Most Redundant OC SCUBA?

[Akimbo]

Very well said John. I'll second that. I hate the little 19cuft I sling too often.

Why not mount it with a bracket?

 

[AfterDark]

Why not mount it with a bracket?

I use it instead of an octo 2nd stage. I want to be able to hand it off. I got sick of switching my 2nd stages when I use a single tank, after using them for IDs; and I never liked the longer hose when used on IDs. So now my regs remain unchanged the longer hose is changed for a shorter but I have to endure slinging that bottle when buddy diving. What was worse was down in NC this year. I was using my IDs for the increased bottom time but was also buddy diving and slung the little ba$tard 2 dives per day.

 

[lowviz]

OK, how about clipping it to a tailpiece rather than your hip? Doing so will pull it out of your way...

 

[Eric Sedletzky]

One of the other things about diving I have come to abhor is the lack of streamlining of today's divers. I am the former Fin Swimming Director for the Underwater Society of America, and hanging tanks haphazardly onto a diver's frame seems to go against why I dive, which is to freely swim in any direction more like a fish than walking like a normal person on land. I relish the time, for instance, when I swam fast in current and surprised a Chinook salmon, which normally stay out of visibility range in the Clackamas River. Or the time I came effortlessly up to a 7 foot sturgeon. Swimming in this manner underwater is very difficult in some of today's configurations.

Today's divers use ineffective kicks (the modified frog kick--I'm a former breaststroke swimmer who actually knows what a frog kick is about) to minimize causing silt-up situations, but doing so does not efficiently propel the diver. The frog kick is for very specialized diving in wrecks or caves where silt-up situations are a hazard. I'm also a "vintage diver" who usually is in the vintage equipment forum, but I'm tired of the emergency of technical diving techniques pulling us away from the weightless, effortless diving I have known most of my life.

SeaRat

This is exactly why I dive a minimalist configuration.
And by minimalist I don't mean a technical minimalist, I think they stole the term. There's nothing minimal about technical diving.
I also don't believe a modified frog kick with the feet up at a 90 degree angle is the end all kick for every scenario.
Great for caves and wrecks and muddy bottoms but worthless for where I dive.
I think it's actually a very unstreamlined kick which puts the lower portion of the legs out of the slipstream and causes drag. It's very unnatural and doesn't feel right to me.


I'm glad to see someone else sees it the same.

 

[ajduplessis]

This is exactly why I dive a minimalist configuration.
And by minimalist I don't mean a technical minimalist, I think they stole the term. There's nothing minimal about technical diving.

Minimalist means taking only the equipment you need for the dive, nothing unessesary. Just because a tech diver takes a bucketload of kit with does not mean its not minimalist. He NEEDS everything he takes with. Please use the term in context.

 

[guruboy]

The argument over the use of redundant/redundancy is literally the most useless thing I have ever read.

lit·er·al·ly
ˈlitərəlē,ˈlitrə-/
adverb

1.
in a literal manner or sense; exactly.

2. informal
used for emphasis or to express strong feeling while not being literally true.

---------- Post added September 25th, 2013 at 12:51 AM ----------

Minimalist means taking only the equipment you need for the dive, nothing unessesary. Just because a tech diver takes a bucketload of kit with does not mean its not minimalist. He NEEDS everything he takes with. Please use the term in context.

Minimalism is not a matter of NEED.

Main Entry: min·i·mal·ism
Pronunciation: \ˈmi-nə-mə-ˌli-zəm\
Function: noun
Date: 1927
1 : a style or technique (as in music, literature, or design) that is characterized by extreme spareness and simplicity

 

[John C. Ratliff]

Minimalist means taking only the equipment you need for the dive, nothing unessesary. Just because a tech diver takes a bucketload of kit with does not mean its not minimalist. He NEEDS everything he takes with. Please use the term in context.

Minimalist diving means something different to a vintage diver than to a technical diver. Here is a list of minimal equipment for a scuba diver in warm water: mask, fins, snorkel, knife, tank, regulator, possibly a weight belt with a quick release. In cold water, then a wet suit with a weight belt is indicated to keep warm. The first photo below shows me in minimal gear, circa 1964. Later we added a vest for floatation on the surface in an emergency, and this became required gear. The photo of the Oregon Department of Fish and Wildlife biologist typifies this gear in about 1975. We did a lot of hard work underwater using just this gear. About six years ago, I had my photo taken at High Rocks on the Clackamas River, in vintage minimalist gear.

A tech diver with a kit is not diving minimalist style. He or she thinks he or she "needs" all that gear, but to breath and swim underwater much of it is not necessary.

When I was in the U.S.A.F., we made parachute jumps with varying types of equipment. This included tree suits when jumping into trees, medical kits, scuba and a life raft when jumping into water, etc. When we jumped simply to enjoy the jump, we jumped "Hollywood." This meant minimal equipment--a parachute and reserve parachute, helmet and boots over our fatigues. It felt good to jump in this manner once in a while, to remember how jumping can be fun and not all work.

The same goes for minimalist diving in the vintage sense.

SeaRat

 

[victorzamora]

Victorzamora, here is the quote in the op-ed:

I did use the word "redundant," but that was secondary. I dive in a river, in high current where regulator performance is crucial. The setup allows twice the air available at the second stage as other configurations. This is done with a regulator that I bought new in the 1980s. But the A.I.R. I would be hard to beat without this configuration by any of the newer regulators today. My point is that this is a redundant system, with the limitation of the O-ring/LP hose failure that has been pointed out. Yes, it is complex, and yes, probably unnecessary for most diving. My whole point was that it was a possibility that may not have been considered by any of you before, and it worked and worked well.

SeaRat

It certainly isn't something I had ever considered before. You get HUGE points for creativity and ingenuity. It is a really cool mental challenge to come up with something other than the "Big 3" gear setups. HOWEVER, my point was that I see no benefit to it in real-world scenarios and see some negatives over the other, more conventional, setups. As for air delivery, I don't think I have ever been "starved" of air with a decent regulator. Every regulator I've owned (6, so not many) has had great performance at depth (130+, I'm just getting into Tech-depths). I have never felt the need for more air. If I needed more air due to true exertion at depth, I would simply stop diving there, buy a scooter, or pull myself along the bottom. There are too many risks associated with extremely high exertion levels in SCUBA.

But still, it's a really cool thought experiment....I just wouldn't call it the "Most Redundant OC Scuba" even by a long shot. I have to ask, how much machining did you have to do to your second stage to get this to work?

 

[halocline]

Redundancy involves having more than one system or necessary item in sequence, so that BOTH need to fail for a diver to lose access to whatever the system provides, like light, gas, buoyancy. For example, sequential o-rings on a manifold. John's 'system' does the opposite; it introduces extra o-rings, hoses, and systems, ANY of which need to fail for the whole thing to stop working. It's actually quite a bit less redundant than simple doubles would be, or a single tank with a bail-out bottle. Unless there's something I'm not thinking of, any leak along the air path in either first stage, or anywhere in the 2nd stage, is catastrophic for this set up. This is because any point along the system from one tank valve to the other is pressurized with no way of isolating. What possible advantage does that offer?

The idea of supplying a single 2nd stage with 2 first stages makes no sense to me whatsoever. Single first stages are designed to supply multiple 2nd stages; they have far greater flow capacity. If John is sensing an increased flow in the 2nd stage, maybe it's because he's feeding it an abnormally high IP, way out of spec for the SP 1st stage and the 2nd stage. While I don't think it would harm the 1st stage (higher IP is in theory harder on a HP seat, but probably without much real-world effect) it can't be good for the 2nd stage, that was designed to react to lower IP. And the air1 (I have several) has a very strong venturi assist that will be increased by the high IP. This makes an uncontrollable free flow more likely. As much as I love the converted pilot and air1, one issue they do have is that under full free flow, the diaphragm can get inverted or pulled off the flange; I've seen it happen a few times. This makes the flow very difficult to stop. Then, the high IP means that an uncontrolled freeflow will empty the tanks that much faster.

John, you add a lot to this forum and have a place in diving history, but with all due respect, this set up is for the birds IMO. Sorry!

 

[John C. Ratliff]

halocline, let me take your second point first. Take a look at these graphs:


The only difference between these is the incoming tank pressure. The top graph represents a tank pressure of 300 psig, at 20 Breaths Per Minute (BPM) with a Tidal Volume of 2 liters for each breath. The bottom uses the same BPM and Tidal Volume, but at 2000 psig. Do you see a difference in the performance? That performance can be enhanced by adding an additional reservoir of air from a second stage at low tank pressure, or higher tidal volume rates. I have a vital capacity of 6 liters, although under normal diving I probably only use 2 liters of that. But I regularly get into river currents, where I breath quite heavily, probably using much of that 6 liter vital capacity in those areas of the river. This means I am drawing a lot more air on each breath than most divers. Here is a cutaway of the A.I.R. I:

Note that this amount of air is immediately available to the second stage from the opposite side of the regulator. According to Scubapro, "Maximum flow performance and safety can be achieved by attaching the A.I.R. I Second Stage to two independent first stages which, in turn, are mounted on separate high-pressure cylinders." (A.I.R. i AIR INHALATION REGULATOR SECOND STAGE, Addendum to TECHNICAL MANUAL for SCUBAPRO REGULATORS, 1979). My experience shows this to be true, as I regularly am in currents exceeding 4 knots, swimming against the current to test underwater swimming techniques. I swim across the current to get access to calmer areas in the river too. Here is my dive area (top part) of the Clackamas River at High Rocks:

I have also tested this concept on the UDS-1, which because of its huge openings in the manifold has very low inhalation resistances at low tank pressures.

Concerning the interstage pressure, I have used that interstage pressure on this regulator for many years, and do not have problems with uncontrolled free flows. It has not affected the HP seat on the Scubapro first stage either. I simply adjusted the balanced diaphragm first stage (Dacor Olympic) to match my readings on my Scubapro first stage. I do have about four (if my memory is correct) washers (2.5 or 5 psig/washer, I think) in the Scubapro first stage, which were placed there a long time ago.

I'll discuss the failure points in a separate post.

SeaRat