JJ dil MAV

[Janos]

Having the ability to switch dil (or plug in off board) is crucial to some dive plans. If you think I want to use 85 meter gas I've needed on the way to a protracted 6 meter swim at max penetration whilst still a good three hours in you're having a laugh.

Why?

If you've got to carry the gas anyway, does it matter if you're carrying a 3l of 15/55 and a 3l of air; or 2 x 3l of 15/55?

As you're running a SP of 1.2 or whatever, from a dil perspective it's very much all the same, shirely?

Genuinely interested as my CCR cave diving has all been shallow.

Janos

 

[Janos]

Yes, sure. It is possible. But not sure controller will give me then real deco in SCR mode.

Assuming a shearwater, that you tell it what dil you're using, and that you flush the loop a few times, then the SW will calculate the deco correctly in normal CC model.

I believe that SCR mode on the SW is only useful if it's not reading the cells.

Janos

 

[Clare]

Why?

If you've got to carry the gas anyway, does it matter if you're carrying a 3l of 15/55 and a 3l of air; or 2 x 3l of 15/55?

As you're running a SP of 1.2 or whatever, from a dil perspective it's very much all the same, shirely?

Genuinely interested as my CCR cave diving has all been shallow.

Janos

All down to preferences.

On a 5plus hour run time I'd rather not expose myself to high set points unless on deco in the end phase. So I'd run a manual set point of between 1 and 1.2 max.

15 per cent O2 is too rich for flushing or for bailing out at 85 meters (as per the dive I had in mind when I posted). I'd run 12 per cent or even 10 per cent. This is not a good gas to have running to your ADV in a shallow section perhaps when barely under the surface or in sumps. It's not too good for a river swim either (I have worn so much gear in the past that I haven't been able to get my head out enough in the river to lose the loop.)

We have to carry stages to bailout on to so gas is available. Being able to use these through the unit gives flexibility. It really isn't something I would recommend all divers do - if your environment does not require it ever then why add complexity or failure points?

The difference which cave divers face is whilst ocean divers are not shallow for long, and can plan their time at each level in advance, cave diving can force some pretty weird profiles on you. As you will know, the up down nature does lead to more dumping/adding gas than OC and thus what is going in to the loop has bigger impact over more of the dive.