Pony bottle questions

[LowDrag]

Hey everybody.

I have been looking at pony bottle threads and have a couple of unanswered questions floating around in my head. I am looking at buying my own tanks next year and I am considering a pony bottle. I know a few people that back mount them but I am not sure whether I would prefer the back vs a slung bottle or not. I am also wondering about bottle size. It seems that a lot of people like 13 cf pony's but I have also seen where some like the the 30 cf pony's better. I have recently upgraded my primary and secondary second stages so I have a primary and second that would suitable for a pony now I just need to figure out which configuration I want to go with.

So my question is not which is better but why do you prefer the rig you have set up? I am just looking for other divers thoughts on why they do what they do.

Thanks everyone for enlightening me...

 

[mouthbreather1]

i to am considering a pony my thoughts after researching is a 30 slung for a few reasons
1: can be shared easily in an o,o,g situation
2: can be easily controlled (turned on and off at the valve without having to reach )
3:can be used for deco when appropriate (repurposed for o2)
4: 30 cf is enough to get out of trouble 13cf is not enough in my mind
hope this helps

 

[tomfcrist]

The back mounted smaller pony tanks(13-19cuft) are just fine, however they are a bit of a hassle when diving off a charter that is less than spacious.

The slung bottles(could be any size) are easy to deal with on the boat and are completely accessible while diving.

I think people that like the 30cuft and bigger tanks most likely have aspirations to get involved in tech diving, as the 30-40cuft tanks are the mainstay for deco gasses.

 

[claymore]

Some charter boats have tank mounts that are not condusive to back mount pony's. There have been instances of breathing off of the wrong second or gas off with back mount.
Slung is a bit more work attaching a slung pony and gearing up. Getting back on board a boat is tough unless the pony is disconnected and handed up, which can be a pain with thick gloves and rough water but with practice and the right setup it isn't real difficult.

I went with a slung 30 because I like having extra gas and I have easy access to the tank valve, reg and spg. In an OOA or low on air situation you just hand off the pony second stage or the whole rig if needed

 

[Roman_66]

+1 to that mouthbreather1 wrote.
Also points : will you start your dive with open valve ? You must to do it if you will connect pony back on main tank, as you don't have access during the dive.
Now think WHAT you will do in case of fail-over situation (free flow/gas leak/unknown noise). I always put 30cu pony on two left D-rings on my any dive with one tank.
I don't use pony as deco tank, so in double configuration and I believe that redundancy of double is enough.
By mounting pony back on main tank your cross cut will be bigger and may catch on line or something else and you will not have chance unleash by yourself.
Pony, connected on two D-rings on left size, does not interfere, you will not feel it under water, but you have full control. You can put 1-2 lb more in your right weight pocket, when in left to compensate pony buoyancy, but I don't feel that I need it. Pony doesn't impact my trim. Check specification, 30cu has -2.0 (full) to -0.1 (500 psi) buoyancy, so you don't need to add/remove any weights.
Regarding pony size : It is very simple, take your average air consumption, multiply 1.7 - 2 (emergency situation) and calculate how much do you need to come to surface from 110 ft (maximum recreational deep).
I assume that you plan to have pony is not just to be able come to surface and go immediately to pressure chamber, so acceding speed should be according to rule.
My calculation shown that I need 19cu. My instructor persuaded me that real size different between 19 and 30 is actually not so big and feeling under water is mostly the same. Price also was pretty close. So I bought 30cu with mount set and still think it was correct decision.

 

[LowDrag]

i to am considering a pony my thoughts after researching is a 30 slung for a few reasons
1: can be shared easily in an o,o,g situation
2: can be easily controlled (turned on and off at the valve without having to reach )
3: can be used for deco when appropriate (repurposed for o2)
4: 30 cf is enough to get out of trouble 13cf is not enough in my mind
hope this helps

Precisely what I was thinking also.

The back mounted smaller pony tanks(13-19cuft) are just fine, however they are a bit of a hassle when diving off a charter that is less than spacious.

The slung bottles(could be any size) are easy to deal with on the boat and are completely accessible while diving.

I think people that like the 30cuft and bigger tanks most likely have aspirations to get involved in tech diving, as the 30-40cuft tanks are the mainstay for deco gasses.

My thoughts are not pointed to tech diving but I do dive with my wife so ease of access plus the ability to have enough air for that odd situation where it may be needed is also enticing. I have not done a charter yet but that is in the near future. There are several dive charters up north in the Puget Sound that I am looking forward to diving and I like the idea of a slung pony being easier.

Another question that comes to mind is buoyancy and trimming out for a dive. How does the slung 30 cf bottle affect each of these? Do divers place more weight on the opposite side of their BC to offset the pony?


---------- Post added October 5th, 2014 at 10:43 AM ----------

+1 to that mouthbreather1 wrote.
Also points : will you start your dive with open valve ? You must to do it if you will connect pony back on main tank, as you don't have access during the dive.
Now think WHAT you will do in case of fail-over situation (free flow/gas leak/unknown noise). I always put 30cu pony on two left D-rings on my any dive with one tank.
I don't use pony as deco tank, so in double configuration and I believe that redundancy of double is enough.
By mounting pony back on main tank your cross cut will be bigger and may catch on line or something else and you will not have chance unleash by yourself.
Pony, connected on two D-rings on left size, does not interfere, you will not feel it under water, but you have full control. You can put 1-2 lb more in your right weight pocket, when in left to compensate pony buoyancy, but I don't feel that I need it.
Regarding size of pony. It is very simple, take your average air consumption, multiply 1.7 - 2 (emergency situation) and calculate how much do you need to come to surface from 110 ft (maximum recreational deep).
I assume that you plan to have pony is not just to be able come to surface and go immediately to pressure chamber, so acceding speed should be according to rule.
My calculation shown that I need 19cu. My old instructor persuaded me that real size different between 19 and 30 is actually not so big and feeling under water is mostly the same. Price also was pretty close. So I bought 30cu with mount set and still think it was correct choice.

Hey Roman, that just answered my questions that I was posting as you were posting but there is one thing you said that I am not quite clear on. I will highlight it in red and maybe you can show me what you meant.

Thanks!!!

 

[LeadTurn_SD]

I has been many years since I've done any deco diving, but I use a 30 cu ft pony (slung) for occasional deeper dives.

I recommend comparing the size and weight and buoyancy differences of the various pony bottles, relative to their capacity, then think about how you plan to use the pony.

For shallow reef dives here in Hawaii, the pony stays home. For deeper reef dives (> 80 feet or so), I like the fact the the 30 give me a fairly large emergency reserve volume. Smaller than 30 I see as a "bailout", no-stop, get me straight up to the surface alive bottle; the 30 gives you the choice of a fully normal return to your exit point with all stops.

Best wishes.

 

[Roman_66]

Hey Roman, that just answered my questions that I was posting as you were posting but there is one thing you said that I am not quite clear on. I will highlight it in red and maybe you can show me what you meant.

And I continued to update my post during you were updating yours
If currently you put 3 lb in each pocket (total 6lb), now you can put 4 lb in right pocket and only 2 lb to left pocket, because pony with 2lb negative on your left size.
Please don't reduce your total weight, because 500psi 30cu pony has neutral buoyancy!
But, as I mentioned I (as many others) don't need it, 2 lb will NOT turn you to any side.

the 30 gives you the choice of a fully normal return to your exit point with all stops.

Exactly !

 

[Nemrod]

Do not get a 13 cf. They do not sling well. Either a 19 or a 30, both sling nicely. Frankly, a 19cf is quite enough but a 30 is just more of a good thing.

But then, pony bottles do not exist so this thread is a figment of my imagination.

N

 

[rongoodman]

If I was going to dive with a pony bottle, I'd take a 30 or 40 cf bottle, and sidemount it like I do my bailout bottle with the rebreather. If I thought I needed a pony, though, I would just do the dive in doubles, either back or sidemounted.