Reg seems to breathe harder when looking up?

[ChrisA]

Reg seems to breathe harder when looking up? Is this normal?

When looking up the diaphragm is on the top of an airspace. The air wants to float up and pushes the diaphragm upward and away from the mouth. This is the same direction the diaphragm is pushed when you exhale it closes the demand valve.

At the surface you can make some regs freeflow simply by holding then mouthpeice up and you can prevent that by holding them mouthpeice down.

 

[John C. Ratliff]

When looking up the diaphragm is on the top of an airspace. The air wants to float up and pushes the diaphragm upward and away from the mouth. This is the same direction the diaphragm is pushed when you exhale it closes the demand valve.

At the surface you can make some regs freeflow simply by holding then mouthpeice up and you can prevent that by holding them mouthpeice down.

ChrisA and the rest of you,

The problem has nothing to do with the regulator, or with this thought about air wanting to float up. It is simply a function of the difference in water pressure between the regulator and the center of your lungs; it is simply a positional problem. Here's a thread, with diagrams by Bill Barada (a long-time ago diving writer) which shows the problem:

http://vintagescuba.proboards2.com/...ction&action=display&thread=1071971414&page=2

This should have been covered in your basic scuba class.

SeaRat

 

[halocline]

Here we go again...there have been a few threads lately on this. Regarding the reg/lungs position, I've read it and it just does not answer a few basic questions for me:

1. If I'm vertical, meaning the reg diaphragm is basically perpendicular to the surface, I can be head up or head down without affecting the way my reg breathes in any significant way. Obviously, there is a huge difference between the relative depths of my reg and lungs in these two positions.

2. As soon as I position myself so that the reg diaphragm is parallel to the water, with the dry side down (looking straight up) the reg gets much harder to breathe. This is the case with every reg I've ever used. Not coincidentally, most well adjusted regs will free flow when the dry side of the diaphragm is up (mouthpiece up) and stop when it's down. You're trying to tell me this would not have anything to do with how easily the reg breathes? Obviously the reg responds strongly to it's position in the water without regards to our lungs.

If you can explain these two questions, I'll believe you. Some guy on a different forum was going on about the "incontrovertable laws of physics" and the "human collective" but he still did not explain the very clear and basic problems I presented.

Now, there is "case geometry fault" which as far as I know has to do with the relative depth and position of the diaphragm center and exhaust valve. This is a much more plausible explanation to me of why the reg breathes much harder when looking up at the surface.

 

[John C. Ratliff]

You're going to have to explain what you mean by "breaths harder." If you are talking about inhalation resistance, the difference would be the water pressure difference between your lung position and the diaphragm. But if you are talking about exhalation resistance, then the relative position of the diaphragm to the exhaust would have an impact. You apparently are fairly sensitive to small changes, as this would be the difference of about 1-2 inches. That would be noticable, at 0.445 psi/foot, or 0.037 psi/inch in salt water. If you look straight up, then with a regulator with a separate, lower exhaust would breathe about 2 inches harder on exhalation than when you tilt your head and get the exhaust at the same level as the diaphragm. If the reg is fine-tuned, and you go head-down with the exhaust higher than the reg's diaphragm, then it will (or should) leak a bit, as the exhaust is over an inch above the diaphragm, and some regs now have an inhalation resistance of less than 1/2 inch of water pressure.

The older regulators, with larger profiles, had a more pronounced difference between the exhaust T and the diaphragm, so this would be more noticable with them than with the miniaturized regs, or regs with a design such as Posiedon uses where the exhaust is in the diaphragm. Some of these older regs had the box tilted in relation to the mouthpiece, so that the exhaust was more in line with the diaphragm in a normal swimming position. The older ScubaPro A.I.R. I and Pilot regulators also incorporated the exhaust in the diaphragm (actually, the diaphragm is the exhaust in these regs), and so had no differential, but still could leak air due to the huge size of the exhaust (diaphragm).

So you do have a good point; does this make sense to you?

SeaRat

 

[pescador775]

I don't see how anybody can claim with a straight face that a single hose regulator breathes the same when the diver is inverted and/or vertical. It is indisputably true that all single hose regs breath harder in the vertical position, regardless or diaphragm positioning, and that this is due to the position of the divers lungs WRT the second stage. It is true that a second stage will free flow when removed and in the mouthpiece up position. That is caused by the second stage venturi and this device is actuated by the first bubble which leaves the mouthpiece. It can be quickly stopped and will not restart if the regulator is flooded. Once the mouthpiece is evacuated and filled with air, in the mouth and isolated from the water column, the effect is cancelled and only the diver's inhalation will restart it. If the pressure differential due to the shape of the mouthpiece were significant then, the instant the mouthpiece were removed, the free flow would not stop, it could not be stopped. No diver is that sensitive to pressure gradients such that he could detect a force differential equivalent to a quarter inch of water column which is what it amounts to. It's mental.

 

[halocline]

I don't see how anybody can claim with a straight face that a single hose regulator breathes the same when the diver is inverted and/or vertical. It is indisputably true that all single hose regs breath harder in the vertical position, regardless or diaphragm positioning, and that this is due to the position of the divers lungs WRT the second stage.

Can you clarify this statement, please? By "vertical" do you mean heads up, and by "inverted" you mean feet up? So in both cases the diaphragm is roughly perpendicular to the water surface? If this is correct, I can definitely claim, with a stright face, that my reg breathes approximately the same in these two positions.

It's my experience that the thing that makes a huge difference in the inhalation effort is when the diaphragm of the reg is parallel to the surface, with the dry side down, i.e., looking at the surface. I believe that this is also experienced by many divers, at least that's what many divers post about. In other words, the orientation of the reg with regards to the surface, rather than the position of the reg with regards to the lungs, has the most effect on the way my reg breathes. (SP MK15/G250)

 

[ShakaZulu]

My reg breaths really hard when I turn the air off?

 

[Darnold9999]

Sorry don't buy the relationship to the centre of my lungs theory. If that were true then the reg would be harder to breathe when I was vertical head up in the water column when my lungs were below the reg and easier when I was vertical but head down. This is not the case. The difference is only when I am on my back looking up and is not my imagination, the difference is quite noticeable.

 

[pescador775]

Here's a flash, every single hose I've used breathes harder in the vertical position, head up, face forward. Currently, I use a MK 25, G250. The lungs/regulator orientation is not a "theory". The differential between the lungs and second stage can be measured, and it is substantial whether inverted or vertical, just reversed.

 

[H2Andy]

ChrisA and the rest of you,

The problem has nothing to do with the regulator, or with this thought about air wanting to float up. It is simply a function of the difference in water pressure between the regulator and the center of your lungs; it is simply a positional problem. Here's a thread, with diagrams by Bill Barada (a long-time ago diving writer) which shows the problem:

http://vintagescuba.proboards2.com/...ction&action=display&thread=1071971414&page=2

This should have been covered in your basic scuba class.

SeaRat

*cough* bull sh... *cough*

i feel better now