Air consumption vs regulator ease of breathing

[John C. Ratliff]

It is a fun regulator to dive, but performance wise, it is out classed by my Scuba Pro. If this was fifty years ago, I can absolutely would dive the crap out of it. But is does have its down sides. It draws a lot harder on full tank. I have a steel 72 that goes with it, but I am not sure I would be comfortable using a 3000 psi tank with it. It wasn't made for those pressures. I love the incredible simplicity of a single stage reg. I can see why the military would like it. I am sure they are bullet proof reliable. I limit the dives with it not because I think it will fail, but because I dive it completely old school, no BCD, no bailout. no gauges (I did get a banjo fitting and a old SP SPG, circa 1960, but haven't used it yet).

I have an DA Aqua Master that I started working on, but haven't finished rebuilding.

The Navy, while the Mistral was approved for Navy use, never really got them. The U.S. Air Force for a while used the Mistral, which they purchased locally.

I would not recommend using a U.S. Divers Company Mistral on any tank pressure greater than 2250 psi. I put one on a 3,000 psi tank, and destroyed the seat (the metal disc for the pin "floats" on a seat material).

Cousteau used the La Spiro Mistral (not quite the same mechanism as the U.S. Divers Mistral) for decades, but the U.S. Navy stayed with the D.A. Aquamaster until they switched to single hose regulators (same as the U.S. Air Force).

SeaRat

 

[CT-Rich]

The Navy, while the Mistral was approved for Navy use, never really got them. The U.S. Air Force for a while used the Mistral, which they purchased locally.

I would not recommend using a U.S. Divers Company Mistral on any tank pressure greater than 2250 psi. I put one on a 3,000 psi tank, and destroyed the seat (the metal disc for the pin "floats" on a seat material).

Cousteau used the La Spiro Mistral (not quite the same mechanism as the U.S. Divers Mistral) for decades, but the U.S. Navy stayed with the D.A. Aquamaster until they switched to single hose regulators (same as the U.S. Air Force).

SeaRat

That’s what I had heard about tank pressure and the mistral.

 

[Twiny]

Just had my regulator serviced and it breathes amazingly easy. (On the tank at home---I haven't had it in the water yet.) It has always been an easy breather, but this tech adjusted it to a fine degree. I have always used very little air, especially for a big guy. I'm usually the last one back on the boat. Wondering if anyone has experienced or has any info on this: Could an exceptionally easy breathing regulator actually make a diver more likely to use MORE air (gas) than just a good regulator? Is a slight bit of breathing resistance a good thing? Maybe a crazy question. Any ideas or experience on this????

See attached extract of Dive Rite Regs manual

 

[Eric Sedletzky]

Did you see the Seinfeld episode where Jerry was cutting the tags from his jeans and sewing on a smaller waist size tag ? I might need to start doing that soon if I keep this up, may be time for another year or longer scubaboard hiatus. No worries, I will keep my Supporter status up .

On subject sort of, the DH regs, most have a strong Venturi to assist inhalation once the air is flowing and yes they can be tuned down to a very low on the bench cracking effort. But, in the water with the regulator perched atop the diver, in the swimming position, they are at nearly their worst despite all the admonitions to take long and slow breaths and long and slow exhalations, I must say, they are like sucking on a vacuum cleaner to get a breath. But the exhalation side of the loop, fantastic! Even JC tired of it so I am in good company. He relocated the housing to his chest and then swam around puffed up like a parade balloon float.

I used to just roll my body right side up and get the mouthpiece about the same level as the can and breathing smoothed right out.

 

[Eric Sedletzky]

CT-Rich,

Actually, it is the position of the demand regulator compared to the center of the lungs, not the mouthpiece, that determines the ease of breathing for the double hose regulator. Here is a diagram which explains it from Bill Barada in a U.S. Divers Company book, “Let’s Go Diving.”*

Two- vs Single-hose reg001 by John Ratliff, on Flickr

What you are describing is the tendency of the regulator to free flow at the mouthpiece if the mouthpiece is above the demand regulator.

SeaRat

*Barada, Bill, Let’s Go Diving, Illustrated Diving Manual, U.S. Divers Company, 3323 West Warner Ave., Santa Ana, CA, November 1962, page 29.

If that’s true, then why is it that when I hold the tank out in front of me with both arms straight breathing off a double hose I can make it breath easier or harder just by raising or lowering the tank?
I did this doing ditch and dons at the deep end of the pool one night while the class was inside doing book work at the university. The reg can was no where near my lungs, as a matter of fact it was about three feet away from my lungs out in front of me.

 

[John C. Ratliff]

If that’s true, then why is it that when I hold the tank out in front of me with both arms straight breathing off a double hose I can make it breath easier or harder just by raising or lowering the tank?
I did this doing ditch and dons at the deep end of the pool one night while the class was inside doing book work at the university. The reg can was no where near my lungs, as a matter of fact it was about three feet away from my lungs out in front of me.

It is not the distance away from the lungs in front of you, but the relationship to your lungs on a vertical basis. Raising or lowering the tank in front of you increased or decreases the vertical distance from your lungs. I’ve done the same on doff and don exercises. The Bill Barada diagram should make that clear, that it is the distance in the vertical water column that makes the difference.

Two- vs Single-hose reg001 by John Ratliff, on Flickr

Broxton Dive 8-10-2015-3 by John Ratliff, on Flickr
I did a doff and don exercise in open water with my DA Aqualung, which gave the regulator a slightly positive position for inhalation (and slightly negative for exhalation) position out in front of me. But it wasn’t the distance away in front of me that made the difference, but rather the distance in vertical terms from the center of my lungs. By the way, this made the DA Aqualung much better at breathing; it has a 2-3 inch breaking effort and no Venturi.

SeaRat

 

[happy-diver]

I know that when I clean the underside of a hull with a DH the mouthpiece is halfway out to release freeflow

before my lungs explode

Great as an exercise but crap for underside of hull cleaning

But I made it and I'm still alive, lucky me, I think

and remember

Mask on face, reg in place
fins on feet till bum in seat