Pony practice...what do you do??

[Buoyant1]

I usually practice deploying it on a safety stop, just to make sure it's part of my "muscle memory".

 

[Puffer Fish]

Some interesting ideas, especially later in your post, that to me sound more in the tech diving realm. The thing I wanted to respond to here is that if you're using a non-recreational blend (50%O2) I think you're clearly talking about deco gas, not a bailout bottle, unless you have a hard bottom of 60ft.

If by some chance an OOA diver went for this gas (thinking it was an octo due to the way the reg is routed) at a significantly greater depth there could be big problems. I guess it's a matter of judgment. I would handle this bottle exactly as a deco stage, clearly marked as such.

I believe there is a fair amount of confusion regarding MOD...I dive with my computer set to a MOD of 1.4...but do not see any issue with a small exposure to 1.6 or higher, as long as my cns level is very low and the duration is extremely short. Would strongly suggest against that if it is not your first dive.

My diving typically involves a first dive of around 90 ft...and I use a maximum short term MOD for the Pony of 1.8 (very short term, as in seconds).. which is 86 ft.

If I am going deeper, then I adjust down the pony to match.

Note: unless you have a multi-gas computer, do not bother doing this.

Note2: As I am actually going to use this tank during the dive, and have to get it refilled, I am never stuck with the mix it has..

You then just do your dive to the no-deco limit, start your accent and when prompted, switch to the 50% mix (around 50 ft). If your pony does not work, you have to have enough gas still in your main tank to safely do the rest of the dive.

In an emergency, switch to the pony and head up.

This is not tech diving... just using a multigas computer would get me burned at the stake.

Why go to the bother?

The dives I normally do are time limited...if I spend more time on the bottom on the first dive, my surface interval will have to be shorter, and the next dive (to around 70 ft) will have to be shorter.

Plus, using the equipment every dive day is great practice.

By doing the above, and staying at the safety stop longer than 3 minutes, I can increase my available bottom time on the next dive by as much as 20 minutes, with a shorter surface interval, while doing it safely.

Looking back over my dive data, here is an example of a typical set of dives:

1. First dive to 86 ft on 33%.. for 56 minutes using the pony for 50 ft up... with 1300 psi left in my 117 cf tank...

2. Surface interval of 51 minutes.

3. Second dive to 83 ft on 36% for 51 minutes, did not use pony, with 1230 psi left at end of dive (not using pony resulted in more main tank usage).

That day represented the highest cns I have been at in 2 years... 34%

Both profiles are flat.

My sac rate was .52 and .51 .. but breathing rate during accent for both dives was under .4 (using gas in Wing and intial jump in tends to be much higher).

 

[Reg Braithwaite]

1. First dive to 86 ft on 33%.. for 56 minutes using the pony for 50 ft up... with 1300 psi left in my 117 cf tank...

2. Surface interval of 51 minutes.

3. Second dive to 83 ft on 36% for 51 minutes, did not use pony, with 1230 psi left at end of dive (not using pony resulted in more main tank usage).

Are those run times or do they include your ascent and safety stop? And how much time do you spend at the safety stop?

 

[Puffer Fish]

Are those run times or do they include your ascent and safety stop? And how much time do you spend at the safety stop?

Time on the pony for the first dive was 11 minutes...add less than one for travel up to the point of switching.

Bottom time on the second was 37 minutes.

I don't push the no-deco limits..and maintain very healthy gas reserves.

At the point I headed up on the first dive, I had 12 minutes of no-deco time left, and 1380 psi.

Had I gone another 6 minutes or more on the bottom, I would have extended my safety stop (I used half the gas in my pony during that dive) to end up at the exit at roughly the same point.

My buddy on that dive was using a suunto... and ran out of no-deco time. or I would have gone down to 1,000 psi.

Fairly difficult to figure this out without software, but in practice, it turns out that, at least with the Galileo...if you use the nitrogen loading bars as a guide, dropping one bar represents at least one letter group...(for an easy way to think of it).. so all one does is stay at 15 feet until you see the bar go down one more than you would normally see.

Typically, that represents around 10 minutes or more minutes of time on the next dive...at a cost of around 3 minutes...sometimes much better. As I did just under 70 trips last year, that represents (at almost no cost to me) more than 8 extra hours of safer bottom time.

Figuring out how my computer would calculate that, compared to software calculations (which were considerably different) and then coming up with how to execute it was no small task......as one has to do dives and then model what the results were. I could find no data that would actually allow me to predict what the computer would actually do...and software assumes a level profile...which even my flattest one was not that smooth.

What I ended up doing was taking the exit info from each dive, and using that (depth and no-deco remaining), and making a profile time that ended with those same numbers, and then modeled the difference using main gas versus higher nitrox.. then compared that to what I actually got at the start of the next dive and the dive planner built into the computer.

Doing it, though, is easy.