Hog D1, updside down breathing is difficult

[TT_Vert]

I've noticed that is very difficult to crack while upside down. I've played w/ the effort knob w/ no luck. I didn't have the presence of mind to try my other second stage to see if it did it. I've confirmed my IP is good (Within specs), my cracking pressure is about 1" (On the sensitive side). I've had these regs a few years now but I don't ever recall them breathing well upside down. I was racking my brain trying to think why this would be but I cannot come up w/ anything. With the reg upside down I'd think the water column would be exerting a direct downward force onto the purge and lever so that wouldn't have any effect.

Any input would be appreciated.

Dave

 

[kelemvor]

I don't know about the D1 but some regs just breathe differently upside down. I worked at an aquarium for a while and found myself upside down often. Initially I used a scubapro r295 for the aquarium but it behaved exactly as you're describing when inverted. I switched to an S600 which was far better when inverted. Initially I was trying to not use my "good" gear at the aquarium because I didn't want to wear it out. So much for that idea.

I assumed it was a characteristic of the second stage. I'll be curious to see if someone with greater knowledge comes along with another answer (tuning etc).

 

[TT_Vert]

Thanks for the input. I should mention that the water temp was 82. I really should have tried my alternate and also cracked w/ the purge to see if it at least breathed normally after cracking.

Dave

 

[tbone1004]

no scubapro style regulator will breathe well if the diaphragm is up, and it is quite possible that it will be wet breathing. If you think about the pressure, when the regulator is diaphragm down like it was designed to be used, you have the venturi effect pulling the diaphragm up which makes WoB quite easy and is the reason that the regulators freeflow if you remove them from your mouth. If you roll over and the diaphragm is up, then now instead of being assisted by the air trying to lift the inhalation diaphragm closer to your mouth, the air is trying to rise and you have to breathe against that pressure differential.

If you are planning on diving upsidedown with any frequency you need to consider a different style second stage. Poseidon, or Oceanic Omega/Hollis 500se. You will experience similar WoB difference if you roll to one side or the other, but they are non-sided there is no difference in breathing face down or face up, and if you have to be in a position where the diaphragm is up for an extended period of time, you just flip it over and it breathes quite well.

 

[BRT]

Direction of the water column makes no difference but the position of the diaphragm in the water column in relation to your lungs makes all the difference. I'll bet the cracking pressure will be fine upside down if you get your legs higher than your head so your chest is at diaphragm level

 

[tbone1004]

uhh what? while it is true that your body orientation will change WoB it is more due to exhalation resistance than anything. If you are head down inhaling will be really easy but you have to fight to exhale, same if you are head up. The regulators orientation in the water matters infinitely more though since in a normal breathing position you are basically controlling when it freeflows. When you are upside-down you have to force it to breathe and that isn't easy to do.

 

[The Chairman]

There will be a difference and that difference can be exacerbated by a poorly tuned regulator.

 

[BRT]

uhh what? while it is true that your body orientation will change WoB it is more due to exhalation resistance than anything. If you are head down inhaling will be really easy but you have to fight to exhale, same if you are head up. The regulators orientation in the water matters infinitely more though since in a normal breathing position you are basically controlling when it freeflows. When you are upside-down you have to force it to breathe and that isn't easy to do.

You think head down and head up both create easy inhalation and hard exhalation? The regulator diaphragm is maintaining air pressure equal to water pressure. If your chest is above it you will inhale easier than if your chest is below it. The water pressure at any depth is the same regardless of if the diaphragm is up or down. If you hooked a snorkel to your mouthpiece so it could be out of the water with the diaphragm of the regulator pointed up your reg would freeflow at the surface with the diaphragm pointed up. Only reason it stops freeflowing when you turn it over is because the water pressure is then greater than the pressure at the diaphragm

 

[TT_Vert]

Thanks guys. I don't often breathe upside down but while on my last trip I saw a guy swimming upside down so it reminded me of my regulator issue. I just wanted to make sure it wasn't perhaps something w/ the regulator itself.

Dave

 

[tbone1004]

Only reason it stops freeflowing when you turn it over is because the water pressure is then greater than the pressure at the diaphragm

which has been my point the whole time about breathing upside-down. You have to inhale against the pressure differential instead of with it when the diaphragm is up. WoB does not change with body orientation, only with diaphragm orientation because WoB is the area under the curve of BOTH inhalation and exhalation. The ideal scenario is you are head down when you inhale and head up when you exhale to minimize WoB, but if you are at 20* down, the inhalation is easier than the exhalation by roughly the same amount that it is harder if you are 20* up. That is not the discussion, the discussion is regulator orientation due to the diver rolling on his/her back. You proved my point with your last sentence