Keel/Rudder design

[Munz]

Older designs with longer lower aspect keels have a much greater mounting area than modern high aspect ones and are more likely to survive a grounding without damage. I suspect we will see increasing keel problems with modern "performance oriented" boats as they get older, having been battered around and grounded during extended cruising.

Let's just hope your local orca pod don't get bored of stress testing rudders, and decide to widen their investigations to include keel attachment integrity......

 

[rogerthebodger]

One of our local boats lost its keel in a race from Mauritius to Durban.

There was all kinds of comments from "it hit a container" "it grounded and not correctly repaired" "it was not built to spec"

The end result was that all 6 crew lost their lives and the boat was found floating inverted some time later wit a full technical investigation showing that the keel ripped a section of the hull out and the boat inverted and found with the mast and sails still in place upside down.

The main point to me is the loss of life for what ever reason and anyone who has a vested interest will have their view coloured by their vested interest.

My current boat has an internal keel and a skeg hung rudder. My previous boat had an integral long keel with the rudder mounted on the stern of the keel so both rudders had a lower bearing for IMHO better support than a spade rudder that is a cantilever beam with the high stress point where the rudder post passes through the hull. A spade rudder shaft has a greater possibility of being bent by hitting something that a skeg hung rudder. Yes the skeg could be damaged and break off but the design can be made stronger than a simple rudder shaft.

Weight is an issue with racing sailboats so the temptation to cut down on the weight and strength is great and for production more material means more cost.

You pays your money and makes your choice. Its also human nature to defend you choice and to object to anyone who criticizes you particular choice.boat design.

If you ae happy with it that's your prerogative. No need to take issue with someone if disagrees with you choice.


BTW Rogue waves are real and we have then along the east coast of Africa with out current flowing NE to SW and the wings either NE to SW changing to SW to NE giving conditions where wave periods and add or subtract to give higher waves at times.

 

[pvb]

As this thread's about keels and rudders, perhaps we should consider best practice in rudder attachment. Some rudders I've seen don't look very robustly attached, especially with an unbalanced rudder resulting in high stresses. Here's just one example - does the forum think the lower bearing attachment to the keel looks adequate?

 

[Graham376]

Let's just hope your local orca pod don't get bored of stress testing rudders, and decide to widen their investigations to include keel attachment integrity......

Why should I worry? It's an old tech Scheel keel, much longer and thicker with wider spaced mounting studs than a modern high aspect one.

 

[Rappey]

Whilst that is not actually a skeg hung rudder but a keel hung that lower fitting poor by design as a rope can slip between the keel and rudder and it does not look that substantial
They have gone to the trouble of making the rudder blade easily removable but used a bracket design that looks like it could easily be bent back if the rudder got caught on a line

 

[pvb]

Whilst that is not actually a skeg hung rudder but a keel hung that lower fitting poor by design as a rope can slip between the keel and rudder and it does not look that substantial

Quite right, that example isn't skeg-hung, so I've edited my post.

 

[Rappey]

This is mine. Have unbolted it and lowered it some 6" to insert a new bush.

 

[Poignard]

As this thread's about keels and rudders, perhaps we should consider best practice in rudder attachment. Some skeg-hung rudders I've seen don't look very robustly attached, especially with an unbalanced rudder resulting in high stresses. Here's just one example - does the forum think the lower bearing attachment to the keel looks adequate?

View attachment 102971

.
Better than many, although I would like to see the straps the arrow is pointing at extended further onto the deadwood with maybe 3 screws per side. Also I dont like the lower edge of the rudder being straight and in line with the lower edge of the keel ( in fact it looks to be a fraction lower). It might impose great strain in a grounding.

Something like mine (but then I am biased, of course!). Although my rudder is so small it might as well not be there when I'm trying to manouvre astern

 

[NormanB]

If you've actually watched the videos of that boat, you'll find that (a) it didn't lose its keel as you claimed, and (b) poor workmanship by Beneteau wasn't alleged.

The couple bought the boat in a salvage auction. It had been grounded at some time and low-quality repairs had been made to the grid structure, leading to water leaks. The couple have been busy removing the low-quality repairs, back to the original fibreglass, so that they can do the repair properly.

Once again, you've got the story entirely wrong.

I can only surmise you have either not watched all of their videos or missed some important detail. As well as the points you correctly point out an additional problem was shown as endemic throughout the matrix members which had very clearly not been laid up properly ( IMHO) and this, allied to the fact that the matrix hull junction relied on ‘sticky stuff‘ rather than being fully tabbed to the hull. This exposes the production boat dilemma of speed and cost of production versus effectiveness. The grounding (s) served to root out the weak link in the structure.

Anyone considering buying a production boat will be well served to quiz the manufacturer on how the integrity of the matrix to hull junction are achieved before parting with their hard earned.

 

[Rappey]

Anyone considering buying a production boat will be well served to quiz the manufacturer on how the integrity of the matrix to hull junction are achieved before parting with their hard earned.

The couple "expedition evans" did contact the manufacturer asking for plans and information how it was all put together and made no suggestion of build quality but their request was denied.

 

[dunedin]

While your boat is sat on the grass, people with production AWBs are out there sailing the oceans.

I don't beleive simply ticking the 'encapsulated keel' box makes a yacht safer.
That big OYster which sank was a grp failure of the upper keel/ keel root.

Spot on. A lot of arm chair theorists, whilst countless others are out there sailing the oceans in a variety of production boats.

And if anybody stops to analyse the examples quoted in the (far from recent) report Coopec referred to, the vast majority were race boats, modified boats, boats which had been grounded bit not repaired properly - and many in all three categories.
Certainly properly engineered fin keels are no more likely to fall off than a Boeing’s wing, and a lot more people have died inshore capsizing their tender than ever due to loss of keel.

 

[pvb]

I can only surmise you have either not watched all of their videos or missed some important detail. As well as the points you correctly point out an additional problem was shown as endemic throughout the matrix members which had very clearly not been laid up properly ( IMHO) and this, allied to the fact that the matrix hull junction relied on ‘sticky stuff‘ rather than being fully tabbed to the hull. This exposes the production boat dilemma of speed and cost of production versus effectiveness. The grounding (s) served to root out the weak link in the structure.

Anyone considering buying a production boat will be well served to quiz the manufacturer on how the integrity of the matrix to hull junction are achieved before parting with their hard earned.

I've watched every single video.

 

[pvb]

This is mine. Have unbolted it and lowered it some 6" to insert a new bush.

That looks substantial.

 

[Rappey]

I've watched every single video.

It's quite fascinating ! I really do admire how totally positive they are.
Their dust removal operation was a bit long-winded and I'm not convinced the box sections of the matrix are as strong now as they should have been, but let's see what they do.

 

[doug748]

It's quite fascinating ! I really do admire how totally positive they are.
Their dust removal operation was a bit long-winded and I'm not convinced the box sections of the matrix are as strong now as they should have been, but let's see what they do.

I think they will do a good job, as you say, they both have a heart like a lion.

Looking at that original construction I doubt anyone would want to have it, if obtaining a boat for long term, offshore sailing.
A heavy grounding effectively zeros the value of the boat.

.

 

[NormanB]

I've watched every single video.

Ah - you just overlooked or ignored the detail.?

 

[pvb]

Ah - you just overlooked or ignored the detail.?

Perhaps you can remind me which of the videos you're referring to.

 

[NormanB]

The couple "expedition evans" did contact the manufacturer asking for plans and information how it was all put together and made no suggestion of build quality but their request was denied.

Yes you are absolutely correct and that was very telling. However I suppose a yacht manufacturer can distance themselves from their responsibility to subsequent owners especially if there is evidence of grounding. But if a prospective new buyer makes this sort of enquiry to the manufacturer they can make their own judgement of the merits of proceeding with the purchase against the sort of response they receive.

 

[Baggywrinkle]

 

[pvb]

They have gone to the trouble of making the rudder blade easily removable but used a bracket design that looks like it could easily be bent back if the rudder got caught on a line

Do you think it's strong enough? I thought it looked rather flimsy.