What was the most influential development in scuba diving?

[Wibble]

I(open circuit) have dived with CCR divers on few occasions. Things I have noticed:
1. They need at least an hr to get ready before departure for the dive.
2. After waiting for an hr and they might turn up and said there is a problem and his/her dive is cancelled.
3. Post dive washing(sterilizing).
4. Excess luggage payment.
5. Most if not all the units have been modified.
6. Spare part is not readily available and major issue will be shipping it back to the manufacturer.
7. Not many operators that I have came across were CCR friendly.
8. There are few more......

I really cannot see many divers would like to spend extra effort, money and time on a rec sport.

We like diving in silence where the fish aren't scared. We like the flexibility of depth choices. We like diving with helium. We like the buoyancy control -- nothing changes. Some of us quite like kit fettling.

Not everyone takes an age to get ready. The only difference with CCR is the three to five minute pre-breathe; everything else is the same as OC. The pre-breathe is done whilst waiting to jump.

Post dive/day's diving, just as with open circuit need to top-off the oxygen and diluent cylinders for the next day's diving -- which will generally either be giving it to the boat/shop or filling from cylinders in the boot of one's car. Analysing and marking up cylinders -- just as for OC -- too.

CCR does have a bit of post dive maintenance faffing where the loop needs rinsing under a tap, the lungs wiped out (depends upon the unit) and the scrubber replacing (sometimes this isn't necessary). Basically we make sure everything's ready for the next day's dive, then go down the pub.


Just like all forms of diving, it's down to the diver to sort their own stuff out. CCR divers tend to be a little more conscientious than OC divers as the rebreather units are a little more complex. I still fill in a checklist for every build.

If diving in a remote location, as with OC, bring basic spares which may include a spare oxygen sensor, batteries and O-rings. These don't take much space.


In my experience, the piece of kit that's been more trouble than anything else is... the drysuit. Replacing seals and gloves, maintaining zips, dumps, etc.

 

[AfterDark]

I(open circuit) have dived with CCR divers on few occasions. Things I have noticed:
1. They need at least an hr to get ready before departure for the dive.
2. After waiting for an hr and they might turn up and said there is a problem and his/her dive is cancelled.
3. Post dive washing(sterilizing).
4. Excess luggage payment.
5. Most if not all the units have been modified.
6. Spare part is not readily available and major issue will be shipping it back to the manufacturer.
7. Not many operators that I have came across were CCR friendly.
8. There are few more......

I really cannot see many divers would like to spend extra effort, money and time on a rec sport.

Which is why I claim CCRs aren't ready for prime time yet. If there's a compelling reason for using a CCR as a means to an end they are more than ready for that; commercial, research, military use but not yet for every day sport diving, IMO

I suspect 50 years from now there'll be some differences perhaps enough differences to put CCRs in the mainstream of diving. Course it won't make any difference to me, I'll be long gone before that.

 

[tursiops]

The octopus was the way for reducing costs for training centers working for-profit, saving on the cost of (twin) tanks with double valves, which were the norm before the success of commercial diving agencies.

You are conflating US and Italian "norms." Twin tanks with double valves were never the "norm" in the US, either before or after the advent of the horrible, malicious, disgusting "for profit" agencies.

 

[Angelo Farina]

You are conflating US and Italian "norms." Twin tanks with double valves were never the "norm" in the US, either before or after the advent of the horrible, malicious, disgusting "for profit" agencies.

Interesting. I did not know that.
During my first course we did use extensively the US Navy manual.
And also in it twin tanks appeared to be the norm, so we were thinking that also in USA the equipment was substantially the same...

Said that, I did never think that for-profit training agencies are devil. Instead I was one of those instructors fighting for making scuba training more easy for everyone, not requiring military-grade fitness and discipline. I was very happy to switch from being a volunteer instructor working for no money in a club to a professional instructor working for a good wage in exotic touristic resorts...
The only thing I always disliked of the American business model is paying instructors "by quantity", a fixed amount for each certified diver. In fact, as a professional instructor, I did refuse that business model. I contracted for a fixed monthly wage, with the freedom of refusing certification to any number of customers that I did not evaluate deserving the certification, without any bad consequence on my income.
Another thing I did always hate are tips, another typical part of the American way of paying people. I hate the tipping method, it is strongly against my ethics. But I understand and accept that in different cultures ethics is also different...

 

[Akimbo]

During my first course we did use extensively the US Navy manual.
And also in it twin tanks appeared to be the norm, so we were thinking that also in USA the equipment was substantially the same...

Double tanks with a reserve valve and single double hose regulator was almost universal in the US Navy for decades. We had to get special permission in the early 1970s to use a single tank and single hose regulator on the Bathyscaph Trieste II.

The reason we were able to receive authorization was the aviation gasoline used for buoyancy was always leaking and it turned the courigaged double hoses into into goo, we were constantly climbing aboard the Trieste, and our dives were all very shallow. Our job was to pre and post dive the boat, which had a pretty extensive checklist along with substantial maintenance requirements.

 

[tursiops]

Interesting. I did not know that.
During my first course we did use extensively the US Navy manual.
And also in it twin tanks appeared to be the norm, so we were thinking that also in USA the equipment was substantially the same...

You and Akimbo are talking military, I am talking recreational.

The only thing I always disliked of the American business model is paying instructors "by quantity", a fixed amount for each certified diver.

This is not a universal practice. Sometimes the pay is per class, sometimes per hour.

 

[Angelo Farina]

You and Akimbo are talking military, I am talking recreational.

I am talking recreational, too. I am not a tech or mitary instructor. We did use the US Navy manual (and tables) in our recreational first OW course, with some adjustment, which were done exactly as we were rec divers, not military ones.
The adjustments were the following:
1) when using the CC rebreather we were limited to shallower depth (10m) than the max depth allowed in the manual (18m).
2) When using air in OC, similarly, max depth was 50m instead of 72m
3) the deco tables had to be used "conservatively", as follows:
- ascending at 10m/min instead of 18
- summing the ascent time to the bottom time
- switching to the next row in the table (a longer time) in case of extra effort.
- always consider the max depth reached, even for just one minute.

 

[tursiops]

I am talking recreational, too. I am not a tech or mitary instructor. We did use the US Navy manual (and tables) in our recreational first OW course, with some adjustment, which were done exactly as we were rec divers, not military ones.
The adjustments were the following:
1) when using the CC rebreather we were limited to shallower depth (10m) than the max depth allowed in the manual (18m).
2) When using air in OC, similarly, max depth was 50m instead of 72m
3) the deco tables had to be used "conservatively", as follows:
- ascending at 10m/min instead of 18
- summing the ascent time to the bottom time
- switching to the next row in the table (a longer time) in case of extra effort.
- always consider the max depth reached, even for just one minute.

When I said "talking military" I mean you were reading from the manual what the military did, and using it recreationally. You were copying military diving. That was not common in the US; lots of single-tank diving done recreationally. The earliest reference I have is the book, "The Complete Illustrated Guide to Snorkel and Deep Diving," by Owen Lee, Foreword by J.Y. Cousteau, dated 1963. He dwells on "Aqua-Lung" equipment, patterned after what Cousteau and Gagnan developed in 1943. on page 141 he says:

"The 71.2 cubic-foot, 2250 psi single tank is the most commonly and most logically used tank in sport diving."​

He goes on to say:

"The 142 cubic-foot double tank, 2475 psi "double" is comprised of two 71.2 cubic-foot tanks with a single o-ring neck and a harness pack. it is commonly used by U.S. navy frogmen and many gung-ho divers, but, frankly, its great weight can be sustained almost exclusively by U.S. navy-developed men and gung-ho enthusiasts. I have donned the heavy "double" for especially deep dives while on a pitching boat and have spent most of my surface time flat on my back as a result. A youngster or a woman would have an impossible time with all that weight. Another disadvantage is that a fully-charged "double" can definitely throw you over the decompression limits, and you have to pay strict attention to your "down time" when wearing them deeper than 33 feet. This renders the double tank blocks most dangerous, for ninety percent of sport divers neglect to record the depth-time of their dives. It is only through the grace of God that we have been spared more cases of the bends as a result, and in my opinion the sale of double-tank blocks should be restricted to qualified professionals."​

 

[Angelo Farina]

Thanks @tursiops , a very interesting citation, which explains many things, not only about double tanks, but also about the concept of deco for rec divers. I see now how the two things are strictly interconnected, and it explains why here in Europe deco theory was taught since the first OW course.
Of course, with a single 10-liters tank at 150 bar, it becomes very hard to exceed NDL, making deco training redundant.

 

[Akimbo]

You and Akimbo are talking military, I am talking recreational.

Agreed, I was responding to the US Navy manual reference.

My Scuba training was in 1962 in Northern California and double tanks were fairly rare. I was only 11 so started with a single 50, but moved to twin 50s as I grew since I had them (and Mike Nelson used them). Everyone else in my class was diving single 72s and about half to two thirds were using single hose regulators. Less than half of them had SPGs.

I would estimate that 66-75% were single cylinders with non-reserve K-valves like the one at the right in this image. The rest were J-valves but were not favored because the pull-rod that came with them were constantly getting hung up and pulled by the kelp that is prevalent in the area. I understand that they were more popular on the in the US Gulf and Atlantic coasts. I never even saw one of those reserve R-valves in the middle.

The K-valve above was essentially the same medical Oxygen valve on small cylinders that is still in use today. The much improved side handle J & K valves came out in 1963 for the Scuba market and was quickly adopted by other manufacturers. Those little top valve handles were really hard to turn with cold hands. Medical Oxygen was also where the yoke clamp came from. Apparently they were also used in Europe.

On the US Navy reference: The standard was double 3000 PSI aluminum 90s (cubic foot) from the late 1950s when the imported steel Triples from France were replaced with these non-magnetic cylinders required by the EOD (Explosive Ordinance Disposal) divers.

Unlike normal pressed cylinders, these were made from aluminum tubing and spun (metal forming process) at both ends to create a "neck" that was tapped for a valve. The bottom end was spun to a near hemisphere and a plug was welded to close the it. These were not DOT certified and were for military use only.

Like all most of the era, they had 1"/25mm cotton webbing connected to the cylinder bands on every set. 1½" webbing was sewn to the 1" webbing around the shoulder area. All adjustments and the belly band were fastened with double D-rings.

This image is from the 1959 US Divers catalog that shows the double and triple manifolds:

This was the last year that USD sold the tapered CGA (Compressed Gas Association) threaded valves before switching to the O-ring sealed cylinders and valves used in the US today. They continued to make the tapered threads for the Navy until they finally ditched the special Aluminum 90s.