Best type of Pony Tank setup?

[Big-t-2538]

So now we have 3.5cf/min for 10 minutes, + 7.0cf for the first minute, or 42cf.

Now this is a bare minimum, as it does not allow for any increase in the donor's RMV, which is of course also likely.

But this puts "rock bottom" awfully close to THIRDS for a single AL80!

Whatever....you came up with 42 cu. ft......I came up with 40. That's not unreasonable for 2 different people....yes...it is in the ballpark of thirds for an AL80...so what? you know what it is...are you not comfortable calling a dive when you reach the calculated point of no return pressure?

you've got a real problem if someone TRULY needs to bail and you're using the typical "be back at the line @ 1000 psi" type of dive planning. You WILL run out on the way up.

...uh...yeah....isn't that why we ran the numbers? We came up with 1550 (mine) and 1635 (yours) as minimum "leave the bottom" pressures.

 

[Genesis]

Whatever....you came up with 42 cu. ft......I came up with 40. That's not unreasonable for 2 different people....yes...it is in the ballpark of thirds for an AL80...so what? you know what it is...are you not comfortable calling a dive when you reach the calculated point of no return pressure?

...uh...yeah....isn't that why we ran the numbers? We came up with 1550 (mine) and 1635 (yours) as minimum "leave the bottom" pressures.

Right.

Now recompute for a dive at 130', and you will find that you pretty much can't do it (its a "touch dive")

This is why 100' is about where I say "doubles" I used to say "pony", which IMHO is also a valid consideration for those depths.

A pony allows me to go to my turn pressure, because I can give it away if my buddy needs gas. While I must still keep my personal reserve in my backgas tank, the extra that I keep for my buddy is now in the other can.

 

[Big-t-2538]

Right.

Now recompute for a dive at 130', and you will find that you pretty much can't do it (its a "touch dive")

Who is going to 130' and why are we doing it on a single AL80 tank?....I'd have one of 2 things...a larger tank with an H-valve...or doubles. just b/c I have a table or a card that says I can get there doesn't mean I have the equipment necessary for the dive. With a single AL80 I'm pretty comfrotable with staying above 100'.

 

[MikeS]

... with an AL80 @ 100', you've got a real problem if someone TRULY needs to bail and you're using the typical "be back at the line @ 1000 psi" type of dive planning. You WILL run out on the way up.

Who is advocating a be back at the line @ 1000 psi for a 100 foot dive? Although we all had different ascent profiles, mine being the least conservative with only a three minute stop at 15 feet, even it has a direct ascent to the surface at 1200 psi.

Mike

 

[Genesis]

The point, Mike and Big-T, is that this is precisely where a Pony comes in handy.

You have the "handoff" gas for your buddy, and now YOUR reserve is only for YOU.

If your buddy ALSO has a pony, now HIS reserve is only for HIM.

My solution for such dives is typically doubles - but I DO see where a pony has application here.

 

[NEWreckDiver]

as has been described... not stuffed but down the right side under the light can then across the chest and around the back of the neck and into my mouth from the right.

A misconception that folks have (not necessarily you) is that the hose is wrapped around the neck... it is only across the back of the neck. This is the most streamlined and snagless configuration possible. It is very easy as well as quick to hand off the second stage by dipping the head slightly. True... it doesn't work with snorkles.

I personally find the long hose makes doing air sharing ascents much easier as each diver controls their ascent independent of the other and can separate enough to even complete tasks such as shooting a bag without undue concern about entanglement. We practice this. It is fun.

Well when this pony bottle debate started, I thought you and I where on the opposite sides of the earth. I too believe the long hose is necessary for 80% of all of my diving. I have never considered a long hose when I dive singles (not so much anymore, only when I am DMing with instructors in the quarry or pool).

DSAO

 

[Big-t-2538]

The point is that this is precisely where a Pony comes in handy.

As would an H-valve with a larger tank or doubles. I thought I mentioned that already.

 

[Genesis]

Yes, you did, as did I.

The "H" valve is a kludge though. To truly be useful it has to be on a pretty big tank, doesn't give you FULL redundancy, and large singles have their own problems (mostly with trim and just being fscking unwieldy) - I'd rather dive twin LP72s than a 130, for example.

 

[Sean326]

Are you saying that carrying a pony does not introduce an entanglement issue?

I carry my 19cuft zipped into a holster made for that purpose under the rt wing of my Ranger LTD with the reg hose strapped to the tank.

1, Easy to deploy for myself by just pulling the reg.

2, Easy to remove the whole tank and hand off.

3, Dosn't stick out any further than my wing or arm (no entanglement issues)

 

[Big-t-2538]

I carry my 19cuft zipped into a holster made for that purpose under the rt wing of my Ranger LTD with the reg hose strapped to the tank.

1, Easy to deploy for myself by just pulling the reg.

2, Easy to remove the whole tank and hand off.

3, Dosn't stick out any further than my wing or arm (no entanglement issues)

To points 1 and 2...I assume that you practice this often enough to feel comfortable handing off the pony in an emergency?

Have you planned how deep you can comfortably go with the pony and have that pony provide gas during the entier ascent?

I don't see how carrying a pony does not introduce an entanglement issue as opposed to not carrying it. And lastly, the way you have your pony affixed to your rig, how do you monitor the pressure in the pony itself?