Wednesday, February 27, 2008

Open or Closed Manifold ?

In the last blog I talked about Hogarthian equipment configurations. It is one thing knowing what a Hogarthian configuration is, quite another to adopt it into your diving philosophy and equipment configuration. What I like about Hogarthian is that most of the hard thinking has already been done! You are being handed a solution that not only has been thoroughly thought out, but has been a decade or more in the testing.
My biggest issue with Hogarthian is that it takes away a certain degree of personal responsibility … all that thinking has been done for you. This can lead to blind adoption and a false sense of security. What do I mean ? Well blindly adopting anything (be it a philosophy or an equipment configuration) will only get you so far. Sooner or later you will come up against something that the designer had not thought about or considered. It is at that point that the system has the potential to fail spectacularly. Having said that, there are not many situations that would fall into this ‘new’ category, especially if your technical diving is within agency limits and well explored dive sites. The problem comes in when you decide to do something that has never been done before.
Key to any successful exploration is the ability to assess the individual risks of the situation you are trying to ‘conquer’. When new risks are identified the entire process of planning a dive needs to come under review and if required, adapted to ensure that every probable risk is mitigated. For me, that means adapting my equipment configuration and that often takes me away from pure Hogarthian. It needs to be said that if you are new to technical diving Hogarthian will get you far and you will probably never need to contemplate changes. However, there is still a school of older, hard core divers who are set in their ways and believe that their way of diving is the best. Which is ok, every diver has the right to choose for themselves (after all the person who pays the price when it all goes wrong is that diver ) however many of these older divers have some influence over the next generation. As a result many old school ideas are still alive and well, when they possible should not be.
My personal equipment configuration was designed to do one thing - gett me to 200 meters or deeper. It was not something that I arrived at on the actual expeditiaon, but rather was prepared years before. This meant that every dive I did was a build up for that elusive deepest dive. The configuration I chose mitigates my biggest fear and risk, namely running out of gas and to that end I quickly (as soon as they became available) moved to an isolation manifold. However, I do not dive my manifold open, nor do I dive with a single spg or both dv’s coming over my right shoulder.
My choices were made to accomplish 4 things:
1) Safeguard at least one half of my gas supply,
2) Enable quick identification of the gas supply that is at risk (left or right cylinder),
3) Limit my immediate task loading and ensure that I am able to retain buoyancy and line control and
4) Ensure that I always know how much gas I have left so that I have the option of a more aggressive survival strategy.
I am not trying to prevent gas loss, but protect what I have and there is the big difference. I am also managing another huge risk, a bottomless, fast descent which is a characteristic of a deep bounce at Boesmansgat. This is the world’s 3rd largest water filled cave and when you do dives deeper than 60 meters you have 200 meters of black water beneath you. Your only connection to light and home is the shot line, that hangs in the middle of this vast black expanse. If you come off that line there is a very, very good chance that you will not find the entrance again.
When I plan these bounces I visualise what will happen in say the even of a catastrophic gas failure. I am descending the shotline… fast. I hear a flood of bubbles. I can’t let go of the line, so have to first gain control (slow or stop), then identify the side that is causing the problem (left or right). If I am close to my target depth the situation is even more critical because I can not afford to go deeper than planned without throwing my decompression out and creating a possible situation later on that I will not survive.
As I have my dv’s over each shoulder, should the problem be with an SPG or power inlator or second stage locating the source of the problem is fast and requires little thought. I like little thought, because initially a large portion of my concentration is busy maintaining control and keeping myself safe. Once I have worked out what the problem is and have control, I can shut the appropriate valve down and assess the damage. At no time have I lost control or lost more than one side of my twin set. I still have buoyancy and I am still on the line. At the most I have sacrificed one half of my gas, and I have already planned to lose that so I have plenty in reserve.
Now the counter arguments to this strategy are that it should not take me more than 30 seconds to isolate. But that is a lot of air you lose, out of both cylinders when deep, possibly everything. In any other situation I agree and in fact when I do normal technical dives I tend to relax and dive my manifold open because when something goes wrong I can immediately focus on the problem without complicating the situation. However, when something goes wrong on a deep bounce there are a whole lot of things that have to come before I can safely get to isolating. And all the while I am losing precious gas.
They also say that diving closed manifold adds to my task loading because I have to change dv’s regularly in order to ensure that each cylinder has more or less the same amount of gas in it (if you dive single cylinders with no balancing of pressure open yourself to the risk of breathing one cylinder down to reserve and then losing the full cylinder, which means that you have no gas. If the pressures were balanced then you would have had at least half of the gas you needed).
I do not agree that the task loading is a significant enough risk to avoid and have been changing dv’s for over ten years so it is no longer something I have to think about. I also plan for dv changing as well as to not change dv’s in the last 50 meters of a deep bounce (accepting the risk of a single cylinder having a significant difference in pressure from the other).
I already know that it will take me time to get to the point of isolation just based on the dive I am doing, add to that the time it took to identify the problem and even if you could isolate in 30seconds, you could be closer to a minute in getting that manifold closed. Every second is precious, a minute… that is both my back mounts. That is if I can actually get to isolating and am not in the middle of a task loading crisis (events never happen one at a time). The longer I delay the less air I have. My back mounts inflate my wings, no gas means I now have another issue, I have to hook up my wings to an alternative inflation source, all the while hanging from a line I can not loose. When my manifold is closed there is no stress, at the most I am going to lose one cylinder and I have planned to get out after that.
I doubt that I will ever be able to rationalize or practice my fears away and fully trust the pure Hogarthian configuration. My diving career has taught me to take responsibility for myself and to accept all the consequences of a dive. That means I need to have thought it all the way through, challenged all the standard ways of going about things and then assessed the risks for myself. I have no intention of re-inventing the wheel, but I want options. I have also found that in many cases people do not understand the motivation behind a decision. Why dive with an open manifold. By making it my business to understand the why I give myself the option of making changes and it is that ability that enables me to solve problems that other divers on standard configurations have been deemed impossible. It is not an approach for everyone… but it does have its advantages.