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The fo2 drop of the RB80 is craziness. I can see why some of the older RB80 divers are starting to use an o2 cell & Petrel to monitor fo2 during dives.

If the RB80 FO2 varies a lot, wouldn't you really, really WANT to have a computer monitoring the O2 in the loop and calculating the tissue loading based on actual FO2 instead of some fixed FO2 that you set? It seems like otherwise could result in getting bent from breathing a lower FO2 than what the computer is set for.
 
If the RB80 FO2 varies a lot, wouldn't you really, really WANT to have a computer monitoring the O2 in the loop and calculating the tissue loading based on actual FO2 instead of some fixed FO2 that you set? It seems like otherwise could result in getting bent from breathing a lower FO2 than what the computer is set for.
In class you have a po2 monitor. We used it to verify real life vs what it's predicted to be. It's for reals always the same as what's predicted.

In class you learn to plan the dive off worst case fo2, to include running tables off that and entering that into a Petrel if diving one. Personally, I put in the worst case fo2 for the bottom and don't plan on any fo2 drop on deco gases. That's an acceptable risk for me. Others might choose differently.

Interesting fun-fact, the fo2 drop's impact on deco shakes out to an effective depth of 10ft deeper. So a 200' dive decompresses like a 210ft dive. Neat.

Regarding the use of a sensor, imo it doesn't add enough value to be worth it for the dives I'm doing. Again, others might choose differently and that's fine.
 
If the RB80 FO2 varies a lot, wouldn't you really, really WANT to have a computer monitoring the O2 in the loop and calculating the tissue loading based on actual FO2 instead of some fixed FO2 that you set? It seems like otherwise could result in getting bent from breathing a lower FO2 than what the computer is set for.

It depends on how much you value safety Stuart. The JJ-CCR electronic are always calculating the inspired po2 to give an accurate decompression model not some crazy voodoo calculations to trick a dive computer, lol.
 
...I am a firm believer that it is a safer configuration for cave diving than doubles. GUE disagrees and they have every right to disagree with that, but it will be interesting to see what happens when they do settle on a sidemount configuration

I actually have a lot of respect for GUE's current stance on sidemount diving.

It's a lot better than some of the other DIR 'off-shoot' agencies, who've tried to sledgehammer sidemount into a backmount consistent approach. Sidemount isn't backmount - it's a very different beast - and no amount of fancy gizmos, principle-bending and inconsistency-blinkering is going to change that.

Attempting to formulate a standard sidemount configuration whilst retaining principles consistent with backmount diving evolution, is like cutting a head of the Hydra.

When you modify one element to meet a given principle, you find that you've created glaring breaches of several other principles. Modify again to resolve those, and find you've broken more.

Chase your tail for long enough...and when you step back to admire the result you see that you've created abominations full of QR failure points, kit that costs 4x anything else on the market, you're using a metal backplate and you have long hoses curled up all over the place.....

My one concern with GUE's approach to sidemount is that of "not for use in open water". I think it's fair for them to designate sidemount as 'cave mission-specific' until such time that (if...) they every crystallize on a standard sidemount rig/approach/system.

That said... if you need to use sidemount on cave mission-specific dives, then you are talking about some pretty advanced caves... tight restrictions and passages. If you've done ALL of your diving in a standardized single/double backmount configuration, then sidemount is relatively alien. Your equipment familiarity is minuscule compared to your experience in a cohesive backmount approach.

You need to amass experience in sidemount long before you use it on advanced overhead dives. That, in itself, presents a strong argument for encouraging divers to use sidemount as often as possible to gain an advanced level of familiarity and comfort in their rig. Hundreds, if not thousands, of hours.

So... you dive sidemount in open-water, because that's a benign testing ground. It's where you can accumulate the many hours of familiarity needed to learn the ropes..... to go from 'novice' to 'expert' in SIDEMOUNT diving.

Anyone that thinks decades of backmount cave expertise translates instantaneously into comparable expertise using sidemount after a relatively small handful of dives is suffering massive complacency - bordering on the delusional.

There many reasons why tight standardization is a beneficial approach to equipment configuration. Not least of those reasons is that the diver themselves enjoys the same intimate familiarity; regardless of whether they dive single or double backmount, cave, wreck or open-water, tropical, temperate or cold water....

Potentially decades of diving in a wide spectrum of conditions and environments - where every single dive contributes to and reinforces the same muscle memory, instinctive responses and equipment familiarity.

Cross-over to sidemount and..... no matter how much you've tried to bastardize a rig to fit with that backmount standardization.... you lose those decades of intimate rig familiarity. That should not be under-estimated.

I think a few divers.... often the ones with the highest reputation and status.... are giving in to ego and doing their best to hammer a square (sidemount) peg into a round (backmount) hole. Deny the fundamental differences and just keep hammering away.

The reason being.... to acknowledge that their authority, expertise and accumulated skillfulness in backmount diminishes substantially when they don a sidemount rig.

Sure, you can preserve sidemount for only complex cave dives. How will the incident report read when the community debate the amount (hours/dives) of actual sidemount experience the victim had when they screw up?

"The victim encountered a _______ problem in very complex cave passage, responded inappropriately and failed to ___________. Despite over 3 decades of technical cave experience, the deceased only had XX dives experience using the sidemount equipment he died in..."
 
@DevonDiver that's my biggest problem with GUE's stance on sidemount and CCR diving actually. If I'm ramping up to sidemount only passages, I want ALL of my dives leading up to that to be in sidemount so if something happens nothing is foreign. Same on a rebreather. Fundamental point of difference but unfortunately like you said, nothing really in sidemount in terms of emergency management really transfers directly to backmount because it's all different. I think when/if GUE finally finishes their sidemount standardization it will be something fairly similar to what we are seeing being taught by Edd and many other sidemount instructors.

@stuartv if you read up on SCR FO2 calculations it's actually quite stable and you program your computers for the FO2 low. This is well documented and verified over the last 20+ years. Only big downfall of SCR like @PfcAJ alluded to is that your diving isn't quite as efficient as OC since there is a FO2 drop in the loop and you can't put in a hot mix because you still need to be able to breathe it at depth.
 
The fo2 drop of the RB80 is craziness. I can see why some of the older RB80 divers are starting to use an o2 cell & Petrel to monitor fo2 during dives.

the biggest concern is hypoxia with the rb80 and that's what's harped on the most during the class for good reason. po2 drop as far as deco is concerned is pretty meh for me. for years and years they ignored the drop altogether MOSTLY without incident

but if you're not on top of it the rb80 will put your ass to sleep pretty quickly. the JJ and the RB80 are both kevorkian machines. lets not kid ourselves
 
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but if you're not on top of it the rb80 will put your ass to sleep pretty quickly. the JJ and the RB80 are both kevorkian machines. lets not kid ourselves

I agree, I just like the warnings that I'm going to kack myself if I don't take corrective actions.
 
@DevonDiver that's my biggest problem with GUE's stance on... CCR diving actually. If I'm ramping up to sidemount only passages, I want ALL of my dives leading up to that to be in sidemount so if something happens nothing is foreign. Same on a rebreather.

I'm sorry, maybe I missed the memo, what is GUE's stance on rebreathers?
 
someone more involved with GUE will have to comment on the official stance, but my understanding is that it is still considered a "mission specific" diving configuration, i.e. don't use it unless you can't do it practically on OC, as opposed to becoming a "rebreather diver". Brought it up because they use sidemount for cave diving where you can't get through in doubles, but not on all cave dives, so sidemount is a "mission-specific" configuration as opposed to a generally accepted configuration.
 
https://www.shearwater.com/products/peregrine/
http://cavediveflorida.com/Rum_House.htm

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