Switching From Steels to Aluminum (bungee style)

[kommisarrex]

I learned on (and use) the ring bungee system, as I primarily dive steel cylinders. Maybe they are not perfect, but they work for me--easy to doff and don, can backroll/giant stride with them, lug cylinders while attached, etc...

Anyway, I have an upcoming trip where we'll be using aluminum. I've read on here that ring bungees are impractical for aluminum due to the buoyancy shift from negative to positive. Are they really that impractical? It's hard to imagine why, as the first stage would probably keep the front end negative and stable. Maybe not?

Are the independent or loop bungees that much better with aluminum, especially with rental tanks and same-sided valves on both sides (no left/right)?

 

[divezonescuba]

i only use al80s. I don't think that makes a difference. More important is what you do with the lower snap. you can move the snap to a lower point when it goes positive or you can use the triangle method. I use the triangle method, but add a piece of bungee to keep it tight. I use the ring system for the upper snap with a bungee choaker.

 

[runsongas]

i run loop with a safety clip. the ring system has the tank ride further down iirc with the valve not as directly in the armpit, so the lower snap is further up on the al80 to in order to line up with your waist compared to a steel tank clipping to a buttplate with rails. this puts it closer to the pivot of the cylinder and the butt of the al80 will end up swinging more. if you have a long torso, it is not as big an issue.

 

[JBFG]

I use the triangle method, but add a piece of bungee to keep it tight.

Do you have a picture of this? I understand the triangle method but what bungee are you adding?

 

[johnnywulff]

Al80 will be negative at the start of the dive let said until you reach +/- 2.500psi at that point is going to be neutral and from +/- 1.800psi gets positive, so I move the lower snap from rear hips D ring to my very front near groin D ring to compensate.
Cheers

 

[JohnnyC]

The ring bungee system is generally pretty meh. It tends to make tanks ride like a stage bottle, and not a sidemount bottle. Your best bet is loop bungees. They pull the tanks higher and behind your armpits. Put the bottom clips on some sliding d-rings and your tanks will be adjustable at all pressures to ride in trim.

 

[divezonescuba]

Ring bungees work great if you use bungee choakers. Webbing choakers or no choakers not so much. webbing choakers are too difficult to use on a rolling boat while you are sitting down. With bungee choakers sidemount tanks are right under my armpit if I have the right length bungee, ring, and quick links. I use bungee choakers on my deco bottles as well so they don't hang down. An added benefit is that because they are under slight tension in the retracted position, the deco bottles are really easy to release off of the dring.

 

[jerrwhy01]

I've used the ring system with AL80's and had pretty good success. They will get floaty at around 2000-ish psi. I put a pair of D-ring on the waist band and move the bottom clip to the waist when they start to float. No problems.

 

[divezonescuba]

Do you have a picture of this? I understand the triangle method but what bungee are you adding?

I don't have a picture of it set up, but it is simple to do.

There are actually two variations. Both involve putting a loop of bungee on a bolt snap ring. You could do this with a double ender, instead of the bolt snap, as in the traditional triangle method.

In both variations, you connect the bungee side to a front dring. The difference is where you connect the bolt snap. In method one, you stretch the bungee and snap the bolt snap to the stage kit lower bolt snap ring which is already attached to your rear dring. In this method, the tank can still flop around a bit, the length of webbing between the stage kit lower bolt snap ring and the lower tank band.

In method two, you stretch the bungee to a dring on the lower band or clamp on the tank about 90 degrees from the stage kit bolt snap. If you set this up correctly, your tank is literally bungeed against your side.

In both methods, you could reverse the connection points, if you found that easier to do. Also, sometimes, I connect the bungee bolt snap first and then the stage kit bolt snap to the rear dring.

The advantage to all this is not having to reposition the dring or have to clip the bolt snap to a more frontal dring when the tank starts to go positive. One potential downside is that you do have a second bolt snap to release if you want to swim with your tanks forward.

 

[DevonDiver]

If anyone claims "great success", it's probably most useful to supplement with photo evidence of the configuration in action.

One person's success could be below acceptable for another...