Metal vs. Plastic 2nd stage

[Greg Barlow]

Didn't the Navy tests include flooding of the first stage prior to pressurizing?
Are there no benefits for cold water diving in a metal second stage?

I'm not aware of the flooding situation. I wouldn't want to flood a diaphragm reg, as they are much less forgiving of such antics than a piston design.

A metal second stage does contribute to the overall cold water performance. My point is that the first stage is most likely to be the culprit in an icing situation. The metal second stage does offer much improved heat transfer, and also in helping to prevent the "dry mouth" that is so prevalent with technopolymer second stages. The moisture in your breath can condense on the walls of the second stage body as it is cooler than one's exhalation gases. The water temp should keep it warmer than that of the freezing point.

If not using a metal second stage then one with metal inserts is a move in the right direction. Many Mares fans miss the Akros lineage that contained such metal inserts. Regs such as the older ScubaPro designs, Atomic models, and Apeks line up utilize a metal air barrel that works in the same fashion as the metal bodied regs.

Greg

 

[Hobbs]

Well.....to know for sure what you're seeing you'd need to be able to block the 2nd stage and see if it starts to flow out of the octopus..... What I've seen more often than not is that one of the 2nds starts to flow during entry and won't stop. Even the octopus. In the case of a frozen 1st you wouldn't expect the octopus to start flowing would you. Even aftre turning off the octopus for a couple of minutes and trying again you often still hear it hissing. If the 1st stage were the problem you'd expect to hear the primary hissing wouldn't you?

R..

actually that is dependant on the 2nd stages konfiguration and type.

if the first stage would freeze on a jetstream or x-treme configuration the air would go out in a safetyoutlet just infront of the secondstage due to the design.
so you do actually know wich is the culprit, not that it changes much, but still.

 

[aquaoren]

actually that is dependant on the 2nd stages konfiguration and type.

if the first stage would freeze on a jetstream or x-treme configuration the air would go out in a safetyoutlet just infront of the secondstage due to the design.
so you do actually know wich is the culprit, not that it changes much, but still.

This is of course right but I can not remember even heared that a poseidon froze
I may be wrong, maybe someone knows of a frozen poseidon ? (Not due to moist air)

 

[CNTdiver]

I prefer metal due to the fact it is not as likely to break as the plastic ones. Mabey it is me but I always have the worst luck 5 minutes right before the dive with things breaking. I would hate to see you abort the dive. As for cold water, the metal ones seem to retain more heat so freezing/sticking does not occur. Hope that helps.

 

[DA Aquamaster]

Second stage freeze ups were almost unheard of with metal second stages due to their extremely good heat transfer traits, but I have seen plastic second stages develop ice in them to the extent that it eventually blocks the lever and casues the reg to stop delivering air. This is one of the few cases when a reg will fail closed and a good argument for using metal second stages in extremely cold water.

Assuming reasonable care, a metal second stage will also look nice when it is 30-40 yrs old, while plastic looks like crap after one or two seasons. I have not noted significnat corroision problems as long as reasonable care is taken to rinse the reg at the end of the day. I have also worked on some regs that were very corroded inside (ie, no chrome left and down to the copper and brass) but still worked quite well. The corrosion in a metal second stage is normally cosmetic and has to progress to the point of leaving a hole in the case or corroding out the supports or seat for the exhaust valve before it is an issue.

As an added bonus, you can drop a tank on a metal second stage and then go dive. Worst case, you pound out the larger dents and then go dive. That is not an option with a plastic second stage as the case will break, or worse, crack and then fail and leak at depth.

Dry mouth is fairly rare with a metal second stage and common in a plastic second stage. It is extremely common in a plastic second stages equipped with a plastic air barrels.

The "metal regs are heavier and increase jaw fatigue" argument is a little flawed. It is not the surface weight that counts but rather the bouyancy of the second stage underwater and a std sized metal second is not excessively negatively buoyant. Mouthpiece design and incorrect hose lenght are two factors that have a lot more to do with jaw fatigue than the weight of the second stage.

Plastic is great for reg manfacturers as they are a lot cheaper to produce and plastic cases do more readily lend themselves to a few more do dads such as flow vane adjustments etc, that are great marketing gimics. But all in all plastic has not led to great leaps in second stage performance.

 

[scubapro50]

look at the brand ...... doesn't matter if its plastic or metal as long as it gives good service. I still have my 1st Voit singlehose from the 60's and it works great but I rarely dive with it due to the lack of LP ports (made out of brass and it will never wear out) I own a SCUBAPRO Mk10 with the classic 2nd stage and will probably never switch. My wife has a Pacer that's all plastic and loves it due to the lightweight and easy breathability.

 

[scubapro50]

I was reading the June 2005 issue of SCUBA DIVING magazine which tested regulators. it stated that one of the highest ranked regulators today (Mares Abyss) has an all-metal, nonadjustable second stage. Made of metal, the second stage is a bit heavier than some other regulators, but it's still comfortable. The Mares Abyss is also U.S. Navy approved (what ever that means). It was named one of the "best" regulators made and a "testors' choice" pick. It is also one of 4 models listed for the Mares/Dacor trade-in program for older Dacor regulators made before 2000. To find out more about the trade in program for older Dacor regulators see www.scubaboard.com/t110024-.html for more information

 

[redacted]

I was reading the June 2005 issue of SCUBA DIVING magazine which tested regulators. it stated that one of the highest ranked regulators today (Mares Abyss) has an all-metal, nonadjustable second stage. Made of metal, the second stage is a bit heavier than some other regulators, but it's still comfortable. The Mares Abyss is also U.S. Navy approved (what ever that means). It was named one of the "best" regulators made and a "testors' choice" pick. It is also one of 4 models listed for the Mares/Dacor trade-in program for older Dacor regulators made before 2000. To find out more about the trade in program for older Dacor regulators see www.scubaboard.com/t110024-.html for more information

I keep waiting for Mares to add a user adjustment to that design. They really seem to get good performance out of that classic doenstream design. But an adjustor like on the high end Oceanic 2nd would probably be both a real, albeit small, improvement as well as a marketing boost. Like a poor divers Kirby Morgan.

 

[DA Aquamaster]

I keep waiting for Mares to add a user adjustment to that design. They really seem to get good performance out of that classic doenstream design. But an adjustor like on the high end Oceanic 2nd would probably be both a real, albeit small, improvement as well as a marketing boost. Like a poor divers Kirby Morgan.

Iagree. Of course an all metal downstream design second stage with a cracking effort adjustment would basically be comparable to a late 60's through early 80's vintage SP Adjustable second stage. It's nice to see the trend is coming back toward what works.