It is the most liberal rule in cave diving.
Personally, I do not believe in the extremely liberal rule of thirds for cave diving. And really this is where there is (in my opinion) not enough taught on the subject in class. As I see it tanks and gas volumes do not get people in trouble or force you to go too far...people do. It is always your choice as a cave diver, purposeful or not (but with training you should be aware of all the variables).
Buddies will certainly limit the dive on air mgmt rules calculated via dissimilar tank calcs. Personally, that is a step I frequently see skipped by dive teams....I get all kinds of reactions when I point this out but most frequently that the 3 man team concept rules out any harm...that's taking a lot for granted in my opinion.
So the point is that if you decide to have more reserves and plan a dive on variables other than gas (and this is the way to plan a dive in my opinion...ie to never reach min turn pressures) then you are inherently safer than the avg team that uses 1/3s (when comparing only gas mgmt systems).
When I speak of 'thirds being the most **liberal**' rule in cave diving' I intend to convey that it is the break even point of a situation where at max penetration you or your buddy have precisely enough gas to exit the cave to ow(doubtful in a realistic case due to heightened consumption rates..etc associated with the failure). I realize that in N FL most of the caves are high outflow and thus you gain a definate advantage for the return journey. The problem I have is that 3rds is not interpreted or processed intellectually by the individual diver today...ie "3rds is the rule that I learned in my class and it is ok to dive to thirds".... This will get some people in trouble.
For instance given a situation that someone posted about in Peacock 3 (which I have had the pleasure to dive on a few *good vis* days and many more 'what is that orange glow 2ft infront of my face' days) if you had an OOA emergency with your buddy losing all his/her gas at the point where you turned the dive would you guys have made it out if no problems (except silt) occurred? What if you momentairly lost the line in that airsharing silt out situation? Are you seeing where I am leading with this?
When there is no failure at furthest pt of penetration (virtually 99.999999999% of the time) my gas mgmt system is 'overtly conservative' but I dive like I train and train like I dive and my training tells me that problems will occur at the worst possible time (furthest pt of penetration). Is there much harm in adding a stage to reserve more gas in your doubles? I understand that this is a personal choice and one that everyone should make for themselves (within the team framework of course) but I just feel it is not given its due course of attention...gas being an almost afterthought to many cave divers (other than 1/3s is a rule of cave diving). This does not even cover syphons, no flow or extremely technique demanding caves such as in the Yucatan.
For the real deep stuff or really long stuff employ the use of one or several dpv's and never touch the doubles (use stages only). So that is 'ultraconservative' to many but gives you an escape plan when the **** hits the fan at three hundred and you breath a stage dry quickly after fouling a spool in the prop of a dpv. Gas reserves in any diving environment need to be stored in the doubles (everything else you can breath dry and jetison not to mention doubles are a source for you and your buddy...I have yet to experience good buddy breathing off of a stage in a realistic overhead environment....)
Personally, I do not believe in the extremely liberal rule of thirds for cave diving. And really this is where there is (in my opinion) not enough taught on the subject in class. As I see it tanks and gas volumes do not get people in trouble or force you to go too far...people do. It is always your choice as a cave diver, purposeful or not (but with training you should be aware of all the variables).
Buddies will certainly limit the dive on air mgmt rules calculated via dissimilar tank calcs. Personally, that is a step I frequently see skipped by dive teams....I get all kinds of reactions when I point this out but most frequently that the 3 man team concept rules out any harm...that's taking a lot for granted in my opinion.
So the point is that if you decide to have more reserves and plan a dive on variables other than gas (and this is the way to plan a dive in my opinion...ie to never reach min turn pressures) then you are inherently safer than the avg team that uses 1/3s (when comparing only gas mgmt systems).
When I speak of 'thirds being the most **liberal**' rule in cave diving' I intend to convey that it is the break even point of a situation where at max penetration you or your buddy have precisely enough gas to exit the cave to ow(doubtful in a realistic case due to heightened consumption rates..etc associated with the failure). I realize that in N FL most of the caves are high outflow and thus you gain a definate advantage for the return journey. The problem I have is that 3rds is not interpreted or processed intellectually by the individual diver today...ie "3rds is the rule that I learned in my class and it is ok to dive to thirds".... This will get some people in trouble.
For instance given a situation that someone posted about in Peacock 3 (which I have had the pleasure to dive on a few *good vis* days and many more 'what is that orange glow 2ft infront of my face' days) if you had an OOA emergency with your buddy losing all his/her gas at the point where you turned the dive would you guys have made it out if no problems (except silt) occurred? What if you momentairly lost the line in that airsharing silt out situation? Are you seeing where I am leading with this?
When there is no failure at furthest pt of penetration (virtually 99.999999999% of the time) my gas mgmt system is 'overtly conservative' but I dive like I train and train like I dive and my training tells me that problems will occur at the worst possible time (furthest pt of penetration). Is there much harm in adding a stage to reserve more gas in your doubles? I understand that this is a personal choice and one that everyone should make for themselves (within the team framework of course) but I just feel it is not given its due course of attention...gas being an almost afterthought to many cave divers (other than 1/3s is a rule of cave diving). This does not even cover syphons, no flow or extremely technique demanding caves such as in the Yucatan.
For the real deep stuff or really long stuff employ the use of one or several dpv's and never touch the doubles (use stages only). So that is 'ultraconservative' to many but gives you an escape plan when the **** hits the fan at three hundred and you breath a stage dry quickly after fouling a spool in the prop of a dpv. Gas reserves in any diving environment need to be stored in the doubles (everything else you can breath dry and jetison not to mention doubles are a source for you and your buddy...I have yet to experience good buddy breathing off of a stage in a realistic overhead environment....)
