Sidemount and "tec" training...

[PfcAJ]

6 cylinders is easily done here https://www.facebook.com/video.php?v=737447146337495&set=vb.516123148469897&type=2&theater

But maybe you have something more constructive to say PfcAJ ? Maybe a reason why sidemount wouldn't work for the courses I'm wanting to do? I'm all ears out to listen, I'm genuinely looking to understand why those instructors don't give me a reason for not allowing sidemount to a course down to 40m.

What you're seeing is some dude swim around with a bunch of tanks. Any dip**** can do that. But can you switch gases efficiently? Can you see your MOD on those tanks? Can you drop them and pick them up quickly? Can you stow used hoses easily? Looks to me like that guy is playing dress-up to impress the sidemount myrmidons. Let's be real, the guy doesn't even have enough regs to put on those tanks. Its theater.

Here's a think: Lose a reg (esp a 2nd stage diaphragm or hose failure) and suddenly you've lost half your gas. With BM, you still can get at all of it. That's significant, in my mind. In a few posts, you'll get the 'feather the valve' people chiming in, followed by the 'swap regs underwater' group. 99% of them have never had to do such a thing for real outside of class or some pre-arranged practice scenario where their bailout scenario might as well be "switch to snorkel".

Almost anything works in a sterile environment, and highly seasoned divers can draw on their experience to get themselves out of dodge. Most divers are not diving in a swimming pool, nor are they highly experienced. KISS.

 

[kr2y5]

Here's a think: Lose a reg (esp a 2nd stage diaphragm or hose failure) and suddenly you've lost half your gas. With BM, you still can get at all of it.

I have always wondered about this assumption. I understand that it takes somewhere on the order of one minute to drain a tank from a free-flowing regulator, and that it also takes time, especially for a relatively new diver, to diagnose the problem and shutdown the free-flowing post, during which time the air is bleeding from both tanks.

 

[Razorista]

...KISS.

If you think about it sidemount is KISS, putting tanks to breathe in a rigid frame on your back is just the last letter of it.

Using more than the first two stages sidemount and backmount are identical. Sidemounters just tend to look better

 

[MSargeant]

I've feathered a valve for about 20mins on deco before, wasn't was a minor inconvenience but nothing difficult. If you do a course and leave it there as opposed to practise and make sure kills are autonomous then yeah, you're running a greater risk of having an "oh ****" moment when things go wrong. Not sure how it takes a while to diagnose a free flow issue, you should know which side you are breathing from or at the least be able to check instantly...

As for the vid, Michur believes that if you're happy with multiple stages on (as with the ludicrous numbers) and being able to access everything, then something like 4 cylinder is like wet stuff from a duck's spine. (Watch the rest of the vid where the pic is from, there are regs on the cylinders.)

Anyway, getting back on track with the OP...

 

[MXGratefulDiver]

AJ, you seem very knowledgeable in sidemount. So I'm wondering ... where'd you get your sidemount training, and how many dives have you done sidemount?

... Bob (Grateful Diver)

 

[Razorista]

I've feathered a valve for about 20mins on deco before, wasn't was a minor inconvenience but nothing difficult.

I did hours of practice dives that way without the other divers even realizing, I consider that very a minor inconvenience.

I think we always play into the backmounters hands that way.

Of course we can do it, but the backmounter can reasonably learn to do that as well.
What he cannot match is seeing the loose hose right before his eyes and simply giving it a twist to stop the leak, or look at it, consider it a minor problem and ignore it.
Next to no situation really requires shutting of a valve more than temporarily or taking any action other than cursing, as a backmounter you never know.

 

[PfcAJ]

AJ, you seem very knowledgeable in sidemount. So I'm wondering ... where'd you get your sidemount training, and how many dives have you done sidemount?

... Bob (Grateful Diver)

I know how to dive, Bob. I also know how to do multi stage deco dives. I know what type of things are apt to fail, and what's involved with fixing problems under water. It doesn't take a rocket surgeon to see the drawbacks of round mount and and losing half your gas from a piddly reg failure.

 

[Razorista]

...drawbacks of round mount and and losing half your gas from a piddly reg failure.

With roundmount that would require 5 or even more reg failures.

 

[kr2y5]

Not sure how it takes a while to diagnose a free flow issue,

My post was in response to the claim that in back-mount you keep "all of your gas", I was simply wondering how accurate that statement really is in practice. I may be very uninformed, and that's why I am posting on ScubaBoard, so that I can be corrected by the more experienced divers, who know what they are talking about, and for the benefit of others, who might be similarly uninformed.

Given the limited knowledge I have so far, a more accurate way to describe the tradeoff would have been that, if we assume an apples-to-apples comparison, and put side by side a very inexperienced sidemount diver against an equally inexperienced backmount diver:

a) In sidemount, the diver predictably loses access to 50% of the gas (since they don't know how to feather valves, or swap regulators).

b) In backmount, the diver unpredictably loses either all gas (in extremely rare circumstances), or an unspecified amount of gas that's being simultaneously bled from both tanks until the diver, who probably has never experienced this kind of situation for real, diagnoses the free-flow, and either shuts down the free-flowing post, or isolates.

I see in the GUE valve drill manual that "at the Recreational/Fundamentals level you should strive to accomplish this drill in under three minutes". Handling free-flow in real-life is probably just a fraction of the valve drill, since we do not have to go through all the motions, but there's also the element of surprise, and the problem solving component. I'd still assume that it may easily take a surprised diver 20-30 seconds until the problem is fully resolved, at which point they may have bled a non-negligible amount of gas. In another document about standards, I see that even for some advanced cave divers, it is expected to take up to 10 seconds to close a free-flowing valve. All this tells me that closing a free-flowing regulator in a real life situation is not instantaneous, especially if it's the first time...

I have never experienced a real free-flow, other than my TDI instructor blowing some bubbles behind my head in a controlled setting, where I knew what to expect, and the first thing that I was taught, anyway, was to isolate to protect half of my gas. I understand that some agencies don't even teach to isolate first.

Given all the above, it seems to me, again, that the claim that you keep all of your gas seems rather inaccurate, but then again, I might be wrong... I would be grateful for clarification. I have always found it confusing that nobody that I know of takes into account the time to fix the free-flow in the gas requirement calculations. If it truly takes just a minute to bleed the whole tank (never tried this myself), and tens of seconds to fix the free-flow, then I would expect this to be a potentially fairly significant factor in the gas calculations.

 

[FishLovingStudent]

Here's a think: Lose a reg (esp a 2nd stage diaphragm or hose failure) and suddenly you've lost half your gas. With BM, you still can get at all of it. That's significant, in my mind. In a few posts, you'll get the 'feather the valve' people chiming in, followed by the 'swap regs underwater' group. 99% of them have never had to do such a thing for real outside of class or some pre-arranged practice scenario where their bailout scenario might as well be "switch to snorkel".

Just to chime in here, I won't comment too much because I am neither tech trained nor a highly experienced diver. But feathering on sidemount is nowhere near as hard as you think it is, I went through an entire an open water training dive doing it without thinking too much about it. And if a noob like me can do it, surely somebody experienced can do it no problem, right?

Switching a reg is not a big deal either if you are moving a working reg that you aren't breathing on (if you are diving multi-tank as in tech) to the malfunctioning tank...my SM instructor told us about a recent dive (at the time) how he did it a reg switch during deco after a tri-mix wreck penetration dive. To him, it was just a minor inconvenience...because he had to service the reg when he got topside. These things in sidemount are a non-issue, at best a minor inconvenience. In backmount though?...

Just my take on things.