Tech Wreck - Opinions on staging your deco tanks for penetration?

[syntaxerrorsix]

I keep my bottles with me on open water dives. I've not had the need to leave a bottle in order to penetrate further. I'm new to caves and working my way through apprentice currently but we stage O2 as there is nowhere else we could use it.

 

[waterpirate]

I think the results of Devon's poll speak for us all. Once you get to here, it is all individual or team risk management. There are to many variables to throw a dart at one scenario fits all. This discussion has pretty well covered all the aspects that boil down to what or how much risk are you willing to accept for the desired result.
Eric

 

[DevonDiver]

Eric - yes, I am actually really pleased with the poll. I didn't know if there were any 'strict methodologies' out there, as a product of agencies or regional variances. Seems that there isn't - where a yes/no is chosen, it's a personal preference, not a taught principle.... same is true for the risk assessment based decision.

70% will stage cylinders - dependent on risk and goal.
Less than 20% have a firm principle to never or always stage.

 

[Ragnar]

I didn't know if there were any 'strict methodologies' out there, as a product of agencies or regional variances. Seems that there isn't - where a yes/no is chosen, it's a personal preference, not a taught principle

I'm sure it's not a huge surprise there is actually a procedure with GUE. For wrecks gas is always carried, while for caves it is never carried past its MOD. I think the reason being is that there is usually no other exit in a cave whereas there usually is in a wreck. Also the fact that there has been only one death that I know of due to a collapsed cave (Parker Turner), while in wrecks there is a much higher chance that rusted metal may collapse or something will fall blocking the exit. Sure, we plan gas for delay, but after dealing with something like that and finding another exit there "may" not be enough gas to also root around looking for deco gas leaving ones options very limited.

 

[DevonDiver]

I'm sure it's not a huge surprise there is actually a procedure with GUE. For wrecks gas is always carried, while for caves it is never carried past its MOD. I think the reason being is that there is usually no other exit in a cave whereas there usually is in a wreck. Also the fact that there has been only one death that I know of due to a collapsed cave (Parker Turner), while in wrecks there is a much higher chance that rusted metal may collapse or something will fall blocking the exit. Sure, we plan gas for delay, but after dealing with something like that and finding another exit there "may" not be enough gas to also root around looking for deco gas leaving ones options very limited.

That's interesting - and was actually going to be the next question I asked: whether diver's had been taught a specific process (stage/not-stage) - taught as in 'agency materials/written in a manual' rather than the personal opinion of their specific instructor.

I can understand the GUE perspective on this - the thinking is rational - but it is also extremely limiting with regards to the scope of access/penetration accessible when wearing all your deco cylinders. In that respect, there seems to be a 'tacit' disapproval of diving into/through extremely limited/restricted areas in a wreck? Basically.. 'swim through', but no 'crawl through'?

 

[Ragnar]

I can understand the GUE perspective on this - the thinking is rational - but it is also extremely limiting with regards to the scope of access/penetration accessible when wearing all your deco cylinders. In that respect, there seems to be a 'tacit' disapproval of diving into/through extremely limited/restricted areas in a wreck? Basically.. 'swim through', but no 'crawl through'?

If it is a strict carry what ya need at all times I guess that is the case, at least on deeper wrecks where larger bottles are needed. Some of this is dealt with via the use of rebreathers, but then what they do with additional bailout bottles I have no idea; probably they have a continuous circle of support divers surrounding the wreck Virtually any sub hatches are a crawl through so I also wonder how GUE would handle a deep dive like that. Of course a sub is a special case which may also only have one entry and exit and "could" be treated like a cave, but my guess is for bigger wrecks you are getting into places that 99% of GUE divers would just simply never go. I know in their cave diving when they get to a restriction that cannot be negotiated with back mounted doubles/rebreather it is simply the end of the line. If, as I understand it, in wreck diving there is no deviation from carrying all deco then the end of the line would come at whatever restriction could not be negotiated with all bottles.

 

[Kevrumbo]

What Can Go Wrong On a Wreck Penetration Traverse ( not taking your Deco Bottle on the Penetration). . .

My incident on the Irako Wreck, Coron Bay Philippines (2007):
Buddy and I made a traverse on double AL80's 30/30 mix, up the propeller shaft tunnel starting at about 39m max depth, and exiting at 28m through the Engine Room Skylights to the deck level.

We lost direction of where the Eanx50 deco bottles were stashed at the deck level; circumnavigated nearly entire shipwreck after egress, and found deco bottles again at MGR (Minimum Gas Reserve/Rock Bottom) Condition Serious (buddy's MGR was encroached being "Critical/Grave" to imminent Out-of-Gas condition); Original Deco Profile was discarded and recalculated on-the-fly; after switching to Eanx50, arrived at the 6m deco hang bar at the same time the boat crew shut-off the surface supplied Oxygen to change out a just expired T-bottle; did backgas break shortly exhausting entire backgas supply, and then switched back over to Eanx50 while waiting (and hoping!) for the surface supply O2 to open up again.

Lessons Learned: sketch the shipwreck in your Wetnotes, with directional "landmarks" (i.e. prominent ship's points & features) to aide in locating your Deco Bottles --if you must leave them at a location other than your point of initial entry . . .Because of ship's symmetry at the amidships egress location along with poor viz, we were mistakenly led to the forward mast instead of the aft Kingpost where we actually placed the Deco Bottles.

A simple wetnote sketch of the shipwreck along with writing down a general compass heading would have prevented this incident. . .

 

[Bombay High]

Devon and Boulder - That is a truly tragic story ...

Kevrumbo - Your kind of story is the reason I carry all my gas with me.