Cave diving on CC is safer than on OC?

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Dive plan - 70 minutes 100 ft, 30 minutes overhead.
O/C setup - Back mount independent doubles, 2 side slung cylinders. All are HP117's with EAN32.
CCR setup - JJ-CCR with 2 slung HP117's with EAN32.
Subsurface planner:
Time to surface @planned 70 minutes is 60 minutes
O/C gas usage of 2/3 available.
CCR bailout gas usage at mid-dive is 2/3 of available.

Is the dive "safer" on O/C or CCR?
“30 minutes overhead” = 15 in and 15 out. Who needs 4xHP117 for a 15min of penetration at 30M? Who uses HP117 as stages?

This plan doesn’t make sense to begin with, why worry if it’s safer or not, especially if we don’t specify cave type?
 
Dive plan - 70 minutes 100 ft, 30 minutes overhead.
O/C setup - Back mount independent doubles, 2 side slung cylinders. All are HP117's with EAN32.
CCR setup - JJ-CCR with 2 slung HP117's with EAN32.
Subsurface planner:
Time to surface @planned 70 minutes is 60 minutes
O/C gas usage of 2/3 available.
CCR bailout gas usage at mid-dive is 2/3 of available.

Is the dive "safer" on O/C or CCR?
Trick question. Both dive plans are equally safe since I'll be sitting in my truck reading a paperback after pulling out the thumb and citing option number 1.
 
"30 minutes overhead" - one direction. HP117's because minimum gas required can't be done on 4 80's in O/C.

Subsurface (5.0.10.0) dive plan created on 5/13/23
Runtime: 130min
depth​
duration​
runtime​
gas​
100ft5min5minEAN32
100ft31min36min
100ft34min70min
100ft2min72min
40ft2min74min
-40ft4min78min
30ft0min78min
-30ft9min87min
20ft0min87min
-20ft16min103min
10ft0min103min
-10ft27min130min
0ft0min130min

CNS: 44%
OTU: 110
Deco model: Bühlmann ZHL-16C with GFLow = 30% and GFHigh = 75%
ATM pressure: 1,013mbar (0ft)
Gas consumption (based on SAC 0.71|0.60cuft/min):
97cuft/2,911psi of EAN32 (0cuft/0psi in planned ascent)
96cuft/2,929psi of EAN32 (0cuft/0psi in planned ascent)
62cuft/1,833psi of EAN32 (56cuft/1,779psi in planned ascent)
— Warning: not enough reserve for gas sharing on ascent!
0cuft/0psi of EAN32
 
"30 minutes overhead" - one direction. HP117's because minimum gas required can't be done on 4 80's in O/C.

Subsurface (5.0.10.0) dive plan created on 5/13/23
Runtime: 130min
depth​
duration​
runtime​
gas​
100ft5min5minEAN32
100ft31min36min
100ft34min70min
100ft2min72min
40ft2min74min
-40ft4min78min
30ft0min78min
-30ft9min87min
20ft0min87min
-20ft16min103min
10ft0min103min
-10ft27min130min
0ft0min130min

CNS: 44%
OTU: 110
Deco model: Bühlmann ZHL-16C with GFLow = 30% and GFHigh = 75%
ATM pressure: 1,013mbar (0ft)
Gas consumption (based on SAC 0.71|0.60cuft/min):
97cuft/2,911psi of EAN32 (0cuft/0psi in planned ascent)
96cuft/2,929psi of EAN32 (0cuft/0psi in planned ascent)
62cuft/1,833psi of EAN32 (56cuft/1,779psi in planned ascent)
— Warning: not enough reserve for gas sharing on ascent!
0cuft/0psi of EAN32

That is a lot of gas for that dive. I plan for a SAC of 0.7cuft/min. For a 100ft cave dive for 30 minutes of penetration, like at Ginnie, Little River, or Twin that would be LP85s or LP108s and a single AL80 stage. Deco is around 10 minutes on oxygen. This is based on my actual profiles.

I don't think I have enough lift to carry four HP117s. That is what 40lbs of negative buoyancy?
 
"30 minutes overhead" - one direction. HP117's because minimum gas required can't be done on 4 80's in O/C.

Subsurface (5.0.10.0) dive plan created on 5/13/23
Runtime: 130min
depth​
duration​
runtime​
gas​
100ft5min5minEAN32
100ft31min36min
100ft34min70min
100ft2min72min
40ft2min74min
-40ft4min78min
30ft0min78min
-30ft9min87min
20ft0min87min
-20ft16min103min
10ft0min103min
-10ft27min130min
0ft0min130min

CNS: 44%
OTU: 110
Deco model: Bühlmann ZHL-16C with GFLow = 30% and GFHigh = 75%
ATM pressure: 1,013mbar (0ft)
Gas consumption (based on SAC 0.71|0.60cuft/min):
97cuft/2,911psi of EAN32 (0cuft/0psi in planned ascent)
96cuft/2,929psi of EAN32 (0cuft/0psi in planned ascent)
62cuft/1,833psi of EAN32 (56cuft/1,779psi in planned ascent)
— Warning: not enough reserve for gas sharing on ascent!
0cuft/0psi of EAN32

Unrealistic descent time, deep stops profile, no deco gas.

Hard pass.
 
"30 minutes overhead" - one direction. HP117's because minimum gas required can't be done on 4 80's in O/C.

Subsurface (5.0.10.0) dive plan created on 5/13/23
Runtime: 130min
depth​
duration​
runtime​
gas​
100ft5min5minEAN32
100ft31min36min
100ft34min70min
100ft2min72min
40ft2min74min
-40ft4min78min
30ft0min78min
-30ft9min87min
20ft0min87min
-20ft16min103min
10ft0min103min
-10ft27min130min
0ft0min130min

CNS: 44%
OTU: 110
Deco model: Bühlmann ZHL-16C with GFLow = 30% and GFHigh = 75%
ATM pressure: 1,013mbar (0ft)
Gas consumption (based on SAC 0.71|0.60cuft/min):
97cuft/2,911psi of EAN32 (0cuft/0psi in planned ascent)
96cuft/2,929psi of EAN32 (0cuft/0psi in planned ascent)
62cuft/1,833psi of EAN32 (56cuft/1,779psi in planned ascent)
— Warning: not enough reserve for gas sharing on ascent!
0cuft/0psi of EAN32
With that plan I’m starting to understand why some might need a rebreather, I could make the dive on OC with a pair of 15ltrs of EAN36 @ 250bar and a 7ltr of EAN50 in 81min.
30M / 70min EAN36 (5500 ltrs)
20m / 1min EAN50
10m / 1min EAN50
3m / 9 min EAN50
 
It's just good-natured goofing around. Florida is the place to be, don't let anyone fool you!
This is how they suck you in, don't listen to Bill.

Florida is just as bad you have always heard. Think of all the mosquitoes, ticks, spiders, sand fleas and no seeums that will miss out on having you around. Who will the alligator, snakes, big snapping turtles, snails, invasive pythons have to stare at? And brain eating amoeba, your brain is as good as anyones. And in winter, who will all the semi frozen giant lizards fall out of the trees on?

And THIS is a typical local businessman.

images


I'm 5th generation Floridian, believe me.
 
https://www.shearwater.com/products/perdix-ai/
http://cavediveflorida.com/Rum_House.htm

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