Well now,

[Porthandbuoy]

I guess the difference is the J class has 50 tons of lead on her keel and will pop up, the other is approaching the point at which it will pop down,

That's the point at which I'd be thinking of taking a reef in on my last boat, a Nic 26

 

[dunedin]

I guess the difference is the J class has 50 tons of lead on her keel and will pop up, the other is approaching the point at which it will pop down,
……

OK naval architect expert, go look up the keel weight in Maltese Falcon and report back.
Is it bigger or less than 50 tons?

 

[Chiara’s slave]

OK naval architect expert, go look up the keel weight in Maltese Falcon and report back.
Is it bigger or less than 50 tons?

And besides, no naval architect is going to design a superyacht where the angle of vanishing stability is less than 30 degrees. Itks more than that on our Dragonfly, which works, and is sailed, on different principles.

 

[Chiara’s slave]

Call me a coward, but the word I'd use is scary.

Flying an amas strikes me as being something to avoid unless you're an out-and-out racing crew and the helm has F1 driver reactions. Coco de Mer was having great fun in the RTI before last, until, all of a sudden, they weren't, I know she is (was?) a cat, but that's the one I remember. IIRC, there was more than one tri that did the same thing.

Our windward ama comes out at about 8 kn of wind, on the beat, by design. It reduces the wetted area. Our main hull might well come out at about 22kn true, but as you say, the fear factor plus just common sense, and the reefing recommendations from Quorning prevents that from happening. That would be the near equivalent of Coco de Mer. But those Gunboats are apparently designed for that. As you know though, you’re dealing with very fine margins. I do not fancy that kind of risk myself.

 

[doug748]

OK naval architect expert, go look up the keel weight in Maltese Falcon and report back.
Is it bigger or less than 50 tons?

I have a feeling you are going to tell me, whilst you are at it lets see the stability curves for both boats.

 

[dunedin]

I have a feeling you are going to tell me, whilst you are at it lets see the stability curves for both boats.

No, you are the one raising claims of instability based upon one photo, and claiming a 50 ton keel on. j Class makes it more stable.

So having started this just asking you to add some objective facts / data to support your assertions.

 

[doug748]

No, you are the one raising claims of instability based upon one photo, and claiming a 50 ton keel on. j Class makes it more stable.

So having started this just asking you to add some objective facts / data to support your assertions.

Read post 20.

I have made no claims about stability that are not in the public domain.

.

 

[boomerangben]

The point of the original video is in response to recent events, not to establish anything about stability. The stability of these boats is already known
Large yachts, it seems, take their stability cues from ship practice rather than small sailing boats. Who realised this, I didn't

We are told that the figures for the recently sunk Bayesian included a downflooding angle as little as 45% and an angle of vanishing stability, on the day, of 75 deg. In stark terms this means the opposite of fail safe, the boat is already flooding, before the boat approaches the point of going over.

The boat pictured in post 1 is from the same yard and built to similar standards. The water is within c 1 metre of entering the boat.

.

The MCA have taken the lead on regulating the construction of large yachts. The regulations are published and in the public domain for free. Look up MCA LY3 and read to your hearts content. Who are we to judge the competence of the experts who have put their reputations on the line in writing that document?

It seems you are surprised by the small angle of down flooding on such yachts. Well LY3 provides guidance on the margin of safety of wind moment over stability and downflooding.

There is of course a limit to what conditions any regulation can account for and clearly designing for an extremely intense micro burst or water spout will unnecessarily restrict this type of vessel. Thankfully they are very rare and might be mitigated by the requirements of weathertight doors and hatches which are also covered in LY3.

I have absolutely no idea what the angle of down flooding is on my boat, nor for that matter know what it’s GZ curve looks like or what the AVS is. But apparently it is self righting. Quite frankly I would sh*t myself if I got anywhere near any of those angles, not to mention spill my tea/coffee/beer depending on time of day. Which is why weather forecasts are so important.

No doubt the report into the Bayesian will make recommendations for either/or/and design, construction and operating this type of vessel and if needed LY3 will evolve if deemed necessary for people’s safety. Or it may be proved adequate in its current state. Who knows. But comparing large yachts to small yachts is like comparing dinghy’s to small yachts. And I would guess you would not accept your yacht being able to capsize for you to right by yourself as a dinghy sailor would

 

[winch2]

So as with the Folkboat and many other boats of different sizes going right up to "superyachts" decks under water when going to windward hard is not necessarily an indicator of poor stability

I agree. At the most basic level of understanding it is a measure of freeboard/beam but yes of course its more than just that. Underwater weight/leverage, above water weight/leverage. Having said that any deck underwater probably means your going slower than the guy who's decks are dry... re balance etc.

 

[doug748]

The MCA have taken the lead on regulating the construction of large yachts. The regulations are published and in the public domain for free. Look up MCA LY3 and read to your hearts content. Who are we to judge the competence of the experts who have put their reputations on the line in writing that document?

It seems you are surprised by the small angle of down flooding on such yachts. Well LY3 provides..........

Very instructive.

However it is possible that someone else put the matter of MCA legislation into your mind 2 weeks ago:

Bayesian.



.

 

[Chiara’s slave]

Downflooding angle on s DF920, about 180 degrees I think

 

[capnsensible]

It would be nice to read a post on here from someone who has sailed a superyacht hard to windward for an objective view.

Doubt that's gonna happen though.

 

[boomerangben]

Very instructive.

However it is possible that someone else put the matter of MCA legislation into your mind 2 weeks ago:

Bayesian.



.

As someone who has studied naval architecture although is not employed as such, I have been aware of MCA LY3 for a considerable time. But point taken - I’d forgotten you had quoted it earlier