Bourbon Dolphin capsizes

The lightship VCG we used was too high. Using the M.D. height will be a good start. In our calcs they used the 300 Tons on the stern and side as per the Norwegian sketch we posted on page 3. Since then, we have learned that this sketch is not accurate. We are told by our office in Aberdeen that loosening those buried anchors out of the mud is still one of the most critical & demanding phase of the job. It is easy to swamp the stern or exceed the rating of the equipment. We will look at some inclining reports.

So far we think all contributions to this topic have been valuable, even from 'them' Limeys, Aussies, Kiwis, Coonasses, etc.

 

Thanks a lot, smartbight. We'll do our simulation based on MD level, for the time being. Let me know what your inclining reports say about lightsip's VCG average position.
Cheers.

P.S. Excuse me for insisting, but may we call you by your first name, instead of 'smarbight' ?

 

Rigertroy; We could use your info. In your trim & stability booklet, there should be a maximum deck cargo condition. Can you take a digital picture of that condition and post it (usually works better & faster than scanning or typing all the items, weights, cg's etc in a table?) You could cover the boat's name if proprietary info is involved.

 

I hate to say it but one of the problems with all this maths etc. is that in "real life" as laseyjack so succintly puts it! and as 'Smartass' or is it 'bright (come on buddy you gotta get a better handle than that it's open to lots of p*ss take!) the breaking out of the anchors etc is a big inponderable! considering the weights involved at these depths (****, they were heavy 'inside' the North Sea!). A 'beeeg' Margin of error needs to be applied at all times (nobodies told the mud or water about all this math). You JUST CAN'T work to fine tolerances up there when you can't see what's going on! something will always upset 'the applecart' as here!!! There's a time for fineline maths and a time to leave it alone!!

So Guillermo I know over the times we've 'chatted' that your bloody good at what you do, but there are times when, in the marine environment especially, we just got to back off the technical stuff and leave it to experience and feel! And sometimes the 'practice of good seamanship' gets it wrong too! (refer to another thread of yours, mate!! a good one [interesting and thought provoking - as always] I might add)

 

Maybe I lost something in this discussion, but what does the type of bottom have to do with anything? They were setting the anchor, as I recall, not picking it up.

 

Yes, Mike. But we are trying to find out here what killed those men: mathematics...? experience and feel...?
Nice to have working together both expertises in this thread.
Cheers.

 

Archy, absolutly buggerall, they had to put the thing down somewhere! The bottom of the sea has a lot to do with it, after all that's the general idea! Stick an array of weights tied to the rig on the bottom and the thing may stay in one place! No bottom no anchoring! sorry being vercicious!

At the time of the job probably nothing but overall it's important that you are aware of ALL the factors affecting the job - maybe in your view it doesn't but to me it's like saying "when you go to the toilet first check nothing will drop out of your pockets when you drop your pants" why your having a cr**, pockets don't come into it - but think about what happens after you stand up! You gotta look at the big picture!

 

Our Operations Dept. in Aberdeen wants answers ASAP. They don't care if we use math or whatever. They say some of their crews are real nervous "New state of the art boat, good weather, turtled in 5 min.??" I can't blame them.

The Port Captain had found & emailed a Norwegian sketch and told us to look at stability during a typical anchor 'break out' phase. He was sure this was it! Since then, witnesses have described a different situation. Also I am not sure snagging can be ruled out. BD was ~ 5000' from the rig

 

For the record I understand anchorhandling and the effect that the type of bottom has on the process. But the type of bottom more influences the type of anchor used, Bruce, Vryhof, etc.

It was stated that the BD was maxing their thrusters so they didn't DRIFT into anchor 3 [already set] with anchor 2 [trying to set]. This means that they had the anchor suspended below the boat carrying the weight of the anchor and chain plus the cantenary. The type of bottom only would enter into the situation if they were PULLING the anchor, which they were not, they were SETTING the anchor. My point is this. Bottom type does signifigantly matter in anchorhandling, but it had absolutely nothing to do with the BD capcizing, hence it lends absolutley nothing to this discussion.

I would also comment that at 1300m water depth I think it is getting pretty close to what is safe for common fluke type anchors and chain. In the GOM we have gone to suction piles and synthetic for deeper moorings, just because of the potential for issues like this due to the very large weights involved with conventional spreads.

 

smartbright,

Opinion only here, but if the anchor was set, as I just said, they would not have had the problem of drifting into anchor 3. You don't pull anchors over the side, nor do you set them over the side. However, if you are pulling the anchor you don't have the full weight on the boat so you can better keep the chain/cable/whatever over the stern. If you are losing the angle and risk tripping the pins, you back off. The weight is on the bottom, not suspended.

Totally different if setting an anchor.

 

Absolutely

I'm lost now.
Don't we have a photo from BD, 40 min before capsizing, carrying the anchor on deck? Don't we have Geir Syversen's testimony?

Snagging may be an strong possibility, indeed. A 'colossal' increase of tension in the winch was reported by Syversen before the listing leading to capsizing, while when the HV had previously lost grip on the chain, he referred to it as 'small'. See post 115.

P.S: Well, it may very well be that Port Captain is also thinking about snagging. The effect on the vessel should be similar to that produced by a break out phase with anchor not giving way (but BD would not had listed to port but to starboard.... )

 

Initially I thought it was a synthetic rode. I was surprised to learn they were using chain for those depths.

 

Gathering several excerpts:

"We experienced a colossal increase of tension. It was very clear that something had happened
........
Now the Bourbon Dolphin started to list a little towards port........ Even with the use of all engine power and all the thrusters they drifted towards anchor number three.
..........
After a few seconds the captain managed to change course some degrees towards starboard. The tension on the anchor chain was reduced a little so that it was possible for the chief mate to lower the pin. After that things happened very quickly.
.........
The chain rushed across to the portside outer towing pin, then it went over the side of the boat. The vessel was listing hard to port as well as drifting quickly to port.
.........
... it seemed to turn sharply and the anchor chain jumped out of the mechanism at the rear of the deck which held it. As the chain ran across the deck, the 75-metre tug lurched one way, then the other, before overturning."

Snagging, full power, and the lowering of the starboard pin combined....???

 

quote form Guillermo: "I'm lost now. Don't we have a photo from BD, 40 min before capsizing, carrying the anchor on deck? Don't we have Geir Syversen's testimony?"

Hi Guillermo
The anchor on deck was most likely for use on another leg of the mooring system, see the pic, and before anyone comments - the gear was rejected and taken off the vessel as unfit for use - was loaded back a few days later and much more neatly, as well as new sockets and other fittings, just thought it might give people an idea of what the deck of an AHTS looks like at the start - some points - water depth between 60-100m, no chain and using suitcase buoys as opposed to the chaser system that I assume the BD was using.

 

Thanks, riggertroy, but I'm still confused.

Another doubt: The BD had filed out 1800 m of chain and deepness was 1300 m. How would it be possible for the chain to get tangled in the bottom? Not enough length of chain.....