Regulator bungie for recreational diver

[g1138]

By its self, its no more likely to fail. But now you have two (the elbow and the regular hose fitting), which doubles the (unlikely) chance of a failure. Given the choice, I'd rather not have extra stuff to break/leak because I like diving, not fiddling with gear. Swivels, otoh, are to be avoided.

All that said, I think configuring your regs the way shown in the above posted Dive Rite video is a pretty good way to do it, elbow or not. Far better than the standard-issue PADI Open Water reg setup that's so common.

No. If you have a 50% probability of a reg failing then that's 50% chance of it failing.
Now take 2 identical regs, each with 50% probability of failing.

Probability of one failing and the other not is 25%. (Mathematical- independent probability)
Probability of both failing is 25%.
Probability of none failing is 25%.
Recall probability of just having only one of those regs gives you a 50% chance of failing.

[-]
So mathematically speaking you decrease the probability of failure by adding failure points. You do not double it. (this isn't my point though, read on)[/-]
Source:Probability - Wikipedia, the free encyclopedia
*see coin example under Math. Treatment - Independent Prob. | fail is heads, not-fail is tails OR vice versa*

Now take the angle adapter. I'm assuming since it has the same hose connection type as a standard reg hose we can assume it has the same probability of failing. Same thing goes as the reg example above.
Since we can't know if there is an actual likelyhood for one brand to fail more often than another or even if a Trident angle adapter will fail more often than a Trident LP hose, we can't really say the above example is absolute.



Basically what I'm getting at is.........guys, stop using that excuse.

Edit:
probability of at least one reg failing 75%.

 

[PfcAJ]

No. If you have a 50% probability of a reg failing then that's 50% chance of it failing.
Now take 2 identical regs, each with 50% probability of failing.

Probability of one failing and the other not is 25%. (Mathematical- independent probability)
Probability of both failing is 25%.
Probability of none failing is 25%.
Recall probability of just having only one of those regs gives you a 50% chance of failing.

So mathematically speaking you decrease the probability of failure by adding failure points. You do not double it. (this isn't my point though, read on)
Source:Probability - Wikipedia, the free encyclopedia
*see coin example under Math. Treatment - Independent Prob. | fail is heads, not-fail is tails OR vice versa*

Now take the angle adapter. I'm assuming since it has the same hose connection type as a standard reg hose we can assume it has the same probability of failing. Same thing goes as the reg example above.
Since we can't know if there is an actual likelyhood for one brand to fail more often than another or even if a Trident angle adapter will fail more often than a Trident LP hose, we can't really say the above example is absolute.



Basically what I'm getting at is.........guys, stop using that excuse.

You're confused. Even the example you give highlights my point.

"The probability of none failing is 25%." The balance of that is 75%. The probability of one of the two hypothetical regs failing has increased from 50% (with one reg) to 75% (with two regs).

So, mathematically speaking, you're wrong.

Adding failure points does not decrease the chance of a failure of a system. That's preposterous. The idea is to minimize the number of things that can break. Adding more things gives more opportunity for things to break,

 

[g1138]

You're confused. Even the example you give highlights my point.

"The probability of none failing is 25%." The balance of that is 75%. The probability of one of the two hypothetical regs failing has increased from 50% (with one reg) to 75% (with two regs).

So, mathematically speaking, you're wrong.

Adding failure points does not decrease the chance of a failure of a system. That's preposterous. The idea is to minimize the number of things that can break. Adding more things gives more opportunity for things to break,

It doesn't flip that way with probability if I remember my math lectures correctly. You have to calculate probability by the likelihood of the event happening. You do not calculate the likelihood of something happening then treat the remainder as the opposite happening.

Use the example of a coin flip and you will see that your balance of 75% makes no sense when you're talking about 50/50.

 

[PfcAJ]

I did. The thing is that there are two coins instead of one. For every flip, there are 4 possible outcomes (HH,TT,TH,HT), and each outcome is equally likely.

In our example, if H=reg failure and T=no reg failure, one 1/4 of those options have TT (no failure for either reg).

 

[g1138]

And I see where I went wrong.

 

[PfcAJ]

its ok, I was wrong about the 'doubles the chances' thing (I think...).

 

[Lorenzoid]

Lorenzoid, the main difference I perceive in regards to hose bowing is this:
With the necklace, you have a 40in hose bowing outside your profile, off your right shoulder. If it's connected to you chest D-ring it should be able to tuck the hose neatly under your arm without causing discomfort. On a necklace the hose can still tuck under your arm, however it will cause a twist in the necklace if done this way (which theoretically for me would be an uncomfortable feeling).
I'm assuming in either configuration you have not been tucking the hose?
. . .

Okay, now that I watched the Dive Rite video posted by TNRonin, I see what you are getting at: tucking in the octo hose under the arm versus allowing it to loop over the arm.

 

[DA Aquamaster]

its ok, I was wrong about the 'doubles the chances' thing (I think...).

The risk increases by 50% - but that's 50% over the existing risk. So a 50% increase in a 50% risk of failure becomes a 75% chance of a failure.

It gets complicated, but extreme examples are useful to show the concepts involved.

If you were solo diving with a regulator design that failed 50% of the time, then statistically on half the dives with a single reg you'd die. The possible work/fail options for a single reg are W and F and those two possible outcomes have equal probability.

If you add a second reg of equally poor reliability, the the options are now WW, WF, FW and FF. So now the bad news is that you'll have 50% more failures (3 of the 4 outcomes involve failure) with at least one reg failing on 3 out of 4 dives. However the good news is that you now only die on 1 out of every 4 dives. In this case the greater failure potential is more than offset by the reduction in dives where you die.

If you add a buddy with equally poor quality regs, you increase the failure rate even further for the team as only 1 of the 16 outcomes/dives results in all regs working (I'll let you do the matrix yourself). However only 1 in 16 outcomes/dives results in both divers dying. And only 4 of the 16 outcomes involves 1 diver dying (assuming no one buddy breathes any more).

But the overall odds of at least one diver dying have now increased to 5 out of 16 dives, so the odds of someone dying are a little higher, but the odds of it being you are now reduced to 3 out of 16 dives.

But at this level of un-reliability you can clearly see the point of diminishing returns involved in the process of adding more regs and/or team mates to the mix (for this particular risk - a three person team does a great deal to reduce other risks.)

----

With that said, all probabilities of failure are not equal so I still use 120 degree elbows on my second stages. It does add another O-ring on each second stage and one that is technically dynamic, and it adds one more fitting that can be left loose. But in practice, the only time I have ever had an annually replaced inlet fitting fail in 27 years of diving has been when that fitting has been left loose. When that happens, the failure is pretty spectacular as about 1/3rd of the o-ring gets extruded, and there is no fixing it under water. However, in side mount, the elbows allow cleaner hose routing with the hoses staying closer to me, and that reduces the probability of snagging a hose on something. Since that probability is much higher in very tight caves and restrictions, it's a probability well worth reducing. Provided that I annually replace the inlet fitting o-rings and provided I use good maintenance practices and pre-dive checks to ensure the fitting are not loose, the risk of failure of either of the additional o-rings in the elbows is infinitesimally small and that additional risk is more than offset by the reduced risks of cleaner hose routing.

 

[PfcAJ]

Mark your calendars, internet. This is quite possibly the first time I've ever agreed with DAAquamaster about anything. The fail rates of elbows are pretty darn low, and I ain't mad at 'em. Swivels though....

 

[JamesK]

Mark your calendars, internet. This is quite possibly the first time I've ever agreed with DAAquamaster about anything. The fail rates of elbows are pretty darn low, and I ain't mad at 'em. Swivels though....

This is signature material here for DA! Lol.