90 degree elbow on second stage

[tbone1004]

@northernone look at the graphs. The majority of the issues that are shown in the regulator performance is due to gas density vs. breathing. Don't let them get below 100ft and it's usually a nonissue. At those depths, the gas density are going to cause CO2 build up a la David Shaw before you really overbreathe the regulator

 

[John C. Ratliff]

I was at my LDS today, and examined two different elbows for the second stage. One was a 90 degree, and one was about a 120 degree bend.

The 90 degree bend elbow had a stem internally, and the air not only had to turn 90 degrees, but it had to go through two holes in this stem in order to get to the second stage. The holes did not necessarily match up to the opening from the first stage either. This, to me, would be a non-starter to put in the pathway for the second stage. You would go from almost laminar flow in the hose through a series of turbulences, and I'm sure that this would really restrict air flow under low tank pressure, and high demand at depth.

The second, the 120 or so degree elbow, looked like it would function very well. There would potentially be some loss due to the change in direction of the air flow, but it did not have any interference internally other than the bend itself, and that looked to be slightly beveled to help the air to go where it's supposed to go, to the second stage.

'Thought I'd throw this into the mix here; not all these elbows function alike.

SeaRat

 

[tbone1004]

@John C. Ratliff amen to that, and the super cheap ones have really bad tolerances. If you want to wince a bit, disassemble the thing and look at the inside. Not cool....

 

[broncobowsher]

If adding an elbow causes issues, you are already way too close to being boarderline before adding it.
I have no issues with putting an elbow on. It can solve hose tug comfort issues.

 

[John C. Ratliff]

If adding an elbow causes issues, you are already way too close to being boarderline before adding it.
I have no issues with putting an elbow on. It can solve hose tug comfort issues.

Yes, you ar correct in that assessment. But my look at the two different elbows indicate that it is important when adding an elbow to determine which is the best design.

Now, another point, and this is my initial point in this thread, is that there are unforeseen circumstances which would put a diver right on the borderline. An unforeseen down-current is one which claimed the life of one of this board's esteemed contributors.

John

 

[John C. Ratliff]

Here is how I have my Mark V/AIR I regulator set up.

38333781255_79af18faa4_b.jpg

John

 

[Flotsam]

Just catching up on thread after a few days diving Jupiter/Pompano, and didn't have time to install and dive the elbow adapter before leaving...

Unfortunately the elbow I bought is probably about as cheap as they get (a $10 DGE adapter), so def having second thoughts about using it. It's been a great discussion, and both points of view make sense - many rec and cave divers use adapters without a problem or noticing change in WOB, but it may have the potential to cause problems in a high stress or workload situation. Guess it would come down to my risk tolerance, so I'll have to think about it some more. The regulator and hose pulling on my mouth mostly bothers me on long dives, and it's more jaw fatigue than pain, so maybe I just live with it... But I think the hose would route better with an adapter, it doesn't know if it wants to be over or under my arm

 

[Akimbo]

Unfortunately the elbow I bought is probably about as cheap as they get (a $10 DGE adapter), so def having second thoughts about using it.

Why not try it on a shallow low-stress dive to see if it solves your problem or not? You can decide then if you want to buy a higher-flow model, get a different mouthpiece, or go for a FFM.