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Long time no sea
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Some advice would be welcome. I have organised a RS trip. People have asked me about hiring 15litre cylinders. I gave them the following advice but am now full of doubt. Am I wrong, right or maybe-ish.

"15 litres cylinders are £25 pw and Nitrox is £60 for 12s and £80 for 15s. I was thinking 12 + Nitrox then fancied a 15. This is £45 more and just not worth it.

Recently Rob and I have been diving to 22m for 39mins in 10c water (drysuit encumbered) Rob has a 15l and comes up with 90 bar and I (12litres) come up with 60 bar. The deco penalty on that kind of diving four times a day will be at the limits. An aluminium 15l is heavier dry but more bouyant ( I know there are some engineers who'll eat me alive if I get this wrong) at 50 bar. You end up carrying more lead to stay neutral at 6m/ 50 bar. This weight/trim will mess with your air consumption negating the value of the 15l. So 45 quid for minimal benefit - just say no.

Believe me 15 litres will mess with your mojo. For air consumption management I will be doing brief CBT for divers sessions."


please be gentle.....:embarassed:
 

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Jonah
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Well, the 15s will probably be steel not ali. You probably won't be doing many square profiles so the deco considerations may vary. Also, your gas fills will most likely be less than you are used to here (maybe 200bar).

Personally, I'd have a 15 of nitrox, to maximise dive time - £45 is pretty insignificant in the grand scheme of things.

EDIT: and remember of course that other people may have wildly different SACs to you and your buddy.
 

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The 15l will propably be steel.

My regular buddy uses a 15l at the same rate that I use a 12l, if he were to go with a 12l it would cut our normal dives short. If he told me it was because the organizer "told him" to do that, I´d be a pretty unhappy camper...
 

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Ginger, Irish, sometimes stroppy
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If you are in doubt about your sac get a 15. I had a 15L hired on a Red Sea liveaboard and never used it, I found I could go into minimal deco on a 12, even using an appropriate EANx. But I am glad I had the option.

I don't think the difference in size etc actually contributes to a noticible increase in air consumption. And as already said, just because the 12s are ali doesn't mean the 15s will be......I have seen both. The lead argument only really makes a difference out of the water and on a liveaboard that time is negligible.

I would say if anyone is worried about air consumption hire a 15, they will probably be more realxed because of it and will end up back on a 12 with a better SAC by the end of the week. That said with 4 dives a day, there is no real need to overstay down there :)

ENjoy the trip ya lucky ....:)
 

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Member
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As posted by others, 15ltr will probably be steel. So [though I don't have any facts and figures] this seems a better tank selection to me than an aluminium 12ltr. Since it's more negative than the ali 12ltr, it's less lead per litre of cylinder.

Personally, I'd rather pay the money, in the full knowledge that it's a complete rip off, and have the gas in case of strong currents, deeper sights, etc.
 

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life is too short
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I always hire a 15l on livaboards, purely because even after an hour down there, and at a 5m stop with 50 bar its sods law that something will be incredibly interesting to stay at 5m or shallower to try and photograph...

(from log book)
one dive at elphinstone, we were dropped off by rib and spent about 55 mins drifting back to the boat, hung on the shot under the boat in about 5 - 10 metres watching the oceanic white tips above (have to say my breathing rate did increase at that point) for at least 20 mins. On a 12 i would be rather too low on air, on a 15l still 30bar ish.

Entirely your choice of course - enjoy the trip. When and where are you goin?
 

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Life is rushing past!
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I've always hired a 15l on livaboards as I really do not like diving with ali's, they are steels, it also gives you a margin of error if as previously mentioned something interesting always appears just as you are getting out, I think I paid £25 for the weeks hire of that and £60 for a week of nitrox or if you think you'll only need nitrox for a couple of dives it was £5 a dive.
 

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Open Wide
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I'll be taking my pony to sharm just so I know I have that bit of extra. Shore based this first time, but maybe liveaboard later in the year :)
 

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Go for the 15 litre as it will give u that little cusion on bottom time !
i used 12 litere cylinders last year and they where ali not steel !!! :teeth:
 

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beyond a mid-life crises into complete insanity!
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I dragged an OOA diver up off the Thistlegorm a couple of months ago. From a depth of 30m with a 3 min stop on the way up we got through just over 100bar from my 15L cylinder.

I work out min gas when dive planning – but to actually use that much gas was a huge reality check.

My sac is usually around 18 in the Red Sea.

It also made me fully realise the benefits of diving a long hose esp with a very stressed buddy attached

I will never again economise by not paying out for a 15L cylinder
 

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I dragged an OOA diver up off the Thistlegorm a couple of months ago. From a depth of 30m with a 3 min stop on the way up we got through just over 100bar from my 15L cylinder.

I work out min gas when dive planning – but to actually use that much gas was a huge reality check.

My sac is usually around 18 in the Red Sea.

It also made me fully realise the benefits of diving a long hose esp with a very stressed buddy attached

I will never again economise by not paying out for a 15L cylinder
a good call that marriane and shows that a little bit of extra gas can make all the difference !!
 

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It's a no-brainer really because the cost difference is not worth stressing about, bearing in mind the total cost of a liveaboard holiday. 4 dives a day and you should be on Nitrox anyway IMHO. The longer bottom times will be a bonus too. 15's will give you longer dives if you want so why not just opt for it.
 

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A Moderate from 04/01/07-24/12/12
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The "12 litre Ali's" are normally AL80's so actually 11.1 litres of gas not 12l. I have seen genuine 12 litre Ali's but they are not the norm in my experience.

If you believe that Nitrox is a safer gas both from extended bottom times, shorter surface intervals and a "better" gas to decompress from then the £60 for "all you can eat" Nitrox makes eminent sense to me....especially over the period of a week's liveaboard diving.

I am going there in June too and have hired a manifolded twinset :). If you are familiar with a twinset already there is an option to use buddy bands and make your own twinset (though the left hand tank may have an incorrectly oriented valve).

HTH
Mal
 

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Some advice would be welcome. I have organised a RS trip. People have asked me about hiring 15litre cylinders. I gave them the following advice but am now full of doubt. Am I wrong, right or maybe-ish.

"15 litres cylinders are £25 pw and Nitrox is £60 for 12s and £80 for 15s. I was thinking 12 + Nitrox then fancied a 15. This is £45 more and just not worth it.

Recently Rob and I have been diving to 22m for 39mins in 10c water (drysuit encumbered) Rob has a 15l and comes up with 90 bar and I (12litres) come up with 60 bar. The deco penalty on that kind of diving four times a day will be at the limits. An aluminium 15l is heavier dry but more bouyant ( I know there are some engineers who'll eat me alive if I get this wrong) at 50 bar. You end up carrying more lead to stay neutral at 6m/ 50 bar. This weight/trim will mess with your air consumption negating the value of the 15l. So 45 quid for minimal benefit - just say no.

Believe me 15 litres will mess with your mojo. For air consumption management I will be doing brief CBT for divers sessions."

please be gentle.....:embarassed:
The 15l will propably be steel.

My regular buddy uses a 15l at the same rate that I use a 12l, if he were to go with a 12l it would cut our normal dives short. If he told me it was because the organizer "told him" to do that, I´d be a pretty unhappy camper...
The only thing i would add to this is that whenever i organise anything, I will give options factually, then let them make up their own minds. I make my own decisions, and let others do the same.
 

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You can't have too much air

On hols in the Red Sea by SAC was around 14lpm, but still asked for a 15L/32% (or was it 36%) when doing the Thistlegorm

OK, the Nitrox was "free", but why not pay the extra for the 15 +/or EAN "just in case"
 

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I use a 15l steel cylinder in the Channel and in the Red Sea. As its "slightly" warmer in the RS my gas consumption is much better and I easily get dives in excess of an hour.

I always use nitrox out there as I feel better on it doing three or four dives a day.

The steel cylinder usually costs £15 for the week. My first liveaboard charged £5 a fill for nitrox that was usually only 28-30%. I felt that was a poor deal but hey I'm on holiday mode. I now go on the boats that give free nitrox.

Best to pay up and enjoy the extra dive time and safety factor. Its amazing how often something good comes along at the end of a dive and you're glad you've got the extra air!
 

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Why not just take twinning bands - not pay for the 15l - and pay for the Nitrox. Check this out with the agent and see if it works out cheaper. Definately a good option depending on the route you are planning.
 

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I've just read these threads and well done to the guy with the OOA diver on the Thistlegorm. That alone should convince you that 15s are best in the Red Sea, and of course the scary white tips must have been worth the extra cost in Nitrox. I wish I'd been there too.
 

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Often dangerous...
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An alternative to a 15 is independent 12s which I like to use on the first two (deeper) dives each day. As a photographer, I'm rarely with the group, so the redundancy is handy and being able to hang out on a deeper profile is useful while everyone else is lurking on or around their safety stops. I need an extra 2 kgs if I'm diving a pair of twelves and its best to hang the extra weights on the lower cam bands to stop the cylinders floating as they empty. Always breather indes off 50 bar alternately. HTH, Tim
 
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