Do you actually see people diving with pony bottles?

[Kharon]

Re. Mounting:

The point I've been trying to make is that there is no formal guidance on this.

Then uncfnp said:

Hmmm. Good question. A pony bottle, used *by the book* is never part of your gas planning for a dive, even drift dives like Cozumel. So no. You can not count it as part of the gas plan.

And you replied:

Which book? I don't think there's a thorough treatment of recreational gas planning anywhere that addresses the use of pony cylinders in a thorough way. I don't think there's a consensus on terminology or on what is and is not a safe gas planning approach for recreational dives.

You err on both counts. The SDI Solo Diving manual covers both issues extensively - very thoroughly. And while there are differing views on what constitutes the "best" gas planning I think the terminology is fairly well established and straightforward. Perhaps it's your derth of education/understanding on the subject that causes you problems.

 

[Coztick]

So is it ok if I take 2 80s and breathe 1 down to 500 psi and start my accent when the other hits 500 psi.?

 

[Coztick]

Thanks for everyone's input.

 

[uncfnp]

Thankyou,
OK, let's say 450 in the pony, another -50 for gauge inaccuracy.
Say start the accent at 600psi and on the boat with 250-300psi?

In this scenario the pony is emergency redundancy so doesn't apply to the dive gas calculations. So I see the question as...is it safe/feasible for me to start my ascents in drift diving at 500 to 600 psi. In my book, and I tend to test the limits, the answer is no. Yes, you have your emergency redundancy but getting back on the boat with 200 to 300 psi is not good diving practice, even for liberal dive management. If for no other reason than you are putting the dive ops tanks at risk for water intrusion if you use just a little more than planned or that gauge is off by just such an amount.

But in short, a dive plan that carries a fair amount of risk of needing your backup gas, and I think ascents at 500 psi do, is poor gas management...IMOH

 

[ljpm]

So is it ok if I take 2 80s and breathe 1 down to 500 psi and start my accent when the other hits 500 psi.?

Seems its not ok if you are using a pony bottle but quite ok if you are using a stage bottle. Please make sure you store your stage bottles and pony bottles separately. You wouldn't want to mistakenly grab a pony and violate any rules.

 

[uncfnp]

Seems its not ok if you are using a pony bottle but quite ok if you are using a stage bottle. Please make sure you store your stage bottles and pony bottles separately. You wouldn't want to mistakenly grab a pony and violate any rules.

Actually no. That is a fairly smarta$$ remark and it is incorrect. And I doubt his sidemount instructor taught him that. Of course I have only had overhead sm instruction and likely sidemount open water has different procedures. Perhaps you could enlighten us?

 

[The Chairman]

First of all, if you are diving 2 80cf tanks down to 500 psi each, then you probably don't have enough gas to accommodate your deco obligation.

I teach that for OW, you should keep 100psi/10 ft of depth for your ascent with 500psi as the absolute minimum. If your dive takes you to 130 ft, you should start up with 1,300 psi. That gives you 800psi to swim away from the boat, 900 psi to get back to the up line and 1,300 to ascend (on a 3,000 tank) That should be enough for you and your buddy to ascend with a safety stop. The presence of a pony bottle does not change this. If you want a longer dive, you and your buddy should invest in bigger tanks, but be careful about that deco!!!

20cf and 13cf tanks should never be used in your gas planning. They are redundancy in case you run out of air AND lose your buddy. If you are truly freaked out, they won't last very long at all. You don't have the gas you think you do.

40cf and above can be used in gas planning, as long as you plan on deco obligations as well. Any decent deco software can sort this out for you. My Petrel does an awesome job telling me what gasses I can use and when. This is the essence of tech diving and not something you should just play with. Learn it right or leave it alone.

 

[markmud]

Wow,

I apologize to all as sometimes I am slow on the uptake. I miss things all the time.

I like what Pete, uncfnp, 2air, Max, Kharon and others have offered to Coztik.

I am wondering what is the root cause or reason for Coztik to think about ponies and/or sidemount this way? Why use a small pony to extend range?

I use ponies and practice with them. I do pony bottle ascents while reestablishing my buoyancy, while shooting an SMB, while doing a deliberately slow ascent and I add a safety stop for the heck of it. I was trained to do these things. I have done several practice ascents from 105 fsw (with all the other actions listed above). I have done three ascents on a single tank-full with a 13 cf bottle from 60 to 70 fsw.

I could not do these things with a starting pressure of 500 psi.

I have done staged decompression and used nitrox as a decompression gas (gas switches).

I was trained to do these things.

If you want to extend your range with stage bottles and deco bottles, have you thought about getting trained? Tech 40 and Solo courses are really good. The best courses a recreational diver can take (IMHO).

I am iterating, what is the root cause that is causing you to ask these questions?

Have you thought about buying a bigger tank if you have a high sac rate?

I apologize to all if I missed the root cause somewhere.

thanks,
markm

 

[DMDavid]

I used to dive with a 13cf pony as a backup safety when doing wreck penetrations but found that the extra bottle only added to the entanglement hazards. Now I only carry a pony bottle once in a while when playing with my bubble blower.

 

[lowviz]

I...//... I now see that there seems to be two major camps on SB: those who insist on (almost) always using a pony, as the effort and inconvenience is minimal relative to the potential benefit; and those who believe that using a pony is more dangerous than not. ...

Still enjoying this thread...

I see three camps: Difference Between Optimists, Pessimists, and Realists - Glowball Web Network

Now we just have to find a pony solution that is acceptable to all three.