Pony bottle .. do i need one at this point ?

[large_diver]

For some folks, it is an additional way to manage risk. Some would argue that the risk of having a first stage failure and a buddy failure at the same time is very low. Others would say that a pony gives you more options.

I've taken DIRF...twice. I passed the course. I agree that buddy skills are very, very important, and I have a buddy whom I dive with 90% of the time, whom I practice with and whom I trust. But I still bring a harness-slung 30cf pony (which I also practice with) when diving in the 80-110 range. Conservative -- yes. But that's how I dive.

And the gas in your main tank won't do the same thing? Since we've established that gas management issues won't leave us where we shouldn't be in the first place, what is the pony providing that your backgas isn't?

 

[ClassAction]

As long as you are diving within NDLs all safety stops are recommended, once you exceed NDLs deco stops are required.(open-water vs. overhead) That is not to say they are optional, that is they are optional in event of emergency where greater danger is presented by employing the stop. Other more obvious overhead environments exist, but a deco obligation is also considered such.



So did you deploy your pony or did you safely ascend on the remaining 54 cuft of air in your tank?

To be clear, nothing is technically "mandatory." The scuba police don't arrest you if you blow your safety stop or deco obligation. My point was that a dive to 100 feet plus an emergency, and presumably, a faster-than-normal assent, does not give rise to an "optional" safety stop in my book. (Note: I'm sure they'll be a few curt responses to this one stating that e.g. "the ascent shouldn't be any faster than normal"; for the record, I come up REALLY slow; but in an emergency, I'm sure my rate of ascent would be a lot closer to the 1'/second than it normally is!). I'm just very careful about safety stops -- call me crazy, but I like to spend a few extra minutes on them even on e.g. a 60 foot dive. No one ever died from spending extra time at 20 feet, air permitting. But that's just me. On the other hand, if you want to do a 160 foot dive and surface immediately without a stop, I'm happy to call that "optional" and I promise not to turn you into the scuba FBI, etc.

When my buddy went OOA I did not have my pony. It was a shallow dive to about 50ish feet if I recall. Yes, we ascended on my tank. We took about 60 seconds to find our anchor line and came up very slowly. And yes, we did a stop.

As for the best size of a pony, I think that having several options would be best in a perfect world. But I didn't want to spring for e.g. a 13, 19, and 30. I don't even notice the 30 when I'm using it. Exception: I spend most of my dives lobstering and the slung tank can get in the way. With my limited experience (and some of you guys have plenty more dives under your belt than I do), I think that an inexperienced diver might need a little more in his pony than an advanced diver for an ascent during an emergency to 100'. Maybe the beginner has never even seen ANY emergency under the water, etc. Again, just my 2 cents...

 

[Green_Manelishi]

For some folks, it is an additional way to manage risk. Some would argue that the risk of having a first stage failure and a buddy failure at the same time is very low. Others would say that a pony gives you more options.

I've taken DIRF...twice. I passed the course. I agree that buddy skills are very, very important, and I have a buddy whom I dive with 90% of the time, whom I practice with and whom I trust. But I still bring a harness-slung 30cf pony (which I also practice with) when diving in the 80-110 range. Conservative -- yes. But that's how I dive.

And others would say that a pony gives more options even if the probability of concurrent first stage and buddy failure is low.

Having carried Al30s and Al40s, my conclusion is that even though a 40 is not much larger, a 30 is still much easier to carry especially if you don't need the gas capacity of a 40.

L_D dives conservatively cause he is a finance guy Entrepreneurs are more likely to dive liberally; solo, no pony. ;-)

 

[Soggy]

A 30 cf tank is also used for deco purposes.

Fair enough. I suppose it depends on what you carry for a single deco gas. If you are only carrying O2, all your stops are shallow and you can get some reasonable time out of it. If you are carrying 50%, average deco depth is around 1.8-2 ATA, which requires a bit more gas, especially when you consider that you need to bring 1.5x your planned gas requirements. I know you tend to carry something weird like 67% and are breathing a real lean nitrox mix on the bottom....I have no idea what a profile with those gasses would look like.

 

[dkktsunami]

gabriel....any luck about my pm

as to your pony bottle dilemma:

Pony bottles are a crutch for bad air management. If you need a pony bottle, then why not just switch to doubles and get more gas AND a redundant gas supply all at once...

Pony bottles should not be perceived as a "crutch" for bad air management. Rather, they are a source of redundant air supply to protect a single tank diver from a first stage regulator failure (and other problems), and this is particularily important for the solo diver. The pony bottle should not be used to extend bottom time. Diving doubles isn't the answer to everything, especially if a single 80 provides much more gas than needed for the specific diving environment.

 

[large_diver]

I think the technical term is "finance weenie" ;-)

L_D dives conservatively cause he is a finance guy Entrepreneurs are more likely to dive liberally; solo, no pony. ;-)

 

[matt_unique]

Fair enough. I suppose it depends on what you carry for a single deco gas. If you are only carrying O2, all your stops are shallow and you can get some reasonable time out of it. If you are carrying 50%, average deco depth is around 1.8-2 ATA, which requires a bit more gas, especially when you consider that you need to bring 1.5x your planned gas requirements. I know you tend to carry something weird like 67% and are breathing a real lean nitrox mix on the bottom....I have no idea what a profile with those gasses would look like.

Ha ha ha! You must have one hell of a memory. I happened to have a 67% mix last summer at some point and must have referenced that in a post???

I'm not certified on "the mix" so my deco is at 160' or less using 70% as a single deco gas. It's the best single deco gas for dives in this range actually, nothing weird about it at all. Do you use V-Planner or Deco Planner? Run some profiles and you will find 70% as a best single gas.

There was a time when I squeezed 24% for back gas but it was basically a waste of money. I use air for these dives now and 70% for deco as I mentioned. 20 min at depth (use 150' as an easy number if you want to check), using 70% deco gas with the obvious switch at 40' requires less than 10CF of gas based on my deco SAC rate. You can easily use a 30 for two deco dives of this profile.

Clearly with a 'cooler' mix, such as 50%, you will be hitting it deeper and of course using more.

--Matt

 

[Soggy]

Ha ha ha! You must have one hell of a memory. I happened to have a 67% mix last summer at some point and must have referenced that in a post???

Yeah, I just remember seeing something that struck me as a really strange number.

I'm not certified on "the mix" so my deco is at 160' or less using 70% as a single deco gas. It's the best single deco gas for dives in this range actually, nothing weird about it at all. Do you use V-Planner or Deco Planner? Run some profiles and you will find 70% as a best single gas.

It *might* get you out of the water a tid--bit faster, but using the mixes I choose to dive lend themselves to some very convenient shortcuts that don't require use of deco software at all. I always check 'new' profiles that I've inferred against V-planner before diving them to make sure I'm in the same ballpark and it's amazing how close they line up. You can infer those shortcuts from any mix, but I find it easier to divide by 2 than Pi or e. I'm not a big fan of diving "best mix" because it makes it harder to remember all the nice shortcuts that allow me to adjust my profile in the water, I can't permanently mark my tanks, and for safety reasons, I prefer getting on a single deco gas deeper.

Actually...I just ran two profiles for 150'/20 mins:
air w/ 50%: 43 mins
air w/ 70%: 42 mins
air w/100%: 44 mins
21/35 w/ 50%: 40 mins
21/35 w/ 70%: 38 mins
21/35 w/ 100%: 42 mins

I would tend to do 30 mins at 150', and here are the profiles for that:
air w/50%: 69 minutes
air w/70%: 67 minutes
air w/100%: 72 minutes
21/35 w/ 50%: 61 minutes
21/35 w/70%: 61 minutes
21/35 w/ 100%: 66 minutes

Of course, that is using my slightly tweaked settings (3 minute extension at the gas switch) and +1 conservatism. With these short times, obviously we are talking a matter of a couple minutes here or there...nothing to be too concerned about, especially if it means making up a best mix that I might have to remix for the next dive if I get blown out or change destinations.

You might consider doing some mix training. At 150', whether you realize it or not, you are seriously impaired on air, plus helium allows you to get out faster. It's a lot more fun that way.

Sorry for the waaaaaayyyyy off-topic post.

 

[drbill]

The whole First Stage Failure argument doesn't wash, we all learned how to breathe a free-flowing reg in OW class. If your first stage happens to blow at the same moment your buddy skills lapse, then begin an emergency ascent and kick yourself for your buddy habits. How many times is that likely to happen before Darwin catches you crossing the street one day anyway?

Depends on when in the dive the first stage blows and how good your buddy is. Not always a safe situation especially where buddies are assigned on boats and not someone you are familiar with.

What if your debris tube clogs and there is NO air coming through your secondary, your octo or you pressure gauge and you are on a deep dive. It happened to me and I was fortunate enough to survive by doing a CESA from depth with no air in my lungs (and diving solo without my pony... never again). Although this is assumed to be a rarity, it happens more frequently than we think.

 

[matt_unique]

Yeah, I just remember seeing something that struck me as a really strange number.

It *might* get you out of the water a tid--bit faster, but using the mixes I choose to dive lend themselves to some very convenient shortcuts that don't require use of deco software at all. I always check 'new' profiles that I've inferred against V-planner before diving them to make sure I'm in the same ballpark and it's amazing how close they line up. You can infer those shortcuts from any mix, but I find it easier to divide by 2 than Pi or e. I'm not a big fan of diving "best mix" because it makes it harder to remember all the nice shortcuts that allow me to adjust my profile in the water, I can't permanently mark my tanks, and for safety reasons, I prefer getting on a single deco gas deeper.

Actually...I just ran two profiles for 150'/20 mins:
air w/ 50%: 43 mins
air w/ 70%: 42 mins
air w/100%: 44 mins
21/35 w/ 50%: 40 mins
21/35 w/ 70%: 38 mins
21/35 w/ 100%: 42 mins

I would tend to do 30 mins at 150', and here are the profiles for that:
air w/50%: 69 minutes
air w/70%: 67 minutes
air w/100%: 72 minutes
21/35 w/ 50%: 61 minutes
21/35 w/70%: 61 minutes
21/35 w/ 100%: 66 minutes

Of course, that is using my slightly tweaked settings (3 minute extension at the gas switch) and +1 conservatism. With these short times, obviously we are talking a matter of a couple minutes here or there...nothing to be too concerned about, especially if it means making up a best mix that I might have to remix for the next dive if I get blown out or change destinations.

You might consider doing some mix training. At 150', whether you realize it or not, you are seriously impaired on air, plus helium allows you to get out faster. It's a lot more fun that way.

Sorry for the waaaaaayyyyy off-topic post.

The whole point of deco on something other than back-gas is to get you out of the water ASAP. For Spring deco dives on the Crane for example 2 minutes makes a difference.

I am intimately familiar with the benefits of mix training and the narc impact at 150'. 160' is my absolute max based on the gases I am currently qualified to breath. Mix certification is forthcoming when I prioritize $1000 for the course.

What's your next investment? Off topic...just curious.

--Matt