Okay . . . I'll reveal my ignorance. What's a "drive" bottle?
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TSandM:
As explained by Todd Leonard:
"Stage and drive bottles are logistically equivalent, just open circuit vs. rebreather. A drive bottle has a "drive hose" in addition to the normal 2nd stage. These bottles are generally planned for use on a given dive, and come back out again at the end of the dive. They are usually carried by the people who will be using them. However, on long dives like the ones you're reading about, setup and cleanup teams will move some of the push team's bottles over the first few-several thousand feet of the cave on their behalf (allowing the push team to move more efficiently).
Safety bottles are bailout gas, and are generally rigged for open circuit. We plan to not use them, and they are generally left in the cave for an entire season of diving, but in the event of any of a variety of failures or screwups they're there to get us home. Back gas is strictly bailout gas as well, so you need to introduce safeties when the dives get long enough that back gas doesn't provide sufficient bailout. A rule of thumb on how many safeties and where to put them is "one per diver per open circuit stage drop."
Rebreather divers carry a "cheater" in the pocket. This is the quick-disconnect that goes on the end of a drive hose, and having one allows us to quickly convert a safety for rebreather use.
For rebreather dives, we usually carry at least one more drive bottle than we plan to use. In effect it's a safety, but it's a safety that can be deployed immediately because it stays with us and already has a drive hose."
So the drive bottle gets hooked into the RB80 somehow, and can be changed out while diving?
lamont
Contributor
so, how are the safeties staged in terms of distance between the drops and numbers of bottles? could an OC swimmer pick up enough bottles at one drop to get to the next one?
The logistics are mind-boggling . . . These are amazing feats.
lamont
Contributor
RTodd:
yeah, i guess you've got enough gas then to swim out on SCR, but you'd lose the scrubbers after awhile...
lamont:
Swimming and other sorts of exertion at depth are hard on the joints, so we try to minimize it at the deep sites. On working dives where we have to lug around some heavy thing, you'll feel it later unless you really force yourself to "work smart, not hard".
Swimming out is always _way_ down on the list of options. We can always bail ourselves out of a single failure, and with a buddy's help can bail out of at least a double failure. Beyond that, we'd tow eachother, and then way, way beyond that, we'd swim. Dives in siphons call for extra scooter bailout, both because the time out magnifies and because it's harder on the scooters during the exit. Long mission oriented dives call for more as well, because we want to be able to CONTINUE the dive in the event of at least one failure.
Our scrubbers are good for 10+ hours, so don't generally become limiting until deco. I've used mine for 13, and I think the guys did even a little longer than that this past weekend. Swimming, of course, they'd be good for somewhat less. Casey and JJ switch into deco breathers for dives where they really don't want to deco on OC.
Thanks for sharing all the info - This really is an amazing feat of organization
Aloha, Tim
Aloha, Tim
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