Diving Truth or Myth

[hilrosepaul]

Originally Posted by BJ

....The BSAC decided to do away with the quarter turn back practice just as have most other training agencies....

I did both Ocean and Sports diver last year in a BSAC club, and was taught to do the quarter turn back. (Edit - From fully OPEN, just in case breko's reading this)

[A. Berk]

I'm sorry but this business of confusing 'a quarter-turn back from fully open' with 'a quarter open from fully closed', I just don't get it... what circumstances induce people to fcuk that up? Its not like your average diver is under fire and has to react like an SAS trooper with lightning-fast reflex actions. You put your DV on the cylinder knowing full-well that the cylinder valve is off - otherwise it'd be hissing very noisily, right? Once the DV is in place you open the valve - it can only go one way from closed - and you wind it 3 and a bit turns until tight-ish then back a smidge. I'm willing to bet an ape could be trained to accomplish that task.

kerBo

[BJ]

Contrary to popular belief, the advice given by training agencies is not Statutory just as Sharia or the laws of the Beth Din do not substitute for the laws of the country (English Law enshrined in Statute as set by parliament). Instructors will continue to teach people what they want to teach them and there is nothing the training agencies can do to change that. Why not write to the training agency of your choice and ask them for an official recommendation? It is your choice if you want to take their guidance. You can always bgger off and do what you like anyway!

[gerbil]

Originally Posted by BJ

Contrary to popular belief, the advice given by training agencies is not Statutory just as Sharia or the laws of the Beth Din do not substitute for the laws of the country (English Law enshrined in Statute as set by parliament). Instructors will continue to teach people what they want to teach them and there is nothing the training agencies can do to change that. Why not write to the training agency of your choice and ask them for an official recommendation? It is your choice if you want to take their guidance. You can always bgger off and do what you like anyway!

Is any one saying anything different or did you just want to take your strawman for a walk?

[Adrian Kelland]

Originally Posted by hilrosepaul

I did both Ocean and Sports diver last year in a BSAC club, and was taught to do the quarter turn back. (Edit - From fully OPEN, just in case breko's reading this)

Old habits die hard.

[ianfirmin]

Most valves have a non-linear response. If it's, say, 10 turns from open to closed then you do NOT get 50% flow at 5 turns. In general the flow increases rapidly as you open the valve from closed. As you open the valve further the increase in flow is much less. So, for instance, for a 10 turn valve the first 6 or 7 turns to close it from fully open may not have much effect. It's only when the valve approaches the seat that significant flow reduction is noticed.

Mr. Berk is quite correct is saying that fully opening a valve has little effect bar stressing the parts. Also that having a manifold valve only a couple of turns open often allows sufficient flow and makes turning it off a far quicker activity than if it was fully open.

ATB
Ian