Pony Bottle weighting question

[DaleC]

I have used a 19cuft, 30cuft, 40cuft and 80cuft stage/pony before and don't adjust my weight because of them. In the water they don't affect trim or bouyancy the way one would think.

There are pro's and cons to handing off a pony. On the one hand it may seem safer to gain distance from a buddy but on the other hand it could be safer to maintain contact; considered from a recreational perspective that one would be doing a direct ascent if switching to a pony and not deco. I guess it all depends on whether one anticipates their buddy losing their mental faculties and trying to drown them - but in that case why dive with them in the first place. I personally would plan to stay with a buddy who has just experienced an OOA to help guide them upwards (but that's just me).

Thinking one needs to buddy breath off a pony is also a little skewed. You will in almost all cases be dealing with one loss of gas; either yours or your buddies. In that case one person breathes off the pony and one off the functional backgas.

 

[gmanstan]

I was actually thinking of "Buddy breathing" not of passing the reg back and forth but as handing that backup reg(pony 2nd) to your buddy the same way he would be on your oct reg.Much in the same way you would with a traditional "air share" only his supply would be off your pony vs your main tank. I also assumed from your original post your pony would be back mounted to tank for redundant(OOA situations) more so than a Stage bottle.I dive with a 19cf as redundant. Question, if diving a 30cf and a 100cf, is there an advantage of this over diving doubles? 72's or 80's?

 

[jar546]

I use a 30 side sling pony and make no adjustment to my weighting. Simply not necessary.

 

[Bob DBF]

The Pony is my emergency gas, we both breathe off my back gas on the ascent. It isn't an emergency untill we're short on back gas, which will bring up planning issues later.


Bob
-----------------------------------
I may be old, but I’m not dead yet.

 

[Hatul]

I sling the 13 or 19 pony, so they're 3-4 lbs negative with the reg and the hardware. In my thinking it does not make sense to dive overweighted for that rare chance you need to use it. So I don't plan to hand off the pony and I remove 3 lbs on the side of the bottle. So the sharing of air is less convenient this way, but we're talking about a rare event.

Removing the weight keeps me in balance and the 3 lbs makes a difference shlepping the thing on land in shore diving.

Adam

 

[GeorgeC]

To clarify, do you have a primary reg, spare 2nd stage(Octo) and a 3rd reg on the pony?

The Pony is my emergency gas, we both breathe off my back gas on the ascent. It isn't an emergency untill we're short on back gas, which will bring up planning issues later.


Bob
-----------------------------------
I may be old, but I’m not dead yet.

 

[Zesty]

Thanks to everyone for their input - I'm gonna keep the weight as is ..........

 

[jar546]

If my buddy is stuck and needs air, I have something to leave with him/her while I get help. There are times, albeit rare that handing off your pony bottle is necessary. Don't live inside the box.

 

[Bob DBF]

The Pony is my emergency gas, we both breathe off my back gas on the ascent. It isn't an emergency untill we're short on back gas, which will bring up planning issues later.

To clarify, do you have a primary reg, spare 2nd stage(Octo) and a 3rd reg on the pony?

When diving in my usual configuration you are correct. I believe that maintaining close contact with the other diver and being in control of the ascent will keep the situation from becoming an emergency.

Occationally I dive with a double hose and I suggest the other diver stay on the pony side and insure he understands that the pony reg is the "octo". Buddy breathing on a double hose is not the fun that Mike Nelson makes look like, and an OOA situation is no time to learn how to do it.



Bob
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In case anyone missed it, while still far better than drowning, having to do a CESA means you have violated two main rules of safety on the same dive: OOA (Out Of Air) and OOB (Out Of Buddy). It's time to re-evaluate your practices before you find yourself OOL (Out of Luck) and seriously injured or dead. NetDoc

 

[DaleC]

I also usually keep two second stages on my back gas and one on the pony. This is partly due to convenience ( not having to swap second stages on and off when diving pony/no pony and partly to allow the second diver access to my back gas as well as my pony gas. I try to be an independant diver but not a selfish one - I don't mind sharing all my resources as long as we both get back up.




"Question, if diving a 30cf and a 100cf, is there an advantage of this over diving doubles? 72's or 80's?"

My answer is based on the assumption that the diver intends to be an autonomous unit and not dependant on their buddies gas.

It's more available gas vs extra weight vs convenience vs gas management strategies: so you have to crunch the factors and determine what's needed and what's possible for your dives.

If you gas plan correctly and say, need 30cuft for reserve gas, then a 30/100 combo really only allows you 70cuft of gas for the dive. 30 in the pony, 30 in back gas. This takes into account a failure of one tank at the worst possible moment (max. depth/duration).

If you use say, a 72/72 independant double combo, this would allow 84cuft of gas for the same dive (assuming a true fill) but it requires you to do regulator swaps and monitor the volume in two tanks (I've always seen this as a positive but others may not).

Using an isolation manifolded 72/72 combo could theoretically allow 114 cuft of usable gas but a failure at max, depth/duration would most likely let too much gas escape before successfully isolating, so your reserve would need to take into account how long it takes you to isolate (thus lessening your usable volume).

Using Al80/80's instead of St72/72's allows for 10 more cuft of gas in total (assuming true fills) but also requires 10 more lb's of lead to be added to the rig (in my case) to compensate for the increased bouyancy of those tanks.

Some people use an isolation manifolded combo like independant doubles by closing the isolator and occasionally equalizing pressure. I understand it in theory but have not dived that way so I'll leave it up to someone who has to describe if they want.