Pony rigs

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Re: Pony rigs

Postby binklebonk » Tue Sep 03, 2013 1:14 pm

Let me bring in another reason (a psychological reason) I think 6l is a good amount (for diving within NDLs):

We adapt our behaviors when things change. You have a pony, it's "enough", it is change.
You will adapt your behavior as you now feel risk is reduced. That "enough" may no longer be enough for the situations you may get yourself in. We all do it to lesser or greater extent, it's called risk compensation. We do it whilst driving, cycling etc.

If you carry a surplus of gas your compensation adjustment may be within that surplus. Or not.

You might say, "well then what if you are carrying a 6l, won't that just drive a greater compensation?" No, not if the discussion is (as it is) bounded by the limits of diving within NDLs in non overhead environments.
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Re: Pony rigs

Postby rambaldi » Tue Sep 03, 2013 1:17 pm

Ulsterkiwi wrote:For a balanced discussion I would argue that the rig I have is useful within limitations as any rig will have limitations. I have seen the 3l v 6l discussion on other forums and inevitably people start quoting SACs, capacities and otherwise displaying their mathematical prowess to show how only a 6l is useful. Absolutely, it is twice as useful as my 3l but not nearly as useful as a 9l and so the merry go round continues.....


Exactly the reason I dive an 18l pony, I would go to the full 20l but it is too hard to get right numbers for importing them. :p
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Re: Pony rigs

Postby Ulsterkiwi » Wed Sep 04, 2013 1:59 pm

binklebonk wrote:Let me bring in another reason (a psychological reason) I think 6l is a good amount (for diving within NDLs):

We adapt our behaviors when things change. You have a pony, it's "enough", it is change.
You will adapt your behavior as you now feel risk is reduced. That "enough" may no longer be enough for the situations you may get yourself in. We all do it to lesser or greater extent, it's called risk compensation. We do it whilst driving, cycling etc.

If you carry a surplus of gas your compensation adjustment may be within that surplus. Or not.

You might say, "well then what if you are carrying a 6l, won't that just drive a greater compensation?" No, not if the discussion is (as it is) bounded by the limits of diving within NDLs in non overhead environments.


I understand what you are saying but I do not really accept that a quantitative calculation of available gas is sufficient evidence to make the assertion you have about what is essentially a qualitative concept, ie to what degree an individual's mind will engage in risk compensation caused by the presence of the pony of "n" size. In empirical evidence terms what you have done is measure the speed of a blue boat as being 25knots, classified 25 knots as being fast and have drawn the conclusion that the colour blue is fast.

Which brings me back to the point I have been trying to make. Perhaps I have not expressed it that well. Surely the thing to really get people talking about is not what equipment we use but HOW we use it....what is our mindset when we undertake any given dive and how have we planned or prepared for that dive.
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Re: Pony rigs

Postby Ulsterkiwi » Wed Sep 04, 2013 2:03 pm

rambaldi wrote:
Ulsterkiwi wrote:For a balanced discussion I would argue that the rig I have is useful within limitations as any rig will have limitations. I have seen the 3l v 6l discussion on other forums and inevitably people start quoting SACs, capacities and otherwise displaying their mathematical prowess to show how only a 6l is useful. Absolutely, it is twice as useful as my 3l but not nearly as useful as a 9l and so the merry go round continues.....


Exactly the reason I dive an 18l pony, I would go to the full 20l but it is too hard to get right numbers for importing them. :p


so what you are telling me is that if I keep using my 15l steelie as my back gas and sling the 12l ones either side I might be getting close to optimum? :wink: :lol:
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Re: Pony rigs

Postby binklebonk » Wed Sep 04, 2013 3:54 pm

Ulsterkiwi wrote:I understand what you are saying but I do not really accept that a quantitative calculation of available gas is sufficient evidence to make the assertion you have about what is essentially a qualitative concept, ie to what degree an individual's mind will engage in risk compensation caused by the presence of the pony of "n" size. In empirical evidence terms what you have done is measure the speed of a blue boat as being 25knots, classified 25 knots as being fast and have drawn the conclusion that the colour blue is fast.
Thanks for that particularly ungenerous reading. :roll:

The analogy would be smelling a little less of straw if you said the speed of the boat was 25 knots, the capacity of the tank allowed for 6 hrs motoring (300l) at that speed and a newly installed emergency tank allowed a further 1hr (50l). The skipper of said boat would then be at risk of compensating for the newly increased margin...

Why do you have an issue with using a qualitative consideration to inform a quantitative decision?

What I have said is that change drives adaptation, and that adaptation can have consequences. If you have just enough, that can become not enough. This compensation varies from person to person but is clearly demonstrated as a real world phenomenon. Should we not consider the most unreliable piece of equipment (us) in the planning?
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Re: Pony rigs

Postby Ulsterkiwi » Wed Sep 04, 2013 4:44 pm

binklebonk wrote:
Ulsterkiwi wrote:I understand what you are saying but I do not really accept that a quantitative calculation of available gas is sufficient evidence to make the assertion you have about what is essentially a qualitative concept, ie to what degree an individual's mind will engage in risk compensation caused by the presence of the pony of "n" size. In empirical evidence terms what you have done is measure the speed of a blue boat as being 25knots, classified 25 knots as being fast and have drawn the conclusion that the colour blue is fast.
Thanks for that particularly ungenerous reading. :roll:

The analogy would be smelling a little less of straw if you said the speed of the boat was 25 knots, the capacity of the tank allowed for 6 hrs motoring (300l) at that speed and a newly installed emergency tank allowed a further 1hr (50l). The skipper of said boat would then be at risk of compensating for the newly increased margin...

Why do you have an issue with using a qualitative consideration to inform a quantitative decision?

What I have said is that change drives adaptation, and that adaptation can have consequences. If you have just enough, that can become not enough. This compensation varies from person to person but is clearly demonstrated as a real world phenomenon. Should we not consider the most unreliable piece of equipment (us) in the planning?


Ungenerous? Not the intent. Critical analysis is not intended to be an emotive response, simply a consideration of the evidence presented.
I have no issue with mixing qualitative and quantitative approaches but by definition a qualitative consideration cannot be an absolute measure of a quantitative variable. Calculating the potential motoring capacity of a boat cannot be done by a description of the mental approach of the skipper driving it.

Your argument (which I happen to agree with) seems to be that we are dealing with a complex situation (contingency planning) and quantitative variables can only model it (how much gas is available, SAC etc) but any prediction we make using that model will have limitations because the model cannot take the qualitative elements into account (the mental approach of the planner). However in making that argument you appeared to be doing the very thing you argue is the limitation. (A 6l pony has X amount of gas therefore the mental approach is moot as X amount of gas covers more contingencies)

I agree a 6l pony is "more" useful because there is more gas available.
I agree having a redundant air supply has an effect on the mental approach to planning.
I agree that planning should consider the weakest part of the equipment to hand.

At this point it all starts to go to custard. What exactly is the weakest piece of equipment? We could make a case for the O ring between the tank valve and the reg first stage. If that fails the size of the pony becomes less significant I reckon. Sure we have more air to leak out with a 6l pony but imagine having an OOA scenario where the pony fails, what is that going to do to my mental state? All I am saying is one cannot draw an absolute line in the sand and say for these circumstances you will cover all your contingencies. I am suggesting that a more helpful line of discussion might be to ask people reading the thread how they approach dive planning. Do they even consider a worst case scenario? If not why not? If they do and come to different conclusions can they explain them? Surely that is more useful than saying this piece of gear is better than that one? Risk management is not about how much or what sort of equipment you have available, it is a question of culture. Culture will always trump hardware and the evidence around its use.
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Re: Pony rigs

Postby binklebonk » Wed Sep 04, 2013 6:21 pm

As I am sure you know, it is poor form to construct a rebuttal on the least sympathetic possible reading.

When I get near a computer again (stupid phone is stupid) I'll try and restate my reasoning step by step and see where it is we start to disagree. All I can assume is that I have not stated myself clearly enough for you to think I have such a radical position.
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Re: Pony rigs

Postby Phantom Menace » Wed Sep 04, 2013 7:11 pm

Scanning this thread makes me pleased I don't take any redundant gas supply on my dives - mainly because I don't take any external gas supply at all.

Of course this limits my dive times and depths (avoiding dives deeper than 25m generally) and I avoid overhead environments (other than the occaisional swim through) ...

Right, back to my corner - carry on the discussion.
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Re: Pony rigs

Postby Ulsterkiwi » Wed Sep 04, 2013 9:53 pm

binklebonk wrote:As I am sure you know, it is poor form to construct a rebuttal on the least sympathetic possible reading.

When I get near a computer again (stupid phone is stupid) I'll try and restate my reasoning step by step and see where it is we start to disagree. All I can assume is that I have not stated myself clearly enough for you to think I have such a radical position.


I am not sure we disagree that much. I think you are right to bring in the various aspects of the discussion. I think some of the reasoning you provide does not actually provide an answer in the way you have presented it but perhaps our main source of divergence is that I think the mental approach is the prime consideration and am not so convinced we need to focus on the size of the pony. Perhaps my mistake is thinking you are focused on the choice of pony capacity.
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Re: Pony rigs

Postby binklebonk » Wed Sep 04, 2013 11:02 pm

Ulsterkiwi wrote:Perhaps my mistake is thinking you are focused on the choice of pony capacity.


If you were under the impression it's all about the size of the pony, then yes that will probably be our point of departure.

The 6l size I was advocating, was based on forseeable worst case scenarios down to 40m with no deco ceiling. That doesn't preclude the use of smaller tanks for shallower diving (given a disciplined diver).

So weakest bit of equipment? The weakest part of any system is the primate operating it.

From our failure to look after and/or properly set up our gear, to our failure to respond to a crisis in a timely and appropriate manner. I think most accidents in diving are the result of our failures rather than our kit.

Culture (as you say) can be key to reducing these failures.

In rebreather diving the culture surrounding the use of set up and pre jump checklists is only now starting to improve (I think) even though the body of literature supporting the use is very large and overwhelmingly positive. Too many people are worried more about looking like newbs than following good procedure.
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Re: Pony rigs

Postby Ulsterkiwi » Thu Sep 05, 2013 12:22 am

Too many people are worried more about looking like newbs than following good procedure.


thats easy, I always look like a newb........
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Re: Pony rigs

Postby Ali Perkins » Thu Sep 05, 2013 2:57 am

Just to bring this discussion full circle. We are debating "how much gas is enough" and "a diver's behaviour/mental approach to diving".

Ulsterkiwi wrote:First dive with the new rig was when I did the F69 after the big storm (trip report is on here somewhere...) So tested out my concerns from the get go. Pony on left between shoulder and hip D Rings and camera rig on the right. Was all good! Hardly knew the pony was there to be honest and we spent a fair bit of time moving through the wreck as well so very happy.


It kind of looks to me like you added a 3L pony bottle to your rig, and now you're diving inside a wreck. I think this is maybe the "risk compensation" Rob (binklebonk) is talking about.
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Re: Pony rigs

Postby Ulsterkiwi » Thu Sep 05, 2013 2:34 pm

Ali Perkins wrote:Just to bring this discussion full circle. We are debating "how much gas is enough" and "a diver's behaviour/mental approach to diving".

Ulsterkiwi wrote:First dive with the new rig was when I did the F69 after the big storm (trip report is on here somewhere...) So tested out my concerns from the get go. Pony on left between shoulder and hip D Rings and camera rig on the right. Was all good! Hardly knew the pony was there to be honest and we spent a fair bit of time moving through the wreck as well so very happy.


It kind of looks to me like you added a 3L pony bottle to your rig, and now you're diving inside a wreck. I think this is maybe the "risk compensation" Rob (binklebonk) is talking about.


Good point. IF I was doing something different to what I normally would do you would be completely right. As it happens, in this particular example, if and when I dive on the bridge section of the F69 I always go inside the bridge for a looksee. I did this before I had the pony and will continue to do so because this part of the wreck normally presents good photo opportunities and with more holes that solid metal it constitutes a very safe way to penetrate a wreck. The hardcore among us might even argue its not a "proper" wreck dive because of that! If you recall I did not make a blanket statement that I never penetrate a wreck or never dive deep. I said I do both.

I think I will still continue to dive in a conservative fashion but you are right though about risk compensation,I will undoubtedly consider doing dives I would not have done beforehand because I have stepped up my preparation a notch. I didnt actually argue with Binklebonk that this was a factor. My "issue" , if you can call it that, was the way he contructed his argument.
So next summer when at the Poor Knights I might have a look deeper into Taravana, I dont know, lots of factors will come into play in that decision, not least of all will be who I might be diving with and how they are prepared. Something else which I would really like to do is get my first shot of a John Dory. They tend to be around the 30m mark and that is something I avoid unless I have to. I would feel safer doing that now with a pony as part of my preparation. Is that wrong? I dont think so. Could I be "better" prepared, of course, that particular curve goes on to infinity!
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Re: Pony rigs

Postby Phantom Menace » Thu Sep 05, 2013 2:45 pm

John Dory tend to be round the 30m mark?? I don't think so. JDs get speared by free-diving spearfishers - you just need to know the right places to look (which is weedlines IMO).

Oh, and despite my earlier comment about avoiding overhead environments on my one breath I will admit to entering the bridge on the Canterbury a couple of times (obviously I didn't stay long).
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Re: Pony rigs

Postby Ali Perkins » Thu Sep 05, 2013 2:58 pm

I've also encountered many a John dory less than 30 metres.

Here's one on the deck of the Canterbury.

Image
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