudder. So this isn't going to be possible either.

A crack detection process if it were possible by perhaps cutting access into the rudder would only tell you whether it has or has not started to crack yet. It would not tell you that it is going to be safe forever.

So the only solution is to remove the problem by replacing or modifying the stepped rudder shaft. It is not clear the an Elan replacement would have been redesigned to eliminate the step. The designer should be contacted to confirm this first.

It would be possible to modify an existing shaft if enough of the glassfibre could be cut away to expose the step or extract the shaft completely. An existing shaft might be re-machined in a lathe to put a short taper with a radius run-out where the step is now. The rudder would then be rebuilt around it. This is still a significant amount of work but not beyond the skills of a reasonable local engineering company.

Any better suggestions anybody?

Cheers, Chris