One for the metallurgists. Rudder shaft

[PCUK]

If it were me; and I know not everyone will agree (or anyone!) Apparently the corrosion has not significantly reduced the strength of the shaft. Clean the corroded area and fit a zinc anode over the area, this will stop any further corrosion as long as the anode is checked and changed as required. As I say, probably a bit out of the box but even if it is only performed as an experiment it could save a lot of unnecessary expense.

 

[Fr J Hackett]

If it were me; and I know not everyone will agree (or anyone!) Apparently the corrosion has not significantly reduced the strength of the shaft. Clean the corroded area and fit a zinc anode over the area, this will stop any further corrosion as long as the anode is checked and changed as required. As I say, probably a bit out of the box but even if it is only performed as an experiment it could save a lot of unnecessary expense.

It's crevice corrosion a zinc anode won't do anything plus they are planning to cross the pacific not a trip around the bay to a local harbour.

 

[vyv_cox]

If it were me; and I know not everyone will agree (or anyone!) Apparently the corrosion has not significantly reduced the strength of the shaft. Clean the corroded area and fit a zinc anode over the area, this will stop any further corrosion as long as the anode is checked and changed as required. As I say, probably a bit out of the box but even if it is only performed as an experiment it could save a lot of unnecessary expense.

The main problem with leaving it alone is that corrosion pits are an excellent stress raiser where fatigue is very likely to initiate. Especially in a spade rudder ( I do not know if this one is that design).

To some extent this can also apply to a weld repair although the risk is far lower.

 

[geem]

The main problem with leaving it alone is that corrosion pits are an excellent stress raiser where fatigue is very likely to initiate. Especially in a spade rudder ( I do not know if this one is that design).

To some extent this can also apply to a weld repair although the risk is far lower.

The rudder is a spade rudder. Single plastic bearing.

 

[scottie]

I don't think sleeving is an option. The bearing is 15mm above the site of the corrosion.
The owner has already contacted Jenneau in the US and France with a view towards a complete replacement rudder as an alternative solution. They are planning a Pacific crossing so the solution needs to be right and strong.

When we sold our Hanse the buyers surveyor wanted a £5-6K allowance for a new rudder having it sleeved cost as I recall about 1/4 of the cost
Jeffa have standard sleeves to do the job

 

[Beneteau381]

A stock and tang are in an oxygen deficient environment and I would have thought when a rudder is built it would not be expensive in either labour nor materials to coat the whole thing, stock and tangs, with resin and glue the foam, glass and filler to the coated metal work.

But I'm no boat builder with an accountant breathing down my neck.

Noting Benny381's and Ben's post - carbon seems to be a way to go. Off the shelf carbon tubes....?

Lightwave cats have carbon stocks and I assume carbon tangs.

In this case - have the stock and tangs made up (by Jenny or A N Other) in carbon and simply, or less simply, add the existing or a clone of the blade, It would not be difficult to make up the profile of the blade, if you can access foam, glass and resin - assuming it is in good condition (and there has been no report of damage).

Jonathan

Note I said glass, well proven in our useage.
Carbon I would not entertain. Failure is too much of a cliff edge from what I can see

 

[geem]

Note I said glass, well proven in our useage.
Carbon I would not entertain. Failure is too much of a cliff edge from what I can see

Weight for weight, carbon is twice as strong as E glass. If you replaced your GRP rudder for an identical one made in carbon is would be twice a strong as the one you have

 

[Beneteau381]

Note I said glass, well proven in our useage.
Carbon I would not entertain. Failure is too much of a cliff edge from what I can see

Going backto when I worked in the NCB in a coal mine, we had an issue with a shaft that needed welding, it was in a reciprocating mechanism driving a coal "shaker" screen. About 4" diameter, we got the area hot with an oxy acetylene "rose" and welded it whilst red hot. Machined it afterwards and it worked ok. The heating allegedly normalised the metal.

 

[Beneteau381]

Weight for weight, carbon is twice as strong as E glass. If you replaced your GRP rudder for an identical one made in carbon is would be twice a strong as the one you have

Its the cliff edge I dont like.

 

[geem]

Its the cliff edge I dont like.

If you were building a rudder in Carbon it would likely be for a race boat or high end fast cruiser where money was no object. You would likely take advantage of the weight reduction that carbon provides. Twice as strong therfore build it lighter. If you didn't do that and built it to the same dimensions to your existing rudder but used carbon there would be no cliff edge. Twice as strong. Your existing rudder would fail long before the carbon one

 

[burgundyben]

Its the cliff edge I dont like.

Surely depends how far away from the cliff edge you are?

Failure mode or design margin. Interesting choice.

 

[Beneteau381]

If you were building a rudder in Carbon it would likely be for a race boat or high end fast cruiser where money was no object. You would likely take advantage of the weight reduction that carbon provides. Twice as strong therfore build it lighter. If you didn't do that and built it to the same dimensions to your existing rudder but used carbon there would be no cliff edge. Twice as strong. Your existing rudder would fail long before the carbon one

Irelevent any way, he wont be going down that route? New standard one?

 

[Beneteau381]

Irelevent any way, he wont be going down that route? New standard one?

I would drop the rudder, split it, get the SS bits out, grind the corrosion, weld it, then normalise it with a big oxy acetylene torch and dress it up. Then rebuild the clamshell. If he is risk averse he will buy a new one

 

[vyv_cox]

I would drop the rudder, split it, get the SS bits out, grind the corrosion, weld it, then normalise it with a big oxy acetylene torch and dress it up. Then rebuild the clamshell. If he is risk averse he will buy a new one

The whole point of using a duplex stainless is that it can be heat treated to increase its strength. If you are going to normalise it you are reducing its strength and you might as well have started off with a 316.

 

[geem]

I would drop the rudder, split it, get the SS bits out, grind the corrosion, weld it, then normalise it with a big oxy acetylene torch and dress it up. Then rebuild the clamshell. If he is risk averse he will buy a new one

He will speak to the welder here tomorrow. See if he has sufficient expertise to do good repair. The corrosion is very close to the bearing mating surface. In the other direction there is the grp of the rudder blade within an inch of where the welding is needed. Cost do everything here are very high compared to the UK. A new rudder may be preferable. Still waiting on costs for that

 

[penfold]

He will speak to the welder here tomorrow. See if he has sufficient expertise to do good repair. The corrosion is very close to the bearing mating surface. In the other direction there is the grp of the rudder blade within an inch of where the welding is needed. Cost do everything here are very high compared to the UK. A new rudder may be preferable. Still waiting on costs for that

If the costs are bad in Curacao is it worth taking the rudder somewhere cheaper like Trinidad?

 

[Neeves]

I crewed on a 38ft all carbon race boat with carbon rudder shaft. It snapped. The quote for new was $10,000US. The way they build the carbon shaft is interesting. They take solid carbon rods and bunch them together then wrap them in carbon cloth. Difficult to make but theoretically strong. Not sure it's a viable build cost on a production boat

In your geographic location it is impossible to transfer what is possible with every facility and skill available that is on offer here, in Oz or the UK, What is viable in the UK might be simply impossible where you are. We don't know and all we can do is offer a cross section of ideas. We have specialist carbon fibre fabricators servicing the marine industry within 10km, fully qualified welders and stock of a full range of stainless and duplex steel about 20km away. McConochie, Ian Murray and other naval architects (who designed the HT steel fin for Wild Oates XI) within 3km and I think Murray still has an interest in high tech performance sailboat building 100km down the coast. Basically one could make phone calls here and have access to in depth expertise and have a strategy planned out within a day.

For your location I have this nasty feeling that it would not be viable to fly a, any, new rudder in - but - I simply don't know - flying in the components for a carbon rudder might be - as I say they are standard on Lightwave 38' cats (replacing the original stainless versions). I have not heard of a Lightwave carbon shafted rudder failing (and our rudder is about 6 years old now)

Whereas your location is gorgeous for a stop over I'm not envious of being forced to use it for a major rudder repair (or any major repair - which is why you are posting here).

As part of the options I might consider filling and grinding down, then making careful use of weather windows head for the US, and its a long way, and replace the rudder there. It is one thing to repair based on ones own risk assessment its another risk assessment for the next person who buys the yacht (and if I knew about it I'd want a new rudder).

Jonathan

 

[geem]

In your geographic location it is impossible to transfer what is possible with every facility and skill available that is on offer here, in Oz or the UK, What is viable in the UK might be simply impossible where you are. We don't know and all we can do is offer a cross section of ideas. We have specialist carbon fibre fabricators servicing the marine industry within 10km, fully qualified welders and stock of a full range of stainless and duplex steel about 20km away. McConochie, Ian Murray and other naval architects (who designed the HT steel fin for Wild Oates XI) within 3km and I think Murray still has an interest in high tech performance sailboat building 100km down the coast. Basically one could make phone calls here and have access to in depth expertise and have a strategy planned out within a day.

For your location I have this nasty feeling that it would not be viable to fly a, any, new rudder in - but - I simply don't know - flying in the components for a carbon rudder might be - as I say they are standard on Lightwave 38' cats (replacing the original stainless versions). I have not heard of a Lightwave carbon shafted rudder failing (and our rudder is about 6 years old now)

Whereas your location is gorgeous for a stop over I'm not envious of being forced to use it for a major rudder repair (or any major repair - which is why you are posting here).

As part of the options I might consider filling and grinding down, then making careful use of weather windows head for the US, and its a long way, and replace the rudder there. It is one thing to repair based on ones own risk assessment its another risk assessment for the next person who buys the yacht (and if I knew about it I'd want a new rudder).

Jonathan

Shipping stuff here from the US is pretty easy. Takes about two weeks. If a rudder is available in the US at sensible money that may be Ben's best option. Shipping costs are not prohibitive

 

[Neeves]

Shipping stuff here from the US is pretty easy. Takes about two weeks. If a rudder is available in the US at sensible money that may be Ben's best option. Shipping costs are not prohibitive

Then taking a rudder from stock might be the way to go.

Shipping stuff from the US to Oz - it needs to be a critical item to justify the costs. Sitting in Sydney we simply don't know the environment nor conditions in your exotic locations and some of our ideas, in Oz, will seem ridiculous.

So be gentle with us - actually we are trying to be helpful .

Jonathan

 

[Yara]

If it were me; and I know not everyone will agree (or anyone!) Apparently the corrosion has not significantly reduced the strength of the shaft. Clean the corroded area and fit a zinc anode over the area, this will stop any further corrosion as long as the anode is checked and changed as required. As I say, probably a bit out of the box but even if it is only performed as an experiment it could save a lot of unnecessary expense.

The question is- how are you going to stop further crevice corrosion? Maybe have a rough surface to allow oxygenated water to get to the area? As a cheapskate I would round the sharp edges of the larger hole, and add some vertical scoring to get the oxygen to the area. Welding and heat could make the corrosion worse when you do not know for sure what the shaft metal is. Then do a coastal cruise for a couple of weeks and check the site for further corrosion.