DevonDiver
N/A
Please read the previous very possible scenario description : ... when reaching for dive buddy regulator its a 22" necklace - ZONK !
Your entire counter-argument seems to be reliant an a fictitious diver who insists upon wearing a 22" hose locked in a necklace. Remove that 'factor' and put the fictitious diver into a longer (40") short-hose with breakaway from the necklace and the story changes dramatically, doesn't it?
1. having two long hoses, which as we discussed would create a multiple hose crossings, and depends on donated hose being cut off by the other stowed at the time long hose
We didn't discuss 'multiple' hose crossings. You mentioned it. It was denied. There would, at worst, be one hose crossing. You know this as truth, so stop exaggerating. If you've ever tried this, you'll know that, in sidemount, that hose crossing doesn't prevent the full deployment of the long hose. Once deployed, the donor has ample time to remove his reg and re-orient it to remove the cross-over.
This is a principle I teach on every sidemount-technical course. If divers opt to route their deco reg around the neck, it crosses the long hose. I get them to donate the long hose at that point (during deco) to illustrate the cross-over. It's never a great learning point, because they can always still fully deploy the long hose. Then the noobie tech diver simply resolves the cross-over. They look at me "so what? dealt with".
I'm surprised this would cause significant problems to UTD trained divers - but perhaps the realities of this remain theoretical to them and thus have suffered a chinese whispers process of exaggeration into full-blown horror stories...
2. some wrote that in complete pitch black black out will somehow signal to the buddy that he should wait (have no idea how long)
I'm guessing any delay would extend to the amount of time it took to unclip the bolt-snap, or pull the breakaway, and donate the long-hose in exactly the same manner as you would do from the mouth.
So... how long to unclip a bolt-snap or pull-and-release from the breakaway? A second?
and the donating diver will detach the tank and again in complete darkness pass the tank with regulator (using one hand, other on the line) to his OOG buddy, hope his buddy wouldn't loose any teeth or end up with crushed skull after getting hit by steel tank, and his OOG one handed buddy will catch the reg with the tank and rescue himself !
You use stage tanks on cave dives? You handle them? Pass them through restrictions? Ever crushed a team mates' skull or knocked their teeth out?
Even as a UTD instructor I just realized that I have to still learn so much !
Maybe to learn diving sidemount, rather than prolonging the attempt to be a backmount diver with sidemount tanks... just a suggestion..
ANSWER TO VERY OFTEN BROUGHT FAILURE POINTS:
Any piece of equipment is a failure point, fin strap, mask strap, going through hose connections, valves, lights etc. Have you noticed that even without having isolatable manifold we (divers) will differ with "possible failure points" on regular basis. for example I dive drysuit and argon bottle, other wetsuit and no argon, its counting two ends of the hoses few more or less possible failure points.
So, in order to justify the z-manifold, one has to abandon the concept of minimizing failure points? We have to just trust towards "good maintenance" and assume that 'nothing that can go wrong, will go wrong'?
Remember as long as something has a proper procedures that team is thought we can solve any arose problem and just go home safely regardless...
You are aware that these sentiments can be used equally to support not using the z-manifold?
Still advantages of UTD isolateble manifold are way grater then cons.
You are absolutely entitled to express that opinion. Be wary of stating, what is a very minority opinion, as a fact.