Pony bottle question

[redacted]

Every time I have used a pony on an away trip, I rented it there. But I guess you could carry it with the valve out and find a shop to do a VIP once you get there too...

---------- Post added May 19th, 2015 at 10:23 PM ----------



Yeah, you are right. 40 is too big.

Or, you can carry your own fill capability. And I have never seen anyone checking for VIP outside the USA.

 

[Locus]

In both activities the line between 'recreational' and 'technical' is not clearly defined, and safe practices rely more on judgement and the avoidance of risky behavior (and conditions) than choice of gear.

I've got to agree with you there.

I don't see much of a tradeoff in extra weight and size at all - in the water, a 40 and a 13 are about the same in terms of buoyancy. If anything, the length of the 40 fits a lot better when slinging...

+1

Why does a solo diver need to keep more than 1/3 in reserve? Therefore a pony sized to approximate the 1/3 capacity of the back gas bottle, enough is simply enough.
N

I use a 100 for back gas, not an 80, making my reserve 40% of my primary supply. So really our proportions are not that far apart.

I wonder if the other divers on the boat know it's there. Assuming it is a boat dive of course...

I have seen divers without ponies take up way more deck space than they need to. Poor gear management can hardly be blamed on the gear.

 

[Dave616]

?... But I guess you could carry it with the valve out and find a shop to do a VIP once you get there too....

That's just silly...

1)Remove valve
2) plug tank Tank Plugs for Tumbling - Dive Right in Scuba
3) pack both in luggage.

 

[doctormike]

But I guess you could carry it with the valve out and find a shop to do a VIP once you get there too...

That's just silly...

1)Remove valve
2) plug tank Tank Plugs for Tumbling - Dive Right in Scuba
3) pack both in luggage.

I don't understand. What's silly? What's different about what you said and what I said?

 

[uncfnp]

I have seen divers without ponies take up way more deck space than they need to. Poor gear management can hardly be blamed on the gear.

That's true. But sometimes it's just a matter of available space. Could you imagine a full recreational dive boat where every diver had a 40 cf pony?

Of course all this is irrelevant. You use the gear you need. But it is a legitimate consideration in the pony size equation. I think that at some point, and each diver must decided that point for herself, there is a "diminishing returns" factor. As doctormike said, it's the "sweet spot" but it is an individual decision.

 

[doctormike]

That's true. But sometimes it's just a matter of available space. Could you imagine a full recreational dive boat where every diver had a 40 cf pony?

Probably a moot point in most cases. The kind of boat where this would be an issue would be a cattle boat, and therefore likely a shallow warm water reef dive. Redundancy for recreational dives is great, but really more of an issue for solo diving, deep diving, or low vis diving. On a boat catering to that sort of diver, a pony bottle would probably not be considered clutter.

Again, I'm not saying that there is no possible situation where you would (a) want a pony, and (b) be on a cattle boat. Just a general trend. I'm big on redundancy, but I have never been on a (non-solo) shallow warm water dive where I either carried a pony or saw someone else using one. The surface is your pony in that case.

Of course all this is irrelevant. You use the gear you need. But it is a legitimate consideration in the pony size equation. I think that at some point, and each diver must decided that point for herself, there is a "diminishing returns" factor. As doctormike said, it's the "sweet spot" but it is an individual decision.

Yup, exactly. These threads tend to become silly and nit-picky because the answer to the question of what's the best pony bottle size is always going to be "it depends"..!

I guess my point is that a 40 is a good thing to standardize on because (a) you can just have one pony without figuring out exactly how much you "need" for different dives, (b) it's IMHO not a particular disadvantage in terms of size or buoyancy or boat space, and (c) you can use it if you go into tech diving, or sell it more easily if you stop diving.

One last point about the benefit of more gas in a pony and the issue of dual failure probabilities. JohnN is correct - it's true that in general terms tech divers don't always consider dual failures because the combined probability (P1 x P2) is usually so low. But that equation has to be calculated in the context of real numbers.

I think that most of us agree that there is some lower limit to an acceptable redundant gas volume (search for "Spare Air" for that discussion). So many of the arguments in favor of 13 or 19 comes down to calculating required gas volumes for ascent from (arbitrary) depths, made by divers with (congratulations!) low SAC rates.

My feeling is that if you can pad your safety margin without a huge downside, that's a good thing. Things like a reg free flow or a short fill are much more common than, say, a burst disk failure. So while we might not plan for losing a first stage on BOTH the back gas and deco bottles, it's not beyond the realm of possibility for a recreational diver's pony to give them less than the anticipated volume when deployed. And padding safety with a reasonable amount of extra gas isn't such a bad idea.

 

[uncfnp]

Probably a moot point in most cases. The kind of boat where this would be an issue would be a cattle boat, and therefore likely a shallow warm water reef dive. Redundancy for recreational dives is great, but really more of an issue for solo diving, deep diving, or low vis diving. On a boat catering to that sort of diver, a pony bottle would probably not be considered clutter.

So let's use an actual dive scenario. My go to boat holds 24 divers. These are 2 tank dives so 48 tanks and of course a few spares. Then add in all the dive paraphernalia, some professional photographers, hunters (some with scooters), coolers...

 

[doctormike]

So let's use an actual dive scenario. My go to boat holds 24 divers. These are 2 tank dives so 48 tanks and of course a few spares. Then add in all the dive paraphernalia, some professional photographers, hunters (some with scooters), coolers...

Sounds like a boat with advanced divers!

C'mon. If people are allowed to bring scooters and coolers, I would be pretty unhappy if the captain told me that my aluminum 40 was superfluous and I was only allowed to bring a 19.

It's a dive boat, not a space ship.

 

[uncfnp]

Sounds like a boat with advanced divers!

C'mon. If people are allowed to bring scooters and coolers, I would be pretty unhappy if the captain told me that my aluminum 40 was superfluous and I was only allowed to bring a 19.

It's a dive restricted space ship. (fixed it!)

Ok. I surrender. 40 cf's for all.

BTW. Its not a Capt restriction but my personal preference not to deal with the bulk of a 40 amid the semicontrolled chaos ...

 

[doctormike]

Ok. I surrender. 40 cf's for all.

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