Bourbon Dolphin capsizes

Guillermo my friend,

Whilst you are brilliant and I have a lot of respect for your ability with a pencil and a calculator/ababcus please rememeber that whilst all Naval Architects do most all of their work using math; God, Chance and Lady Luck have never heard of mathematics and there are times when all your fine calculations just go to rats! Which is of course why you invariably allow a certain amount extra for ??????? Your vessel above, which you state is bigger than the BD and is also a straight anchor handling tug (there are differences - small but there are) the margin for error, given that the statement was for weight in excess of 300t doesn't appear much does it? minimal to say the least really!! Still will be interesting to see what you produce!

Mike (the Walrus)

 

I'm afraid that's not entirely true. Let's see:

"According to legend, Pythagoras, by divine guidance, discovered the mathematical rationale of musical consonance from the weights of hammers used by smiths. He is thus given credit for discovering that the interval of an octave is rooted in the ratio 2:1, that of the fifth in 3:2, that of the fourth in 4:3, and that of the whole tone in 9:8. Followers of Pythagoras applied these ratios to lengths of a string on an instrument called a canon, or monochord, and thereby were able to determine mathematically the intonation of an entire musical system. The Pythagoreans saw these ratios as governing forces in the cosmos as well as in sounds, and Plato's Timaeus describes the soul of the world as structured according to these same musical ratios"

As we see here, maths and the gods are in intimate comunion....

 

As we see here, maths and the gods are in intimate comunion....
Do you think, you could give me maths lessons, IF i supplied the wine, not your Espanol stuff, neither your Fr. or Georgian, but some good vin rouge from here or S.A.?

 

Not my Gods mate!! Good smiths who make good tools but none of this namby pamby stuff about poetry!

If it ain't drum and bugle it probably ain't worth playing anyway!!!

 

ll

im not guillermo but here goes .the square root of 1is 1 . if you put 2 and 2 together you get the answer .sometimes its 4 and sometimes its 22 it depends wich way you look at it [punn intended] now can i have the wine

 

I said I cant do math, but rithmatic!! yes I can do mental stuff with the speed of summer lightening
Um well i could post you some Spanish stuff

 

I think the first picture should be mirrored. Seams like it's listing to stard board.

Annyone good with photoshop that could play around making a good photo ducumentary?

 

The report of the Sunnemore District Court has been published, posted on Bourbon website. This official record varies at times from the previous news reports (no surprise ). One noteable difference is that testimony by the 2nd mate states that, when the starboard inner pin was lowered, the line whipped across the stern to the outer port pin and did not ride over the cargo rail. He states that there was a severe list to port at this point. He goes on to state that Bourbon Dolphin was "drifting at high speed towards port" and that "large parts of the cargo deck disappeared under water". "At this moment", he says, "both the main starboard engines had stopped. The vessel was now listing 90 degrees."

This testimony, of course, differs significantly from the earlier reports and diagram in various newspapers claiming that the line was over the cargo rail and leading over the side. More questions will likely be raised about stability.

Equaly important, IMHO, is the testimony here by BD's alternate captain that, more than once during the planning meetings, concern was expressed over Bourbon Dolphin's ability to handle the main load at those depths. He is firm in his statement that the plan as developed had Bourbon Dolphin assigned the assist role, not primary.

http://bourbon-online.com/media/corporate/xs_9376_bourbon_offshore.pdf

 

Most interesting, Charlie, although somewhat confusing to me.
I have doubts about the 90º list.
If the chain did not went over the side....What kind of forces are needed to capsize a vessel like this pulling from the outwards port pin? Huge, indeed!
Interesting to know GM was 0.26 m when leaving Lerwick.
Cheers.

 

Thanks Riggertroy for the info on your boats (nice spreadsheets). This confirm the trend in higher VCG's, especially on the latest HATS.
Guillermo, we are working on some loading conditions.

In the report of the Sunnmore District Court (thanks Charmc) two things caught my eye:

1_ A departure GM of 0.26 m = 0.853 ft
No doubt it met the IMO stab criteria and it gives a comfortable ride, but in my books I would prefer ~2.0' = 0.61 m
some of you would complain... too snappy? How does that compare with the Royal Navy SafeWalrus?

2_ The passive stabilization tank being used during anchor handling.
All the water went to the low side and aggravated the list?

 

I'll love to know your results.

Yes, seems pretty low for me too, even for a departure from port condition....and for sure not enough for anchor handling operations, in my opinion.

That may very well have happened.

Very interesting.

 

Confusing to me, also. I leave analysis of data to you and the others who are professional designers and NA's.

I suspect the testimony about a 90 deg list was figurative, meaning it was extreme and beyond the point of recovery.

One question seems crucial from an operations standpoint: Why was BD's role changed from assisting to primary tug?

 

Do they measure GM when under way with the passive anti-roll system working? That would produce a distorted result, wouldn't it? Anybody knows?

 

If when sailing from Port the passive anti roll tanks where in use the free surface moments would (should) have been included.
Personally I find the GM to be extremely low, I would have to work very hard on the AHTS, AHT, PSV vessels I have served on to achieve such a low figure, have a play with the spread sheets I posted earlier and you will see.
I would like to know what the tank loadings were and why they had such a low figure.
From memory we never had a GMf < of less than 1.0m when handling anchors.

 

You will note that I pointed out early on in this thread the fact that this vessel was very narrow [17m] for an anchor handling vessel. Also note the speed advertised at 17+ knots. In this case, speed killed.

In my experience, and I have designed many PSVs and AHTS vessels, the worst case for stability is never the departure condition, it is the 10% condition. In this case the departure condition was noted at .23m GM. They then traveled to the site burning fuel, and then deployed anchors, which removed chain from their lockers. All of this would tend to increase KG therefore lower GM. However I would surmize that the .23m GM was a transit condition and not anchor handling, for which they should have had another condition run. The transit condition would likely have included the anti-roll tanks while the anchor handling condition should not have them included. Anchor handling should NOT be done with anti-roll tanks active, especially if your GM is as low as it obviously was. The testimony noted different opinions on the anti-roll tanks, with one witness saying they were active and another saying they were not. Likely both were correct in that they were active in transit but not active when anchor handling.

I have never designed an AHTS with a GM [worst case] of less than .8m, and that one often concerns me. While I am sure that the BD met the stability criteria, there was just NO margin, and personally as a designer of this type of vessel, I do not feel that this was prudent of the designer, the shipyard or the owner. Everyone can make a mistake, but there are obvious solutions to problems such as these. It is called fixed ballast and many vessels are fitted with it.

On anti-roll tanks, the free surface is taken into account in the loading conditions, based on the level of water in the tanks. It is a simple reduction in the vessel's GM due to free surface, no more, no less.