Breakin' out my handy dandy calculator... average no-stress RMV of oh, shall we say .6 CFM.... If I'm spearing at uh, 120' or so... and something interferes with my ability to monitor my gas (as Zen says) "such as seeing a fish and going after it, pursuing it after your strike, and often in hunting you will push your air management to the limits because you have not taken any fish or perhaps you see some action toward the the end of your dive, also, you don't follow a rigid dive plan when you are hunting, because you are hunting and exploring, and you often don't know where it's going to take you," so that I just can't pay adequate attention to my gas and run out and so, decide to calmly make my way to the surface with my "redundant" gas supply in my Spare Air.... Hmmm...
At 30 fpm (we are still going to adhere to normal ascent rates, aren't we? I mean, would we actually plan to put ourselves in extremis and have to make a rapid, high stress ascent? Nooooooo, not us) we'll need 240 seconds, that is, four minutes, to make our ascent. At an average depth of 60 feet during that ascent, that means that we'll calmly use about 7 CF of gas, only four more than I have in my Spare Air (oh, I have a double spare air, so I'm only one CF shy... hooray!).
But let's be realistic. In the scenario where the situation actually causes me to be so inattentive as to run out of gas, there's likely more going on than when I'm breathing at .6 CFM. In fact, from experience I know that in a typical engagement (not a balls-to-the-wall fight, mind you, but a typical spearing, from spear release to subduing and stringing the fish) my air consumption goes up to about 1.2 - 1.5 CFM, and on a balls-to-the-wall engagement it zips up to over 3CFM - and at that rate, even if I make a 120 FPM ascent from 120' (one minute) I'll burn 6CF and increase my chances of DCS by God knows how much - but too much.
For me, then, I require some other option than a spare air. My personal plan is to never allow *any* fish to interfere with my gas plan. When I was young and immortal I'd say to myself "you can shave it a little more" but I have learned a little patience over the years. There'll be another fish another day, and if dinner's in jeopardy there's always Winn Dixie.
Because there can be emergencies that cause gas to go away quickly other than inattention, I do carry independent gas when spearing solo, be it doubles or a pony. If a pony, my personal minimum size is 30CF, which actually will, unlike a spare air, allow a safe ascent, complete with safety stop, in the event of a catastrophic gas loss.
If your diving style allows for the possibilities you've expressed, and therefore a chance that you'll inadvertantly run out of gas unexpectedly because of the way you choose to dive, almost anything other than a Spare Air would be better. Even a good old fashioned "J" valve will give you 8 CF!
But don't just take my word for it. The next time you're out spearing, just after stringing a fish, take your reg out of your mouth and plug your Spare Air in, and make an ascent. If you're happy with the results, great - but I expect you'll find out that we old farts ain't just blowin' smoke when we advise against a Spare Air as a viable "redundant" gas source for a spearo.
E.
At 30 fpm (we are still going to adhere to normal ascent rates, aren't we? I mean, would we actually plan to put ourselves in extremis and have to make a rapid, high stress ascent? Nooooooo, not us) we'll need 240 seconds, that is, four minutes, to make our ascent. At an average depth of 60 feet during that ascent, that means that we'll calmly use about 7 CF of gas, only four more than I have in my Spare Air (oh, I have a double spare air, so I'm only one CF shy... hooray!).
But let's be realistic. In the scenario where the situation actually causes me to be so inattentive as to run out of gas, there's likely more going on than when I'm breathing at .6 CFM. In fact, from experience I know that in a typical engagement (not a balls-to-the-wall fight, mind you, but a typical spearing, from spear release to subduing and stringing the fish) my air consumption goes up to about 1.2 - 1.5 CFM, and on a balls-to-the-wall engagement it zips up to over 3CFM - and at that rate, even if I make a 120 FPM ascent from 120' (one minute) I'll burn 6CF and increase my chances of DCS by God knows how much - but too much.
For me, then, I require some other option than a spare air. My personal plan is to never allow *any* fish to interfere with my gas plan. When I was young and immortal I'd say to myself "you can shave it a little more" but I have learned a little patience over the years. There'll be another fish another day, and if dinner's in jeopardy there's always Winn Dixie.
Because there can be emergencies that cause gas to go away quickly other than inattention, I do carry independent gas when spearing solo, be it doubles or a pony. If a pony, my personal minimum size is 30CF, which actually will, unlike a spare air, allow a safe ascent, complete with safety stop, in the event of a catastrophic gas loss.
If your diving style allows for the possibilities you've expressed, and therefore a chance that you'll inadvertantly run out of gas unexpectedly because of the way you choose to dive, almost anything other than a Spare Air would be better. Even a good old fashioned "J" valve will give you 8 CF!
But don't just take my word for it. The next time you're out spearing, just after stringing a fish, take your reg out of your mouth and plug your Spare Air in, and make an ascent. If you're happy with the results, great - but I expect you'll find out that we old farts ain't just blowin' smoke when we advise against a Spare Air as a viable "redundant" gas source for a spearo.
E.
