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Article: THE FIVE WAYPOINTS AND SIMPLE ASCENT BEHAVIOR
- Thread starter Doppler
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blue steal
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Thanks, a good read.
billgraham
Contributor
Cool, Steve. No one ever taught me how to calculate the off gassing ceiling, I like it a lot!
Is that a ratio deco concept?
Is that a ratio deco concept?
OP
Haldane pointed to the ratio or relationship between his theoretical tissue groups (well the controlling group) and ambient, so perhaps we can call all of it ratio something. The relationship between max depth, gas used and off-gassing ceiling is a wee bit more complex than my methods make it out to be but within four ranges (≤ 40 metres); (≤55 metres); (≤70 metres); and (≤ 100 metres) we can ballpark a number that seems to be workable.
Take care, buddy.
pickens_46929
Contributor
Nice article Steve! Learned something I must say.
One thing I would add that most sport divers either forget or simply don't get is that the surface interval is really surface decompression. That the purpose is not simply to rest up for the next dive and see if you are feeling any effects from the first dive. For people pushing the sport diving tables, things like exercise or exertion aren't wise.
One thing I would add that most sport divers either forget or simply don't get is that the surface interval is really surface decompression. That the purpose is not simply to rest up for the next dive and see if you are feeling any effects from the first dive. For people pushing the sport diving tables, things like exercise or exertion aren't wise.
Hi Doppler,
nice article.
I was wondering if there could be a better way to determine the off-gassing ceiling rather than just "a little less than one and a half bar / ata shallower than the average depth".
Shouldn't the off-gassing ceiling be somehow tied to the compartments? and if so, which one?
As you know, in the Haldanian model different compartments do have different off-gassing ceiling - and all of them are dynamic as they depend on the dive profile.
If I put your dive above into divePAL I am quite puzzled with the results as I don't see any relationship between the off-gassing ceiling point and the various compartments.
More specifically, as you can see in the image below, the off-gassing ceiling point (calculated as per your rule) is at 20.5m (average depth at the beginning of ascent was 35.5m) and is above the off-gassing ceiling for compartments 1 and 2, and below all the other compartments - including the leading one (c5).
Maybe I am just day dreaming and there is NO relationship between compartments and the off-gassing ceiling as it is an empirical construct that we can't box into a formula?
Alberto (aka eDiver)
nice article.
I was wondering if there could be a better way to determine the off-gassing ceiling rather than just "a little less than one and a half bar / ata shallower than the average depth".
Shouldn't the off-gassing ceiling be somehow tied to the compartments? and if so, which one?
As you know, in the Haldanian model different compartments do have different off-gassing ceiling - and all of them are dynamic as they depend on the dive profile.
If I put your dive above into divePAL I am quite puzzled with the results as I don't see any relationship between the off-gassing ceiling point and the various compartments.
More specifically, as you can see in the image below, the off-gassing ceiling point (calculated as per your rule) is at 20.5m (average depth at the beginning of ascent was 35.5m) and is above the off-gassing ceiling for compartments 1 and 2, and below all the other compartments - including the leading one (c5).
Maybe I am just day dreaming and there is NO relationship between compartments and the off-gassing ceiling as it is an empirical construct that we can't box into a formula?
Alberto (aka eDiver)
OP
Hi Alberto: (good work on your program by the way)
As far as I know, the term and principle of the off-gassing ceiling is a construct of dual-phase or bubble theory and therefore not directly related to "tissue groups" at all since these are a concept favored in neo-Haldanian models. The plan with dual-phase models is to employ a strategy that helps manage the appearance, growth and proliferation of bubbles... as opposed to the old-school tenet used in neo-Haldanian ones that states: "If we keep these tissue groups below their M-valves, no bubbles will form." Since doppler studies begun in the 70s and continued until now show us that bubbles DO form even after/during? the most conservative profile, for me at least, the science behind anything related to tissue groups has a sort of hollow ring to it.
However, the main point of the technique presented here is not to replace any existing working decompression model or PDC, but to get the diver (in this case a sport diver) to develop a more structured approach to her dive planning and execution... specifically the speed at which she surfaces... and also to sow the seeds of "correct" behavior should something hit the fan at depth. For example, if something goes pear-shaped during a dive at say 60 metres/200 feet, the following the behavior outlined here, a diver can make it to a depth of about 35 metres before she really has to "think." At that point she can start to consider what her options are. Similarly, a sport diver following the same general guidelines will modify his ascent to follow a variable speed that will get him to a spot where he is effectively off-gassing rather than on-gassing when he begins to slow his ascent... and the evidence seems to tell us that a moderately slow ascent during the last bar before a safety stop is a good practice.
As far as I know, the term and principle of the off-gassing ceiling is a construct of dual-phase or bubble theory and therefore not directly related to "tissue groups" at all since these are a concept favored in neo-Haldanian models. The plan with dual-phase models is to employ a strategy that helps manage the appearance, growth and proliferation of bubbles... as opposed to the old-school tenet used in neo-Haldanian ones that states: "If we keep these tissue groups below their M-valves, no bubbles will form." Since doppler studies begun in the 70s and continued until now show us that bubbles DO form even after/during? the most conservative profile, for me at least, the science behind anything related to tissue groups has a sort of hollow ring to it.
However, the main point of the technique presented here is not to replace any existing working decompression model or PDC, but to get the diver (in this case a sport diver) to develop a more structured approach to her dive planning and execution... specifically the speed at which she surfaces... and also to sow the seeds of "correct" behavior should something hit the fan at depth. For example, if something goes pear-shaped during a dive at say 60 metres/200 feet, the following the behavior outlined here, a diver can make it to a depth of about 35 metres before she really has to "think." At that point she can start to consider what her options are. Similarly, a sport diver following the same general guidelines will modify his ascent to follow a variable speed that will get him to a spot where he is effectively off-gassing rather than on-gassing when he begins to slow his ascent... and the evidence seems to tell us that a moderately slow ascent during the last bar before a safety stop is a good practice.
Hi Doppler,
thank you.
That explains why I could not find a relationship between off-gassing ceiling and compartments
Is there any good paper you could point me that discuss off-gassing ceiling in a bubbles contest?
Also, I like this your "variable ascent rate" approach and, if you don't mind, I am going to include it in the deco planner portion of divePAL; right now we are using a default 10m/min for the whole ascent.
Alberto (aka eDiver)
thank you.
That explains why I could not find a relationship between off-gassing ceiling and compartments
Is there any good paper you could point me that discuss off-gassing ceiling in a bubbles contest?
Also, I like this your "variable ascent rate" approach and, if you don't mind, I am going to include it in the deco planner portion of divePAL; right now we are using a default 10m/min for the whole ascent.
Alberto (aka eDiver)
Kevrumbo
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-click on Thread View link below and then scroll down to my post for pdf attachments-Hi Doppler,
thank you.
That explains why I could not find a relationship between off-gassing ceiling and compartments
Is there any good paper you could point me that discuss off-gassing ceiling in a bubbles contest?
Also, I like this your "variable ascent rate" approach and, if you don't mind, I am going to include it in the deco planner portion of divePAL; right now we are using a default 10m/min for the whole ascent.
Alberto (aka eDiver)
http://www.scubaboard.com/forums/vb...le-five-waypoints-simple-ascent-behavior.html
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Steve,
Great article, but incredibly conservative. I have made in excess of 15,000 dives now. Most of those dives were made with a rigorously controlled ascent rate of 60 fpm and no "safety" stop, with no ill effects. All of your concepts aid in understanding what is going on, but I really question the need for either slowing one's ascent rate to 10 fpm or making a "safety stop." The only change that I made (until the new revision of the Navy tables) was being an early adopter of deep stops and faster (120 fpm) ascents to my deep stop.
BTW: the initial purpose of "safety stops," as explained to me by Pilmanis, was to slow recreational divers down (according to Egstrom, they were ascending in pre-computer/ascent meter days at 100 to 150 fpm) and to assure that they did the last ten feet with a higher degree of control, instead of accelerating through those last few feet and popping to the surface.
Great article, but incredibly conservative. I have made in excess of 15,000 dives now. Most of those dives were made with a rigorously controlled ascent rate of 60 fpm and no "safety" stop, with no ill effects. All of your concepts aid in understanding what is going on, but I really question the need for either slowing one's ascent rate to 10 fpm or making a "safety stop." The only change that I made (until the new revision of the Navy tables) was being an early adopter of deep stops and faster (120 fpm) ascents to my deep stop.
BTW: the initial purpose of "safety stops," as explained to me by Pilmanis, was to slow recreational divers down (according to Egstrom, they were ascending in pre-computer/ascent meter days at 100 to 150 fpm) and to assure that they did the last ten feet with a higher degree of control, instead of accelerating through those last few feet and popping to the surface.
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