Wireless

[darkpup]

Not to jump over you on this, but waiting until close to rock bottom to surface is really not a great solution as your rock bottom number has changed due to the increased gas loss. In an emergency where your buddy needs to rely upon your gas supply there may not be enough to make a safe ascent.

On the other hand, I wont be hypocritical and say that I have never dove with a slow leak at the yolk vavle before.

I'm not worried about it. I came up with that scenario to see if anyone would address it as you did.

I think the key word in my original statement was "close" to rock bottom. Close could mean 300psi, 500psi, 800psi, Xpsi to rock bottom, and that safety margin, taking the leak into consideration, is flexible based on the type of dive you're doing along with how your team decides to address the issue. Whatever margin of safety you decide to take would be your "close" to rock bottom amount.

Does this make sense?

~ Jason

 

[darkpup]

Wouldn't the more genernal DIR answer to the question be - the only redundant equipment needed is the minimum equipment for life support that will insure a safe and independent ascent to the surface?

Yes, if that answer works for you. Your answer approaches the question from the core fundamentals of DIR and its minimalist approach to diving. This works for some, but not all.

Some people learn differently, and come at the question from different angles to reach the same level of understanding that your answer does for you.

It's not wrong to question DIR. It's just wrong to troll in the DIR forum

~ Jason

 

[dtkachev]

I don't know too much about it, but based on what I have learnt is that DIR was developed based on experience, and its development was/is based on people asking questions. The only way to learn is to ask questions, and I don't see any need for anyone to get heated about something, especially when you are trying to explain something.

I believe that the only way to learn is to question things until they make perfect sense for an individual who is learning, and the only way for it to happen to provide a logical validity of the point. By heating up, the point anyone is trying to prove will not be any more logical or legitimate.

In my opinion, DIR is so good because it is based on experience and logical reasoning achieved through questioning. And the only way for it to maintain its status of being as good as it is, is for people to continue questioning every single aspect of it, as it will keep DIR on the edge of better and safer diving.

The only way for people to become better is to question things, and if you are true believer in DIR you will take your time explaining things to people that are seeking advice and are willing to learn. There never is a stupid question, especially when the life of at least two people is dependent on the question.

Once again, I may be wrong, but those were my two cents on the discussion becoming so heated. Speaking about the original question, having two spg's will make me less sure about the gas supply i have available, as I will be not sure which of the two spg's is broken, which of them failed if there is no visible damage. If one of them fails, I will call the dive as it is, at least for me, and my buddy, I believe, it is safer [exactly the same sequence as I would do with one spg, hence the redundancy is spg's will not help me, and will introduce another point of failure on the first stage]. Once again, it depends on the risk margin your team decided to accept.

I may be wrong with what I am say, if I am, don't take it personally, I would truly appreciate your explanation.

 

[Kevrumbo]

The only Open Circuit Bottom Mix situation I can see having two analog SPG's is if you're diving Sidemount/Independent Doubles. Entails a different process for Gas Management as well as general technique; very specialized and not a common operating procedure within the DIR realm. . .

 

[MonkSeal]

The only way for people to become better is to question things, and if you are true believer in DIR you will take your time explaining things to people that are seeking advice and are willing to learn. There never is a stupid question, especially when the life of at least two people is dependent on the question.

I agree with you but at the certain point when question is answered and explained I realy see no reason for additional explanations when everything is clear.

Speaking about the original question, having two spg's will make me less sure about the gas supply i have available, as I will be not sure which of the two spg's is broken, which of them failed if there is no visible damage.

Just want to stress one thing (I believe that it was metioned earlier in this thread but it seems that's not noticed): You have backup SPG. That's one that is clipped to your left hip D-ring. Your primary SPG is your bottom timer. Knowing you consuption per e.g. 5 min time segment (in psi/bar) for particular tank(s) at particular depth, you can easily know how much gas you have. Quick glance to SPG will confirm that (or not ).

 

[DIR-Atlanta]

The only Open Circuit Bottom Mix situation I can see having two analog SPG's is if you're diving Sidemount/Independent Doubles.

Independent doubles are not DIR, therefore sidemount diving is not DIR. Sidemount diving is a whole different thought process from a gear configuration standpoint, and DIR principles don't really apply there (other than the general recommendation of streamlining to reduce entanglement hazard).

 

[DIR-Atlanta]

Having two of something doesn't mean I'm twice as likely to have a problem! If I owned two cars, I'm not twice as lucky to have car trouble keeping me from getting to work.

If you and your co-worker drive separate cars to work, then that doubles the chances that one of you will have a flat tire, versus making the same trip if you ride together. Doubling the exposure (in this example, the number of tires in contact with the road), also doubles the risk of failure.

Silly logic...

Not silly at all - as rjack321 pointed out, it's all a matter of probabilities, which are mathematically calculable.

Um, a man with one watch just knows what time the watch reads. Nothing more, nothing less.

If you ask a man with one watch to tell you the time, what does he do? He looks at his watch and tells you what it says. It's the same with your SPG. If you have (in effect) two SPGs, how do know which one is accurate?

If you want a backup to the SPG, then use your bottom timer or your buddy's SPG (as has been suggested). Either one will work for that, provided you know something about your respective SAC rates.

 

[Rainer]

If you and your co-worker drive separate cars to work, then that doubles the chances that one of you will have a flat tire, versus making the same trip if you ride together. Doubling the exposure (in this example, the number of tires in contact with the road), also doubles the risk of failure.


Not silly at all - as rjack321 pointed out, it's all a matter of probabilities, which are mathematically calculable.


If you ask a man with one watch to tell you the time, what does he do? He looks at his watch and tells you what it says. It's the same with your SPG. If you have (in effect) two SPGs, how do know which one is accurate?

If you want a backup to the SPG, then use your bottom timer or your buddy's SPG (as has been suggested). Either one will work for that, provided you know something about your respective SAC rates.

My questions were all answered, but for some reason you're having trouble with what I think is really simple logic concerning the probabilities of independent operations. It doesn't matter that having two SPGs doubles the chance of ONE failing (add the probabilities). The point is that the chance of having a problem (which is NO spg) goes down signiticantly (multiply the probabilities). Given all the other responses, however, this just isn't important...

 

[Rainer]

If you ask a man with one watch to tell you the time, what does he do? He looks at his watch and tells you what it says. It's the same with your SPG. If you have (in effect) two SPGs, how do know which one is accurate?

And wrt this, you've got to be kidding, right? The point is, most of the time they WILL agree. Knowing that they don't agree is useful information (means there might be a problem). In fact, if you want to know which one is right, do what everyone has already said, use your brain and figure out which is correct based on your SAC, depth, and BT. With one SPG, you wouldn't know you had a problem unless you did these exact calculations. Look, I buy why the second spg isn't needed (thank you everyone for your responses), but your logic here is really off base!

 

[DIR-Atlanta]

most of the time they WILL agree. Knowing that they don't agree is useful information (means there might be a problem). [...] With one SPG, you wouldn't know you had a problem unless you did these exact calculations.

There is more than one way to determine that you have a faulty SPG, without the use of extra unnecessary gear. In fact, in most cases you don't even need a backup anything to tell if an SPG has malfunctioned. For example, if you are cruising along for a few minutes and the SPG doesn't move, then that's an indication of a problem - could be a faulty gauge, could be a left post roll-off. Check the post, and if it's on, then you know it's the gauge. Same thing if the reading drops significantly, without any obvious indication of a gas loss (i.e. no bubbles).

I'm sorry if you believe that I am over-simplifying. The gist of this is that there is more than one way to get the info that you need, using the resources (including instrumentation) that you and the rest of your team already have at your disposal. It does require a little more awareness and understanding of potential failure modes and their causes.

The point of the discussion is that the gauge should be used to confirm what you already know (or can calculate) from other independent sources. In effect, it becomes the backup. That's all we're trying to say.