Should we get pony bottles?

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I was in 60 Ft. of water & my buddy was about 30 Ft away .

A buddy 30' away might as well be at home watching television.

But before you throw your buddy under the bus for being so far away, remember it takes two divers to lose a buddy.

Solo is just fine, but needs to be a plan, not an accident.

flots.
 
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To answer your question you need to calculate the minimum amount of gas needed for 2 divers to safely ascend.


If you do the math, it may help you ascertain whether you are diving with enough gas, so here we go:


For your 110ft dive, lets set your average depth at 50ft for this exercise.


average ATA (50ft) = 2.5
sac rate = 1.0 (calculating for panicked rate)
time to ascend = 8.5 minutes (x2, to calculate for your buddy) = 17 minutes
Gas needed for 2 divers to ascend = 42.5 cubic ft
Converted to PSI in a single AL80 = 1700psi


This gives you 1300psi of usable gas for the dive, meaning you need to be on the surface with 1700psi remaining in the tank.


If this is not the case, then you need to bring more gas, or change your dive plan to accommodate the amount you intend to bring.

Isn't your calculation saying you must start your ascent with 1700 psi in the tank? Or am I missing something?
 
My 1 St. failed on me about 7 years ago & had to make a emergency assent ..I was in 60 Ft. of water & my buddy was about 30 Ft away . Current was ripping North ..You got to make a quick desecession .. Do I try to get to my buddy make signal there is a problem & out of gas ?? Or do I make a emergency assent ??? NOW DO NOT FORGET CURRENT IS RIPPING !!!! By the time I get to him I would swim 50 + feet & make a signal..
DOES HE RESPOND FAST !!!! TIME IS AN ISSUE .. Now tell me "what would you do " ?????

Mike your use of fonts is kind of annoying. We may be older than you but we can see just fine.

As Jim pointed out you and your buddy screwed up. Under bad conditions you should stick closer to your buddy not father away. I am sure your dive training agency did not tell you to be 30 feet away from your buddy is fine.

To answer your question, if my choices are swim 30 ft into the current to get to my buddy or go to the surface, I would take the surface. Especially if the second stage is free flowing and can take a breath or two from it on the way up.
 
so my decision has been made for me. My wife cant dive for a few months (9 to be exact :D)... i will continue to dive because my skin doesn't take well to being out of the ocean for long

now i must decide on how i carry the pony around, I like the modular nature of slinging but i also like the neatness of tank mount, which i'm leaning to right now...

i'm not looking to break the break the bank on this setup (i'll use her reg until she returns and i'm looking at a 13 or 19 cu bottle), there are some lovely tank mount solutions out there but they are to expensive

i like the simple and diy nature of this setup:

https://www.youtube.com/watch?v=j0sdSL-ng-g

any other cost effective suggestions are welcomed

thanks
 
This is my setup - 2 tank bands and an X-brace. I looked at that you tube when I was deciding, and I don't like worm clamps or the sloppy nature of what he had. The X brace is a bit pricey, but its a clean setup. You could weld up something similar if you have the pipe. Either way, I like using tank bands...and does have that donate-able aspect, which some people like. Wasn't my prime concern...
 

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Think carefully when choosing pony size. 13 cu ft may get tight if you are trying to make a civilized ascent from 130ft in anger. 30 and 40 cu ft make great ponies allowing you to make a legit ascent from the maximum recreational depth even with a tripled SAC rate due to hypercapnia or plain old freaking out.


Here's a quick back of the napkin calculation with some sloppy rounding to highlight my point: let's say the average diver has a SAC of 15 liters per minute. A 19 cu ft tank filled to 3000psi contains about ~550 litres. You're at 40 meters depth and your SAC doubled because bad, bad things just went down and you would really like to go home now.

You will make a civilized ascent at ~10 meters / minute. Not doing so most likely invalidates your deco model/table.

You are only within your NDL if your ascent speed matches that of your decompression model which for. Most recreational models is about 10 meters per minute.

The journey from 40m to 30m will use 150 litres. Your 10 cu ft tank now has 400 litres left. You consume 120 litres to get from 30 m to 20m. You now have 280 litres left. I'm assuming we would skip safety stop and have no deco obligation when the emergency started.

The remainder of the journey to the surface will use 150 litres. You will reach the surface with 130 litres left and likely feel very very fatigued from making such an ascent.... Not much room for error and a total disqualifier of 13 cu ft tanks as emergency ponies.

Please consider 30 and 40 cu ft.I don't sell tanks so I don't care what y'all do but please look at the numbers. Nothing worse than carrying a piece of equipment that gives you a false sense of security.

Sent from my Nexus 7 using Tapatalk
 
Think carefully when choosing pony size. 13 cu ft may get tight if you are trying to make a civilized ascent from 130ft in anger. 30 and 40 cu ft make great ponies allowing you to make a legit ascent from the maximum recreational depth even with a tripled SAC rate due to hypercapnia or plain old freaking out.

My pic has a 19 pony in it, though I would agree with the above if I had it to do again. A 30 is only a bit longer and a bit fatter than the 19 and not much more expensive. I consider the 19 a CESA bottle. That is if I have to go to it, I'm doing a CESA to 15' then I'll sit and burn the tank out to recapture the safety stop until its empty and finish with a CESA to the surface. This given that I'm doing NDL diving. With a 30, I could relax a bit more on the ascent. In my case, my wife and I both dive 19 ponys, so in effect the two of us have a 30+ for such an emergency - the buddy plan being to grab her to go up with me. When I go solo, I'll buy a 30 for myself....
 
CESA bottle is a cool term for the sub 30 cu ft tanks. I will use that term going forward.

I carry a 40 on recreational dives and simulated a by-the-book ascent from 40m with a ten minute deco obligation at 3m and it worked well. Had a lot more than half left which means I could have done it with a distressed SAC of 30 l/min. A 30 would have been close and anything smaller is now to be referred to add a CESA bottle. CESA beats death but if I can choose I don't take anything smaller than my beloved 40.

Sent from my Nexus 7 using Tapatalk
 
@ maniago could you send me a link to the x brace... i have some very good welders in my family maybe i can get them to make it

@ mr. black
during this whole thread i did and re-did calculations etc and based on my breathing and my diving and 19cu is ideal... 13cu is cutting it close so in reality i will end up going with a 19cu... if CESA is the term we're using then yes i'm good with that as it's exactly what I'm looking for...

in case of an emergency with my primary tank (and my buddy isn't available) i have a way to make an emergency accent... something that allows me to get to 15' at maximum safe speed and then burn the rest there.
 
I carry a 40 on recreational dives and simulated a by-the-book ascent from 40m with a ten minute deco obligation at 3m and it worked well. Had a lot more than half left which means I could have done it with a distressed SAC of 30 l/min. A 30 would have been close and anything smaller is now to be referred to add a CESA bottle. CESA beats death but if I can choose I don't take anything smaller than my beloved 40.

I would be a little concerned incurring a deco obligation with a single tank. Ponies are really just for recreational diving where you don't have deco obligations. At that point I would be looking at doubles or a larger stage.
 

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