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

[waterpirate]

Here I think that the strong current would be a accepted reason over shaky navigation, also the depth would come into play given a failure. A post failure in 130fsw would not be as big a deal to me swimming back to get my deco gas. A failure in 165 may prompt an immediate ascent from my position on the wreck.

Tide can be a huge issue up here as well. Changing current,vis, temp, ect. My favorite tech charter suppy's and hangs deco gas starting at 40fsw, that does not preclude me from carrying my own bottle as well. It is just an un nessasary risk to stage bottles outside a wreck IMHO unless team supported/expedition type diveing.
Eric

 

[DevonDiver]

Here I think that the strong current would be a accepted reason over shaky navigation, also the depth would come into play given a failure. A post failure in 130fsw would not be as big a deal to me swimming back to get my deco gas. A failure in 165 may prompt an immediate ascent from my position on the wreck.

Are you assuming a longer chain of issues here? To abandon your deco gas, in result of a catastrophic valve failure/gas loss...and... no team mate available to share gas (1/3rd planning) for the return to your tanks?

If I lost back gas, I think that make me even more hungry to recover my deco tanks - as I now wouldn't be able to conduct deco on my back gas (if I could before). At worst, an air-sharing ascent to the MOD of my leanest deco gas... then relax...

Tide can be a huge issue up here as well. Changing current,vis, temp, ect. My favorite tech charter suppy's and hangs deco gas starting at 40fsw, that does not preclude me from carrying my own bottle as well. It is just an un nessasary risk to stage bottles outside a wreck IMHO unless team supported/expedition type diveing.
Eric

I've dived on dedicated tech boats that had surface supplied O2 at 6m etc... that'd make no impact on my decision to carry and/or stage deco gasses either. I see it as a 'nice-to-have', but not something that features in my planning.

 

[Ragnar]

I've occasionally left bottles on the outside but usually when entering to work a specific area rather than outright exploration. After knowing a wreck and if there is no other way out of that area than the way in I have no problem with it as if not returning to the same point deco is of little importance However, if exploring a greater area where there are most likely alternative exits I try to always take it with me as it opens up other opportunities if needed and I believe it is the safest way. Given that, if I know I'll be navigating some tight spaces I'll generally plan the dive with only one deco bottle AND enough back gas to deco out without it. I only dive back mounted doubles but with only one deco bottle it can easily be unclipped at the rear, swung forward, and held in front when navigating tight spaces. When going through smaller hatches usually all that is needed is the proper lean angle to get the bottle down more toward the corner of the hatch and get through diagonally, no need to unclip. For round hatches like in a sub that are really tight unclipping is needed and also let the air out of your wing for the extra few necessary inches. I guess I'm at the point where I begin to question weather I am someplace I should be if I can't negotiate an additional 40cf bottle. For more aggressive dives that require 80's the reward vs increased risk has to be seriously weighed as now you are talking a much bigger deco obligation AND the decision to leave them behind. Maybe in a harbor like yours and mine, but I sure wouldn't be monkeying around with that in the open ocean.

 

[Rhone Man]

I don't want to pretend I am some vastly experience wreck penetration diver (less than a dozen penetrations does not constitute any kind of serious sample), but based on my limited experience:

When I was taught about wreck penetration I was taught always to stow the cylinders outside (entanglement risk) and always to run a continuous guideline attached to the same point. That made sense to me, and the training was predicated on the basis that you would be twisting and turning through narrow passages with lots of entanglement hazards and sharp edges, and the risk of silt-out was very high.

Post-training, I realised that actually very few of my penetrations were ever likely to be what I had trained for. In fact, thinking on it now, I cannot recall a single penetration I have done that was like the books suggested they would all be (although maybe that says more about me...). Accordingly, most of them I do have the freedom to move about, even carrying one or two cylinders.

And I am always mindful of another experienced wreck diver who once told me - if things ever go wrong, you really do not want to be separated from your gas if you can possibly help it. So I tend to carry them with me. If I knew the penetration meant I could not, then I would stow them. But that hasn't happened to me yet.

 

[waterpirate]

Devon,
My failure chain supported carrying the stages. I.e. if the post had a failure, if you have your stages clipped off to you, you could begin an immediate ascent without haveing to go recover your stages at x place.
Eric

 

[DevonDiver]

Eric, makes sense... it does potentially cease a failure chain... no argument with that. That said, a properly planned tech dive, should permit recovery of stages, even allowing for failure/unforeseen deviation in the first instance.

Thanks for the input - I'm not arguing... just pushing my knowledge and challenging my own ways of thinking.

 

[Bombay High]

In my opinion, having all my gas with me allows me to stay focussed in the event of a problem. I have less to think about, and I am confident in the fact that I have all my gas with me and therefore more time.
Having said that, I will never penetrate a wreck to the point where access is difficult with the gas I am carrying.
If I cannot go through with all tanks, then I do not penetrate any further.

On a separate note - is there a link to the Rouse accident / incident ? Cant find anything through the search.

 

[DevonDiver]

The Rouse accident/incident is described in 'Shadow Divers' and several follow-on books on the same subject, incl 'The Last Dive'.

In summary, a father/son team did a deep air dive and penetrated a u-boat. The son got trapped by falling debris - causing severe narc/panic. The father entered the compartment and freed him. They exited via an alternative egress, both now heavily narc'd. In their confusion, they mistook the layout of the wreck and searched in the wrong area for their (staged) deco tanks. Having blown their bottom time, not found their deco tanks, they began an ascent. Panic followed them and the son accelerated to the surface (Dad followed), blowing all deco. Dad died soon after surfacing. Son died later in hospital.

 

[boulderjohn]

Chris and Chrissy Rouse were a father/son diving team who met their end while diving the submarine featured in the book Shadow Divers. Their deaths are discussed in that book, and they are the subject of the book The Last Dive. Because they were alone during the key parts of the story and because only Chrissy could describe what happened while in intense pain, it is not totally certain what happened. They were planning to investigate a specific section of the submarine, at a depth of 230 feet. The father (Chris) had had some financial setbacks and decided they could not afford helium, so they were diving on air. Chrissy went into the heavily silted out section by himself because there was not much room, while his father stayed outside the hole through which he entered. Chrissy took a reel with line for navigation.

Apparently some sort of fixture collapsed on Chrissy, trapping him. Chris realized this and went in after him. He managed to free him, but in doing so created a total silt blackout. Somehow they lost the line they were using--it was found to be doubled over, etc. (I am hazy on that part.) They finally found an exit, but it was not the one they had used to enter. Not finding their deco bottles there, they were now apparently confused by narcosis into thinking their bottles had been taken and did not know what to do.

Their friend Bernie Chowdhury had earlier been in a somewhat similar situation and had gone to the surface. He was seriously bent as a result, but he recovered through intense recompression treatment. The Rouse's apparently decided to do the same thing, even though they really had other, better options. Chris died on the surface; Chrissy made it through some recompression treatment but eventually died. The autopsy showed that his heart had nothing but foam in it.

I wrote this from memory and would welcome any corrections on the fine points.

EDIT: Andy beat me to it.

 

[Dive Bug Bit Me]

I've been enjoying this thread as it's making me consider my approach.

The exploits of the shadow divers were unbeievable. I have the utmost respect for all involved. My recollection was that the wreck is at about 220ft. I have never penetrated a wreck below 140ft, so I am beyond my experience here.

Hypothetically, I would plan this dive with Trimix. I would also probably sling an 80 of oxygen, and an 80 of deco gas for deeper (somewhere between 100 ft and 70 ft). Now I have double 120s or 130s on my back and two 80s under my left arm. This is only one 40 short of the configuration that I used to get wedged in one of my previous posts.

Now I imagine wearing that with a life raft (if memory serves) falling onto me while inside a tight submarine at depth. Those guys were pushed to their limits to get Chrissy free with no stages hindering their arm movents or providing extra entanglement risks and bulk. Long and short of it, in their case with tight space and the entanglement issue, I am not convinced they would even have made as far as they did with an extra two 80s clipped on.

Then again, it's easy to arm chair quarterback a situation that would frighten me even at 5 ft of depth.

On a separate note, I will never stage my gas well inside the wreck. It's either within 2 ft of the exit, or clipped onto me.