inverted manifolded twins

[rjack321]

What if the diver in question is not a "standard" diver. Standard configurations assume the standard diver will be able to reach his valves. The OP mentioned reaching valves is a problem with the diver in question. There was some good advice about looking at the dry suit/undergarment fit, stretching exercises, etc. But what if the problem with reaching valves goes beyond that. I had a friend in college that lost a lot of mobility in one shoulder after a bad car accident. Other than that, he was very fit and capable physically. I know there is no way this particular friend could have reached valves at the top. Probably even sidemount valves would be a problem. I would have to say that if this friend was a diver, inverted valves would probably be his best bet.

If he can't reach sidemount valves he's got NO business in doubles with a deco bottle(s).

The diver in question seems to have:
no instructor to ensure he's using proper technique to reach his valves
not checked his suit
not checked his undies
not tried a stretching regime for a few months

Yet he's considering buying cages and a new set of hoses to invert his tanks - what's wrong with this picture?

 

[elan]

We have no information on why the buddy has problems reaching the valves. Further speculations are just plain dumb...

 

[Slamfire]

Why chose a configuration that is suboptimal (bordering on dreadful) for wreck penetration when something as simple as changing the undergarment or drysuit can remedy the issue of reaching the valves in their upright orientation. I ordered a UK made drysuit once (Northern Diver) and it was cut just awful for reaching valves so its not too big of a leap for me to suspect that the OP's issues could be readily solved with a better suit.

Beat you to the post by a few seconds. In my previous post I give a hypothetical example of why somebody may chose a "suboptimal" configuration.

Nobody called it a death sentence. But I'll go out on a limb and say the reason most UK divers are using doubles and getting into deco is to see wrecks.

True, before I did nobody had mentioned death sentences.

Until the OP or the diver in question state what is going to be their diving environment, everything else is speculation. All we can do is offer advise without prejudice about different scenarios and different solutions. The diver in question will then chose whether to take it or not. If he does not act according to your advise, there is little likelihood that will affect you or your diving. I do not think the Eagle's Nest will be closed because the diver chose to use inverted doubles in the UK. Since this is not going to affect the people offering advise, there is no need to become abrasive, belligerent or have a patronizing tone towards the other counterparts participating in this discussion.

 

[ucfdiver]

What if the diver in question is not a "standard" diver. Standard configurations assume the standard diver will be able to reach his valves. The OP mentioned reaching valves is a problem with the diver in question. There was some good advice about looking at the dry suit/undergarment fit, stretching exercises, etc. But what if the problem with reaching valves goes beyond that. I had a friend in college that lost a lot of mobility in one shoulder after a bad car accident.

Not being able to hear them causes just as many problems as not being able to reach them IMO. Sidemount is a MUCH better option than inverted doubles.

Everyone I know that complained they couldn't reach their valves in backmount was doing it improperly and after some training can quickly shutdown a valve.

 

[Akimbo]

… A friend of mine had his doubles come out of the back of his truck bed while driving and not a single cu ft of gas leaked out. I've seen valves bent at a 90 degree angle from smacking the ceiling hard on a DPV, but not a single cu ft of gas lost there, either. 99.99999% of the time it's a reg, ...

A lot of bailout bottles were worn valve-up by commercial and US military divers in the early days of light-weigh masks and hats. I have seen two, and heard of several more, IP hose fittings being snapped off at the first stage due to accidental impact. Damaged hoses were much less common. To be fair, these work conditions are far more abusive to gear than sightseers more concerned about stirring up silt than completing a job before the clock runs out. Zero visibility is the norm in these trades rather than a dangerous situation.

Unfortunately, there is a lot of failure analysis and engineering derived from working divers, fire fighters, and mine rescue teams that is worthy of investigation. I don’t recall ever hearing of first stage damage to any valve-down rig, though I would be very surprised if it has never happened.

Continual risk management and evaluation should be part of the culture rather than frozen is some imaginary bible. Valve-up or down is irrelevant. Being fully informed in order to make sound engineering compromises for any particular situation is the point.

 

[ucfdiver]

A lot of bailout bottles were worn valve-up by commercial and US military divers in the early days of light-weigh masks and hats. I have seen two, and heard of several more, IP hose fittings being snapped off at the first stage due to accidental impact. Damaged hoses were much less common. To be fair, these work conditions are far more abusive to gear than sightseers more concerned about stirring up silt than completing a job before the clock runs out. Zero visibility is the norm in these trades rather than a dangerous situation.

Unfortunately, there is a lot of failure analysis and engineering derived from working divers, fire fighters, and mine rescue teams that is worthy of investigation. I don’t recall ever hearing of first stage damage to any valve-down rig, though I would be very surprised if it has never happened.

Continual risk management and evaluation should be part of the culture rather than frozen is some imaginary bible. Valve-up or down is irrelevant. Being fully informed in order to make sound engineering compromises for any particular situation is the point.

I was referring to recreational diving, since this is a recreational forum (and yes, Tech diving for fun is recreational in my book). This usually involves somewhat clear water where communication with a buddy is possible and desirable. Navy/Commercial divers take lots of risk unnecessary for recreation and it's infrequent that anything they do is related to what we do.

 

[DaleC]

I always approach gear configurations from a stand alone POV and don't have the problem of filtering everything through some preconceived ideas of what is standard or optimal or not. Optimal depends on the application; benefits you are trying to gain the most from and risks you are trying to minimize.

Some of the issues raised here have merit and some of them don't (IMO).

I can't speak to the (increased) ability of reaching the isolator because I haven't tried it. It should be noted that not everyone dives with an isolator though and for those app's the inverted cylinders are of interest.

Having to spin the tanks around to fill them is a non sequitor, who cares? You also have to lay them down when transporting but I've never heard that as an excuse for not diving a rig.

Damage to the valves is an issue while diving in the upright position (otherwise cave/wreck divers would not be concerned with hose routing to cope with rolloff) but damage to the valves in the inverted position could also an issue. How far this can be mitigated by design is up for debate. I have seen some inverted Cousteau rigs that look quite protected (valve wise) and we shouldn't forget that some RB divers have their tanks inverted as well. How do they get away with it or do they have it wrong too?

Custom hose lengths is also not a valid issue when viewed from a stand alone POV. It is only custom in regards to a standard length which doesn't apply if one doesn't have a standard. Hose length is what it is, you can buy all kinds. For many PADI rigs 7' and 22" hoses are custom.

Hearing a leak is valid and I would be very interested in learning what divers using inverted tanks think about this issue.

Thinking that "no one" dives this way any more is just myopic "there are far more things in heaven and earth than can be dreamed of in our phylosophies" to loosly quote the bard. Even the reasons that inverted cylinders have fallen out of favour in N.A. civilian diving may have more impetus than simple pragmatics. I don't think anyone here thinks change occurs in diving based solely on what works and what doesn't without some external influences. May be the early N.A. divers just didn't want to look "french". Currently we use PSI here while most of the rest of the world uses BAR measurement; does that make them or us wrong?

Looking at the issue doesn't mean one has to dive this way though it seems some become violently opposed to any other configuration because they fear somehow, if it is valid, they might be "forced" to dive it. A lot of useful information can come about from exploring and understanding how gear works/functions and why. I'm able to see the good and bad in most systems and still appreciate them if not for any other reason than expanding my understanding of dive systems as a whole.
I like diving; not just my way of diving.

 

[rjack321]

I always approach gear configurations from a stand alone POV and don't have the problem of filtering everything through some preconceived ideas of what is standard or optimal or not. Optimal depends on the application; benefits you are trying to gain the most from and risks you are trying to minimize.

The myriad of pretty big negatives are fairly well described...

The benefits of inverting:
smack the ceiling as hard as you want
reach the left and right posts quite easily (although this gets more complicated with multiple deco bottles on and suit inflation bottles)

You got more? I can't think of any?

btw UK cave/sump divers are not using inverted tanks. It seems that only UK wreck crowd still does. What about north sea ocean divers makes inverting "optimal"?

 

[DaleC]

Have you actually dived an inverted system... and what myriad of pretty big negatives?

I'm willing to consider that not hearing your gas could be a big negative (and I would like to understand better how inverted divers rationalize this) so that's 1 - otherwise, I can't see anything else. You can include valve damage at rest if you want but then you have to consider it against valve damage potential while diving in the valve up configuration.

You are pretty sarcastic about smacking the tanks on an overhead but I can't tell you how many roll off/counteracting hose routing, breaking plastic valve handles, manifold entanglement threads I've read so maybe it could nonsarcastically be consider a benefit.

You say ease of access except for multiple deco/stage/inflation bottles but what if the diver doesn't carry them. You can't assess every configuration as good or bad based solely on how you, in particular, might dive. Or I guess you can but your assessment would then have to be considered narrow in scope.

The ease of isolator access is still an unknown for me personally so that may or may not be 2 negatives. I have to say (?).

Everything else is not a "big" negative.

I know I would not convince you or ucf diver to "switch teams" as it were; you have your system it works for you and I respect that.. but, why does love of your system cause you to denigrate others? I wonder if you guys even realise how many years of exploration and experience you look down upon with your dismissive attitudes.

 

[ucfdiver]

what myriad of pretty big negatives?

1- Cannot hear your valves.
2- Cannot see your buddy while solving entanglement or gas issues.
3- Cannot rent doubles setup for this configuration from most shops.
4- Additional unneeded cages for the valves.
5- Whacky hose lengths.
6- Stage/Deco bottles block access to the valves.
7- Cannot reach isolator.
8- It looks silly.