regarding single bungee tank security when one side drops - video

[Razorista]

Hello Everybody

I started making my own creative commons sidemount training videos for my own use.
More or less I want to stop showing material I did not make myself in trainings my fellow local instructors and I organize.

One of those I made especially regarding a recent discussion on the advantages and disadvantages of the different modern bungee systems.

It shows the (non)effect of dropping one of the tanks from the bungee.

 

[Razorista]

And here is another 'extended' edition:

 

[Neokian]

Cool videos.
I can't help but notice you're continuously using your fins in what seems to be an effort to maintain your orientation in the water. Are you sure your trim is okay?

 

[Razorista]

No, trim is off, tank one completely empty, tank two a few bars left.
Wanted to make a freeflow vid with empty tanks directly afterwards.
With the camera sitting on a stone I can't keep perfectly horizontal.

Edit: btw: thanks

 

[shoredivr]

I know you're banned at the moment. Two things. Gas has weight, so this isn't a complete picture if you've drained the tanks. They'd have more weight when full and hang more.

And the front end of that tank *is* hanging down anyway, away from your body. The back end is sticking up from the plane of your body. If you were horizontal, the tank would be nose down at a 45 degree angle. Trying to do any overhead in a wreck or cave that tank is dragging either it's nose in the mud or its butt along the ceiling: it is *not* a non-event.

It is not streamlined for an open water dive, something you have mentioned several times; that sidemount divers are "superiorly naturally streamlined". Not so with a missing bungee.

Even with a nearly empty tank, you've disproved your point.

 

[Coztick]

And the front end of that tank *is* hanging down anyway, away from your body.

Bungeed back to the D ring like this can't lift the valves up behind the shoulder regardless of tension.
Try boltsnaps back to the bungee and watch them disappear.

 

[PhatD1ver]

Cool videos.
I can't help but notice you're continuously using your fins in what seems to be an effort to maintain your orientation in the water. Are you sure your trim is okay?

I think that's a little nit picky, he's dead on with his buoyancy playing with the tanks. Even with his trim out of whack due to the tank filling. I'm still not convinced, the tank didn't fall away like it really would if diving in trim, for some reason it just hung there at the waist.

I'll note the even when I'm at a hover, my feet do something similar, it's called happy feet, and I've had it for my entire life. I'm one of those people looks like I gotta pee with my leg bouncing or foot constantly in motion. I can still hold a hover.

 

[Coztick]

Having near empty cylinders is no excuse for poor trim.

 

[PhatD1ver]

Having near empty cylinders is no excuse for poor trim.

he made me mad with his responses to Andy too, but I figure in the name of goodwill towards men, etc, we cut him a little slack here. He's trying to pose and run a drill in front of a camera. I think he demonstrated all right, yes, with all the blowharding he does, we really could hold him to a higher standard, especially since like a junkyard dog, he won't let this go. Clearly, the tank doesn't 'drop' like most of us would expect, the bungee is pretty lose I notice I wonder what actual trim position really looks like.

I've lost a tank (rental, no stems just stubs) many times since converting to SM, I hate wrapping the valve, or 1st stage, so I adjust my tank strap and rear clip position to force a little more tension on the stub (I also have made a little STUB EXTENDER, that with the rap of a screwdriver or plastic mallet seats up on a stub pretty well to create a fake stem to wrap the bungee on).

Point here is, the argument hasn't been proven because he's demonstrating in clear, open water, and not in a channel or passageway as we described in a wreck environment. And in that dark environment, dropping a tank is a terribly inconvenient thing (and thus I'll wrap whatever I have to to guarantee no drop, including clipping off the boltsnap on the neck to my should d-ring.

 

[Razorista]

...he's dead on with his buoyancy playing with the tanks.

Ah, at least one who does not let his feelings affect his eyesight
No, really, I was quite proud when seeing the video myself for the first time.
I am not a very good diver and to me that looks like someone far above my real skill level.

To me fin movement was not important for this in any way and I did not care for 'looks' at all.
Drifting a few centimeters feels like a total loss of control nowadays.
The end result surprised me, I expected to have to zoom into the video and constantly correct for drift and depth changes (would probably have tried to not show the fins at all in that edited version).

I'll note the even when I'm at a hover, my feet do something similar, it's called happy feet, and I've had it for my entire life. I'm one of those people looks like I gotta pee with my leg bouncing or foot constantly in motion. I can still hold a hover.

Exactly.
It depends on situation, sometimes moving the fins in a relaxed way is just the easiest and optimal way to do it.

he made me mad with his responses to Andy too,

I still do not understand what I am supposed to have said to him. Language gap perhaps.

I've lost a tank (rental, no stems just stubs) many times since converting to SM,

I practiced that a lot first, so it happened to me only rarely in reality.
But even when it happens surprisingly sometimes, I am always happy for the additional practice.
I really do not mind at all, often dive with tanks partially attached or one carried in a hand to bubble check depth or hanging loose clipped to a front hip D-ring and not bungeed at all.

I also have made a little STUB EXTENDER, that with the rap of a screwdriver or plastic mallet seats up on a stub pretty well to create a fake stem to wrap the bungee on).

Had one of those made for me too, never used it.

Point here is, the argument hasn't been proven because he's demonstrating in clear, open water, and not in a channel or passageway as we described in a wreck environment.

Hard to make a video there. I also do not see the point of that.

And in that dark environment, dropping a tank is a terribly inconvenient

Darkness does not change anything. Me, you, everyone can handle it blindly with minimal training.
The tank touching something would be an conceivable risk.
Real practical experience helps with that and shows with a few tries that tanks never 'drop', except extremely heavy ones exceeding roughly 8lbs negativity.
On all normal tanks it is a non-issue.

thing (and thus I'll wrap whatever I have to to guarantee no drop, including clipping off the boltsnap on the neck to my should d-ring.

I don't, or very rarely.
I do not like to clutter D-rings and prefer mobile and removable tanks in wrecks or any kind of restriction.