Using a pony. Mix?

[tbone1004]

60 was straight out of my as$, but he said shallow on air, so I figured 60ft would suffice for that. I still roll with err on the side of safety which is having a pony be as rich as reasonable for that dive, but there is also a reason I don't do single tank diving below 60ft if I can help it, and certainly not when coming anywhere near NDL's. Double LP72's for all of my recreational open water/ocean diving unless I need more gas.

 

[kwinter]

We've had this discussion umpteen times before. If you like to practice and breathe off your pony so that it will need filling often and you are a cheap arse bastard like Dumpster, then you fill it with air. If you understand the physiology and recognize that you will only need to top off the pony once a year, then you fill it with 32% or 28% (1.6 or 1.4 at the 40m limit of recreational diving) and leave it alone. The richer gas is better, no matter what your back gas was.

 

[Dr. Lecter]

Part of the preference for air in a pony may come from not considering 130' to be an actual limit for rec diving. I know I don't want to have to worry about how deep my redundant air source can go on any given day, and I suspect dumpster has a similar concern. Ironically, I dive a pony more now, because I scrapped the 'doubles for everything' approach in favor of either going CCR for real dives or just single tank/DPV for everything else.

 

[Colliam7]

I'm signed up to take a U-boat Diving course. Part of the recommended equipment is a pony bottle, so I found an AL30 on CL for a good price and bought it. Now I'm wondering what to fill it with.

Fill it with air. As several posters have already noted, that is the least expensive option, the most flexible option and the safest option for the recreational diver.

So, correct me if I'm wrong, but the pony bottle is ONLY for emergency OOA situations.

No real need to correct. You are not wrong. Now, I might word the statement a little differently. The pony bottle is NOT part of your gas supply for the dive as planned. You should plan your dive - depth(s) and time - on the basis of what you have on your back (or, side, if diving single cylinder sidemount), with appropriate reserves built in. Having said that, anyone who dives a pony bottle is well-served by practicing - regularly - with that bottle, so that switching in a stressful, emergency situation is mechanical, fluid, and requires no extraordinary thought or effort. So, I would encourage you to periodically switch to your pony bottle, for example at your 15 ft safety stop, on a regular basis, just for practice. You may decide that you want to practice switching at depth, again to maintain proficiency. Technically, in those cases you are using the bottle for something other than an emergency OOA situation. But, your general premise is nonetheless correct.

I'm particularly concerned about the example scenario where I'm at 110' on EAN32 and have air in the pony. Suppose I am 1 minute from my NDL (for EAN32) and, for whatever reason, I have to switch to the pony (i.e. air). Is that potentially going to put me in a mandatory deco situation? I think it would not. I *think*, in that scenario, when I switched to the pony it would be no different than if I had been diving on air the whole time and gotten to 1 minute from my NDL. I.e. I would do a normal ascent immediately, with a standard safety stop, and be fine.

I won't say you are overthinking the issue, but you certainly do have a creative imagination for 'what if' scenarios. However, you are correct - switching to air, and completing a normal ascent will not necessarily put you in a mandatory decompression situation that requires stops or procedures beyond those associated with a normal ascent. As an example, if you dive to 130 ft on air, relax and watch the NDL on the PDC count down to 0, then start increasing, and begin a normal ascent when the PDC shows a mandatory deco obligation of ~ 5 minutes, by the time you pass ~75 ft, the PDC will once again show NDL remaining, and that time increases as the ascent continues to the 15 ft stop.

Fill your pony with air. Use your pony as an emergency reserve. Practice with it. Plan - and execute - your dives in a careful, prudent manner. Life will be good.

 

[stuartv]

Thanks, all. I think I understand the issues well enough now. Annnd... I think I will just wait until the classroom part of my U-boat course and ask the instructor what to fill it with. If he doesn't have a specific direction for me, then I will use the info from you all to decide. Probably go with air for starters. At least for what's in there during the training dives I do during the course.

Like I said, though, if the instructor says "fill it with X", then I will fill it with X. At least until I'm through with the course.

Again, thanks for all the input and insight.

 

[uncfnp]

Edit... I see the OP posted as I did.

 

[hroark2112]

I fill mine with 100% O2. Anyone dumb enough to be OOA on a dive with me should breathe the 100% and tox.

OK I'm kidding. I keep mine filled with good ol' 21%. Top it off when I fill tanks, it's always ready if I need it.

 

[Dr. Lecter]

I fill mine with 100% O2. Anyone dumb enough to be OOA on a dive with me should breathe the 100% and tox.

OK I'm kidding. I keep mine filled with good ol' 21%. Top it off when I fill tanks, it's always ready if I need it.

You joke, but I've had instances where I was diving single tank and a 40 of 100% for light deco and had to shoo a low on air cattleboat diver towards their DM and away from the "pony" I mean, I'm the guy not from your boat...on a DPV...with only one second stage on a 22" hose attached to his head with a necklace...am I really your best option for air on a deep wreck crawling with divers??

 

[Lorenzoid]

Now that the actual question has been addressed, may I ask what is a U-boat course? Is it like a combo Deep/Wreck course with the addition of how to use a pony bottle?

 

[stuartv]

The U-boat Diving course is:

2 days of classroom devoted to all things U-boat. History, battle tactics, etc, etc.. Taught by an expert in the field.
2 days of classroom to cover the SDI Deep and Wreck specialties.
1 day of confined water training.
2 days of open water diving to complete the SDI Deep and Wreck specialties.
1 day field trip to dive a sunken U-boat (U-352) off the coast of NC

All of the above including any extra info and training relevant to specifically diving a U-boat.

The course required equipment includes a wreck reel, and an SMB. Recommended equipment includes a 30 cu ft pony.

The course is offered by BAREG (https://www.facebook.com/pages/Batt...nd-Expedition-Group/197605283676035?ref=br_tf), of which I am a new member. A more thorough description of the course is posted on the BAREG FB page.