GramsciBeat
Contributor
As a recovering air hog the OP has provoked a serious case of SAC envy on my part. But I am also a little confused around what the issue is; if I understand correctly the OP comes up after one dive with 2/3 of a tank left and is loath to pay for that tank to be filled.
If he does not want to refill the tank, what prevents the OP from using the same tank on the second dive, and planning the dive so that he uses another third of the original air supply, which will still result in him surfacing with a third left. That will leave him well within the recreational standard of starting an ascent with a minimum of 50bar in the cylinder*. If he is unable to plan his gas usage so as to ensure he does that, then he should definitely not be incorporating multiple cylinders into his dive plan - if he can do the plan, then he does not need to use a pony or doubles.
I really think utilising a pony as part of a standard gas plan at such an early stage is making matters unnecessarily complicated. &, personally, I would only ever use a pony as a redundant air-supply for use in an emergency situation.
*Where I dive, we don't believe in Alis - but I assume they would be filled to an equivalent of 200 Bar?
If he does not want to refill the tank, what prevents the OP from using the same tank on the second dive, and planning the dive so that he uses another third of the original air supply, which will still result in him surfacing with a third left. That will leave him well within the recreational standard of starting an ascent with a minimum of 50bar in the cylinder*. If he is unable to plan his gas usage so as to ensure he does that, then he should definitely not be incorporating multiple cylinders into his dive plan - if he can do the plan, then he does not need to use a pony or doubles.
I really think utilising a pony as part of a standard gas plan at such an early stage is making matters unnecessarily complicated. &, personally, I would only ever use a pony as a redundant air-supply for use in an emergency situation.
*Where I dive, we don't believe in Alis - but I assume they would be filled to an equivalent of 200 Bar?