Most desirable Scubapro 2nd stage?

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FWIW, the ScubaPro guy also talked about people saying that a metal reg (like the A700) doesn't give as bad cotton mouth. He said he has asked SP engineers about that and the engineers claim that "that is impossible."

I have never breathed a metal reg, so I have no clue. Again, I'm just trying to learn more from the experienced folks, which I can fit into my newly expanded knowledge framework.
 
Cotton mouth is real, more of a problem for some people. The metal 2nd do work. It's not a miracle, but it is a help and can make a difference to susceptible people.
A dive friend was bothered enough he got one of those Apollo in line hydration units. I let him try a metal 2nd. He bought one. It convinced him, and he already had a reg so he didn't need the additional expense.

In respiratory therapy there is a small device called an "artificial nose" technically a [heat moisture exchanger]. They are not very big for the job they do (neither is you nose but the work it does is flat out remarkable) but are effective enough that they are used extensively for short term mechanical ventilation over a heated moisturizer due to lower cost, simpler maintenance, and reduced probability of infection. Metal 2nds work in a similar fashion but with (much?) lower efficiency.
 
Nice! I will caution you though that from that picture, that might be a very, very, very early MK-2 (or 3). I have one, and cannot find the correct seat for it. Nobody believes me, and when I showed them the picture, essentially, it is said I have a "unicorn"....

Thankfully, I was able to flip the seat, and likely gave a good bunch of years ahead with it.
 
@rhwestfall, i believe you are referring to my pic. If so, does that mean I can sell the "unicorn" for a big pile of cash to buy more regs with? I have found that enough is never enough.
 
More like "crap, this is going to be a challenge"..... :eek:
 
When he said that, I responded with "so, is that why so many people say that they like the way an old BA breathes better than the newer regs?".....

He said that the newer stuff (e.g. G260) breathes way better than the BA. I think he claimed something like 30 - 40% better. He said one big reason for that is that the newer 2nds have a much bigger exhaust port (i.e. mushroom valve) which makes a large contribution to overall lower WOB......

So, now I've heard the academic answer. What is the "real" answer?

The "real" answer is simple. It's a matter of feel and personal preference. Evaluating second stages on some level is a little like wine tasting; there are norms but it's also subjective. The ANSI numbers are almost meaningless in terms of giving a picture of how the reg actually feels in the water.

Using the exhaust valve size as an example, it's true that a bigger valve will lower exhale effort and this lowers the WOB numbers, but most people don't care too much about small variations in exhale effort. There's much more psychological attachment to the sensation of how easy it is to take in air than there is to expelling it. Our perception of breath is VERY sensitive, just like our sense of taste (to further the wine analogy).

There are other examples but the bottom line is to try out different regs and see which YOU like. The mumbo-jumbo provided by the dive gear companies is often misleading and hyped, even if it's packaged along with helpful info about service procedures and techniques. Their goal is to sell new regulators above all else.
 
Cotton mouth is real, more of a problem for some people. The metal 2nd do work. It's not a miracle, but it is a help and can make a difference to susceptible people.
A dive friend was bothered enough he got one of those Apollo in line hydration units. I let him try a metal 2nd. He bought one. It convinced him, and he already had a reg so he didn't need the additional expense.

In respiratory therapy there is a small device called an "artificial nose" technically a [heat moisture exchanger]. They are not very big for the job they do (neither is you nose but the work it does is flat out remarkable) but are effective enough that they are used extensively for short term mechanical ventilation over a heated moisturizer due to lower cost, simpler maintenance, and reduced probability of infection. Metal 2nds work in a similar fashion but with (much?) lower efficiency.

Thank you for that. I am going to read up on the artificial nose then, if it makes sense to me, ask the ScubaPro guy what he thinks of it, as it relates to the question at hand.

It has become somewhat of a moot issue for me. I will be buying new, current model regs. I was debating between the G260 and the A700. The reality of metal regs and cotton mouth is of lower priority, to me, than some other things I have learned that have now sold me on the G260 over the A700 anyway.

The "real" answer is simple. It's a matter of feel and personal preference. Evaluating second stages on some level is a little like wine tasting; there are norms but it's also subjective. The ANSI numbers are almost meaningless in terms of giving a picture of how the reg actually feels in the water.

Using the exhaust valve size as an example, it's true that a bigger valve will lower exhale effort and this lowers the WOB numbers, but most people don't care too much about small variations in exhale effort. There's much more psychological attachment to the sensation of how easy it is to take in air than there is to expelling it. Our perception of breath is VERY sensitive, just like our sense of taste (to further the wine analogy).

There are other examples but the bottom line is to try out different regs and see which YOU like. The mumbo-jumbo provided by the dive gear companies is often misleading and hyped, even if it's packaged along with helpful info about service procedures and techniques. Their goal is to sell new regulators above all else.

Well stated. Got it.

The other thing the SP guy said is that the easier exhalation contributes a good amount to reduction of CO2 retention and also to lowering SAC. Any thoughts on that? I understand that a reg with a higher WOB might still "feel" better. But, it seems like a reg that doesn't feel as good could still give objective performance that is better - at least for some situations. E.g. maybe it doesn't matter on a recreational drift dive. But, on a working technical dive, one might choose the one that is objectively better, even though it doesn't give as nice a feel.

Is my thinking on the right track here?

As a side note, I observed something that I thought was interesting. As part of my class, I tuned several 2nds. An R195, an S600, a G260, a C350, and an A700. Part of the "check" was to verify that with the VIVA in the Pre-dive position, hitting the purge did not start a freeflow, but putting VIVA in the Dive position and hitting the purge did start a freeflow.

Generally, in the Pre position, hitting the purge was done without doing anything with the mouthpiece, which was installed. After putting it in the Dive position, we would spread the mouthpiece wings out wide to clear the opening of any possible extra back pressure. All of the 2nds would freeflow with the VIVA in Dive, the mouthpiece spread like that, and a solid push on the purge ... except the A700. We could tuned and re-tuned it and could not get it to freeflow ... until we just took the mouthpiece completely off. With the mouthpiece removed, VIVA in Pre would not freeflow and VIVA in Dive freeflowed no problem.

It left me wondering if the A700 mouthpiece is actually done cleverly, to provide just the right amount of back pressure so that you can tune it very light and still not freeflow. Or is the mouthpiece very UNclever and overly restrictive. I.e. it will feed you PLENTY of gas at 1 ATA ambient, but perhaps it would actually give less-then-ideal performance if you were using it on a deep dive with extra high gas density.
 
One of the reasons 2nds don't have bubble distribution baffles anymore is the friction on exhalation. People don't think about exhalation WOB as breathing seems to be all about inhalation. But, if you pay attention, you EXPEND energy inhaling (regs are designed to minimize that part of the work), but unless you actively blow, exhalation is PASSIVE RECOIL.

Take a big breath....hold it 5 seconds, then do nothing except relax and >>>let it go. See?

So, anything that impedes that exhalation contributes to WOB. Larger exhalation valves and no baffles lower that WOB.

How much is enough? The machines can give you some objective data. Does that actually matter? IMO lots of regs now are designed to satisfy machines, not so much people.
I have an old metal conshelf. The exhalation valve is small by modern standard. It has a good bubble baffle. BUT, on mine old age and poor storage or something kind of squashed the baffle. I tuned it, I dove it. Inhaled fine, exhalation was decidedly restricted and I noticed it. Pulled the baffle, put it in really hot water, and shoved large round things in the baffle and let it cool. Yay, not squashed anymore. 2nd dive > much better. But now, not a whole lot different than my more modern regs with larger exhalation valves and little to no baffle.

Note, I'm a recreational diver with modest SAC, but I do dive NW sites in current a lot so occasionally I need a pretty decent throughput.
 
Halocline hit the nail on the head, "personal preference". I've owned/own 156BAs, G260s and G250s. I have/had them all cracking at around .9". They all breathe very well. My preference is the 156 followed by the G260 then the G250. I just like the "way" the 156BA breathes a little better than the others, it's not a significant difference but enough for me to notice.

In my stable the king for ease of breathing is the D400 but could quite happily live with only one of any I've listed. Having said that I've had the most headaches/issues tuning the Ds. I wish SP would do a run of new metal orifices, they have become the bane of my existence. I have a rogue one that is about one more seat change from having a hammer taken to it.

As far as "cotton mouth" goes I've never noticed any difference between metal or plastic. YMMV.
 

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