Rudder nightmare at sea

[bfloyd4445]

Originally Posted by Bluewaters2812

Haha, the Admiral says thanks ... she has not been called a beautiful mermaid before lol. Jokes aside, she is to me.

Your comment makes me feel that I did do something right

...from what you are saying she is a beautiful mermaid and you should tell her so more often or maybe she will have you keelhauled

[hellosailor]

The net sounds good. A tarp with lines tied to all four corners would also work, if there's any chance of the post pushing through the netting. With either one, I think I'd put a 5 or 10 gallon bucket in the center, cinch the tarp up around it, and drop some weights in the bucket, so it formed up a bit like a funnel and encouraged the post to get trapped in the bucket, instead of sliding off to the side and then down.

FWIW on the betadine, throw it out now. Word got around 5-10 years ago that betadine is actually a very bad idea because that nice red color makes it impossible to see if a wound is actually going red and infecting! So the new washes are strongly recommended to be "white", non-staining, as the emphasis now is on catching infections as soon as possible.

Maybe the Nooze are just doing too good a job, but there certainly is a continuous stream of nooze about "totally resistant" crud of all kinds these days.

[Bluewaters2812]

Originally Posted by bfloyd4445

...from what you are saying she is a beautiful mermaid and you should tell her so more often or maybe she will have you keelhauled

Haha, if she would allow me I would post a pic (and I think you might agree).

[Bluewaters2812]

Originally Posted by hellosailor

The net sounds good. A tarp with lines tied to all four corners would also work, if there's any chance of the post pushing through the netting. With either one, I think I'd put a 5 or 10 gallon bucket in the center, cinch the tarp up around it, and drop some weights in the bucket, so it formed up a bit like a funnel and encouraged the post to get trapped in the bucket, instead of sliding off to the side and then down.

FWIW on the betadine, throw it out now. Word got around 5-10 years ago that betadine is actually a very bad idea because that nice red color makes it impossible to see if a wound is actually going red and infecting! So the new washes are strongly recommended to be "white", non-staining, as the emphasis now is on catching infections as soon as possible.

Maybe the Nooze are just doing too good a job, but there certainly is a continuous stream of nooze about "totally resistant" crud of all kinds these days.

Thanks , I hear you but must be honest, use alcohol first to cleanse then use Betadine and the combo works like a charm. Make sure you change dressings/plasters once every 24 hours otherwise ouch! I speak from experience. Typical me, I neglected a wounds a few times and felt the soreness grow. Self-inflicted I know.

[bfloyd4445]

Originally Posted by minaret

In this pic you can see where they brushed it with gelcoat after they had lost the chemical bond. Now the gel is flaking off. Where it has already flaked off you can see the original layup clearly. It looks super rich to me. If that was my boat I'd cut a small sample of it and burn test it for resin/fiber ratio. I bet it's way off.

That would certainly be just one (probably very important) factor. The other is that this is a terrible design. All the load is put right on the edge of the lower bearing, right where it failed. This is not a good place for composites.

I too had the same thoughts. My guess is that one of two things happened: was damaged ar some time by being struck above the bearing causing a fracture which went unnoticed allowing water in. Could have happened in backing into a dock etc.. Or poor layup in the factory.

thanks for posting the pictures they have taught us all what to look for when inspecting our boats to see if they are seaworthy or not

[Bluewaters2812]

Originally Posted by bfloyd4445

I too had the same thoughts. My guess is that one of two things happened: was damaged ar some time by being struck above the bearing causing a fracture which went unnoticed allowing water in. Could have happened in backing into a dock etc.. Or poor layup in the factory.

thanks for posting the pictures they have taught us all what to look for when inspecting our boats to see if they are seaworthy or not

You're welcome, hope it helps.

[bfloyd4445]

Originally Posted by Bluewaters2812

You're welcome, hope it helps.

How long have you owned the boat? I'm wondering if a previous owner hadn't of smacked her tail on something

[DeepFrz]

The other is that this is a terrible design. All the load is put right on the edge of the lower bearing, right where it failed. This is not a good place for composites.

I would have thought Carbon fiber/epoxy would be a good material for this.

What would you recommend, minaret?

[minaret]

Originally Posted by DeepFrz

I would have thought Carbon fiber/epoxy would be a good material for this.

What would you recommend, minaret?

Titanium.


That's not carbon/epoxy. Don't even think its an epoxy layup, let alone carbon. If this was done right with carbon uni pre pregs and e glass machine woven on a mandrel it would be the bomb. Also would be very very expensive.

In that thickness a carbon pultrusion would probably be plenty strong too. But woven is better than straight uni.



http://en.wikipedia.org/wiki/Pultrusion









1 - Continuous roll of reinforced fibers/woven fiber mat
2 - Tension roller
3 - Resin Impregnator
4 - Resin soaked fiber
5 - Die and heat source
6 - Pull mechanism
7 - Finished hardened fiber reinforced polymer

[DeepFrz]

http://www.google.ca/url?sa=t&rct=j&...55123115,d.b2I

I'm not sure about price but these guys think they can match OEM prices.

I didn't think OP's rudder post was carbon. Looks like a very poor layup to me, whatever it is.

[leftbrainstuff]

Here's some comments on the problem with using composites for highly loaded safety critical items like your primary means of steering. I've provided them to assist you in being able to understand the technical aspects as you work to get your vessel repaired. Note that I'm not criticising the manufacturer of the yacht.

Some of the comments on the composite failure are interesting. The rudder has obviously been in service for a while so comments about gelcoat and voids is somewhat spurious. I would not be making professional judgements on the actual failure mechanism without careful inspection at both the macro and micro level.

Using a composite post is great for the manufacturer but a less than ideal option for the boat user. Here's why. A composite post is cheap and easy to make and meet the manufacturer's build quality control. Composites have high specific stiffness (stiff and light) but poor abrasion resistance (low hardness) and very low toughness compared to a structural steel option. They make sense for well maintained performance and racing yachts where they are inspected frequently or parts are replaced on a strict schedule.

As an engineer i would consider this design (foam filled composite post) to be non optimum when offshore cruising and as a yacht owner i would consider the design to be insufficiently robust necessitating frequent inspection and / or replacement. A risk based rationale for the manufacturer using this design would likely pass a spreadsheet cost benefit analysis due to the low probability of occurrence. I always demand risk based assessment to include probability, severity and detectability. Often detectability is ignored because it will discount many cheaper options for the manufacturer.

A solid steel rudder post, either heat treated high strength martensitic stainless (4xx series) or a lower strength corrosion resistant alloy such as 316L is tougher than a composite option and therefore will typically fail gracefully giving you feedback that something is wrong. A tubular option could easily meet the strength requirements but also introduces buckling as a failure mechanism. This is why the older blue water yachts typically have a solid rudder post which is way over designed from a static strength perspective.

Note that the primary failure mechanism for a rudder post, that i would use during design will be low cycle fatigue after a high point stress loading from an impact. This is why rudder posts typically didn't fail from an actual impact but generally some time after at a stress loading that can be less than the design stress level. Pros and cons

Option 1 - replace rudder with a manufacturer supplied item
Pros
- Potentially a relatively simple fitment providing no other structural damage
- potentially some form of guarantee although in practice this will be limited and will favour the manufacturer and not you
Cons
- Foam filled composite rudder post will always fail catastrophically and will be not survive any impact.
- a prudent risk based approach will necessitate that you have a secondary rudder

Option 2 - design and fabricate a steel rudder post and bearing mounts
Pros
- design can both functional and survivable by design and material selection
- can build in fail safes rather than just shear off
- can be intentionally designed to fail gracefully
Cons
- your location may not give you access to a competent designer and fabricator
- you will need to ensure the new design doesn't introduce any new emergent problems. The manufacturer may counter that the rudder is designed to be sacrificial to avoid impacting the integrity of the hull during a rudder impact. This is an entirely plausible design decision and is the reason why yachts are classed as either coastal or offshore rated.

Personally, in your current situation cruising offshore, Option 1 plus a secondary rudder is probably the best you can manage. I would place lots of pressure on the manufacturer to support you because their choice of design is a significant factor in your current dilemma and many of their yachts travel the globe. Their reputation is important and it is in their best interests to see you back sailing asap.

[hellosailor]

Deepfrz, you make a good point:
":I didn't think OP's rudder post was..."
For that matter, unless the OP bought the boat brand new, there is no certainty that the rudder even was original to the boat. I know someone who got a surprise while measuring a used boat for new sails--the mast and boom were not original ! Close, sure, but not close enough to use stock sails.

leftbrain-
your engineering points also take no account of the failure modes of stainless. There is no way, at least, no way used in any production, to seal and bond a steel rudder post to the frp rudder shell on a permanent basis. So that combination will ALWAYS eventually suffer from water incursion, and that will lead to crevice corrosion on the steel rudder post. Always.
Then there's the layup, usually a mild steel or iron armature is welded to that post to carry the forces of the rudder itself. And again...moisture instrusion eats the armature and the welds, unless you can find a manufacturer who has used long-term compatible (read: identical and expensive) materials for all the "steelwork" in there.

Composites can fail, sure. Airbus had a rather famous rudder failure that way in 2001 or 2002 wasn't it? Fall down, go boom, over the Rockaways while departing JFK. But, composites and glues also have an enviable record holding the wings onto combat aircraft all over the world.

Bad engineering, bad production, easily can outweigh the virtues and vices of the materials. Stainless rudder posts in frp rudders are just a time bomb though, an integrally bonded composite rudder-and-stock isn't such a bad idea to avoid those.

[leftbrainstuff]

Originally Posted by hellosailor

Deepfrz, you make a good point:
":I didn't think OP's rudder post was..."
For that matter, unless the OP bought the boat brand new, there is no certainty that the rudder even was original to the boat. I know someone who got a surprise while measuring a used boat for new sails--the mast and boom were not original ! Close, sure, but not close enough to use stock sails.

leftbrain-
your engineering points also take no account of the failure modes of stainless. There is no way, at least, no way used in any production, to seal and bond a steel rudder post to the frp rudder shell on a permanent basis. So that combination will ALWAYS eventually suffer from water incursion, and that will lead to crevice corrosion on the steel rudder post. Always.
Then there's the layup, usually a mild steel or iron armature is welded to that post to carry the forces of the rudder itself. And again...moisture instrusion eats the armature and the welds, unless you can find a manufacturer who has used long-term compatible (read: identical and expensive) materials for all the "steelwork" in there.

Composites can fail, sure. Airbus had a rather famous rudder failure that way in 2001 or 2002 wasn't it? Fall down, go boom, over the Rockaways while departing JFK. But, composites and glues also have an enviable record holding the wings onto combat aircraft all over the world.

Bad engineering, bad production, easily can outweigh the virtues and vices of the materials. Stainless rudder posts in frp rudders are just a time bomb though, an integrally bonded composite rudder-and-stock isn't such a bad idea to avoid those.

I could go into endless detail on the myriad failure modes of stainless but that isn't going to be particularly helpful to the OP. What my post was focussed on was giving the OP some information that he can use to make an informed decision in his current predicament. The key points in comparing composites and 'stainless' steel used in this situation where a rudder is configured as a single shear design is that any composite post will nearly always fail catastrophically while a solid metal post will nearly always yield when overloaded or struck and therefore avoid the uncontrollable situation the OP faced.

[bobsadler]

Re the query on off-centre emergency rudders: Hydrovane self-steering vanes can act as an emergency ruddy. They can also be installed off-centre (as mine is and it works fine). There are photos on the Hydrovane website illustrating such installations.

[goboatingnow]

I would say it again , in my experience of rudder failures or partial failures, there was always preexisting damage.


I would most certainly get a response from beneteau

Note for an analysis of stainless steel rudder stock failure see MegaWatt sinking

Dave