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Discussion Starter · #1 ·
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If I wish to use my twins as a single tank ie dive with the manifold open and I cannot reach the valves would using a pony strapped to the twinning bands  be a daft idea.Ideas,help, abuse, slaps to the head all welcome.
Second question will we see rubber glad gimps on the YD take over of the holiday cottages  if so do I need to bring a blindfold to protect my other half?
 

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Hi Nigel,
Not a daft idea but if you have deco to do then it would be pretty useless. If you are no stop diving in recreational depths then it would be OK.

My opinion is, learn your shutdown procedures. I have recently done my first two dives for advanced nitrox and was starting to get the hang of the shutdowns, they still need work but I am confident that I will be there shortly.

What level of training are you at ? I am sure that if you meet up with a few of the 'Troops' they will help with the drills.  I personally would go this route and forget the pony, learn to use the manifold.

Good luck
 

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Discussion Starter · #3 ·
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Phill
as it stands at the moment i just cannot reach any of the valves Im just not bendy.
I was thinking of using the pony just as a redundant air source on non deco diving
 

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Until you can isolate it might be wise to carry it as a redundant air source, but personally I would carry it like a stage/deco bottle i.e. hung on the side of your harness, just clip it on before you enter the water, unclip it as you leave..
 

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Yeah Nigel that would work OK, and as Dave says the ideal way would be to sling it like a stage.

I am not very bendy either as I found out with the first shutdown drill. It takes time and a bit of moving and shuffling and then all of a sudden you get a handfull of knob ........ooohhhhh eeerrrr !!!
Its a great feeling when you do.....( This is getting worse ).  I always wondered why my mates that I dive with always practiced a shutdown when we dived and now I know, its a case of practice and more practice and I have got lots to come, but it is actually good fun learning new skills.
 

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Nigel

Assuming you don't have some kind of muscular or skeletal deficiency or injury, you must be able to reach your valves.  All it takes is a little practice.  You should learn to reach the valves in preference to strapping a pony cylinder to your bands, which just creates a whole lot of new problems.  If you really can't reach your valves (and assuming you have no deficiency/injury etc.) there is something wrong with your equipment.  Is your dry suit or undersuit too tight?  Are your cylinders in the right position relative to your harness?  Is your harness too tight?

Asuming all is well with your equipment, have you tried stretching exercises?  Try putting your right hand on the back of your head and then tracing your fingers down your spine.  Simultaneously, trace the thumb of your left hand up your spine.  Does your thumb meet your fingers?  Now swap over.  Does the thumb of your right hand meet the fingers of your left hand? (this way is much more difficult if you are right handed).  Try these exercises at home.  In the car, try reaching back and holding the head restraint and then lean forward.  You can feel the muscles in your shoulder stretching.  These are the ones that need the work.  You don't need to be a contortionist.

In the water, what is your trim like?  Don't try to do these shutdowns whilst kneeling, gravity is working against you.  Try to keep in a horizontal position and neutrally buoyant.  Whilst reaching back with your right hand for your valves, give the tanks a push up your back with your left hand.  Also, keep your elbow from sticking out (kiss your elbow) you will find you can reach back further like that.

You will be surprised what a little stretching can do.  Once you can reach your valves don't stop there. Keep practicing!  Manipulate your valves on EVERY dive.  On a safety stop PRACTICE again.  Strive for perfection and do not settle for second best.

Hope this helps.

See you in Anglesey?

Bob
 

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Hey Nigel,

Seriously top-drawer advice from all the guys here - we know, as we're either trying to perfect the shut-down drills as we speak or have been perfecting/becoming adept at them for while now.

One comment I did pick up on, which has not been addressed yet, is that your manifold should always be OPEN (in and out of the water, and when getting your tanks filled) - until such time (on a dive) as you have to effect an isolate and shut-down due to gas escape from either pillar-valve.

Good luck mate and let us know how you're getting on. Please feel free to join us at the Cape or when the 'Mid-week Crew' gets to Stoney for drills. It's also a good time now to get them practised and learnt - what with the season about to be upon us and all.

Ben and I did the drills in the Cape yesterday and I had to undo my waist buckle and hitch the twins up to sort mine out - Ben managed also with a neutrally buoyant head-down-and-hutch-up trim - but we both managed is the point. There are no points for style and no right or wrong way to do this essential task - AS LONG AS YOU CAN DO IT!!

Good luck mate.
 

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Just a quick question - how long do you have to shut down and preserve enough gas to make your deco obligations/ascent feasible (if you are just using twins)?

I know there are no points for style, but surely speed is of the essence.  What I have no idea of is how much speed.  Do you need to be able to shut in 2 secs, 10 secs, 30 secs??  

If you have to undo a waist band and hitch your tanks up to be able to reach the valve, and then shut the valve how long does that take you, Bren?  Would you do a 30m dive, for example, with your shutdowns requiring that degree of "fiddling"?  I ask because I cannot see reaching valves being easy for me (long back and short arms!) and therefore I am questioning whether even looking at diving twins is worthwhile.

Cheers

Lou
 

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Check this out as appeared in Diver a while back - depends on where the gas loss is coming from and how large your twins are - 7's or 10's and you need to be very quick and 35 seconds would appear to be the slowest time on any size if I recall correctly.
<a href="http://www.divernet.com/technique/0102twins.htm

HTH" target="_blank">http://www.divernet.com/technique/0102twins.htm

HTH</a>
Paul
 

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I was disappointed in that article when I first read it.. John Liddard admits that "Isolation manifolds generally make me nervous", I'm really not sure he was the best person to write an article on how well they work.

Why anyone would bother to test results of taking up to a minute to do a simple isolation I may never know. Even when they do admit "Before moving to a rebreather I had always dived with independent cylinders and balanced my gas by switching regulators ... because I'm not very physically flexible. Even with a remote knob for the isolator I find it difficult to do an isolate and shutdown quickly."

Reach over shoulder, quick half-turn, and it's done. 1-5 seconds maybe, 15 seconds no. "if the time to isolate (T1) was 15 seconds, the diver would have an additional 35 seconds to close the relevant cylinder valve (T2) before crossing the point at which he would have been better off without the manifold"

If my times were 15 and 35, frankly I'd consider myself deserving of the OOA situation I found myself in. I'd be downright embarassed to be that slow. A couple of seconds to isolate, a few more to do the shutdown because the valves are open all the way, and you're done.

If the scenarios had been more realistic, the article would have been a lot more worthwhile.

(Edited by Dominic at 9:46 am on Feb. 18, 2003)
 

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I'd agree with that - time is of the essence down there and 35 odd seconds seems a rather long time !!

Paul
 

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Discussion Starter · #12 ·
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Now let me get my head round this.
Do I leave the manifold open and treat the twins as one tank,if so do I only use one pressure gauge.
or do I dive with it closed and use each tank with a seperate reg and swap every 50 bar.
confusing or what!!!!
 

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My personal take on it is:

If you want independants, use independants.

If you dive with a manifold, use the manifold.

If you have a manifolded twinset, leave the manifold open at all times unless an emergency occurs. If you are going to dive with it closed, you might as well use independant cylinders right from the word go.

A manifolded twinset is more likely to fail than an independant. Two pressure gauges are more likely to fail than one. Adding all the failure points of two systems to one setup is the worst thing to do. Decide what you want out of your setup, and build around it. Don't try and kludge two systems into one.

If you can't reach the valves, a twinset is no better than a single clyinder, so either invert the set, or save money and dive a single.

YMMV.
 

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Nigel,

If you're intending to dive manifolded twins, then yes, leave the manifold isolation valve open at all times unless you have to effect an isolate and shut down due to escaping gas.

If you're diving independent twins (i.e. no manifold, and swapping regs to breath every 50 bar or so to balance your gas loads), then the issue becomes academic.

1st things 1st: have you decided on which twins rig you'll be diving (manifold or independents)? If so, tell us and we can give you the pros-n-cons of each set up so you can make an informed decision.

HTH.
 

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Discussion Starter · #15 ·
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Bren
I have at the moment twin 12s on a manifold I have only used them twice at stoney with andy 2 tanxs I have gone from a 15lt single with a pony.
I haved moved onto twins for the extra dive time.This would seem to be a steep learning curve.
This afternoon I have had on my  rig on in the garage and for the life of me I could not reach the valves.how ever the twins are better balanced and it sits better than a single and pony
 

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I inverted my tanks for the first time this weekend, can reach the valves easy as pie in two seconds, feels very comforting.
Chee-az
Steve
 

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Discussion Starter · #17 ·
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Steve
you would recomend inverting twins then,over a slob knob?
 

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Hi Nige,

I think most of us who have swapped to twins find that they are better balanced than a single and pony, I would deffo agree there.

I won't say 'don't worry', but practice is what a number of us are going through at the moment to learn and be more proficient at doing our isolation and shut-down drills, so keep at it.

You say you've tried to do it the garage - OK, then what you need to do is go to the platform at either Stoney or the Cape and try to reach your valves and practise shut-downs there - in the water. Try this 1st and let us know how you get on. We can either dive with you and practise together or talk you through what you need to be doing from there on.

And when you're practising, try and do it with someone with a similar rig-config to you - i.e. banded, manifolded twins - NOT a single/pony or inverted twins. You'll have enough to enjoy working out one rig to begin with.

HTH
 

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Discussion Starter · #19 ·
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Bren
thanks but Id hate to be my buddy on the forth coming dive in wales !!!!!!
 

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</span>
[b said:
Quote[/b] ]You say you've tried to do it the garage - OK, then what you need to do is go to the platform at either Stoney or the Cape and try to reach your valves and practise shut-downs there - in the water.
<span =''>

Agreed - I can't reach my valves when standing up, nor can anyone else I know of: The weight of your kit drags them too far down.
The only place to find if you can reach the valves is in the water.
 
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