Twin sets and stuff like that

[Kirstie]

Originally Posted by Mark Davies

[font=Comic Sans MS][color=indigo]If you are woried about your air consumption you will be far better placed with two single 15s than a set of twin 12s in any case.

It's interesting that you should say this. My air consumption is also quite high (made more so by me fretting about it) and Paul suggested to me that I start using a single 15 instead of a 12. I've resisted so far as, to me, it feels almost like cheating, or taking a step backwards. I've got this idea in my head that I should be working to improve my consumption on a single 12, rather than resorting to a bigger cylinder. Stupid, I know, but there you are.

I'd even made up my mind that this year I'd start using the twin 12s and maybe doing shorter second dives, but this thread has put me off this idea a bit! I wouldn't be diving twins to pose, purely to give myself more air. Having said that, I'm looking to do slightly deeper dives this year (up to about 40m) but I reckon most of my diving will be under 30m.

Funnily enough, last summer I was practising with twin 7s at Drawna Rock. I did the whole dive on a single 7, as I inadvertantly turned the manifold valve off before jumping in. Because I thought I had loads of air, I was relaxed and didn't think about my breathing. Not that I'd recommend this way of improving one's consumption, of course!

[MATTBIN]

Originally Posted by Kirstie

It's interesting that you should say this. My air consumption is also quite high (made more so by me fretting about it) and Paul suggested to me that I start using a single 15 instead of a 12. I've resisted so far as, to me, it feels almost like cheating, or taking a step backwards. I've got this idea in my head that I should be working to improve my consumption on a single 12, rather than resorting to a bigger cylinder. Stupid, I know, but there you are.

I'd even made up my mind that this year I'd start using the twin 12s and maybe doing shorter second dives, but this thread has put me off this idea a bit! I wouldn't be diving twins to pose, purely to give myself more air. Having said that, I'm looking to do slightly deeper dives this year (up to about 40m) but I reckon most of my diving will be under 30m.

Funnily enough, last summer I was practising with twin 7s at Drawna Rock. I did the whole dive on a single 7, as I inadvertantly turned the manifold valve off before jumping in. Because I thought I had 14l of air, I was relaxed and didn't think about my breathing. Not that I'd recommend this way of improving one's consumption, of course!

I dive twin 12's and if needs be I take one of the indies (the near empty one) out and slide another one (full) in for the second dive, some of my buddies decant from another cylinder for a second dive. I really dont get this macho my sac is so little I hardly breathe at all rubbish, you need what you need, you pay for it, you lug it about, take what you need and sod 'em. Skippers are fun though when you lug a load of kit on their boat, I wonder why, does it increase the boats fuel consumption drastically. Just started reading "The last Dive" again, to do the Andrea Doria, the Rouses took 40 cylinders and that included some J's of 02, 24 people on the boat, that's the sort of boat we need in the UK, plenty of space and stop all this you cant bring that on here rubbish.

Matt

Matt

[And]

Originally Posted by Sparky750

Not too sure where to post this so if it needs moving please move it.
Last nights club night got me thinking and also the thread about diving quarry's my SAC is quite high being new to the sport etc and as most on here seem to dive twins i feel that i can't go on YD gigs in case i shorten someone else's dive and feel a muppet. Chatting to a few club members last night it became apparent that nobody dives twins or has any desire to do so in the club. How do i learn then do i just buy the stuff jump in and hope for the best or did you actually train with an agency etc I'm not thinking of doing it right now until i've got a bit more experience i was just looking at how i can progress my diving hopefully later this year as i'm trying to get in as many dives this year as i can.

Hi

You don't need a twinset. You just need more time in the water. I have to say that I have never actually worked my SAC out, and although I do dive a twinset, I am happy to dive a single and in fact have a set of single regs and a couple of single steel cylinders for that very reason. My last dives were with Fiona last weekend and they were simply two dives of 30-40 mins each, and an average depth of about 12 mtrs I'd guess. I am sure that you would manage that.

You are welcome to come along with me when I post on the need a buddy section, and if I was you, and I wanted more diving experience, then the need a buddy section is very useful.

The VAST majority of members on YD are single cylinder divers, its just that all the gobby ones dive a twinset and that can give a false first impression

Andy

[MATTBIN]

Originally Posted by And

Hi
The VAST majority of members on YD are single cylinder divers, its just that all the gobby ones dive a twinset and that can give a false first impression

Andy

How very dare you!!!!

hate to say it but I think you could have a point, except I would have said it was the rebreather/DIR lot

Matt

[Mark Davies]

Originally Posted by Kirstie

Paul suggested to me that I start using a single 15 instead of a 12. I've resisted so far as, to me, it feels almost like cheating, or taking a step backwards. I've got this idea in my head that I should be working to improve my consumption on a single 12, rather than resorting to a bigger cylinder.

You've got a number of options, but look at it objectively and manifolded twin 12s rarely come out as the most sensible. Too many people use poor SAC as a reason to get twins and then in reality end up doing two dives in a day on a single fill, which is in fact less available air than two single 12s!

Matt's solution of independant twins and then using a third, full cylinder for a second dive has merits, but then you're using three tanks with the transport problems involved with that (if that's relevant to you).

Some people use a 12 and a pony and then regularly rely on their pony. If you're going to do that you might as well just have a 15 and save the bother. Add an H valve and regain the redundancy you get with the pony.

Twin 7s are a cracking idea - especially 300 bar if you can get the fills. Plenty of gas, redundancy, comfort, the lot. The only set-back is you need two sets for a two-dive day and that becomes expensive when you factor in the costs of maintaining 4 tanks. And they cost a fair bit to buy in the first place.

It's all about what you need and what suits you. There's no 'cheating' about it. As Matt says, for some people no amout of dive time seems to bring down their SAC. There's no point in trying to fool yourself that you can get away with less when you need more - and there's no shame in that.

[Kirstie]

Originally Posted by Mark Davies

You've got a number of options, but look at it objectively and manifolded twin 12s rarely come out as the most sensible. Too many people use poor SAC as a reason to get twins and then in reality end up doing two dives in a day on a single fill, which is in fact less available air than two single 12s!

Matt's solution of independant twins and then using a third, full cylinder for a second dive has merits, but then you're using three tanks with the transport problems involved with that (if that's relevant to you).

Some people use a 12 and a pony and then regularly rely on their pony. If you're going to do that you might as well just have a 15 and save the bother. Add an H valve and regain the redundancy you get with the pony.

Twin 7s are a cracking idea - especially 300 bar if you can get the fills. Plenty of gas, redundancy, comfort, the lot. The only set-back is you need two sets for a two-dive day and that becomes expensive when you factor in the costs of maintaining 4 tanks. And they cost a fair bit to buy in the first place.

It's all about what you need and what suits you. There's no 'cheating' about it. As Matt says, for some people no amout of dive time seems to bring down their SAC. There's no point in trying to fool yourself that you can get away with less when you need more - and there's no shame in that.

Thanks for that, Mark. I know I shouldn't worry about the amount I use, but it's embarassing being the first one to 100 bar or 50 bar every time

I'm aiming to do far more dives this year so that'll probably help. I'm going to keep a close eye on my consumption while we're away, as I'm sure it improves even over a short period of time like a fortnight's diving.

I do want to use the twin 12s, but that'll come gradually as I work towards deeper dives over the summer. And if it means having a short second dive, well, so be it. I don't really want to go down the single 12 and pony route and, as you say, twin 7s aren't enough for a two-dive day, which most of mine are. Pity, 'cos they felt comfy and balanced, and weren't too heavy.

Perhaps Buoyant Babe will agree to a lung swap. Then I, too, can do 60 minutes at 40m on a single 12

[Buoyant Babe]

Originally Posted by Mark Davies

Twin 7s are a cracking idea - especially 300 bar if you can get the fills. Plenty of gas, redundancy, comfort, the lot. The only set-back is you need two sets for a two-dive day and that becomes expensive when you factor in the costs of maintaining 4 tanks. And they cost a fair bit to buy in the first place

Originally Posted by Kirstie

twin 7s aren't enough for a two-dive day, which most of mine are. Pity, 'cos they felt comfy and balanced, and weren't too heavy.

Perhaps Buoyant Babe will agree to a lung swap. Then I, too, can do 60 minutes at 40m on a single 12

I have been on several YD gigs and like Sean said earlier I have never seen anyone bothered about the different tank and kit configurations people dive with. We are all there to have a good time diving. I've dived with YD on a single 10, single 12 and now twin 7s.

Like Kirstie points out, I am blessed with a tremendous pair of lungs and can get two dives out of both my twinsets (twin 7 232s & 300s). After about 100 dives on singles, I thought very hard before going on to my 'baby' twins and decided to get them for a number of reasons: I wanted redundancy and extra gas, even if I only get one dive on them, but didn't fancy the faff of the counterweghting I would probably need for a pony; I can't stand up in a single 15l, yet for some reason have no problems with either set of twins as they are lovely and balanced; A single 12 is nearly enough for me to do two of my average dives but not quite - I hate faffing around swapping tanks over in between dives; I will be able to do slightly deeper and longer dives on a single set of twin 7s.

I didn't intend to get two sets, but while I was waiting for my 300s to arrive, a set of second hand 232s came up that were just too good to miss. As I get free air, I can do a weekend trip with both sets and not have to pay for fills.

So, to agree with many others on this thread, the assumption that everyone dives twins is wrong. There are only two of us in our club who do so, the other person being Dave (KeyLimePie) and he is going DIR.

Like Kirstie and others have also said, relaxing is the best way to decrease your SAC, and the best way to relax is to get out there and dive and get used to what you are doing.

However, as Woz said, my twin 7s are the mutts nuts and I love em to bits!

Helen xxx

[pieater]

Originally Posted by Mark Davies

Too many people use poor SAC as a reason to get twins and then in reality end up doing two dives in a day on a single fill, which is in fact less available air than two single 12s!

I'm obviously being a bit slow here, can you expand on the concept of having less available air please?

[Mark Davies]

Originally Posted by pieater

I'm obviously being a bit slow here, can you expand on the concept of having less available air please?

No you're not being slow - my point only makes sense within a context and I didn't really explain it properly.

Your regulators don't keep going until your tanks are empty - they actually stop delivering gas when tank pressure drops to a certain amount. That will vary depending on your regulators but for the sake of argument let's say it is 10 bar.

Now, I'm making the comment in the context of using a half-empty twinset on a second dive rather than a full, second single 12. Most people make the assumption that 110 bar in twins is the same as 220 in a single - it isn't.

The twinset will stop breathing at 10 bar, when you have 24 litres left - giving you 2616 litres of useable air. The single stops at 10 bar when you have 12 litres left - giving 2628 litres.

Of course it is marginal (30 seconds on a safety stop?) and obviously you can factor it in to your diving - but who does? I'm not saying it is critical - just making the point that using a twinset for two dives doesn't always help. I'm just being pedantic really.

Kirstie's experience with the twin 7s raises the point that on a first dive with all that excess air you may be more relaxed and so save a fair bit of air as a result - then it might work - but that's not a given.

[Mal Bridgeman]

Originally Posted by Mark Davies

No you're not being slow - my point only makes sense within a context and I didn't really explain it properly.

Your regulators don't keep going until your tanks are empty - they actually stop delivering gas when tank pressure drops to a certain amount. That will vary depending on your regulators but for the sake of argument let's say it is 10 bar.

Now, I'm making the comment in the context of using a half-empty twinset on a second dive rather than a full, second single 12. Most people make the assumption that 110 bar in twins is the same as 220 in a single - it isn't.

The twinset will stop breathing at 10 bar, when you have 24 litres left - giving you 2616 litres of useable air. The single stops at 10 bar when you have 12 litres left - giving 2628 litres.

Of course it is marginal (30 seconds on a safety stop?) and obviously you can factor it in to your diving - but who does? I'm not saying it is critical - just making the point that using a twinset for two dives doesn't always help. I'm just being pedantic really.

Kirstie's experience with the twin 7s raises the point that on a first dive with all that excess air you may be more relaxed and so save a fair bit of air as a result - then it might work - but that's not a given.

Mark - What you seem to be suggesting here is that the first single 12 can be breathed to 0 ??

Mal