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mrivken
November 26th, 2009, 02:32 PM
I did search and read existing pony(bailout not staging) bottles related threads but have few unanswered questions anyway:

1. People mentions using DIN regulators for pony to make setup more streamline.
I am diving in area where Yoke used exclusive . So, if I buy DIN regulator and bottle with DIN valve, how I will able to fill bottle ? Do I need to put valve insert every time befor filling and take it out before mounting regulator or some simpler method exists ?

2. How often it needs to be refilled (of course if it was not used/freeflowed) ? I assume that I will need to take few breathes before each dive (normal pre-dive check) but with smallish 13CF bottle it can deplete bottle fast enough.

3. What type of pony gauge you would recommend:
a) mounted directly on the bottle;
b) using hose strapped to the octopus;

BTW: I am planning to keep it strapped under bladder wing of my Ranger LTD with regulator pointed down.

Thank you,

MR

idocsteve
November 26th, 2009, 02:46 PM
I dive in the NE Atlantic and use a single AL80 with a 19 cubic foot pony bottle for bailout purposes as I have not yet taken the plunge to a doubles set up with a sling bottle. A 13 is a bit small for use as a bailout from any real depth.

It's strapped to the main tank. I like that set up because it's behind me, out of the way and secure.

My pony bottle uses a yoke valve, which I recommend since that's what's available in your area. I don't see DIN being all that much more "streamlined" than yoke.

My pony bottle has a little mini gauge that screws right into the first stage, it doesn't have a hose, and it's easy to tell at a glance if it's close to full. I have no clue what you mean about that stuff about "valve insert before filling and mounting regulator". One breath before each dive of the day won't deplete the tank all that fast and you need to make sure it's delivering breathing gas, that's the only way to do it.

I change the gas in that tank once a year, assuming of course that I haven't used the tank.

I have taken it to Florida on one occasion since I knew I'd be solo diving. The dive shop did a quick visual and refilled it for me on the spot.

RonFrank
November 26th, 2009, 02:49 PM
I use a 19CF bottle, and would recommend that size even if a couple friends are happy with the 13CF.

I'd skip the DIN setup unless you use DIN for other valves. There is little point in using DIN for the sake of using DIN.

I mount my pony on my tank. I do so as I often carry a camera UW, and don't want to have a bottle in my way (Sling). However some of my buddies sling their pony's, and that works very well also.

I use a standard first stage, a Zeagle ZX octo, and a standard brass gauge. I've read less than flattering things about the tiny pony gauges, and if they are mounted on the first stage you can't read them easily.

Honestly an SPG is not all that necessary except for the fact that these bottles don't carry much air, and if they have a slow leak, they maybe empty when you need them if you have no way to monitor the pressure.

keithdiver
November 26th, 2009, 02:49 PM
First of all you want to figure out what type of diving you are going to do. Are you diving with doubles or single tank? If you are nitrox certified you should fill the tank with 40% nitrox. My advice would aslo be to get a tank that is bigger than 13cu. you want something that can get you out of a jam if you have one. I would look at nothing smaller than a 30 cu. it is all negative weight, and it will not hurt you carrying it. As far as a reg , look at one that is 02 clean Oms workhorse, zeagle, somewhere in that line. You also do not want a peanut gage for air, you want something that you will be able to read without a problem..

Michael_Lambert
November 26th, 2009, 02:53 PM
If you are nitrox certified you should fill the tank with 40% nitrox.

I think this is bad advice.

Nitrox or not, You need to carry the gas that is required for your dive. Using a pony as an emergency air source would mean you want to have a mix in it that will match your bottom mix.

Having a 40% mix in your emergency gas supply and diving to 130 feet might not be wise.

For the hassles involved with diving a stage or pony i would recommend at least a 40CF. We dive with 80's only due to where and how we dive, however the cost involved for a 19CF and regs and rigging you might as well sling a 40 and have enough gas to work with.. When diving fun local dives i will carry a 40 of 50% just for cleaning up on our safety.

willembad
November 26th, 2009, 02:56 PM
you should fill the tank with 40% nitrox. My advice would aslo be to get a tank that is bigger than 13cu. you want something that can get you out of a jam if you have one. I would look at nothing smaller than a 30 cu.

So you recommend a pony big enough to bail out on from considerable depth but wants him to fill it with a gas he can not use at that depth?

Willem

idocsteve
November 26th, 2009, 02:58 PM
I've read less than flattering things about the tiny pony gauges, and if they are mounted on the first stage you can't read them easily.

Honestly an SPG is not all that necessary except for the fact that these bottles don't carry much air, and if they have a slow leak, they maybe empty when you need them if you have no way to monitor the pressure.

I'm curious what you heard about the tiny pony gauges that are less than flattering? It's a simple device, I can't imagine what problems there would be.

Regarding "reading them easily", yes it's nearly impossible to see the gauge unless you get within a few inches of it, while diving that would be almost impossible but that's not when you're going to check it. Like you said, the gauge is only necessary to monitor for leakage over time, and that's done when you check the gauge during your predive check.

Michael_Lambert
November 26th, 2009, 03:05 PM
I have dove several times using the "Button Gage" and found it nice, out of the way and when needed easy to view.

bamamedic
November 26th, 2009, 03:32 PM
I wouldn't have a problem putting a button gauge on a pony bottle...however, if you're mounting the bottle valve down, it's going to be impossible to read the button gauge unless you unclip the bottle.

Big thing is to make sure you can reach the valve in whatever configuration you mount it in.

As far as pony bottle size goes....what's the maximum depth that you plan on diving with this setup? Assume a significantly elevated SAC rate due to stress, add an extra minute or two for solving a problem at depth if it occurs, and a 30fpm ascent rate, and make sure that the 13 c.f. cylinder holds enough gas for the diving you plan on doing.

AndyNZ
November 26th, 2009, 03:43 PM
Opinions are like ar$eholes - everyone has got one. I suggest taking a good look at the various responses and choosing the most sensible advice.



1. People mentions using DIN regulators for pony to make setup more streamline.

As has been pointed out, using DIN for the sake of DIN is somewhat arbitrary. My suggestion would be to set it up with a DIN-K valve (this is a 200bar DIN vavle, that you screw an insert into to make it yoke) and a regulator that can be converted to DIN easily (e.g. Scubapro, Apeks). Set it up as a yoke and see how you go with it. If you find the yoke assembly is catching or is in danger of being hit hard enough to dislodge it, then shift everything over to DIN.

Then just buy a DIN fill adaptor - it takes a couple of seconds to screw in to the valve by hand when filling and isn't an inconvenience.



2. How often it needs to be refilled (of course if it was not used/freeflowed) ? I assume that I will need to take few breathes before each dive (normal pre-dive check) but with smallish 13CF bottle it can deplete bottle fast enough.

There's no real answer to this question other than "it depends". It will need filling every time you decide to do a dive where the pressure has dropped to a point where it doesn't contain enough gas to enable you to surface safely.

The only way you can know what this pressure threshold is, i if you work out your breathing rate and understand how to do minimum gas calculations. Do a search for "minimum gas reserve" or "rock bottom" and you'll find plenty of examples of how to do these calcs.

FWIW, my personal opinion is that a 13 cu ft bottle is too small for all but the shallowest of dive. I would urge you to take a good look at your diving profiles, and do the calculations to work out how much gas you need to surface safely from the depths you are planning to dive to - not just now, but in the future. To my mind, a 13 cu ft bottle is just about big enough for an average diver to make an emergency ascent from somewhere in the 20-30m range, but with no safety stops or much vestige of control. I'd definitely look into a 19 cu ft or larger.



3. What type of pony gauge you would recommend:
a) mounted directly on the bottle;
b) using hose strapped to the octopus;

I prefer to have an SPG on a 6" hose that bends back on itself and is tied with a loop of caveline. It's nice and clear, easy to read and doesn't get in the way. But, this only really works if you are carrying the bottle as a "slung" tank.

If you go with another form of carrying, you need to take a good look at your hoses - where they are, how long they need to be, whether they cause confusion etc. Your pony SPG needs to be very distinctly placed and recognisable from your main gauge. It's a real bu&&er when you realise half way through the dive that you've been looking at your pony gauge by mistake, and in fact your main tank is near empty when you thought you had 200bar.....



BTW: I am planning to keep it strapped under bladder wing of my Ranger LTD with regulator pointed down.

This begs a whole set of questions - firstly, are you taking the pony on every dive? If you get everything set up perfectly for the pony, then you decide to leave it behind.... does it change anything on the rest of your configuration? One of the nice things about a slung pony is that it changes nothing - it's a self contained unit, you pick it up and clip it on when you need it. It also give you better access to the valve, easy visual contact with the SPG etc. You can also unclip is during the dive - either because you need to pitch it, or because it's easier to give it to someone who is OOG than to share air etc.

Have a look at how to calculate the size of bottle you need, if it's bigger than 13 cu ft then have a look at how to sling a tank. If you can get by with a 13 cu ft, and want to carry it in your Ranger then make sure you get it right - hoses all the right length (you may need custom made hoses), things positioned so they don't cause confusion etc etc.

Also, be vary wary of having any gas mix in your pony that is different from you backgas. Switching to a richer nitrox mix is very uncool, switching to a leaner mix is less immediate but it does potentially push you into having a deco obligation due to the switch - that your computer won't know about, and do you have enough gas in a 13 cu ft tank to extend your safety stops enough to clear it????

Jorgy
November 26th, 2009, 03:54 PM
I have a 19 CF pony......

First a button gauge, too small and hard to read........

Small OMS gauge on 6" HP hose - worked well but made a "big" clump of stuff at the top of the tank, I sling my pony on my left side and I run my back gas gauge under my arm and clip it on my D-ring, so with my pony gauge it meant two gauges right next to each other........

So I settled on a 1" gauge - see picture below, large enough to read but small enough to not be in the way.........

I top off my pony every time I fill my tanks......I take a few breaths of the tank on each dive to check it works and practice deploying it.......so I loose a bit every dive......

My LDS tops them off for free, so it is no big deal........

Hope this helps...........M

elan
November 26th, 2009, 04:01 PM
The OP has clearly mentioned that he is rigging a bailout bottle. Readability of the gauge is irrelevant under water. It's only used to check if you have enough gas or not to bailout while preparing for a dive. You do not include bailout bottle into the dive gas calculations so knowing the current pressure of the bailout bottle is useless. Once **** hits the fan you just start your bailout. There is no point of looking at the gauge :)

bamamedic
November 26th, 2009, 04:07 PM
I understand your point, but at least for me, it would be kind of nice to have a pressure gauge that's readable underwater....particuarly on a deeper dive, when trying to decide if one has enough gas to stay for a safety stop.

AndyNZ
November 26th, 2009, 04:08 PM
The OP has clearly mentioned that he is rigging a bailout bottle. Readability of the gauge is irrelevant under water. It's only used to check if you have enough gas or not to bailout. You do not include bailout bottle into the dive gas calculations so knowing the current pressure of the bailout bottle is useless. Once **** hits the fan you just start your bailout. There is no point of looking at the gauge :)


There are two school's of thought on that - my personal view is that there is every point in looking at the gauge.

For example, you may have forgotten to close the tank valve during the dive and a small freeflow has led to you having half a tank... so 6 cu ft of gas (the same size as my drysuit inflation bottle!). You are at 30m, is 6 cu ft enough to get you up? Do you end the dive, do you close the tank valve and go shallower to a depth where 6 cu ft is enough.... and so on.

Another example, you've bailed out and an ascent... a 13 cu ft is woefully small in my opinion. Is it better to be able to see the gauge and how fast it is dropping (so you can either vary your ascent rate or relax your breathing)or would you rather you just run out of gas half way up?

There is no definitive answer as to whether or not you should be able to see the gauge or not - you are correct, as am I. We make a choice to decide what to do - but simply telling someone what to isn't giving them the option of informed choice! :D

idocsteve
November 26th, 2009, 04:09 PM
I understand your point, but at least for me, it would be kind of nice to have a pressure gauge that's readable underwater....particuarly on a deeper dive, when trying to decide if one has enough gas to stay for a safety stop.

The idea is to have enough gas remaining in your primary tank for the safety stop, which should be considered mandatory for dives greater than 60 feet.

AndyNZ
November 26th, 2009, 04:13 PM
The idea is to have enough gas remaining in your primary tank for the safety stop, which should be considered mandatory for dives greater than 60 feet.

If you've had to bail out, thanks say to a catastrophic equipment failure (tank neck o-ring... rare but possible), you're relying on the pony.

Yes, you should size your pony so that it contains enough gas to do the ascent and a safety stop... but you can only size it on the basis of a best gas of what your stressed SAC rate is.

If you can see the gauge, you can choose to shorten or extend your safety stop depending on what led up to the bail out. If you can't see your gauge, you're just shooting blind.

bamamedic
November 26th, 2009, 04:14 PM
The idea is to have enough gas remaining in your primary tank for the safety stop, which should be considered mandatory for dives greater than 60 feet.

I guess I just assumed that if I'm bailing to my bailout bottle, that something horrible has happened to my primary tank (massive freeflow, alien zombies stealing my gas, oh, I don't know) and I'm stuck having to ascend on my bailout bottle...thus, having to complete a safety stop on my bailout bottle.

idocsteve
November 26th, 2009, 04:15 PM
If you've had to bail out, thanks say to a catastrophic equipment failure (tank neck o-ring... rare but possible), you're relying on the pony.



I guess I just assumed that if I'm bailing to my bailout bottle, that something horrible has happened to my primary tank (massive freeflow, alien zombies stealing my gas, oh, I don't know) and I'm stuck having to ascend on my bailout bottle...thus, having to complete a safety stop on my bailout bottle.

I see your points.

elan
November 26th, 2009, 04:15 PM
I understand your point, but at least for me, it would be kind of nice to have a pressure gauge that's readable underwater....particuarly on a deeper dive, when trying to decide if one has enough gas to stay for a safety stop.

If you include your pony into the gas calculations for the dive it's a bad thing IMHO. You suppose to have enough gas in your main tank to be able to ascend from any point of your dive together with your buddy breathing harder than usual.

idocsteve
November 26th, 2009, 04:18 PM
If you include your pony into the gas calculations for the dive it's a bad thing IMHO. You suppose to have enough gas in your main tank to be able to ascend from any point of your dive together with your buddy breathing harder than usual.

I made the same assumption you did when reading the post you and I both quoted.

That's true in a nonemergency routine dive situation, as opposed to an emergency that has depleted your primary much sooner than expected.

Read the three posts above yours, it's clarified rather well.

elan
November 26th, 2009, 04:19 PM
There are two school's of thought on that - my personal view is that there is every point in looking at the gauge.

For example, you may have forgotten to close the tank valve during the dive and a small freeflow has led to you having half a tank... so 6 cu ft of gas (the same size as my drysuit inflation bottle!). You are at 30m, is 6 cu ft enough to get you up? Do you end the dive, do you close the tank valve and go shallower to a depth where 6 cu ft is enough.... and so on.

Another example, you've bailed out and an ascent... a 13 cu ft is woefully small in my opinion. Is it better to be able to see the gauge and how fast it is dropping (so you can either vary your ascent rate or relax your breathing)or would you rather you just run out of gas half way up?

There is no definitive answer as to whether or not you should be able to see the gauge or not - you are correct, as am I. We make a choice to decide what to do - but simply telling someone what to isn't giving them the option of informed choice! :D

You have the valid point. Though I think 13 cuf is a bit on the small side.

bamamedic
November 26th, 2009, 04:21 PM
If you include your pony into the gas calculations for the dive it's a bad thing IMHO. You suppose to have enough gas in your main tank to be able to ascend from any point of your dive together with your buddy breathing harder than usual.

I was under the assumption that I was discussing the issue of something horrible happening to my primary cylinder, thus having to bail out to the pony bottle to complete the ascent. Every diver should plan to be able to complete a safety stop with adequate reserves in their primary cylinder, but one in a blue moon, there might be some horrible massive equipment failure that might render the primary cylinder unusable.

If I have a readable gauge, I'll feel a lot more reassured about my gas supply...I'll know if I have enough gas in my pony bottle to complete my safety stop, and I won't feel nearly as rushed during the ascent because I'll know exactly how much gas I have left.

At least that's my two PSI :)

Michael_Lambert
November 26th, 2009, 04:21 PM
The idea is to have enough gas remaining in your primary tank for the safety stop, which should be considered mandatory for dives greater than 60 feet.

In a ideal world :D

Jorgy
November 26th, 2009, 04:24 PM
Having a gauge makes me feel better.........

When I setup my gear prior to the dive and I pressurize the reg, I like to look at the gauge and see 3000 psi........

I also keep the valve open during my dive, so I guess I could have a small freeflow that could over time drain the pony......

With it slung right under me, I'm guessing a free flow would not remain undetected, but I also take pictures, it is easy to get caught up in the dive and not pay as much attention............no excuse I know.......but I like having a gauge............

If I did ever have to use the pony to get to the surface, I would like to know how much gas is left, this would make me feel better as I do my safety stop, I realize that due to stress my breathing rate would be much higher than normal, once I got near the surface then knowing if I had 1500 psi or 200 psi would make a difference.......

I also use the pony reg to check the back gas tanks once I get on a boat - that way I am not hooking up my BP/W to an empty tank........any my pony setup is just so simple.......

M

AndyNZ
November 26th, 2009, 04:24 PM
You have the valid point. Though I think 13 cuf is a bit on the small side.

Yeah, 19 cu ft starts to give you options.

Personally, I use a 30 cu ft. If you get it rigged right you don't even notice it. And it gives you lots of options! :cool2:

elan
November 26th, 2009, 04:29 PM
I was under the assumption that I was discussing the issue of something horrible happening to my primary cylinder, thus having to bail out to the pony bottle to complete the ascent. Every diver should plan to be able to complete a safety stop with adequate reserves in their primary cylinder, but one in a blue moon, there might be some horrible massive equipment failure that might render the primary cylinder unusable.

If I have a readable gauge, I'll feel a lot more reassured about my gas supply...I'll know if I have enough gas in my pony bottle to complete my safety stop, and I won't feel nearly as rushed during the ascent because I'll know exactly how much gas I have left.

At least that's my two PSI :)

Yeah I got your point, though the same applied to the pony, before the dive you should make sure the pony has all the gas for doing all necessary steps for you and as a big plus for your buddy.

Besides one should not forget about the buddy. Depending on the conditions he can also be the backup source.

elan
November 26th, 2009, 04:32 PM
Yeah, 19 cu ft starts to give you options.

Personally, I use a 30 cu ft. If you get it rigged right you don't even notice it. And it gives you lots of options! :cool2:

I used the one for some time but after switching to double tanks I was wondering why the hell I was wasting my time with the 30cuf pony :) More streamlined, more options no clutter :)

bamamedic
November 26th, 2009, 04:35 PM
Yeah I got your point, though the same applied to the pony, before the dive you should make sure the pony has all the gas for doing all necessary steps for you and as a big plus for your buddy.

Besides one should not forget about the buddy. Depending on the conditions he can also be the backup source.

Very true, and a good, attentive buddy pretty much negates the need for a pony/bailout bottle.

When I'm diving to rec limits with a diver from my usual collection of buddies, I don't really worry about carrying a bailout, as my spare gas is on my buddy's back (or on his/her sides ;))

AndyNZ
November 26th, 2009, 04:43 PM
I used the one for some time but after switching to double tanks I was wondering why the hell I was wasting my time with the 30cuf pony :) More streamlined, more options no clutter :)

But more weight and more complexity! Actually identifying and resolving failures behind your head are hard work.

70% of my dives are in twin 95s, the rest split between a single 95 + 30 pony, twin 72s or sidemounted 80s.

It's horses for courses - there's no one configuration that is perfect.

mrivken
November 26th, 2009, 04:46 PM
First, I want thank you all for excellent suggestions.

1. I am planning to use it up to 90feet depth NDL single tank dives and only for emergency bailout or looking for my buddy. But most of my dives is shallow shore dives (<70feet) and "dry" weight is consideration to me. So, I will consider to buy 2 different bottles (13 shallow shore, and bigger then 13 for deeper boat dives)
2. I am not diving nitrox yet, but it very good point to have matching mix in main tank and pony.
3. Thank you, I will look on what I need to be able sling it with/on Ranger LTD.
4. I want to buy Zeagle Rezort First Stage Regulator use it with my Oceanic Alpha 8 octo and put Zeagle Octo Z Combination Regulator Inflator on my BC, so I will able to donate or my primary or pony if it needed.
5. Looks like button gauge will good enough to tell if pressure to low and pony need to be filled.
6. I am diving mostly in California and I am kelp magnet :), so I thought about using something like this one: Valve, Convert Din To Yoke - eBay (item 350275523285 end time Dec-05-09 18:09:00 PST) (http://cgi.ebay.com/Valve-Convert-Din-To-Yoke_W0QQitemZ350275523285QQcmdZViewItemQQptZLH_De faultDomain_0?hash=item518e0c52d5)
So, if I need to refill bottle only once in few months that is not a problem.


Thank you,
MR

Michael_Lambert
November 26th, 2009, 04:49 PM
When you buy the tank you need or want, just make sure you buy it with a 200 BAR DIN valve.. it would come with the screw in adapter. At least all mine have :D

AndyNZ
November 26th, 2009, 04:57 PM
So, I will consider to buy 2 different bottles (13 shallow shore, and bigger then 13 for deeper boat dives)

If you can, try and get hold of a larger tank first - preferably borrowed - and try it on a shore dive.

You may find that the extra size doesn't cause you any problems, in which case you can just buy one!

elan
November 26th, 2009, 05:01 PM
But more weight and more complexity!

Not necessarily true, with our cold waters I calculated my dry weight was the same between double HP100 and single HP100 + 30cuf + all the lead

I actually found it less complex. :eyebrow:

hudson
November 26th, 2009, 05:23 PM
First, I want thank you all for excellent suggestions.

1. I am planning to use it up to 90feet depth NDL single tank dives and only for emergency bailout or looking for my buddy. But most of my dives is shallow shore dives (<70feet) and "dry" weight is consideration to me. So, I will consider to buy 2 different bottles (13 shallow shore, and bigger then 13 for deeper boat dives)


From experience, this would be unnecessary, unless you want maximum ease of carrying for travel/flight. In the water, there is no difference in ease of handling between a 13 and 19, I've slung both. Even on the surface the difference is minimal.

For refilling, you need to figure out your SAC - then google Rock Bottom Calculator for a spreadsheet that'll tell you how much gas you'll need for an ascent from 90ft. You can allow for a fast ascent rate to ~40ft and slower after that, and also minimize the safety stop duration with minimal increase in risk of DCS, and you'll see 13cuft is sufficient from an ascent from 90ft, even including ~200psi for gauge error, ~100psi for minimal gas to breathe and another ~200 psi for fudge factor or surface breathing.

However this would require a refill after losing only a few hundred PSI from the AL13. With the AL19 you can have the cylinder 2/3 full and still be ok. Download the spreadsheet and run your own numbers.

Regarding total rock bottom, you only really need to reserve enough rock bottom for one diver to ascend in your backgas, not two. The reserve for the second diver is in the pony.

AndyNZ
November 26th, 2009, 05:57 PM
I actually found it less complex. :eyebrow:

Try dealing with a manifold or first stage failure, then compare it with dealing with issues whilst either sidemounting or using a slung pony. Being able to see what you are trying to resolve is inherently more simple than trying to work out what is going on behind your head!

diverrex
November 27th, 2009, 12:43 AM
I have a 13 cu ft pony. That was a mistake. A 19 is only slightly bigger but has 50% more gas. A 13 is much better than a spare air but I'd never recommend one to anyone, a minimum of a 19 is what I recommend.

Nitroxnut01
November 27th, 2009, 07:46 PM
I don't normally post but since I used to sling on my left side a 19 cuft bottle when doing deeper then 80 ffw dives figured I'd post. I used to dive deep with a 19 until I found the article by NWGratfuldiver (nwgratefuldiver.com/articles/gas.html) on gas management. I figured my bailout and found that the 19 was to small but ended up going doubles anyway. The first question you had, any dive shop worth their salt should have a din to yoke fill converter. I ran a yoke on mine but have since going to doubles changed just about everything to din. The second question you had, filling it. What i did was check the tank to see if it was at 3000, if it wasn't because I'd used it to practice with or just from checking it I'd fill it. The 3rd question, I started with a button gauge then moved to a larger one because I couldn't see it. But with mounting it behind you it doesn't matter the size because you will not be able to see it during the dive. With the stage and deco bottles I use now, i have a small brass gauge on a 6 in hose. As for the size of the tank run the numbers from the article. I did some quick back of the page math from what info you have given. For a bailout at 90 ft :
Assess the problem and change to bailout
2 x 3.72 x 1.5 = 11.25
Assent to 20 feet for stop at 30 ft per minute
3 x 2.67x1= 8.01
Stop at 20 feet for 3 minutes
3 x 2.81 x 1 = 8.43
Assent to the Surface at 30 ft per minute
1 x 1.20 x 1 = 1.2
11.25+8.01+8.43+1.2 = 28.89 or 29 cuft

So a 19 would not do it for you and a 30 might cut it close. Other posters have pointed out that your buddy should be there and have enough gas for you and him to get to the surface. But if you don't know the buddy or if the buddy sucks down his air might not have enough for both of you. The nice thing about a slung tank is, if they are OOG and you don't have enough to safely take both of you to the surface, a slung bottle can be handed off. That is my 500 psi on it.

Doc Harry
November 27th, 2009, 08:17 PM
Try dealing with a manifold or first stage failure, then compare it with dealing with issues whilst either sidemounting or using a slung pony. Being able to see what you are trying to resolve is inherently more simple than trying to work out what is going on behind your head!

Since you guys are "Down Under," aren't you also doing it upside-down? :D

Diverpro1
November 27th, 2009, 10:47 PM
This chart may be helpful.


[attach][attach]68477

Druid
November 28th, 2009, 05:19 PM
I change the gas in that tank once a year, assuming of course that I haven't used the tank.




I top off my pony every time I fill my tanks......I take a few breaths of the tank on each dive to check it works and practice deploying it.......so I loose a bit every dive......

My LDS tops them off for free, so it is no big deal........




This is my biggest issue with pony cylinders - people buy one because it provides "redundancy" but they never actually practice using it. So when the **** does hit the fan and they need the pony, they forget they have it/don't use it correctly/otherwise **** up and they slide deeper into the incident pit*. A pony is a good idea for no deco dives under 30m/100ft, but you need to practice its use regularly. Start at 6m and work your way down to the maximum depth you dive to, switch to your pony and ascend, doing any safety stops required. Jorgy is making some effort, but I would suggest making a habit of ascending on the pony from depth on say 1 dive in 10.




*There was a well publicised incident in the UK of a fairly experienced diver who failed to surface from a dive a couple of years ago. When his body was recovered his pony was empty, but his main cylinder was still full. It is believed that he began the dive breathing off his pony, when he drained it he spat out the reg, found his pony reg and put that in his mouth. Of course, the pony was empty and he was inside a wreck at 25m... :(

Jorgy
November 29th, 2009, 09:50 AM
You have a good point......

So on surfacing from the last dive of a trip or weekend I will do it on the pony.....

That will also give me a better sense of how far 19 CF will go......

Normally, I do it the practice at the safety stop....to help pass the time.....

Your incident makes another point, make sure your pony reg is completely different that you back gas reg......that way you can never mix them up......

M

saudio
November 29th, 2009, 08:54 PM
I've been using a pony bottle for many years of solo, photography diving. I see a lot of discussion here about the best size to use, and I gave that a great deal of thought before settling on a 13 cu ft tank.

Obviously, more is better. But in my case, and your mileage may vary, a 13 cu ft was the largest size and weight that was easily manageable for traveling, rigging, and changing from tank to tank on multi-tank dive days. I take the 13 everywhere, and use it on every dive. If it was a 19, and most certainly if it was a 30, I would be tempted to forgo the tank in certain circumstances. It is absolutely useless if it isn't with you on the dive.

No, 13 cu ft is probably not going to get me to the surface, with a 3 minute stop, from 130 feet. But I don't spend too much time at that depth, and really, the tank doesn't have to get me to the surface with a safety stop to save my life. It's got to get me to a depth where I can continue to the surface without air, or it has to get me to the nearest other diver. A 13 will do that.

I back mount mine, with the 1" gauge on the first stage, and check the pressure before every dive. I bungee the second stage around my neck. I use an Atomic Z1 first and second stage.

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