cammd said..
I've seen some comments on social media stating its not a construction or design issue, the boat hit a rock!

Are people serious, the keel shouldn't fall off because you hit something, every boat suffers a grounding at some time.

MikeJohns said..




Designed to class, in this case it's said to be DNV.
Whether plans were approved by DNV and the keel was supposed to have been engineered by a professional, or even whether they supervised construction is what the insurance companies investigator will be looking at if they are compenetent. Often there is minimal investigation, or forensic failure analysis unless the coroner is involved. But the payout amount might result in a proper investigation.

The design phase of the Oyster 825 (2011–2012) and its subsequent production run (2014–2017) directly overlapped with the introduction and enforcement of the ISO standards that started to mandate keel strength.
Under ISO 12215-9[/b], <!--qkimaf Bs0fKe_58/HugV6--><!--cqw1tb Bs0fKe_58/HugV6-->a sailboat's keel, its internal supporting structures, and the hull must be specifically engineered to withstand a longitudinal grounding at it's maximum operational speed <!--TgQPHd|||[[]]-->. ISO provide a formula derived from experimentation that is used to calculate this , with a factor of safety.

The ISO standard mandates that the keel attachment and hull laminate must be robust enough to survive the dynamic forces of hitting an underwater obstacle without catastrophic failure. That includes hitting anything, rocks reefs or even hard sand, the deceleration and energy dissipated has a similar energy profile.

The bulk of the collision energy is absorbed through hydrodynamics provided that the boat is free to rotate longitudinally. When it's free to trip on it's keel the loads are a lot lower than the worst case design loads.

A lot of earlier keels were attached bolted through laminate that was woefully deficient, designed to the earlier very popular ABS OSRY standards , the standard was amended before it was abandoned in favour of ISO, but there are still designers who mistakenly use it. There are also a lot of sailboats designed to dodgy standards. That makes grounding a bit of a lottery and means keel loss from grounding is an accepted phenomena, even by insurance companies.

Everytime a keel is engineered nowadays there is a requirement to show structurally that the keel can handle just such a collision without sinking or making the boat innoperable. That doesnt mean no damage, and any hard grounding on a modern design warrants a full inspection of the laminate and keel bolts.

I have lost my prior login on this forum, so now I cant post attachments.

cammd said..


Pulled into Mackay today and spotted her on the hard as we were having a pizza for dinner.

Kankama said..
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.

julesmoto said..






Apparently there was a racing Volvo 60 in around 2017 that hit a reef at full tilt-maybe 19 knots-and didn't lose it's extremely high expect ratio keel. Obviously it can be done. There is video and stills on the web. It happened at night-not that that is an excuse for the navigator. The keel continued to survive robustly on place the next morning by which time the rear of the boat and the rudders were toast.

Maybe they should cast a bit of flexible rigging wire into the keel and have it coiled up and secured to something strong inside the hull like an anchor rode is. That way the keel could still hang there holding the yacht upright although would probably still sink pretty rapidly from water ingress where the keel bolts were ripped out or the rear punched a big hole in the hull.
Wonder what the internal bracing was like on that Volvo 60 because it obviously can be done allbeit maybe at the cost intrusive structures in the center of the boat accommodation. Plenty of trailer sailers get by with accommodation intrusions such as floor to ceiling centre board cases however

scruzin said..





Designing a bolt-on keel structure that can withstand a high-speed impact is extremely challenging. Because the impact point is 2m or more below the hull attachment point, the impact force is multiplied exponentially resulting in massive dynamic bending. I think it if it weren't such a hard problem, it would have been solved by now.

Of course, there is a solution, and it's an encapsulated keel that is structurally part of the hull. Or a multihull :-)

JonE said..
<snip>
This oyster had a long chord encapsulated keel no? And hit an unmovable object hard at high speed. And was built well after 1983.