Randy43068
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Amen!
Pony and spare air pointers....
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Amen!
Oops, missed the "lower" part of the OP's statement.
Many agency standards allow training dives to be conducted in the 40-45m range using a single tank plus appropriately sized stage. My Suunto gives an 7 minutes NDL at 42m, my VR3 gives me 6 minutes at 41m.
Depending on the dive, this may be "enough" to plan a multilevel dive with a few minutes at depth and then ascend to a shallower depth - obviously this won't work if you're on a wreck on the bottom of a lake, with nothing to look at shallower than 40m.
You can readjust the MGR for your shallower levels, and stay with in the NDLs. We quite often do 60+ minute run times on a single tank (plus bailout) with maximum depths around the 40m mark.
A twinset is one answer, but it's not the only answer. Each solution comes with it's advantages and disadvantages.
Gerbs
Contributor
If you are diving with deco obligation, or deeper than 30m (100ft) then you should be diving with redundant first stages for a start. (think redundancy)
As for terminology, pony: reserve and stage: planned for use during the dive is what I usually encounter.
For sizing your stage/pony... work out how much gas you need for the intended use - I assume you want to allow for at least one of your buddy team to be able to cover a complete out-of-gas situation.
So... Assume one regular issue diver, switching to a new tank to finish the dive...
Ascend from 40m --> Surface at 10m/min with a breathing rate of 25l/min@1bar: 4 minutes, with an average depth of 20m --> 3bar.25L/min.4min = 300l@1bar.
Assume a reasonable deco obligation from the dive... 42m/19 min seems not too unreasonable.
This gives, using the Han Deco2000 tables, 2min@9m, 4min@6m, 10min@3m. Make that 1.9x25x2+1.6x25x4+1.3x25x10 =580L@1bar
Give it 2 minute for the initial situation to get sorted for 250l@1bar.
This would give a total gas use to surface of 1130L@1bar or 40 cuft.
So, to Ascend from a fairly involved decompression dive for one diver needs 40 cu.ft or close to 1200 Bar-Liters of air. A 5,7L (40Cu.ft) stage would be the ideal pony for this dive.
All Part of the CMAS* and ** syllabus.
Adjust for high-octane Nitrox carried for faster decompression. This would get to CMAS*** / Nitrox** level. Ask me again in a year or two.
Now, a 40 cuft wil be .65kg negative full and about .7kg positive when empty. This should be a manageable buoyancy variation.
Personally, I would rig this bottle in such a way that I could hand it to the diver needing air - rigging the thing as a stage allows 1. Reg Stowage and 2. Handover.
So... I would strongly consider carrying a 40ft filled with air or Nitrox32 rigged as a stage for when things go south.
Don't dive further than your gas can take you back!
And get the book and/or the training for what you are doing!
Gerbs
ps. When I dive we don't usually carry a spare, but tend to turn the dives early enough that in the team the gas is sufficient for one person to have a total loss to surface breathing a secondary regulator. We use two separate first stages, though.
As for terminology, pony: reserve and stage: planned for use during the dive is what I usually encounter.
For sizing your stage/pony... work out how much gas you need for the intended use - I assume you want to allow for at least one of your buddy team to be able to cover a complete out-of-gas situation.
So... Assume one regular issue diver, switching to a new tank to finish the dive...
Ascend from 40m --> Surface at 10m/min with a breathing rate of 25l/min@1bar: 4 minutes, with an average depth of 20m --> 3bar.25L/min.4min = 300l@1bar.
Assume a reasonable deco obligation from the dive... 42m/19 min seems not too unreasonable.
This gives, using the Han Deco2000 tables, 2min@9m, 4min@6m, 10min@3m. Make that 1.9x25x2+1.6x25x4+1.3x25x10 =580L@1bar
Give it 2 minute for the initial situation to get sorted for 250l@1bar.
This would give a total gas use to surface of 1130L@1bar or 40 cuft.
So, to Ascend from a fairly involved decompression dive for one diver needs 40 cu.ft or close to 1200 Bar-Liters of air. A 5,7L (40Cu.ft) stage would be the ideal pony for this dive.
All Part of the CMAS* and ** syllabus.
Adjust for high-octane Nitrox carried for faster decompression. This would get to CMAS*** / Nitrox** level. Ask me again in a year or two.
Now, a 40 cuft wil be .65kg negative full and about .7kg positive when empty. This should be a manageable buoyancy variation.
Personally, I would rig this bottle in such a way that I could hand it to the diver needing air - rigging the thing as a stage allows 1. Reg Stowage and 2. Handover.
So... I would strongly consider carrying a 40ft filled with air or Nitrox32 rigged as a stage for when things go south.
Don't dive further than your gas can take you back!
And get the book and/or the training for what you are doing!
Gerbs
ps. When I dive we don't usually carry a spare, but tend to turn the dives early enough that in the team the gas is sufficient for one person to have a total loss to surface breathing a secondary regulator. We use two separate first stages, though.
Hello y’all,
Thanks a million for all the answers...
Scubaboard members are indeed precious…
I use an Mk17 (diaphragm) first stage from Scubapro...so I beleive to be ok vs. the cold.
First of, I’d never realized how close this was to tech. diving…
It was just natural progression…with the years, dives got to be deeper, colder and darker (I forgot to mention, I do 50% of my dives at night…
The other thing is that if I go for twins, I need to reconfigure every thing (I use a Scubapro bcd jacket, that will not take twins, my spare air is on it…
Si I am in for some serious $$$: new bc (back plate and wings), new octo, at least one new tank (I have one 80 al and one 100 steel) new valves…
What’s more my buddy is…my wife…so it every $ times 2…
I am afraid she’ll recommend free-diving soon…
lol
Thanks again
Thanks a million for all the answers...
Scubaboard members are indeed precious…
I use an Mk17 (diaphragm) first stage from Scubapro...so I beleive to be ok vs. the cold.
First of, I’d never realized how close this was to tech. diving…
It was just natural progression…with the years, dives got to be deeper, colder and darker (I forgot to mention, I do 50% of my dives at night…
The other thing is that if I go for twins, I need to reconfigure every thing (I use a Scubapro bcd jacket, that will not take twins, my spare air is on it…
Si I am in for some serious $$$: new bc (back plate and wings), new octo, at least one new tank (I have one 80 al and one 100 steel) new valves…
What’s more my buddy is…my wife…so it every $ times 2…
I am afraid she’ll recommend free-diving soon…
lol
Thanks again
Hello y’all,
Thanks a million for all the answers...
Scubaboard members are indeed precious…
I use an Mk17 (diaphragm) first stage from Scubapro...so I beleive to be ok vs. the cold.
First of, I’d never realized how close this was to tech. diving…
It was just natural progression…with the years, dives got to be deeper, colder and darker (I forgot to mention, I do 50% of my dives at night…
The other thing is that if I go for twins, I need to reconfigure every thing (I use a Scubapro bcd jacket, that will not take twins, my spare air is on it…
Si I am in for some serious $$$: new bc (back plate and wings), new octo, at least one new tank (I have one 80 al and one 100 steel) new valves…
What’s more my buddy is…my wife…so it every $ times 2…
I am afraid she’ll recommend free-diving soon… lol
Thanks again
Ha ha ha...don't think that will stop the cash hemorage!
I bought myself a new pair of C4 fins this year.... They were expensive but worth it.
All the best, James
diverdowndude
Contributor
3)What is the difference (if any) between a pony bottle and a "stage" botlle...?
A stage bottle is one that you are planning on leaving somewhere and returning to later. A pony travels with you....
+8 on training/diving with doubles with an isolation valve manifold
A stage bottle is one that you are planning on leaving somewhere and returning to later. A pony travels with you....
+8 on training/diving with doubles with an isolation valve manifold
AfterDark
Contributor
Your doing these dives now so training my or may not do you a lot of good. The doubles with 2 regs is the way to go. If your concerned about your buddy then put a octp. on each reg. I dive in deep cold water here in NE mostly solo so I use a pony with a reg but, I'm only taking care of myself. In your case you stated that providing your buddy with air is one of your concerns, this means you need a lot of air. Toting double AL80's or better yet some of the larger steel tanks 90, 100..... will give you plenty of air to share. Also if you find ourselves in the situation that requires both of you doing decom with one tank you'll both have 2nd stages with the octp rig. It really is the best of both worlds the safest with the most options.
So then is a stage bottle different than a deco bottle?
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