Blue Sparkle
Contributor
I'd like to find out more about the idea of diving with a smaller or larger tank to accommodate lower or higher air-consumption rates.
For example, let's say I'm diving in Florida with a dive buddy who uses more air than I do, and we're renting tanks. The default tank is therefore an AL80.
I have had (qualified) people recommend that I use an AL 63, since I use less air and am fairly short waisted. I've also read on the forum where (qualified) people have recommended to someone who uses more air than their buddy to dive with a larger tank, so that they don't have to turn the dive early.
This sounds logical, but leaves me with a question:
I (thought I) understood that the buddy is supposed to provide backup air in case there is a problem with the other buddy's tank/regs/etc. So in that case the buddy pair would have to turn the dive when the "lowest" buddy was down to half the amount of air to provide emergency air for the "highest" buddy, right? So wouldn't we still end up having to return sooner because of air supply?
To illustrate what I'm trying to say (even I can see I might not be writing it clearly), let's say I'm using an AL 63, and my buddy an AL80, and that if all went well we would both have used half our air at the same time. Then (if I have this right and it's very possible I don't - go easy on me!) I would have about 31 cu. ft. of air left (1500 psi) and my buddy would have 40 cu. ft. left (1500 psi). Again, if all goes well we should plan to both be back at the surface at 500 psi.
But... what if in a worst-case-timing scenario, something happens to my buddy's air supply/regulators at exactly the furthest point into the dive? (I'm not saying we would have agreed to turn the dive at 1500 psi, but just giving example figures that are simple to calculate.) Then wouldn't "we" be short on air because my "half" is smaller than my buddy's "half" --- even though if both our dives went fine we would be surfacing both with about 500 psi left?
I suppose in an OW environment we would surface wherever we were, but...?
I'm guessing there is something wrong with my logic, so I thought I would ask here.
Sorry if I've got errors in my assumptions here; I'm pretty new to diving so I haven't done much more than very basic planning yet. In other words, on my last dive trip my buddy and I both dove with rental AL 80's, and we ascended so that neither of us went below 500 psi. However, that typically had me back on the boat with 1400 - 1500 psi. Hence my question.
B.
For example, let's say I'm diving in Florida with a dive buddy who uses more air than I do, and we're renting tanks. The default tank is therefore an AL80.
I have had (qualified) people recommend that I use an AL 63, since I use less air and am fairly short waisted. I've also read on the forum where (qualified) people have recommended to someone who uses more air than their buddy to dive with a larger tank, so that they don't have to turn the dive early.
This sounds logical, but leaves me with a question:
I (thought I) understood that the buddy is supposed to provide backup air in case there is a problem with the other buddy's tank/regs/etc. So in that case the buddy pair would have to turn the dive when the "lowest" buddy was down to half the amount of air to provide emergency air for the "highest" buddy, right? So wouldn't we still end up having to return sooner because of air supply?
To illustrate what I'm trying to say (even I can see I might not be writing it clearly), let's say I'm using an AL 63, and my buddy an AL80, and that if all went well we would both have used half our air at the same time. Then (if I have this right and it's very possible I don't - go easy on me!) I would have about 31 cu. ft. of air left (1500 psi) and my buddy would have 40 cu. ft. left (1500 psi). Again, if all goes well we should plan to both be back at the surface at 500 psi.
But... what if in a worst-case-timing scenario, something happens to my buddy's air supply/regulators at exactly the furthest point into the dive? (I'm not saying we would have agreed to turn the dive at 1500 psi, but just giving example figures that are simple to calculate.) Then wouldn't "we" be short on air because my "half" is smaller than my buddy's "half" --- even though if both our dives went fine we would be surfacing both with about 500 psi left?
I suppose in an OW environment we would surface wherever we were, but...?
I'm guessing there is something wrong with my logic, so I thought I would ask here.
Sorry if I've got errors in my assumptions here; I'm pretty new to diving so I haven't done much more than very basic planning yet. In other words, on my last dive trip my buddy and I both dove with rental AL 80's, and we ascended so that neither of us went below 500 psi. However, that typically had me back on the boat with 1400 - 1500 psi. Hence my question.
B.