Why aren't BC bladders elastic?

[gr8jab]

I'm not sure that I'm thinking straight about this. Maybe there is an obvious reason I have not considered.

Why are BC bladders not made of inflatable elastic tubing? Something resilient and strong would be required. However, I think it would offer some benefits. The elastic tubing would provide a slightly positive pressure, so a touch more air would be required for the same displacement, but nothing noteworthy. But, also:

1. No worries about holding the dump hose up high.
2. No worries about which dump valve to use.
3. No worries about body orientation to get the air near the dump valve.
4. No water to drain after each day!

I don't know the failure rates for current non-elastic bladders, and I don't know if they would increase with elastic bladders.

Thoughts...

 

[eelnoraa]

You want to be able to hold air in the bladder if there is a leak. 1, 2, 3 you listed is intended.

 

[DevonDiver]

Would you really want a BCD that actively and positively ejected gas at any, or every, opportunity... leaving you without buoyancy?

Pinhole leak? down you go....
Slightly weakened OPV spring? down you go....
LPI o-ring a little old? down you go...

 

[Centrals]

Great idea!
So no more bungy wing?

 

[DevonDiver]

Great idea!
So no more bungy wing?

The old GI article is worth quoting, to demonstrate the principle:

Elastic wings are a disaster waiting to happen. They can not be operated safely by mouth, they lose their gas if ruptured, they can not be breathed like normal wings, and they cause more drag than normal wings.
Doing It Right Gear Configuration by George Irvine

 

[Centrals]

The old GI article is worth quoting, to demonstrate the principle:

Don't agree at all!
It is a myth.

 

[ajduplessis]

And if George cant orally inflate an elastic wing, the nobody can. Sorry Chuck.

 

[gr8jab]

You want to be able to hold air in the bladder if there is a leak. 1, 2, 3 you listed is intended.

OK, I see that a bladder failure would be more critical if it were pressurized. However, I think that 1-3 are not intended, but rather a consequence of a safer design. Some of those new BCs with dump/inflate levers activate all the valves at once (at least I think I was told that), minimizing 1-3.

 

[eelnoraa]

... Some of those new BCs with dump/inflate levers activate all the valves at once (at least I think I was told that), minimizing 1-3.

Too many dump valves are the source of unreliability especially the dump valves in shoulder. If those valve leak or get stuck open, you really have no way to retain air in practice. You can't dive head down all the time. That is why tech divers use wing with only on dump (butt dump) and there is no shoulder dump, no pull dump in elbow.

Aqualung i3 is a cool idea. I have used it and had fun. But I don't think it will ever make it into more demanding dives

 

[tbone1004]

1. No worries about holding the dump hose up high.
2. No worries about which dump valve to use.
3. No worries about body orientation to get the air near the dump valve.
4. No water to drain after each day!
Thoughts...

Edit:
1: equipment solution to a skills problem: should only ever have to come straight forward as that is the highest point of the wing. Anything above that is a skills problem

2: equipment solution to a skills problem: BP/W's have one dump valve, ergo skills problem if you can't figure out that there is only one. Multiple dumps are useful in sidemount wings if you have an extra one at the bottom, but not necessary and not part of this discussion. That is merely a convenience factor. Backmount rigs do not require multiple dumps, this includes pull dump elbows on the top inflator, which are also an equipment solution to a skills problem.

3: equipment solution to a skills problem: no rationale here, simply a skills problem. If you're in good trim, you shouldn't have to change body position unless you are trying to get everything out for a safety stop or something where you roll to the slightly right and go slightly head down. If trained properly, this is automatic and requires no critical thinking

4: equipment solution to a skills problem: If you dump properly, there is no water ingress unless you don't purge the inflator when you orally inflate at the surface. Only other time would be if you're orally inflating during the dive, but then again, you're supposed to rinse the inside of the wings to prevent bacteria growth, so this is a moot point.

unintended consequences
1. reduced abrasion resistance
2. reduced puncture resistance
3. increased costs of material