Shut down drills...

[Pink & Fluffy]

I also have the same problem with my twin 7s I cannot reach any of the valves so I dive with the manifold shut ,and use them as 2 independant  cylinders ,so at least if there is a failure on one of them I will have some gas in the other cylinder as I  breath each cyliner down at the rule of 3rds . any problems with one cylinder I switch to the other and abort the dive . for me this seems to work ,as even if I could reach the valve by the time I realise what is happining and workded out which one has gone wrong and struggled to turn it off . all the gas would have gone .

[daz]

I have recently started playing with twin 7's after using inverted twin 10's for some time.

I found I could shutdown all valves first try, however it was a bit of a struggle.  Since then I have moved them up in the bands so the top band is about 1" below where the cylinder starts to round off.

The shutdowns are easier, quicker (Although definitely not as quick as on my inverts)  Also it has moved the weight distribution a bit so I am not as feet heavy.

My 10's are staying inverted though as my trim is fine and shutdowns are a PIA with them valve upwards.

Daz

[Davey Willo]

Go Daz!!

The few seconds longer that it may take isn't a real concern Daz as it takes ages for a free flowing reg to spew forth all of ones air.... During our fundy class we had to dump air down to 35 bar for a weight check and I couldn't believe how long I was hanging there with the purge button depressed.... everytime I looked at my spg it had hardly moved.

God know's what people on the surface were thinking because there were three of us hovering at 6m purging like crazy... it must of looked like white water on the surface.... Although saying that nobody attempted to come to our aid.. lol.. bastids!  

[daz]

Having tried both methods I will vouch for the fact that shutdowns on a traditional rig are perfectly adaquate as long as you can actually shut them down and the rig is comfortable.  How low the cylinders are and any restriction in the suit can make a world of difference.

Having said that the 10's are at this time staying inverted.  Performing shutdowns is just not happening unless I move them much higher up.  If I move them higher up on my back I end up head heavy and plowing a furrow with my face.   And to improve trim by adding weight near the waist area I just end up over heavy.

So 2 morals to this story....

Don't use twin 10's.  If you can lift 10's you can probably lift 12's.  (Don't suppose anyone want's to swap a set of 300 bar 7's for a set of twin 10's do they )

If you can't do shutdowns no matter what you try.  Then give it a go with inverts as long as you are willing for the extra cost of valve guards, custom hoses etc.  

Daz

[daz]

Originally Posted by [b

Quote[/b] (Dave Williamson @ Jan. 16 2004,11:59)]The few seconds longer that it may take isn't a real concern Daz as it takes ages for a free flowing reg to spew forth all of ones air.... During our fundy class we had to dump air down to 35 bar for a weight check and I couldn't believe how long I was hanging there with the purge button depressed.... everytime I looked at my spg it had hardly moved.

Dave,

I must give this a try sometime just to get an idea of how long it takes (Should scare the crap out of my buddy as well   )..

I would hazard a guess that certain regs such as Poseidons and Oceanic Omegas may be able to lose more gas more quickly due to their design (OK I know the DIR answer to this one   ).

Just one observation,   surely there is a reasonable difference between how much air is lost from a freeflowing reg at 6m and a freeflowing reg at 35m.

Still the bottom line is that I can do shutdowns on my 7's,  I can shutdown the isolator reasonably quickly as well,  well quick enough for me not to consider inverting (Ask me again after I have a freeflow at 30m  

Daz

[Fraser]

Originally Posted by [b

Quote[/b] ]I would hazard a guess that certain regs such as Poseidons and Oceanic Omegas may be able to lose more gas more quickly due to their design (OK I know the DIR answer to this one   ).

Hi Daz,

There is a letter on DNet from a chap that purged his Poseidon regs at 30 odd metres in Stoney Cove (in response to an article about shutdown drills) and noted the results:

Here

It seems that Poseidon regs will bin the contents of your cylinder that much faster than other regs.

HTH,

Fraser.