7L Pony?

[Mal Bridgeman]

Originally Posted by Daz217

Thanks for the replies. Yep was just thinking of it as a larger pony really i.e. more bailout gas(No intention of inc it in my air calcs)
I have a Kent tooling clamp. Tried side slung didn't really like it but could manage oK with it. Might give it a whirl and see what it's like

So if this is an emergency supply, what kind of gas requirement are you going to get into with a 15ltr single that a 7l "pony" is going to be needed to get you out of?

[Daz217]

Well if there is a first stage failure/freeflow on the 15 then i have 7 to bail out with instead of 3.
Just thought 30M wreck 15 goes boobies skyward better to have more in reserve than less.
Dunno just thinking about it and thought i'd see what others thought.

[Mal Bridgeman]

Originally Posted by Daz217

Well if there is a first stage failure/freeflow on the 15 then i have 7 to bail out with instead of 3.
Just thought 30M wreck 15 goes boobies skyward better to have more in reserve than less.
Dunno just thinking about it and thought i'd see what others thought.

Assuming that you are doing no deco, no overhead stuff, then doing your ascent the way I do, you would take 6mins to get to the surface which using a 3ltr pony pumped to 200 bar, you would have to breathe at rate of 50l/min for the whole of the 6 mins before you would start to run short....and that's heck of a SAC rate to sustain for that long. Using most agency ascent rates it takes 3mins so that's 100l/min and using PADI's RDP it's less than 2 mins so 150l/min.

Having more is not always good in my view because the extra effort of lugging this 7l around with you probably isn't worth it and ... when you start to suffer the narcosis confusions it can lead you to justify making poor decisions .... "It'll be alright just to do a bit of deco cos I have the 7l pony" or perhaps "I'll just have a look inside here, because I have the 7l with me in case I get in trouble".

If you are worried about these sorts of things then talk to your buddy about it and make sure you are working together underwater to ensure each other's comfort.

If you are thinking "I need a twinset to be comfortable doing the diving I want to do", then go buy a twinset and seek appropriate training ...either with an instructor or mentors that can help you would be my advice.

HTH
Mal

[Daz217]

Fair points Mal. As i say just thinking out loud really. You are probably quite right. Although i like to think i am a bit more sensible these days with regard to pushing my limits All my Diving is No Deco stuff hardly ever any overhead stuff other than the odd cavern and the inside of the Stanegarth
Thanks for your input seems sensible points well made.

[Richard Mason]

Originally Posted by ardhill

I would have thought a steel 7l would have been a bit heavy to side sling with a single tank?

Would it not unbalance you?

One of the blokes in my club has a 5L steel pony clamped to his 12L.....it's a pain in the arse; heavy and unbalanced. Almost as much faff as a twin, with none of the benefits. I didn't read the "steel" bit, I'd assumed it was Ally, for some reason.

[Dangerous Dan]

When diving on a single I've been side slinging a Ali 40, which I found absoloutely perfect, lovely balanced, nice bouyancy characteristics, not too much hassle out of the water and a nice amount of gas.

Dan

[Scuba-D]

pesonally i wouldnt go there. 3L should be suficiant to get u to the surface from 30m (providing no deco), but dont forget ur buddy shouldnt be to far away with some air to. so i dont think it would be worth the extra baggage.

[Garf]

Originally Posted by Scuba-D

pesonally i wouldnt go there. 3L should be suficiant to get u to the surface from 30m (providing no deco), but dont forget ur buddy shouldnt be to far away with some air to. so i dont think it would be worth the extra baggage.

Just to extend what you are saying, I wouldn't take it as red the pony is always enough to get you out of bother. It should be ideal at 10 metres per minute, but you have to think about whether you would be happy doing that. I personally would want a slower ascent, even on a min (no) deco dive.

Let's take the ascent as I would do it, even in an emergency. Assuming a min deco ascent (slow to 3 metres per minute from 50% of the depth), then let's say you have

1 min on the bottom to sort out the problem
2 mins ish to get to 15 @ 9 metres per minute then slow down....
1 min to get to 12
1 min to get to 9
1 min to get to 6
1 min to get to 3
1 min to get to 0

so 8 minutres on the bottle at an average depth of 2.5 ATAs, with a SAc of 30 (you're under stress) gives you 600 litres of gas. A pony at 200 bar gives you 600 litres of gas.

So make sure you get a good fill

In seriousness, most people would do a faster ascent in an emergency than we plan for, but it's worth stopping to think from time to time about what how much gas you would actually have availble in am emergency. You certainly wouldn't have time to muck about.

[Lee C]

I used a 15 with a side slung 7 before I moved onto twins,I offset the weight by putting one kilo more weight on the opposite side & found it balanced fine after a few exploratory dives.

Lee C

futures lookin so bright I gotta wear shades

[MATTBIN]

Originally Posted by Mal Bridgeman

Assuming that you are doing no deco, no overhead stuff, then doing your ascent the way I do, you would take 6mins to get to the surface which using a 3ltr pony pumped to 200 bar, you would have to breathe at rate of 50l/min for the whole of the 6 mins before you would start to run short....and that's heck of a SAC rate to sustain for that long. Using most agency ascent rates it takes 3mins so that's 100l/min and using PADI's RDP it's less than 2 mins so 150l/min.

Having more is not always good in my view because the extra effort of lugging this 7l around with you probably isn't worth it and ... when you start to suffer the narcosis confusions it can lead you to justify making poor decisions .... "It'll be alright just to do a bit of deco cos I have the 7l pony" or perhaps "I'll just have a look inside here, because I have the 7l with me in case I get in trouble".

If you are worried about these sorts of things then talk to your buddy about it and make sure you are working together underwater to ensure each other's comfort.

If you are thinking "I need a twinset to be comfortable doing the diving I want to do", then go buy a twinset and seek appropriate training ...either with an instructor or mentors that can help you would be my advice.

HTH
Mal

Just after I started diving there was a post on Divernet by Vic (remember him, I bet Chasey does ), anyway he posted they had documentry proof that a diver drained a 3l as his sac hit 100lpm (surface rated, so he hit 400l/min at 30m), drained a 3l in moments, well 1 1/2 minutes actually. It is more than possible, rare, one would hope, but possible.

Matt