Has anyone tried this for AL80s?

[divezonescuba]

This is a thread on AL80s. It is not a thread on AL versus steel. So, if you use steel that great, but this has nothing to do with that. Having said that:

One of the recognized advantages of AL is the ready availability of standard not modular valved AL80s almost anywhere in the Caribbean.

One of the recognized disadvantages of AL is the shift in Bouyancy as the tank becomes increasingly depleted. The butt end of the tank becomes positive. Several methods have been employed to address this including weights on the tank, sliding drings and moving the bottom clip to a more frontal dring. Another method is to bungee down or use a double ender on a front dring to prevent the tank from floating up.

I would like to know if anyone has experimented with the use of bungee, strap, or cordage fed thru a dring or loop of webbing on the belt to prevent the tank bottoms from coming up. Although there are many variations on this, the concept basically works like this.

A bungee, strap, or cordage section which I will call a leader is attached to the bottom of the tank. The leader can be some combination of those materials. This could be with a triglide and a tank band or just a loop thru a hose clamp. The leader is perhaps 15 to 18 inches depending on your setup. At the end of the leader is a bolt snap. The leader preferably 5/16 inch bungee is fed thru the waist dring or preferably a loop of webbing fixed on the belt. The leader is then clipped to the top tank bolt snap ring. Obviously the top bolt snap is used in conjunction with something like a ring bungee with choker system. There should be some tension on the leader bungee.

The leader is easy to snap as it is up near the top of the tank. When the tank is negative, it hangs down slightly off of the dring or webbing. When the tank is positive, it cannot float up significantly because it is trapped in the fixed webbing loop or fixed dring. I think that the tank can only rotate up and down around the webbing or dring axis. The smaller the dring or webbing loop,the smaller the tank can rotate.

The concept provides some movement of the tanks due to the non rigid attachment with the webbing loop or dring and bungee. So if you need to move the tank out to reach a front dring for clipping a decotank or getting into a pocket, you can do so.

So what I am asking is if anyone has tried something like this. It does not seem to be in either the Neto or the Loflin references.

If no one had tried this yet, I will do so and report back on this concept.

Thank you.

 

[bamafan]

For bm stage diving that is popular in Florida with the large steel tanks and scooters there are a few variations. The Neto method is one that works. For your main tanks I don't know why you would fool with this. Just adjust your attachment point as the buoyancy swings. If someone recommends putting weight onto an Al80 just run from them.

 

[divezonescuba]

The Neto method is something different. For stage tanks if I remember correctly.

The whole purpose of this is to make it easier to attach and to avoid the changing attachment issue.

 

[lermontov]

not sure how this is more efficient than your standard set up -what are you gaining?
to clarify your just tensioning the rear of the tank using bungee to hold it close to the d ring? so you could in fact clip the leader off anywhere to achieve suitable tension

I guess you could just form a loop on each tank feed them through the d ring and use a double ender to connect them together around your tummy? that would keep them under tension to take up buoyancy when it gets empty

 

[MichaelMc]

There is a triangle method of:
- clipping the full tank off to the rear as normal with a bolt snap
- adding a double ender from the bolt snap finger hole to a forward belt mounted D ring, where you would have normally moved it to.

When heavy, the bolt snap to rear holds it up.
When light, the double ender to front holds it down.

Fairly similar to moving it, but you clip it to both places at the same time.
Not sure I follow your method.

 

[runsongas]

it would make it harder to unclip the tank when needed. this is a bad equipment fix for a skills issue.

 

[MichaelMc]

Hmm, I think I understand your method.

As I understand, using say a single thickness of bungee cord:
- attack bungee to tank bottom, say under hose clamp as normal for the cord to the normal boltsnap.
- run bungee through say d-ring where you want tank anchored if D is bent forward
- clip a bungee end bolt snap off someplace convenient with tension on the bungee, say a more forward d-ring on belt.

EDIT: Or, use a bungee loop. Pass it with no bolt snap through the rear D, which could now be smaller. Use a double ender to clip to forward D. Just a small variation, and with more fiddly bits, but similar to the bungee and double ender across the belly method above or as used with some sidemount wings. Actually, it now looks the same as lermontov's just without making each side dependent on the other.

Result is you've eliminated any change in the tank attachment point by:
- removing the 'swing' length of the bolt snap and bit of cut-able cord from it to the tank.
- pulling the attachment D flat forward due to the bungee tension
You can still pull the tank out a bit by stretching the bungee

Except your description seems to clip off the bungee/cord to the forward tank, which seems harder than a more forward D ring on the belt. The more forward D seems cleaner and still gives some cord exposed that can be cut in an emergency and lets you do the attachment under tension.

Interesting. I would not have been worried about the act of moving the bolt snap when the tank gets light. But it seems tighter having removed the 'slack' length of boltsnap and cut-able leader in the normal system. Not sure it is worth the extra complexity.

 

[Mike1967]

 

[MichaelMc]

Modifying Michur's method a bit, you could:
- clip to rear as normal
- tie a loop of bungee through a second boltsnap's eye
- cinch that bungee to the rear bolt snap eye, by passing it through rear eye, then its bolt snap through the bungee.
- stretch the bungee forward and clip off to a forward D.

The stretch takes the bit of bolt snap loose play out of Michur's method, but requires a bit of custom kit, the bungee loop and boltsnap assembly, and a more forward D-ring, than just a standard double ender as Michur used. If you keep the bungee length short enough, the loop should not accidentally come off the rear eye after you unclip it from the front.

 

[guruboy]

what is your motivation for doing this over the other methods?