Is a Pony Bottle too complicated for a beginner?

[grf88]

Why panic when you have the minimum gas to get both you and your buddy to the surface at that ascent rate already calculated in the dive plan? (which as you stated is a lot of time and gas)

Panic and hasty movements causes the drain of despair. No one wants that.

I guess I should leave you to it as you are making a great case for the use of a pony bottle.

 

[lexvil]

Let's you and I do a virtual dive to 80ft on single AL '80s, shall we? And in that dive, you have a seat failure where you start to lose your gas supply.

Dive Plan:

A critical goal in planning a dive in open water is determining how much gas is necessary for an emergency scenario, as you have listed above.
With that in mind, we want to plan for one diver to suffer an out-of-gas emergency during the deepest part of the dive, which provides sufficient reserves for any range of potential problems within the buddy group.

Let's make a few educated assumptions that leave us all with a bit of room for conservatism.
1. Let's assume that our average surface consumption rate is ~ 20 L/ 0.75 cuft per minute.
2. The assumed ascent speed will be on average 3m/10 ft per minute.
3. The average depth of the ascent is used for all calculations. Divers should attempt to maintain a controlled ascent of between 20 to 30 feet per minute and follow minimum deco (MDL/NDL) profiles. This is based on a slow but foreseeable ascent rate that provides some wiggle room for safety. Also, the 20 L/ 0.75 cuft per minute SCR is approximate based on the outcome of an average diver in most situations.
• MG should never be less than 40 bar/600psi to account for inaccuracy and/or readability in SPG's.
Let's determine our minimum gas for the dive.

Consumption= 0.75 SCR x 2 divers= 1.5 cuft /min

ATA: (80ft / 2 = 40ft); (40 ft / 33 +1 = 2.2 ATA

Time: 11 minutes (10ft/min ascent rate plus one minute at depth to resolve the problem and initiate an ascent.

1.5 x 2.2 x 11 = 36.3 cuft of gas or (36.3 / Tank Factor 2.5 x 100 = 1,452 PSI or to make it easier on the SPG 1450 or 1500 Psi to be conservitive.

• Our plan states that if we share gas from the deepest point of the dive, we require at least 1500 psi in our AL80 to reach the surface while safely transferring from one cylinder.
So, @lexvil, at what point during the dive will we need to call it and head to the surface if all goes according to plan?

Remember I never said your were wrong but didn’t you mention zero viz? If you lose your buddy how do you air share? A pony is a buddy the rides with you at all times and easy to find no matter the viz.

 

[Hartattack]

Do you consider an ascent rate of 10m/min a panicked ascent?

Why would it need to be 10 meters a minute when you have 1100 L MG in a 12 L tank?

 

[Hartattack]

Remember I never said your were wrong but didn’t you mention zero viz? If you lose your buddy how do you air share? A pony is a buddy the rides with out at all times and easy to find no matter the viz.

I did not mention zero viz, as I would not dive in those conditions recreationally or with new divers. But, to answer your question, I use a primary light as my way of communication. Side to side sweeps would be the way I would communicate and OOG situation to my buddy. (Also what I teach my students)

 

[tursiops]

Why would it need to be 10 meters a minute when you have 1100 L MG in a 12 L tank?

LOL. You calculated a minimum gas need based on a poor assumption.
Do it again based on a reasonable assumption.

 

[Hartattack]

LOL. You calculated a minimum gas need based on a poor assumption.
Do it again based on a reasonable assumption.

Give me an example. But, justify your ascent rate with sound judgment, Master Instructor (whatever that means). Mine was conservative and gave way more gas and time needed; you're trying to justify rushing in an emergency; that way of thinking can get both divers killed, I am not sure why this is your thought process, but I bet it's because you hate being wrong from your other posts and troll comments.

 

[CT-Rich]

Did I ask or state anything about a pony bottle or increased SCR yet? I think it would be nice to have @lexvil answer the question and we continue our virtual dive before being interrupted, no?

I believe this is a discussion. If you have a lot to say, feel free to make the post longer. I think once you hit the send button, all are free to respond (at least my understanding). I appreciate your posting an example dive plan.

Personally, I find planning like this overly complicated and prone to a lot of assumptions (which, to be fair is the point of planning). Most weekend putter around the reef diving won’t require this much detail and newbie divers will get lost/confused. Where I dive tides and currents are the great unknowns that can have a large effect on air consumption because a the direction and strength of the current can significantly change hour to hour.

Are you taking all that math in the water? Are you expecting OW certified divers to do that level of planning?

What you have in your example is a process for planning. What will this dive look like? What is the information that gets written on the slate and the diver needs to know and work around. When I am in the water, the only thing I care about is time, depth, direction, current pressure, turn pressure, NDL, temperature and direction of current and where am I exiting. There are a bunch of location specific details, but I am not doing any math if I can help it.

 

[Hartattack]

I guess I should leave you to it as you are making a great case for the use of a pony bottle.

Prove me wrong, but please provide your calculations on how a pony bottle is better than, 1500 psi reserve for emergencies and a 23 minute bottom time at 80ft without unnecessary task loading and weight distribution on a new diver.

 

[CT-Rich]

I am by showing that a new diver does not need one with an example that all of you asked me for or criticized. So with my example, what is our minimum gas for our planned dive and at what psi should we call it?

Your plan, you tell us.

 

[tursiops]

Give me an example. But, justify your ascent rate with sound judgment, Master Instructor (whatever that means). Mine was conservative and gave way more gas and time needed; you're trying to justify rushing in an emergency; that way of thinking can get both divers killed, I am not sure why this is your thought process, but I bet it's because you hate being wrong from your other posts and troll comments.

10m is STANDARD on most computers. It does not imply an emergency.
3m/min is non-STANDARD except in the deco world of GUE. This is a beginner forum, not a deco forum Get on topic.

Hint: once you've gone through all this off-topic stuff about min gas, I hope someone says...but what about a free-flow/seat-failure/blown hose/lost-buddy, etc.
The TOPIC is a pony bottle; it is for those things, NOT a replacement for having enough gas if nothing goes wrong.