Will be interesting to see why, but from pics it doesn’t appear to be a hull failure.

Talk at the club tonight was it hit a whale not a rock, but in that 1st photo it seems close to the marker?

Seems a bit different from the normal Beneteau disease and also from the way it's sister ship went down as the keel doesnt look to have parted at the hull although I guess you could call that stub part of the hull even though it appears to be quite deep.

From what I can find out online the sister ship had a failure of the internal keep support matrix due to being glued rather than tabbed but the company issued a statement saying that they had gone back to conventional methods and had retro corrected existing hulls using conventional construction which presumably means they were pulled apart and tabbed.
Accounts of the hammo sinking are interesting because apparently there was time for a rescue boat to pull up alongside with a big diesel pump and transfer it on board before the pump proved inadequate and the boat eventually turned turtle after taking on more water.
Hard to see how the boat could remain upright especially with full sail up and only that small stub in the picture conteracting the mast-even if the stub itself carried some ballast.
The keel possibly hung on for a little while possibly by a couple of bolts or a couple of layers of fiberglass before totally letting go and causing the full capsize.
It will be interesting to see the final report although I don't even seem to be able to find a proper report of the sister ship going down despite the fact that it was apparently salvaged off the bottom.

saltiest1 said..
Will be interesting to see why, but from pics it doesn’t appear to be a hull failure.

I wonder if is the bolts that failed or the structure.

I’m not going to cast any shade, I had a very experienced guy on the helm when we hit a rock in Moreton bay. We were under kite too, so moving at a pretty decent clip. It folded the keel back , so we got away with superficial damage only.
It’s a horrible sound listening to the crunching and tearing noises emanating from your pride and joy.
Just glad everyone up there is safe.

Kankama said..
It isn't okay for a keel to fall off because owners shouldn't hit a rock, because eventually we all do stuff up. That is why we wear seat belts in cars, have crumple zones and other safety features and why we wear harnesses and inflatable vests on boats. Because things can and eventually do go wrong, including hitting rocks at speed with our boats. I have hit three in about 35 years in my boats and I reckon I am pretty good on the water, twice going at more than 7 knots - all the times the boats were fine (but my heart rate and daggerboards were not). In all cases I was an idiot, but for 99.99 percent of the time I care properly for the boat, just sometimes it has to cater for me neglecting my duty or for a multitude of bad choices to line up the Swiss cheese.

So it should not matter what the boat hit, ANY boat should be able to hit the ground at a good clip and not fail. So it doesn't matter if the Oyster hit a whale or rock, there is no way that the keel should fall off - it was poorly designed or built. There is no getting around the fact it was found to be unfit for purpose. Oysters don't do 20 knots so you don't have to design for hitting a rock/whale/container/sunfish/log at those speeds, but you do have to engineer and build the keel to hit something up to 10 knots or so.

There might be an argument for dedicated racing boats to be built light. An intended short life span where speed is the number one purpose sailed by people who know that stuff ups will break the boat and accept that risk, I dont think anyone expects an Imoca to survive a hard grounding unscathed, the people that sail them know a stuff will break something. I think you could argue that type of sailing boat should have very different standards to cruising or everyday use general purpose boats.

That Oyster doesn't fit into that dedicated racer category its a cruising boat primarily.

You cant buy an old F1 and turn it into your daily driver but you can buy a old maxi and turn it into your cruising yacht. Wont be long before we see a foiling Imoca as someones youtube project. There's an idea to build a youtube sailing channel with a point of difference.

JonE said..
F**k me lads, a 50+ tonne boat hits an immovable object at probably well over 10 knots (kite up).

Something needs to break yeah?

Easy to say "keel shouldn't break" but it's not grazing the sandy bottom or bumping a rock whilst parking.

Nup, the bottom of the boat should be peeled off before the keel lets go. The hull to keel connection should be the strongest part of the boat imo.

See NBJS when ran he into a rock with his contessa when he nodded off, that's what should happen, it broke the boat but didnt drop the keel off.

Yeah I understand what your saying, do you think the keel should be like circuit breaker that lets go and saves the hull from damage in the event of a large impact.

I think the opposite, I think hull should be wrecked before the keel comes off it.

That's cool. Always interesting to get a look at that high-end kit.

By they way, your "Queensland" post over on SA nicely illustrates what I was thinking about "something has to give way".....😀

"Should polish out"

Kankama said..
..... I once recommended Percy Island Lagoon to a Leopard catamaran owner. It is great I said, you dry out every low tide but you are secure and able to walk all over the island. He told me the cat was not designed to sit on its keels - I was flabbergasted. What is the point of having a cat if you can't sit on the keels. Who designs these stupid boats? Why would anyone buy one?

Pretty much everything involves compromises, perhaps the guy had, say, a family of 4 and would only get buy in for them to come on extended cruises if they all had space?
98% of custom builds are 3 cabin with fully 1/4 of the boat given over to a head, why would you choose to sleep next to someone that snores to have more space that I'd use for less than 10 minutes a day?
Sure, a production build cat is a pretty fragile egg shell but observably strong enough to even circumnavigate carefully if you chose. As to sailing qualities a Leopard isn't horrible from my 2 week charter, considerably better than a Seawind 1000 with bagged out sails. That boat, IMO, in that condition, would be considered unseaworthy as it literally could not make progress to windward in any sea state above millpond !

Energy going somewhere is a good point - it is what car designers have to do. back in the bad old days, car makers didn;t want to know about adding safety features like crumple zones, safety cells, soft interior furnishings and air bags. In the end, the US government got around the industry's reluctance and the big car companies head in the sand mentality by stipulating that all government cars would have to have air bags. With such a big contract on offer, one of the big companies blinked and now we all have air bags.

Getting energy somewhere is pretty easy IF someone thinks about it. First, put a small crumple zone on the bottom and front of the keel, a crash box. Cats and tris have been doing something similar for decades. Newick even designed a crash box into his dagger cases. In my case the entire tip of the board is cut off and reglued back on. It broke off when I hit a rock at 7-8 knots - zero damage to the case. How much hassle to implement? Almost none. Weight, performance, build issues? None. Upside - I still have a boat, instead of a waterlogged cat with a case ripped through its bum. Tens of thousands maybe vs me in the shed with some cedar and glass.

A good fast cruiser could easily have a small foam/glass section at the front and bottom front of the keel - with a layup sufficient to slip it fine but with enough foam to cushion any 11.5 knot impact. All you need is to increase the time - doubling the time of stopping halves the force. It could be small and do a huge difference. As time of impact is directly proportional to distance - if the Oyster's keel deflected 1cm in the above example (lead deforming) and you put on a small 10cm crash edge, you would increase the distance by 10 times and reduce the force by something similar. At virtually no cost or hassle during the build. So the guys would still have a boat.

Also make that root long and add one extra tight but weaker than normal keel bolt at the front on the centreline. This one would take the initial load and break. Rock climbers have tight stitching that lets go on safety devices to reduce impact loads when falling. Its a oncer but it saves the boat.

I needed to make a new tip and glue it on my cat when I hit the rock at 7 knots or so. If my 500mm chord, 1.6m deep board, into a cedar and 600gm glass hull show absolutely no damage after hitting a rock when I was stupid, then a boat built like a brick dunny can also do it. You just have to do what I did when I built it. Think just a bit about what could happen and work a fix up.

Sparau - As for Leopards - no they are just dumb. To not dry out is awful in a cat and it causes issues when lifted. A yard near me doesn't lift some Lagoons because they put one on its kesl and it crunched and caused a court case. Considering it is really easy to build them properly, I can't understand it. Again there is no reason that an engineer couldn't do this - the builder just cant be bothered. As for Seawinds - you must have got bad one. Most sail pretty well and almost no Schionning has had a racey window designed in about 15 years - those days are gone thankfully.

I do shake my head at dumb design because, having built and designed boats, I know that you can make the boat better with a bit of forethought. It aint hard but it does require you to acknowledge the problem. The fact that any cruising keel falls off is a problem that can be fixed. It is just engineering and building, it aint hard.

According to the locals this morning noone has done anything about the hull. Its been left to drift south unmarked between Cape Conway and Shaw Island. More danger for all, especially at night.

julesmoto said..

shaggybaxter said..

JonE said..
That's cool. Always interesting to get a look at that high-end kit.

By they way, your "Queensland" post over on SA nicely illustrates what I was thinking about "something has to give way".....😀

😀😀😀😀
I hope that bloke gave himself an uppercut. I love those cars.
Found a picture of the aftermath of the rock incident. Still hurts me to see this pic, but as this thread highlights, it could be so much worse.

What am I missing? That boat looks fine to me and not the aftermath of anything. Vulnerable looking keel but certainly intact.

Close up for you. As I said, it needed fairing. Ugh.
Finot would get a chuckle over it being vulnerable. The design has been around since the 80's and they've never had a failure.

Kankama said..
I was sleeping and worked out that one reason monos that hit something are vulnerable is that the keel bolts are then put in shear. Sailors have had problems with shear for ages. Wooden sailing ships have hogged and leaked for aeons because designers and builders did not understand shear. Seppings started putting diagonal bracing on ships and that made British ships much better than others.

So when keel hits a rock, all the bolts are put in shear. This bad news because they are sized for tension. This is usually okay because the shear loads are way lower than tensile loads. But in a dramatic stop the bolts fail in shear. So one way around this would be to have one keel bolt at the front aligned at about 45 degrees down and aft. This would be excellent at taking the shear load and save the other bolts. It would cost bugger all and could save the boat.

I think working out how loads are distributed from sudden stops is important. When I hit the bottom in my cat, one reason the case did not split is that I had wrapped uni kevlar sideways aft of the case and also even more around the back of the case, which was then led forward and spread out, just in case the daggerboard tried to go back through the hull. Took a couple of hours to do, cost bugger all. Maybe saved the boat when I hit the rock.

Correct me if I am wrong but it seems quite a few of these keel failures are not due to the bolts breaking, the structure they are attached to fails.

I wonder if we will ever find out about this oyster. What was the outcome of Nextra the Farr X2 that lost her keel, was that a bolt failure or something else.