Just in case anyone wants to dive backmount independent doubles

[johndiver999]

Here is why, this configuration became obsolete about the mid 1990's with the advent of commercially produced din isolator valves. And by the 2000's just about every manufacturer were making din isolator valves at a reasonable price.

I used independent doubles back in 1995 (and Sherwood had a decent isolator valve then), as did a lot of tech divers, and even we didn't reverse the one tank. But "we" quickly learned how stupid that configuration was.

Fast forward to 2021, you have a PADI Master/TecRec/ TDI Trimix Instructor hocking a 20 year old obsolete configuration, but worse, adding his won special convolutions to it.

To steal a quote from a "famous" tech diver, a video like this is "Farm Animal stupid".....

Thanks for the explanation. I see others have added some more specificity in their critique - which is helpful to those of us who are uninformed.

 

[jadairiii]

Thanks for the explanation. I see others have added some more specificity in their critique - which is helpful to those of us who are uninformed.

Also notice, which is typical of these types, the OP has disappeared from the thread. Even he cant justify it's stupidity.

Like a drive-by shooter, they slow down just long enough to blast some idiocy at the forum members, then "speed off" never to return to the scene of the crime......

 

[johndiver999]

Also notice, which is typical of these types, the OP has disappeared from the thread. Even he cant justify it's stupidity.

Like a drive-by shooter, they slow down just long enough to blast some idiocy at the forum members, then "speed off" never to return to the scene of the crime......

Yeah he just joined, made a few posts and ran off (2008 and 1700, respectively)

 

[SlugLife]

No probs .... I'm entertained .... by it.

We should start up a new thread, stupidist dive rig setups you have experimented with.

I have to say I have done some stupid things, whether I'd be brave enough to post them ... I'll think about it.

I would never .... ummm .... even consider the idea of doing something non standard! Minimalist Setup for Small River Diving (~15ft or less)? Ok, fine, but at least I asked before just going out and doing something silly.

I'll let you have the honors of creating the thread, I've created a bunch of threads lately.

 

[kensuf]

As great as sidemount is, I'd say that was the right call. He can of course still pursue side-mount training and equipment, but this is a much quicker, less complicated, and less expensive way to solve his use-case.

They also jump off of boats. I'm not a fan of sidemount and boats, I think doubles are a better solution there. I know it can be done, but that's a completely different discussion.

 

[Jack Hammer]

Also notice, which is typical of these types, the OP has disappeared from the thread. Even he cant justify it's stupidity.

Like a drive-by shooter, they slow down just long enough to blast some idiocy at the forum members, then "speed off" never to return to the scene of the crime......

Well he hasn't logged in since just after he posted that video. I suspect he been pretty busy arguing on the phone, 1992 wants their gear back.

 

[Celt]

Don’t know why he set them up like that but independent doubles are a simple way to carry a large amount of air without the weight when handling manifolded doubles.

 

[100days-a-year]

Have had the absolute pleasure of hauling up double LP 140s onto a pitching boat. Would still prefer that to having someone on the boat with a goony configuration.

 

[John C. Ratliff]

Let me throw something else out here, as being a “vintage diver,” I have dived some really different configurations. One interesting one was to use my A.I.R. I regulator from Scubapro to attach two first stages to the same second stage. I used independent doubles for this configuration, and it worked quite well. I would not use it in technical diving, as you still have the potential of a second stage failure depleting air supply from both regulators, but you would not need to reverse the one cylinder, and you would provide much more air to the second stage for deep diving (Scubapro recommended this for deep diving with the A.I.R. I regulator). I’ll post a photo when I get to my other computer (I’m on my iPad right now).

SeaRat

PS, I did have one cylinder reversed, but that was to keep the J-valve on the outside. Note that I needed to ensure that the interstage pressure on each regulator was the same, in this case, 140 psig (probably actually 135 as this gauge is off by 5 psi). Note that I used a MR-12 first stage on the IP gauge photo, and a Dacor Olypmic first stage on the other photo. Both are diaphragm first stages, which made adjusting the IP easy to ensure that it matched the Scubapro Mk 5.

Why is it so important to have the same interstage pressure in each first stage? Well, so that you draw down the pressures evenly on both tanks. In the above video on independent doubles, you’ll note him saying that he had to have a gauge on each cylinder, and switch every 500 psi or so. This is to keep those cylinders “balanced” weight-wise. But with both cylinders feeding into one second stage, and having the same IP, each cylinder’s pressure falls at the same rate, even if they are independent right to the second stage regulator.

 

[KenGordon]

Here is why, this configuration became obsolete about the mid 1990's with the advent of commercially produced din isolator valves. And by the 2000's just about every manufacturer were making din isolator valves at a reasonable price.

I used independent doubles back in 1995 (and Sherwood had a decent isolator valve then), as did a lot of tech divers, and even we didn't reverse the one tank. But "we" quickly learned how stupid that configuration was.

Fast forward to 2021, you have a PADI Master/TecRec/ TDI Trimix Instructor hocking a 20 year old obsolete configuration, but worse, adding his won special convolutions to it.

To steal a quote from a "famous" tech diver, a video like this is "Farm Animal stupid".....

Your manifolded twinsets are obsolete too. Only an mad person or billionaire would try using such an expensive to run and non optimal gas mix setup to do a dive past 40m. The only modern use of a twinset is as a bank for trimix to top up the 3l cylinder of dil taken on the dive.

The problem with the OP is not that independent twins are an obsolete idea, but that his particular configuration was never proper and is just plain stupid. Using this bloke’s stupidity to beat up a configuration which has particular advantages and disadvantages is just as stupid as having a regulator on backwards.