New to rebreather diving

[helodriver87]

Edit: Rjack explained it better

 

[doctormike]

I dive manually, so I don't change the setpoint at all during my dive, but I can't imagine it would be appreciably more difficult on a NERD.

Maybe we are splitting hairs here, but I find it a lot easier to interact with a wrist mounted console than the NERD. The NERD is great for a display, but once you start using it as a controller, you can move it enough to move it out of your line of sight. Since you have to push the left or right button individually, doing that on a NERD would cause it to move around or even come loose, unlike on a wrist mount. Not the end of the world, but far easier to just look at your wrist and tap a button IMHO, especially since it's only done a few times during a dive. The only time I actually interact with the NERD buttons during a dive is when I go to the compass.

With digital communications, you don't have the same need for redundant monitoring to validate during the dive. The sensors are going to the same ADC board on the JJ so you aren't reading a different group of sensors. The ADC conversion is going to send the same signals to the SOLO board and the OBOE board. Since communication is now 2-way, and there are no isolator boards or any of that nonsense, the only reason for the secondary monitor while on the loop is in case the primary fails, not to validate like it used to be.

Right, I was referring to a failure, not to comparing the readouts. I agree that with three cells feeding both boards, that's not the point of redundant PO2 monitoring.

You certainly want something up in your face, so may as well make that everything you need and then the other can get tucked away if you don't want the cable on your arm, or just left on your arm. Second reason to have it is in case you bail out and don't have a BOV, you'll then want to not have to pull the loop down every time you need to look at the computer.

This I don't agree with. I want the data in my face, I want the buttons elsewhere. Just like if Shearwater offered a way to hit the MAV or the ADV from the loop, I wouldn't want it. I never tried the DiveSoft BOV, but wasn't that the point of that design? I guess you can get used to anything, but putting extra stuff on the loop seems like a step backwards.

I can always find my wrist, and the cable on my arm has been a non-issue for me. If the wrist controller fails, I can stay on the loop and ascend manually with the deco and PO2 information right there on the NERD, with a 0.7 parachute. I'm not sure I understand what you are saying about bailout with respect to the advantage of a controller in the NERD. If you bail out and you have tucked away your wrist display, then yes, you have to pull down the loop for deco. Isn't that another reason just to leave the Petrel on your wrist and use that? Or are you talking about simultaneous controller failure and some other reason to bailout?

Again, nice clean JJ design - the MAV, controller and ADV are just where I want them. And if you want to tuck something away that's not that useful during a dive, it's the SPGs. JJ does this, instead of having them clutter the front, like other units. There's something that you rarely look at during a dive.

 

[rjack321]

Interesting - would someone mind describing the KUR-style configuration? Guessing that's something like side mounted lp85s for bailout and al30s for onboard diluent and o2?

I'm not particularly well-versed in blending, but what about the 50s makes them hard to top up with a small booster?

The non- GUE way aka KUR way for caves
Sidemounted 85s or 120s, 7.25" tanks slightly preferred but you can do it with 8" tanks
dil and wing fed from left SM tank
bungied backup on left SM tank
BOV on left SM tank (all of this may or may not get sourced from one QC6 on a manifold)
long hose on right SM tank, clip off to right shoulder
Onboard O2 on the right, 3L is most common
Onboard 3L "dil" on the left is converted to suit gas

No Al30s, by the time you need that much O2 your scrubber has long since expired

CCR boosters will burn up trying to regularly top up double 50s. The HI booster only has a 1:20 ratio and wont go over 3000psi with 150psi drive gas. The Kiss baby booster is the same. The baby haskel can sort of do it with a 1:25 ratio but still maxes out around 3300psi. They are meant to boost O2 and dil into 2/3L bottles and maybe the occasional 40. It will take hours and generate a ton of heat and burn up seals trying to use those to top off 50s, especially if your source gas pressure is low.

 

[rjack321]

oops

 

[flymolo]

The non- GUE way aka KUR way for caves
Sidemounted 85s or 120s, 7.25" tanks slightly preferred but you can do it with 8" tanks
dil and wing fed from left SM tank
bungied backup on left SM tank
BOV on left SM tank (all of this may or may not get sourced from one QC6 on a manifold)
long hose on right SM tank, clip off to right shoulder
Onboard O2 on the right, 3L is most common
Onboard 3L "dil" on the left is converted to suit gas

No Al30s, by the time you need that much O2 your scrubber has long since expired

CCR boosters will burn up trying to regularly top up double 50s. The HI booster only has a 1:20 ratio and wont go over 3000psi with 150psi drive gas. The Kiss baby booster is the same. The baby haskel can sort of do it with a 1:25 ratio but still maxes out around 3300psi. They are meant to boost O2 and dil into 2/3L bottles and maybe the occasional 40. It will take hours and generate a ton of heat and burn up seals trying to use those to top off 50s, especially if your source gas pressure is low.

Cool. Thanks for explaining!