PONY Question

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I understand - I'm just not sure that toting a Al80 which is about 24" long (or more) is the way I want to go for a 60 ft dive! I mean, I don't think I've EVER seen ANY recreational divers where I dive toting around AL40's as PONY's!
 
That's why, buoyancy aside, I use a steel 46. Its smaller than an AL40, running from just under my arm to just past my hip (I've never measured it). Its far shorter than the 120 I'm carrying on my back. Even better, when I start to do two deco bottle dives (one with 50, one with 100), I'll just add another 46.

As for what other divers do, I'm not overly interested. I would not trust some of the people I've seen diving to blow bubbles in their soda without screwing it up (my regular buddies are not included in this. If they were, they wouldn't be my regular buddies).

All I can say is that you should not rely on paper figures or what other people say or do. You should take the pony out to the dive site and test it in realistic conditions (elevated breating rate, a few minutes on the bottom, normal ascent with stops). See what happens and let us know.
 
I sure will, next dive - and IF I find 19 cu in isn't adequate, I'll step to the 40.
 
Northeastwrecks once bubbled...
My SAC rate varies between 0.4 and 0.7, depending on whether I'm working, working hard or hanging.

I reviewed my log for that dive. I started on the pony about 1 minute [...] I deployed the pony at about 95fsw. [...]unhooked the line and fouled the hook (2 minutes max). [...]and, unless the emergency were life threatening, I would do it in real life.

Dan, I dispute the validity of your tests... yes, if you have a 40 cuft bottle, then you can finish up your dive, but sucking on the 19, by design, is a life threatening emergency.

If one is diving with a pony bottle as a bailout bottle [13 cuft or 19 cuft], you should treat it as 'better than an emergency ascent'. The attitude I treat with my pony bottle is that if that regulator ever goes in my mouth... I've killed myself.

Now lets switch to the math... 2 minutes @ 95 w/ .6 SAC = 4.65 cubic feet of air. 4.65 cubic feet of air at 20 ft is over 4 1/2 minutes, or over 7 minutes with your hang SAC rate of .4.

Mathematically a 30 fpm ascent and 3 minute stop at 15 fsw, allows for an ascent from 140 fsw with a 19 cuft pony bottle and an SAC rate of 1.

I don't disagree with your point of going with a larger bottle if your going to go with a pony, I just disagree with your claim that it's not enough air to safely ascend from recreational depths.
 
Spectre once bubbled...
If one is diving with a pony bottle as a bailout bottle [13 cuft or 19 cuft], you should treat it as 'better than an emergency ascent'. The attitude I treat with my pony bottle is that if that regulator ever goes in my mouth... I've killed myself.

That's a great way to put it. If the pony reg goes into your mouth at 90 feet, you've essentially done something that should have killed you. Thanks for that, what a perfect way to view that pony.
 
If one is diving with a pony bottle as a bailout bottle [13 cuft or 19 cuft], you should treat it as 'better than an emergency ascent'. The attitude I treat with my pony bottle is that if that regulator ever goes in my mouth... I've killed myself.

Very well stated
 
Spectre once bubbled...

If one is diving with a pony bottle as a bailout bottle [13 cuft or 19 cuft], you should treat it as 'better than an emergency ascent'. The attitude I treat with my pony bottle is that if that regulator ever goes in my mouth... I've killed myself.

To my way of thinking using the pony is a form emergency ascent, albeit with less risk than a controlled swimming ascent. But if I ever have to use it I’ll be thinking, “damn was a smart for bringing this along” rather than “I’ve killed myself.”

While it cannot be overly stressed that a pony should not be used in lieu of good gas management, there are situations beyond your control.

Mike
 
Spectre once bubbled...


Dan, I dispute the validity of your tests... yes, if you have a 40 cuft bottle, then you can finish up your dive, but sucking on the 19, by design, is a life threatening emergency.

If one is diving with a pony bottle as a bailout bottle [13 cuft or 19 cuft], you should treat it as 'better than an emergency ascent'. The attitude I treat with my pony bottle is that if that regulator ever goes in my mouth... I've killed myself.

Now lets switch to the math... 2 minutes @ 95 w/ .6 SAC = 4.65 cubic feet of air. 4.65 cubic feet of air at 20 ft is over 4 1/2 minutes, or over 7 minutes with your hang SAC rate of .4.

Mathematically a 30 fpm ascent and 3 minute stop at 15 fsw, allows for an ascent from 140 fsw with a 19 cuft pony bottle and an SAC rate of 1.

I don't disagree with your point of going with a larger bottle if your going to go with a pony, I just disagree with your claim that it's not enough air to safely ascend from recreational depths.

Jeff,

I agree that the pony is for emergencies only. Our disagreement goes to the appropriate response to the emergency.

You seem to be saying that you will ascend immediately on the pony. By your numbers, it seems possible to to an IMMEDIATE ascent using a small pony. I presume that your calculations are based on very little bottom time and an immediate ascent to 20 feet for the safety stop.

I'm saying that an immediate ascent might not be possible, desirable and/or or appropriate. I posted earlier about some of the reasons why I might not want or be able to do an immediate ascent. For example, I might want to get back to the up line. The could be other people down there (such as my buddy or divers on a dive for which I am the DM) who might be in need of assistance or who are also low on air. Finally, it might take a few minutes to recover from whatever caused me to deploy the pony in the first place. Regardless, I might need to stay down longer than I want. I don't think that your calculations take this into account.

I use the 46 as a deco bottle and not as a pony. The fact that it is a redundant air supply is, for me, a bonus and a stop gap until I bite the bullet and order my doubles. I'm not suggesting that it is the perfect solution. However, I do believe that a diver should not limit their options or plan on being able to make an immediate ascent if they run into problems. For that reason, I believe that a larger bottle is appropriate.
 

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