Gas Management With Sidemount

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Especially on DPV/Scooter, switching out regs on the fly -there's always a chance of a freeflow. Also contaminated water -i.e. Engine room bunker oil; Cargo Hold aviation fuel --in the Truk Lagoon wrecks . . .it would be nasty to get a mouthful of that on clearing a switched reg.
Well you can get off the trigger for the 5 to 10 seconds it takes to make the gas switch or opt to delay it to your next stop. Most of the time when scootering in caves I'll be breathing a stage anyway and gas switches aren't going to happen nearly as often.

We heard that argument from you already. It's not an issue for 99.9% of diving applications. And I'd be worried about my skin, suit and the rest of the gear when swimming around in something as aggressive as aviation fuel.
It's a 100% issue of diving applications for those of us Wreck Divers who regularly dive on Indo-Pacific WWII Wrecks sunk-in-action. On UTD Z system sidemount, there is no issue of freeflow on reg swapping between bottom mix tanks or taking in a mouthful of contaminated water inside a wreck --->because we don't swap out regs (the Long Hose Primary is breathed all the time in the wreck unless donating to Out-of-Gas Buddy). And on Scooter in open water crossing shipping lanes, you don't have time to be off trigger for 5 to 10 seconds to futz with anything especially with super tankers/container ships bearing down on you. . .
 
SM noob here.

Now, I was thinking was why not first breath 30 bar / 500 psi from the one tank, and then be breathing 60 bar / 1000 psi to reduce the number of switches.


Hi thats exactly what I do and teach, even for tec Dives. works like a charm :)
 
I'm assuming you have practiced this, what is your difference in gas usage when feathering the tank vs. not?
It was part of my SM training and is not difficult, nor is there gas loss. I got into a rhythm of want to breathe, open valve slowly and a little bit, breathe, close valve.
 
It was part of my SM training and is not difficult, nor is there gas loss. I got into a rhythm of want to breathe, open valve slowly and a little bit, breathe, close valve.

How was this skill incorporated into training, specifically how did you evaluate gas usage and conclude that no more gas was used when exiting while feathering a valve than when not feathering?
 
Because none was exiting between the reg and my lips. The key is to slowly and partially open the valve.

Try it.
 
Because none was exiting between the reg and my lips. The key is to slowly and partially open the valve.

Try it.

How was this incorporated into training? I'm asking about gas consumption (i.e. usage), not loss. I'm happy to assume perfect valve management but want to know how you measured gas consumption when feathering a valve.
 
...//... The key is to slowly and partially open the valve. ...
What she said.

You pull on the secondary and get nothing. Calm down, no problem. Crack the valve and take your breath while you immediately re-close the cylinder. If you do it correctly you will just inhale the bit of gas you added to the lines. After a couple of cycles you will begin to believe that you can get air anytime you want and the anticipation disappears.

If you do this correctly, your SAC (RMV) won't change enough to mess with your calcs.
 
If you do this correctly, your SAC (RMV) won't change enough to mess with your calcs.

I'm wondering if anyone has done an actual exit while feathering a valve. Trying to get an answer to that (and not a step-by-step on how to work a valve :wink:) seems difficult to impossible. If this was part of training surely it would have more information?
 
https://www.shearwater.com/products/teric/

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