Pony Bottle

[Cave Diver]

Second, we have shown the OP how SB truly functions - someone asks a question, and many post helpful replies. Some, however, choose to not reply to the question and instead shout "You're gonna die."

Sometimes "You're gonna die!" is a helpful response.

 

[Gombessa]

Edit: I missed the part about stressed SAC rate. What is a good value to use? Double a resting SAC? Higher?

I's different for every person, but likely you'll need more than double your resting SCR. Most people are not resting when they're actually diving, and most people use double their normal diving rate for their stressed SCR. Even low-stress tasks, such as leading a dive, or performing well-practiced drills, make a noticeable impact on my breathing rate.

Add to that the fact that when you're really stressed, it's amazing how much over double working SCR you can actually go, and how incredibly involuntary that is and difficult it is to get under control. Another aspect is that people tend to compete with themselves to lower their SCR and, like trap times at a drag strip, oftentimes start to think of their lowest resting SCR as their typical SCR. IMHO, in terms of your emergency gas supply it makes more sense to skew conservative than liberal. At the very least, I'd go with double with your actual working SCR. I can hit 0.4 on calm dives, but my highest working SCR is closer to 0.6. I use 1.3cu/min for my emergency SCR based on conservatism and actual experience. A typical number you'll see here is 1.0, but I imagine many of the people using 1.0 have more years of diving and more comfort in the water than I do.

This also dovetails into the whole "theory vs. practice" debate. A lot of times we use seemingly reasonable assumptions when working the numbers. Sometimes it works out; somethings we may be caught by surprise when the reality of the situation differs from what we've calculated--hopefully we haven't put ourselves at the very limit of what we can handle when that occurs. A lot of people are smart and/or diligent and will re-calculate or confirm their numbers when they have new or more accurate information, but I only mention this for the benefit of those who may be skimming the thread and only take away "19cf makes me good to 130ft" without thinking through what it means or whether it's realistic for them.

 

[Dr Wu]

........"19cf makes me good to 130ft" without thinking through what it means or whether it's realistic for them.

There are many examples such as this. Many people do not give any actual thought to the practicality of the devices they choose to dive with.

They just "know" it will work for what they need and when they need it.

 

[dumpsterDiver]

Originally Posted by Gombessa

........"19cf makes me good to 130ft" without thinking through what it means or whether it's realistic for them.


There are many examples such as this. Many people do not give any actual thought to the practicality of the devices they choose to dive with.

They just "know" it will work for what they need and when they need it.
__________________


I ran my primary tank down to the "hard to breath" pressure about a month ago at 110-120 ft when I was totally out of breath from swimming very hard. I made the ascent using the 6 cu-ft pony bottle up to my safety stop at 20 feet (where I switched back to my large LP Steel tank and did a leisurly 3 minute hang on the remaining gas. I surfaced with just 800 lbs in the pony. I might have stopped at 50 feet for only a minute.

I would have definitely felt a lot better if I had a buddy or a larger pony bottle, but the 6 cu-ft bottle did it's job, even if I did not do mine. I'm thinking this might be the first time I have ever HAD to use a pony.

People do need to be aware of a much higher SAC rate on an ascent, but my expereince is that a diver can temporarily decrease their breathing rate if they try very hard to shut the thighs down, keep the arms still and try to ride the bouyancy of the BC with a minimum of physical exertion. And of course they need to try very hard to breath slowly and deeply in the most efficient manner possible. If a diver can manage this skill for just a few minutes they should be able to avoid blowing a ton of gas on ascent.

I know when I am wearing my 6 cu-ft, if I go on it at depth, I absolutely must be on my way up or I will not make it. Zero time for fixing problems on the bottom. When I had my little "problem" a month ago, I left a piece of gear on the bottom, because I was unwilling to suspend my ascent and drop back down 15 ft to retreive the piece of gear. (I was unwilling to risk not being able to do a safety stop).

A 19 cu-ft bottle is more than enough to go from 120 to the surface, unless the diver is in a total panic or is unable to maintain a decent ascent rate. I use a 13 cu-ft pony considerably deeper than that.

 

[Dr Wu]

Gombessa,

Interesting point - I should check and re-check my calculations. At the time I arrived at something like 128 (?) ft. Time to run those numbers again.

Edit: I missed the part about stressed SAC rate. What is a good value to use? Double a resting SAC? Higher?

So you just found out now that the pony bottle you have been advocating and relying upon is inadequate for your needs.

You don't find that odd? You aren't a little frightened by having been such a proponent of something that probably would not work when you needed it?

 

[Dr Wu]

People do need to be aware of a much higher SAC rate on an ascent......

And yet in this thread alone you have a very verbal proponent of his pony bottle that had no idea about that whatsoever.

 

[Cave Diver]

People do need to be aware of a much higher SAC rate on an ascent, but my expereince is that a diver can temporarily decrease their breathing rate if they try very hard to shut the thighs down, keep the arms still and try to ride the bouyancy of the BC with a minimum of physical exertion. And of course they need to try very hard to breath slowly and deeply in the most efficient manner possible. If a diver can manage this skill for just a few minutes they should be able to avoid blowing a ton of gas on ascent.

So, just to play devils advocate, wouldn't you think that people to whom all those conditions apply and are able to meet them, are probably the very same people who wouldn't really need a pony bottle in the first place?

 

[Gombessa]

I ran my primary tank down to the "hard to breath" pressure about a month ago at 110-120 ft when I was totally out of breath from swimming very hard. I made the ascent using the 6 cu-ft pony bottle

I guess that's the other extreme; what would take me 25-30cf DD can do with 6cf. Everyone just has to honestly assess their own capabilities and physiology and determine who they're closer to, if either. I don't imagine I'll ever get to DD's SAC level in an emergency--and if I'm lucky enough to have it my way, I'll never find out.

 

[dumpsterDiver]

....Why would you give a stupid, careless and poorly trained person a tool that could potentially kill them if they operated it stupidly, carelessly or contrary to training?

Answer: Because that is their right.

Learning to use a pony bottle is far easier than learning to work a BC. It is probably less dangerous too.

I bet a higher percentage of people have embolized due to uncontrolled bouyant ascents (which were precipitated by an inability to use a BC) than people who have been killed by screwing up with a pony bottle.

 

[Crush]

So you just found out now that the pony bottle you have been advocating and relying upon is inadequate for your needs.

You don't find that odd? You aren't a little frightened by having been such a proponent of something that probably would not work when you needed it?

Wrong. I know the difference between resting, swimming, and stressed SAC. I just misread the post.

I assumed what I believe to be a reasonable stressed SAC. I was just checking what others thought.

"Dr" I am willing to entertain the notion that there is more than one way to achieve an end. I wish that you were equally open-minded.