Couple questions on a pony bottle for bail out

[DaleC]

1. Why not just use bigger tanks? HP100s are small and the best "bang for buck" in terms of weight for a given amount of gas. Size wise they are no bigger than two individual tanks.

2. Agree about the skill for valve shutdown...but you also need skill to use a pony bottle effectively. By the way, how do you share gas with a buddy if you have to switch to the pony bottle? Are we all solo divers now?

3. Also, most recreational divers I see around here with pony bottles are using them to extend their dives (pseudo stage bottle) instead of for redundancy.....and without training to boot.

1. Sure bigger tanks give more gas but at some point one must consider practical application. Most vacation divers who want simple redundancy are probably not going to encounter double 100's at dive resorts. Probably Al 80's.

But let's assume local diving where one owns St100's. If you twin them with a manifold you are now committed to doubles for every dive (or go through the hassle of breaking them down). Accepting that, you are now limited to smaller second dives or using an additional stage (as noted in the last two posts). If you use 1/2 gas on dive one you now only have (effectively) a single 100 with which to dive while retaining a reasonable reserve, which is not certain as it depends on how quickly and accurately one shuts down the valves. If you supplement with a stage you might as well have used a pony in the first place.

2. Not the same sort of skill. If you dive valve open you need only be able to effectively deploy the second stage, something any BOW diver should be able to do. Valve shutdowns with doubles is far more complex and the remaining gas supply depends on proficiency.

Gas sharing is as follows. I encounter a failure. I switch to my pony. I give my buddy the thumbs up. We ascend. In rec diving we plan for one failure because a direct ascent is supposed to be available.

3. I can't speak to improper use by some as a reason for gear selection. Wouldn't the same divers abuse doubles in some way? However, I often use my pony to extend a dive if it is part of my dive plan. If I know I need 20cuft for reserve but am using a 40cuft pony I can use 20cuft for the dive itself. I do this at the beginning of the dive then switch to backgas thus knowing I have a reserve I will not accidentally breath through.

---------- Post added July 16th, 2014 at 05:01 PM ----------

To swing 20 lbs that would have to be some really long or deep dives!

A 130 (16L) has about 10lbs of nitrox gas weight in it

Really though, once you add the weight from the manifold and bands and extra regulator (~5lbs -ve all together) you don't need much. If using steel tanks it's even better and you would need even less weight.

The point is, if you breath through most of your backgas (and supplement with a stage) you will become nearly 20 lb's lighter between the beginning and end of your dives. How do you compensate? Either you ditch some weight between dives or you enter on dive one up to 20 lb's negative. Most technical divers know this and that is why redundant BCD's of some sort are used, because a diver cannot otherwise overcome the negative buoyancy they enter with, should a failure of one occur.

Diving a single 72 with a 19cuft pony I will become 4lb's lighter during the dive, something I can compensate simply by using my lungs. I often do these dives without any BC because I can be (practically) neutrally buoyant throughout the dive.

[video=youtube;QpsR3EBysg8]https://www.youtube.com/watch?v=QpsR3EBysg8[/video]

 

[uncfnp]

A single larger tank and good gas management will beat all of those points.

You still just don't get it do you? A pony is redundancy for self reliance. Solo or buddy, it is for catastrophic equipment failure or gas loss to enable the diver to perform self rescue. When used as a pony and not a stage bottle it is not counted in my gas management calculations and has absolutely nothing to do with the size of my tank.

---------- Post added July 16th, 2014 at 10:02 PM ----------

Looking back at your post, I think you are confusing pony, "pseudo stage" and stage. If it is used as a stage, it's is a stage and not a pony. Semantics maybe but an important clarification here I think.

 

[lowviz]

...//... I often use my pony to extend a dive if it is part of my dive plan. If I know I need 20cuft for reserve but am using a 40cuft pony I can use 20cuft for the dive itself. I do this at the beginning of the dive then switch to backgas thus knowing I have a reserve I will not accidentally breath through. ...//...

Perfectly acceptable and well stated.

...//... I think you are confusing pony, "pseudo stage" and stage. If it is used as a stage, it's is a stage and not a pony. Semantics maybe but an important clarification here I think.

Indeed!

In addition, there is a degree of complexity that DaleC so nicely pointed out. A properly sized pony can add a great deal of flexibility and true redundancy to your diving.

 

[Greg_Vic_Diver]

1. Sure bigger tanks give more gas but at some point one must consider practical application. Most vacation divers who want simple redundancy are probably not going to encounter double 100's at dive resorts. Probably Al 80's.

But let's assume local diving where one owns St100's. If you twin them with a manifold you are now committed to doubles for every dive (or go through the hassle of breaking them down). Accepting that, you are now limited to smaller second dives or using an additional stage (as noted in the last two posts). If you use 1/2 gas on dive one you now only have (effectively) a single 100 with which to dive while retaining a reasonable reserve, which is not certain as it depends on how quickly and accurately one shuts down the valves. If you supplement with a stage you might as well have used a pony in the first place.

I'm not really sure I get the argument. How do you have less gas for dive two with double tanks than if you had two separate single tanks? If one was practicing proper gas management and did the same dive one would do with a single HP100, you would have an entire tank of gas + at least the reserve gas from the previous dive in your double tanks giving you more gas for dive two. This is one of the main reasons to use them....no need to tear down gear for the second dive you can leave it on the beach for the surface interval.

] 2.[/B] Not the same sort of skill. If you dive valve open you need only be able to effectively deploy the second stage, something any BOW diver should be able to do. Valve shutdowns with doubles is far more complex and the remaining gas supply depends on proficiency.

Gas sharing is as follows. I encounter a failure. I switch to my pony. I give my buddy the thumbs up. We ascend. In rec diving we plan for one failure because a direct ascent is supposed to be available.

How about this scenario: your buddy has an emergency and somehow runs out of gas. You start sharing gas (octopus) , calm your buddy down and begin to ascend. You then yourself run out of gas as you had not planned for a stressed buddy also breathing your back gas at the same time. You're not at the surface yet and only have the pony - I see a bad situation turning worse that didn't need to happen if one practiced proper gas management which is the point I am trying to make here.

]

3.[/B] I can't speak to improper use by some as a reason for gear selection. Wouldn't the same divers abuse doubles in some way? However, I often use my pony to extend a dive if it is part of my dive plan. If I know I need 20cuft for reserve but am using a 40cuft pony I can use 20cuft for the dive itself. I do this at the beginning of the dive then switch to backgas thus knowing I have a reserve I will not accidentally breath through.

I think if proper gas management was practiced which means always having enough gas for you and your buddy to deal with an emergency and ascend safely to the surface (including safety stops) from your maximum depth - there would be no issues.


---------- Post added July 16th, 2014 at 05:01 PM ----------

The point is, if you breath through most of your backgas (and supplement with a stage) you will become nearly 20 lb's lighter between the beginning and end of your dives. How do you compensate? Either you ditch some weight between dives or you enter on dive one up to 20 lb's negative. Most technical divers know this and that is why redundant BCD's of some sort are used, because a diver cannot otherwise overcome the negative buoyancy they enter with, should a failure of one occur.

I think you got this backwards. Why would you have to ditch weight between dives if you are getting lighter from using up gas? You're weighting should be the same, you just wouldn't need as much gas in your wing/BCD to compensate. Proper weighting is a whole other discussion - I'll try to keep on the pony bottle topic...but it's hard not to diverge Also, most technical divers I know use a drysuit as the redundant buoyancy source.

---------- Post added July 16th, 2014 at 09:27 PM ----------

You still just don't get it do you? A pony is redundancy for self reliance. Solo or buddy, it is for catastrophic equipment failure or gas loss to enable the diver to perform self rescue. When used as a pony and not a stage bottle it is not counted in my gas management calculations and has absolutely nothing to do with the size of my tank.

---------- Post added July 16th, 2014 at 10:02 PM ----------

Looking back at your post, I think you are confusing pony, "pseudo stage" and stage. If it is used as a stage, it's is a stage and not a pony. Semantics maybe but an important clarification here I think.

Yes, I agree a pony adds a degree of redundancy for self reliance, no issues there. My entire question was why is it better than using proper gas management and manifolded doubles if one needs the redundancy?

 

[lowviz]

OP says:

...//... Thank you for the response but I have no intentions on diving doubles or getting into that type of diving any time in the near future. ...//...

...//... If you are worried about redundancy, double up your tanks with a manifold. ...//...

You brought up doubles, this thread really isn't about doubles.

...//... Even without a buddy, what makes a slung pony better than a set of manifolded doubles? Why is it a better choice?

All you have to do is clip a pony onto to your singles rig and you have a TOTALLY independent supply of gas...

...//... How about this scenario: your buddy has an emergency and somehow runs out of gas. ...//...

What if you did first?

Isolatable manifolded doubles have a failure point that will compromise your entire gas load. A pony is as simple as a totally redundant suppy can possibly get.

...//... My entire question was why is it better than using proper gas management and manifolded doubles if one needs the redundancy?

This thread is full of wetsuit divers that see your suggestion as potentially dangerous due to massive overweighting.

 

[Greg_Vic_Diver]

All you have to do is clip a pony onto to your singles rig and you have a TOTALLY independent supply of gas...

Yes, it's independent meaning if something goes wrong with one of the two you don't have access to all the gas

Isolatable manifolded doubles have a failure point that will compromise your entire gas load. A pony is as simple as a totally redundant suppy can possibly get.

Please enlighten us on what the failure would be? There are no single failures that would result in a total loss of all the gas. The manifolded doubles allow you to have a regulator failure and still have access to ALL your gas. A pony system with a single tank would mean a single failure would automatically result in the loss of all gas in either the pony or backgas.

This thread is full of wetsuit divers that see your suggestion as potentially dangerous due to massive overweighting.

Thread isn't about weighting and only time issues arise is when people use steel tanks (singles OR doubles) along with a thick wetsuit and don't have enough ditch-able weight (or not weighted properly to begin with) ...but we're all big boys and gals right? this is the advanced scuba forum

 

[lowviz]

...//... Please enlighten us on what the failure would be? There are no single failures that would result in a total loss of all the gas.

Who is "us"? If you mean "you" see below:

Two 'within the realm of reason' failures. The isolator itself and this: http://www.scubaboard.com/forums/dir/481170-some-question-about-doubles-2.html#post7109366

...//... Thread isn't about weighting and only time issues arise is when people use steel tanks (singles OR doubles) along with a thick wetsuit and don't have enough ditch-able weight (or not weighted properly to begin with) ...but we're all big boys and gals right? this is the advanced scuba forum

Diving is holistic, it is always about weighting.

 

[rivers]

So you had a pony for your doubles...

No slight to you as I sometimes do the same. I also dive an Al 40 or even an 80 stage with a single if I want more gas but don't have my doubles.

But that raises an interesting point regarding weight. If you dive a single/pony for each dive your weighting will not change, compensating for between 5-8lb's of gas expended during the dive. If you dive doubles and use a stage you could have a weight swing of 10-20 lb's (roughly) between the beginning of dive one and the end of dive two. So you need to be pretty negative or change weighting between dives.

I only use 4kg (roughly 8.8lbs) for sea dives, and even if I don't have my stage, I'm pretty overweighted just by the weight of gas in my tanks. My stage is a 200 bar 7 litre aluminium, so it's pretty neutral in the water when full.
And it's not a pony for my twins . If it were, I wouldn't use the gas in it for the dives.

 

[Greg_Vic_Diver]

Who is "us"? If you mean "you" see below:

Two 'within the realm of reason' failures. The isolator itself and this: http://www.scubaboard.com/forums/dir/481170-some-question-about-doubles-2.html#post7109366

Those would result in loss of only half the gas, not the entire load.

 

[lowviz]

*sigh*