MHK
Guest
Given the back and forth in a different thread I thought I'd start a another thread to discuss the reasons behind the thinking of not using a computer. Let me make two disclaimers in the opening paragraph. 1) I'll be happy to answer any questions either publicly or privately, but what I won't do is engage in an overt flame war over the issue. I'll lay out our thinking, I'll entertain different points of view, but I will not denigrate the process with abject banter. 2) The context with which we approach this issue is from the perspective of efficiency, I'll specifically avoid buzz words like "right" -v- "wrong" and I'll stipulate that either way you approach the issue you aren't likely to die. In other words, the " Do it this way or you'll die" allegation is beyond the scope of this analysis.
That being said, our thinking is that many [not all], but many divers become reliant on a device that could fail. To the extent that device fails then the diver is left without essential diving information. Moreover, as agencies start to move towards eliminating tables from the curriculm in favor of teaching computers it's starts the slippery slope downward. Would you prefer your child never learn basic math in school just because they have the ability to use a calculator??
Secondly, the way we approach a dive is to teach divers to turn their brain on underwater not to turn it off and rely on devices. We try to build in a protocol called situational awareness, which basically is taking 5 minute snap shots of your dive, including max depth, average depth. Furthermore, computers eliminate from many pre-dive planning and the analysis and impact of various mixes and profiles. Many believe that decompression theory is an exact science in terms of depth and time. In other words, many don't recognize the benefits associated with deep stops, or the importance of shaping the ascent profile [or "deco" curve]. These critical pieces of information are accumulated over time when a diver takes note of his dive profile, generally speaking many divers simply look at the pixals on their computer in terms of whether they are in the green, yellow or red and then base the repetitive dive plan on pixals. Obviously, if the computer then fails, the diver will generally lack the wherewithal to continue diving.
Thirdly, many divers are sold on the computer as a way to extend bottom times. That is partially true when the choice is limited to tables -v- computers. However that is only part of the equation. To the extent that the algorithm in the computer is set to a conservative gradient to provide a certain amount of "padding" more often then not you wind up with modest levels added bottom times.. For certain some models allow for the adjustement in gradient factors, but the fact is that many lack sufficient knowledge to understand the impact of the change in gradient factors.. The concept of course is that by the "padding" you reduce the very benefit they purport to give you.
Next, recently you've seen a trend towards RGBM based algorithms, but primarily most in-water computers use a Buhlman based algorithm set to 65% - 80% gradient factor. We refer to Buhlman as a "bend and treat" model. What we mean by that is that it tries to get you shallow as quickly as allowable [60' per minute] when a given tissue group reaches it's M-value, and then keeps you shallow to allow for elimination of accumulated nitrogen.. Buhlman specifically notes in his studies that advent of microbubbles but bases his algorithm strictly on saturation and desaturation of N2, accordingly he ignores bubble formation. As such when you attempt a hybrid of bubble mechanics and free phase ascents, Buhlman will unnecessarily penalize you because you incorporated deep-stops and/or used a 30 fpm ascent rate. This of course will generate longer decompression then actually necessary.
Nothwithstanding the foregoing, as diver's progress into helium based diving few in-water computers provide for gas switches, proper algorithms and are by-in-large cost prohibitive, usually in the $1,000+ range. We feel that money can be better spent elsewhere whether it be on proper equipment or training that will allow a diver to compute these calcualtions without the need for devices that can fail..
Hopefully that more fully explains our thinking, but I remain available to answer questions consistent with the disclaimer in the opening paragraph..
Regards
That being said, our thinking is that many [not all], but many divers become reliant on a device that could fail. To the extent that device fails then the diver is left without essential diving information. Moreover, as agencies start to move towards eliminating tables from the curriculm in favor of teaching computers it's starts the slippery slope downward. Would you prefer your child never learn basic math in school just because they have the ability to use a calculator??
Secondly, the way we approach a dive is to teach divers to turn their brain on underwater not to turn it off and rely on devices. We try to build in a protocol called situational awareness, which basically is taking 5 minute snap shots of your dive, including max depth, average depth. Furthermore, computers eliminate from many pre-dive planning and the analysis and impact of various mixes and profiles. Many believe that decompression theory is an exact science in terms of depth and time. In other words, many don't recognize the benefits associated with deep stops, or the importance of shaping the ascent profile [or "deco" curve]. These critical pieces of information are accumulated over time when a diver takes note of his dive profile, generally speaking many divers simply look at the pixals on their computer in terms of whether they are in the green, yellow or red and then base the repetitive dive plan on pixals. Obviously, if the computer then fails, the diver will generally lack the wherewithal to continue diving.
Thirdly, many divers are sold on the computer as a way to extend bottom times. That is partially true when the choice is limited to tables -v- computers. However that is only part of the equation. To the extent that the algorithm in the computer is set to a conservative gradient to provide a certain amount of "padding" more often then not you wind up with modest levels added bottom times.. For certain some models allow for the adjustement in gradient factors, but the fact is that many lack sufficient knowledge to understand the impact of the change in gradient factors.. The concept of course is that by the "padding" you reduce the very benefit they purport to give you.
Next, recently you've seen a trend towards RGBM based algorithms, but primarily most in-water computers use a Buhlman based algorithm set to 65% - 80% gradient factor. We refer to Buhlman as a "bend and treat" model. What we mean by that is that it tries to get you shallow as quickly as allowable [60' per minute] when a given tissue group reaches it's M-value, and then keeps you shallow to allow for elimination of accumulated nitrogen.. Buhlman specifically notes in his studies that advent of microbubbles but bases his algorithm strictly on saturation and desaturation of N2, accordingly he ignores bubble formation. As such when you attempt a hybrid of bubble mechanics and free phase ascents, Buhlman will unnecessarily penalize you because you incorporated deep-stops and/or used a 30 fpm ascent rate. This of course will generate longer decompression then actually necessary.
Nothwithstanding the foregoing, as diver's progress into helium based diving few in-water computers provide for gas switches, proper algorithms and are by-in-large cost prohibitive, usually in the $1,000+ range. We feel that money can be better spent elsewhere whether it be on proper equipment or training that will allow a diver to compute these calcualtions without the need for devices that can fail..
Hopefully that more fully explains our thinking, but I remain available to answer questions consistent with the disclaimer in the opening paragraph..
Regards
