Another lost keel

[flaming]

I can think of 5 possible causes.

1. The engineering on the keel and/or keel attachment was incorrect.
2. The manufacture of the keel and or/attachment was incorrect.
3. When the boat was put together after shipping to Aus, it was put together incorrectly.
4. It had sustained damage that weakened the structure
5. The failure was the result of a collision that was outside of the design parameters.

Of all of those I think 4 is very unlikely as the boat was brand new and had supposedly only done a few days sailing. 5 is probably also fairly unlikely, although not impossible, as there doesn't seem to be a lot of damage to the hull other than the missing keel.

 

[vyv_cox]

I can think of 5 possible causes.

1. The engineering on the keel and/or keel attachment was incorrect.
2. The manufacture of the keel and or/attachment was incorrect.
3. When the boat was put together after shipping to Aus, it was put together incorrectly.
4. It had sustained damage that weakened the structure
5. The failure was the result of a collision that was outside of the design parameters.

Of all of those I think 4 is very unlikely as the boat was brand new and had supposedly only done a few days sailing. 5 is probably also fairly unlikely, although not impossible, as there doesn't seem to be a lot of damage to the hull other than the missing keel.

A bit early to speculate based on one not very good photo but it appears that there are a few chunky bits of keel at the fracture site. It might be that what can be seen is torn grp but if not the failure would seem to be brittle, rather than fatigue or ductile overload. Points to a heat treatment problem given that apparently the keel strut was cast.

 

[Poignard]

A bit early to speculate based on one not very good photo but it appears that there are a few chunky bits of keel at the fracture site. It might be that what can be seen is torn grp but if not the failure would seem to be brittle, rather than fatigue or ductile overload. Points to a heat treatment problem given that apparently the keel strut was cast.

Seeing as how interior comfort is not a factor in these boats, in your opinion as an engineer wouldn't it be better to continue the keel up through the hull and bolt it to the underside of the deckhead (rather like a keel stepped mast is arranged but upside down)? There would obviously have to be a bolted flange and a reliable seal where the keel passes through the bottom of the boat, and it would add more weight, but I should think it would be much stronger.

 

[vyv_cox]

Seeing as how interior comfort is not a factor in these boats, in your opinion as an engineer wouldn't it be better to continue the keel up through the hull and bolt it to the underside of the deckhead (rather like a keel stepped mast is arranged but upside down)? There would obviously have to be a bolted flange and a reliable seal where the keel passes through the bottom of the boat, and it would add more weight, but I should think it would be much stronger.

No doubt that would be a far stronger arrangement but it puts weight above the water line, not ideal in a specialist race boat. I remember the first time I saw one of this type of boat ashore in Hamble, being astonished at how slender these struts were, with a huge lead torpedo at the bottom. There must be a hell of a stress at the exit from the hull.

 

[fisherman]

A boatbuilder told me that some high performance boats are designed down to the minimum achievable scantlings, in his words, "if they don't break occasionally they're too heavily built"

Belt, braces, and velcro to the shirt tails for me.

As a completely amateur bar room engineer, I would go for half keel depth inside the hull and thoroughly braced transversely and for/aft, as a rule of thumb (I just invented)

 

[jamie N]

Sorry Fisherman, I'd go for the internal bracing to be diagonally set within the boat, in all 3 dimensions. As for your shirt tails though, I bow to your greater knowledge...

 

[Laysula]

30 kts of wind and a 2 metre swell??????????????? That's summer conditions in the Irish sea.

 

[Chiara’s slave]

30 kts of wind and a 2 metre swell??????????????? That's summer conditions in the Irish sea.

I’m not very familiar with the Irish sea, but it’s really not a terrible lot of wind. I’d probably avoid that if I could, but if it appeared en route, I wouldn’t be unduly concerned about breaking my boat. And most of you would consider mine the more radical design.

 

[Praxinoscope]

A few years back a couple of us ended up in the Celtic sea with winds of 55kts gusting 60, in my old Invicta 26, the boat was quite happy it was the crew which was a bit iffy.
I am not a marine engineer, so bow to others such as vyv_cox who have far greater knowledge on boat design and construction, but it does seem to me that there seems to be a move to over reduce weight, which in some cases, whilst relying upon theoretical stress maximums leave little or no margin for the unexpected which the sea is very good at providing.

 

[Frank Holden]

I’m not very familiar with the Irish sea, but it’s really not a terrible lot of wind. I’d probably avoid that if I could, but if it appeared en route, I wouldn’t be unduly concerned about breaking my boat. And most of you would consider mine the more radical design.

Some in the northern antipodes may have missed it but the South/Central coast of NSW has been experiencing some rather extreme weather over the last week and I would suggest that 30 knots ( and I think it was a bit more than that) Live: SES performs dozens of rescues as evacuation orders issued for more parts of Sydney from the SE blowing in off the southern Tasman Sea and over the south going current would be producing a rather nasty short steep sea state. It was enough to make this one lose power and very nearly end on the beach. https://www.news.com.au/technology/...s/news-story/27a78df8f02c55967d8a77ef974d2f4e

Meanwhile re extending the keel into the boat. Surely within the hull it could take the form of a web and be quite light - relative to a solid bit.

 

[Chiara’s slave]

We do have similar stretches of water, I understand. And it’s fairly obvious the reporting of this leaves something to be desired, seems that includes the wind strength. All the same, a nasty steep chop is to be expected fairly frequently, in many parts of the world. You’d hope that was taken completely into consideration during design and manufacture. I guess we’ll all have to wait to discover the real cause of this accident.

 

[Neeves]

Wild Oats XI and other similar yachts have similarly shaped keels. Wild Oats' keel was based on a machined piece of 800 MPa steel, specifically Bisplate 80, with the bulb bolted on. I have seen them with a flange welded to the top (where it is bolted to the yacht) but some cant and then protrude into the interior. Casting steel is fraught with problems and Classification Societies, CS, will not only want to examine the keel and its design but also demand they approve the casting facilities.

For those of you still young, the original Rocna shank was based on Bis 80 and the shank of the next iteration of Rocna, namely, Vulcan has a machined shank (and I assume a fairly high MPa steel). To obtain CS approval of an anchor or keel the casting facilities would need to be declared and approved, Rocna, Vulcan, Mantus M2 etc - its an expensive operation and some will not pay. Fabricated anchors, like Spade or Excel, or keels don't need to jump through the same hoops - just design, the welding and proof of use of approved steel quality.

Having worked with Bis80 I had assumed machining it would be expensive but apparently its common place and Vulcan shows its not going to be prohibitively expensive.

I do wonder in this case - why did they cast?

I might have thought, simply use a rectangle piece of HT steel, weld on flanges, fill to profile, bolt on bulb (cast lead) - job done. But maybe I'm simply showing my total ignorance.

Jonathan

 

[Neeves]

Some in the northern antipodes may have missed it but the South/Central coast of NSW has been experiencing some rather extreme weather over the last week and I would suggest that 30 knots ( and I think it was a bit more than that) Live: SES performs dozens of rescues as evacuation orders issued for more parts of Sydney from the SE blowing in off the southern Tasman Sea and over the south going current would be producing a rather nasty short steep sea state. It was enough to make this one lose power and very nearly end on the beach. https://www.news.com.au/technology/...s/news-story/27a78df8f02c55967d8a77ef974d2f4e

Meanwhile re extending the keel into the boat. Surely within the hull it could take the form of a web and be quite light - relative to a solid bit.

The conditions developed to 11m swells

Efforts to move cargo ship stranded off Sydney suspended after tow lines snap in wild weather

Jonathan

 

[Skylark]

I liked this comment in the article:-

“until it’s fully investigated we are at best speculating and at worst mindlessly gossiping”

 

[davidej]

A boatbuilder told me that some high performance boats are designed down to the minimum achievable scantlings, in his words, "if they don't break occasionally they're too heavily built"

Didn’t Colin Chapman say something like that?

And killed a few drivers in the process!

 

[flaming]

I liked this comment in the article:-

“until it’s fully investigated we are at best speculating and at worst mindlessly gossiping”

Yes it would have been a good quote, if the article hadn't then gone on to speculate a lot about the decisions of the sailors to go, and not mention at all that it's absolutely not acceptable that the bloody keel is missing....

 

[flaming]

Statement from team Nexba, posted on their facebook.

STATEMENT
As our close followers may be aware, team 'nexba' capsized in the very early hours of Saturday morning. The team were completing a 100nm qualifier and had left Pittwater early Friday afternoon to be back in Pittwater by early to mid-Saturday morning.
Around 1am on Saturday morning as the team made their way home to Sydney in light to moderate breeze and 1-2m seas, the boat capsized. After spending 15hrs drifting out to sea with the upturned vessel, the team were rescued and are now safe on land, and have recovered in hospital with minor injuries. They are not yet ready to talk about their ordeal in a public forum and are grateful for space at this time. They will release a statement when they are ready.
The girls wish to say:
“Thank you everyone for your kind words of support, we are so grateful to have survived an awful ordeal and for our amazing community of family, friends, fellow sailors (basically family) and all of the incredible people who assisted in our rescue effort.
Thank you so greatly in particular to everyone who assisted in the team’s rescue effort, especially the incredible and highly trained team from the HMAS Brisbane, the crew of the Arietta Lily, the water police, marine rescue, 000 and the many parties who helped in communicating our position.”
A full investigation into the events leading to the boats inversion and the efforts made by the team to survive will be conducted so that others can learn from this experience and avoid such a terrible ordeal.
We will see you all on the water again very soon. xx

 

[Skylark]

Yes it would have been a good quote, if the article hadn't then gone on to speculate a lot about the decisions of the sailors to go, and not mention at all that it's absolutely not acceptable that the bloody keel is missing....

No doubt there will be plenty of time for the armchair yacht designers to suggest improvements once the facts are established and a report issued. I simply find speculation and mindless gossiping (quoting) to be in poor taste.

 

[Neeves]

Statement from team Nexba, posted on their facebook.

Another question - why did it take 15 hours drifting out to sea.

Jonathan

 

[Tranona]

Didn’t Colin Chapman say something like that?

And killed a few drivers in the process!

Reminds me of watching an early Elan leaving the road into the bushes and disintegrating. not impressed to see a length of rebar used as reinforcement in the doors! Fortunately the driver survived as the bushes absorbed most of the energy.