Doubles vs Sidemount
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bakodiver391
Contributor
I had the pleasure of diving with a gentleman who is a former world record holder on scuba. He dives manifolded doubles with the isolator valve closed and breathes the tanks down equally. This gives the best of both worlds in that you can only lose half your back gas but can access both tanks after sorting out the problem (if indeed there is any gas left on the problem side). Worth considering on higher risk dives. I will eventually go to sidemount as my old bones continue to deteriorate.
DaleC
Contributor
That's what I do. I used to dive independent doubles but put the isolator in for ease of filling. However, I have the onset of frozen shoulder syndrome on my right side and can't reach the post effectively so keeping it (the iso) open for me is a no no. So it's still Independent doubles but with the possibility for manifolded use.
I've also been diving sm recently but even the internal rotation/hand to armpit needed for hose routing and clipping in aggravates my shoulder.
Getting old sucks.
I've also been diving sm recently but even the internal rotation/hand to armpit needed for hose routing and clipping in aggravates my shoulder.
Getting old sucks.
Sounds like Mr record holder doesn't understand the principles of diving manifolded doubles. The manifold should be open, and only gets closed if there is a problem with one of the tank valves leaking. Any other failure(first stage issues, free-flows) would be controlled by shutting down the appropriate post, thereby still giving access to all the gas in both tanks. The high risk dives you mention would be safer with this type of practice.
DaleC
Contributor
He probably understands how valves work but is able to be flexible in his application.
Is it true you can't put deco mix in a pony bottle because a pony is only to be used in an emergency?
Is it true you can't put deco mix in a pony bottle because a pony is only to be used in an emergency?
He's going to wack himself someday breathing the wrong mix. Judi Bedard was diving Eagle's Nest in 2005 and ended up breathing pure helium because of an isolator which had been closed during filling. She passed out on the dive due to hypoxia, but her buddy rescued her and she managed to survive. I believe she even dives again but I'm not sure about that.
Isolators should remain open except for a functionality check and when there's an actual manifold failure underwater (which are very rare compared to regulator issues).
PfcAJ
Contributor
Former world record holder for what?
Dale,
Bummer about your shoulder, youappear to be working around it.
The pony bottle as i look at them is a bottle who has zero purpose for the dive as planned. It is a CESA bottle of sorts. As such you do not want your bottom mix in it if it is not breathable near the surface. If it had deco mix in it it would be a deco bottle and not a "pony" If the bottom mix can be brethed on the surface then i have seen opinions that the pony will have the same gas in it. This avoids the gas change issues with hardware and computer settings in already higher than ideal stess level. My pony has air in it. Since your pony would be for accent and a safety stop if possible then any gas in it probably would not have any effect as far as a deco /safety stop aspects would provide. I personally dont see anything wrong with say 32 in it and staying above 100 ft. (for failure at depth) with a shallow hard bottom. There is not many situations that one can legitimately use a pony . I invision a <100 ft dive , single tank , and a stuck spg and finding you are out of gas. Anything beyond that and your diving doubles and there is no need for a pony.
More directly to the the question asked. Deco is going to be 50-100%o2 and a failure at depth makes that an unusable gas. I guess you could use 50% since by the time you get a couple of breaths you will be with in the depth sone for 50%,,,, but it woud be no good if you were entangled at say 100 ft. So no to deco and fill with a surface breathable gas. You cant go wrong with just plain air.
Bummer about your shoulder, youappear to be working around it.
The pony bottle as i look at them is a bottle who has zero purpose for the dive as planned. It is a CESA bottle of sorts. As such you do not want your bottom mix in it if it is not breathable near the surface. If it had deco mix in it it would be a deco bottle and not a "pony" If the bottom mix can be brethed on the surface then i have seen opinions that the pony will have the same gas in it. This avoids the gas change issues with hardware and computer settings in already higher than ideal stess level. My pony has air in it. Since your pony would be for accent and a safety stop if possible then any gas in it probably would not have any effect as far as a deco /safety stop aspects would provide. I personally dont see anything wrong with say 32 in it and staying above 100 ft. (for failure at depth) with a shallow hard bottom. There is not many situations that one can legitimately use a pony . I invision a <100 ft dive , single tank , and a stuck spg and finding you are out of gas. Anything beyond that and your diving doubles and there is no need for a pony.
More directly to the the question asked. Deco is going to be 50-100%o2 and a failure at depth makes that an unusable gas. I guess you could use 50% since by the time you get a couple of breaths you will be with in the depth sone for 50%,,,, but it woud be no good if you were entangled at say 100 ft. So no to deco and fill with a surface breathable gas. You cant go wrong with just plain air.
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