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Re: [PSUBS-MAILIST] FW: sub ops
What exactly happened in Doug's incident?
-Sean
On 16/01/2011 6:01 PM, Sean T. Stevenson wrote:
I get the immediate impression that fore and aft (pitch) stability
analysis is probably not being given the same care and attention as
the transverse (roll) case in many cases. The same considerations
apply to both, and in fact an argument can be made that fore and aft
stability is more critical.
In any case, small vessels are inherently prone to significant motions
due to both the sea and the movement of occupants within, and
accordingly, MBTs should be designed to accommodate the worst case
scenario motions (i.e. all possible motions within the
point-of-no-return surface stability limits) without the loss of
ballast air. For this reason, I am a fan of totally enclosed MBTs.
Realistically, though, as PSubbers we are already making concessions
to our intended use - apart from Carsten, I don't think anyone is
meeting the mininum freeboard requirements of ABS etc. Commercially,
PSub size boats like the Nuytco Deepworkers must be hoisted on deck
before hatches are opened. At the Vancouver conference, by applying
maximum transverse thrust in alternating directions, at the natural
frequency of the vessel's roll, I was able to roll the DW to a pretty
good angle - and that was still on the hook! (Phil, if you're reading
this, I wasn't trying to break it - honest). The point is, it
wouldn't take much effort on the part of the occupants to put a
surfaced PSub hatch awash, so the question becomes, when determining
to what extent you comply with the commercial design guidelines, how
much safety do you make inherent to the mechanical design, versus the
operating procedures and simple assumption that the vessel occupants
are not going to put the vessel at risk?
As an off-the-cuff suggestion, it seems logical to me that a surfaced
vessel with MBTs blown should be able to accommodate its design crew
complement on the weather deck without significant risk of stability
failure, when operating in the design sea state.
-Sean
On 16/01/2011 5:16 PM, Alan James wrote:
Hi all,
This whole issue of buoyancy seems to have been under rated.
There was Tao Xianglis oil barrel sub that went bow up & had to be
dragged from the water.
Doug's Argonaut Junior surfaced too quickly & on the backward bounce
compressed his ballast air
& sank to the bottom before he could adjust it. & now Jim's boat.
It's a bit of a wake up call in this area.
Regards Alan
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