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And yes planning software is used...
And no... this is certainly not about saving money...
Regular NON-WHEEL Dive Tables for Multi-Level Dives???
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And yes planning software is used...
And no... this is certainly not about saving money...
Piscean
Registered
Big James,
Piscean.
P.S. I don't think that the table take into account the safety stop unless you are in the required safety stop zones (even then I am not sure - that would be interesting to know).
Posts like yours really make me glad I read this stuff. I was wondering why there are different limits for the multilevel dives on the wheel that are not the same as the NDL's and I bet that that is the reason. Thanks man you made my day.
Piscean.
P.S. I don't think that the table take into account the safety stop unless you are in the required safety stop zones (even then I am not sure - that would be interesting to know).
Safety stops and deco stops count as neutral time, don't ad to the bottom and don't ad to the surface interval. Otherwise one would never get out of the water.
Se7en
Contributor
Hey noshow
I'm going to give you a very simple answer to your question.
Yes. Doing what you described does work.
There is actually a simpler way to do it than calculating dives with 0 surface interval, but I'm not going to attempt to describe it, as I don't want to confuse you into doing something unsafe, and it gives exactly the same result as what you are doing.
FWIW, I was actually taught this method on my PADI OW course a dozen years ago, however I have since had younger PADI instructors tell me that the method is not valid. As the wheel is constructed from the same source data as the table, I suggest that they simply do not understand what the tables / wheel are modeling.
Now the more complex answer
I used this method for calculating multi level dives for many years. Then I bought a computer (alladin pro), and verified that the computer would give me longer bottom time than calculating the multilevel profile. (As you would expect, as you always end up diving more conservatively that the absolute limit of the square profile sections you plan with the table).
I also started planning some decompression dives at the same time, and made the effort to understand decompression theories, M values, and human physiology.
I now have the view that all dives require correct decompression, which may be as simple as correct ascent rates. I also always like to do safety stops at 5m, and make a sport of seeing how slowly I can ascend from that safetystop to the surface.
Co-incidentally, I feel a lot more awake after diving
If you want to use the tables to calculate multilevel diving, I'd suggest that it is OK, however keep away from the limits at any depth, and always do a safety stop, and a slow final ascent.
I'd also strongly recommend extending your education in the area fo decompression theory. UPs recommendation of a gue course is probably quite good, but I'd be more general and say that anyone who can explain M values, and how they are used to develop dive tables would be a good start.
(Although this stuff is covered in the PADI encyclopedia of diving, I'd suggest that most rec instructors have merely learned it, rather than understanding it)
After doing all that so you understand what's happening, buy a computer and follow it. It makes recreational multilevel dives way simpler, so you can spend more time watching the fish swim, or the iron rust (depending on preference)
ciao
Mike
I'm going to give you a very simple answer to your question.
Yes. Doing what you described does work.
There is actually a simpler way to do it than calculating dives with 0 surface interval, but I'm not going to attempt to describe it, as I don't want to confuse you into doing something unsafe, and it gives exactly the same result as what you are doing.
FWIW, I was actually taught this method on my PADI OW course a dozen years ago, however I have since had younger PADI instructors tell me that the method is not valid. As the wheel is constructed from the same source data as the table, I suggest that they simply do not understand what the tables / wheel are modeling.
Now the more complex answer
I used this method for calculating multi level dives for many years. Then I bought a computer (alladin pro), and verified that the computer would give me longer bottom time than calculating the multilevel profile. (As you would expect, as you always end up diving more conservatively that the absolute limit of the square profile sections you plan with the table).
I also started planning some decompression dives at the same time, and made the effort to understand decompression theories, M values, and human physiology.
I now have the view that all dives require correct decompression, which may be as simple as correct ascent rates. I also always like to do safety stops at 5m, and make a sport of seeing how slowly I can ascend from that safetystop to the surface.
Co-incidentally, I feel a lot more awake after diving
If you want to use the tables to calculate multilevel diving, I'd suggest that it is OK, however keep away from the limits at any depth, and always do a safety stop, and a slow final ascent.
I'd also strongly recommend extending your education in the area fo decompression theory. UPs recommendation of a gue course is probably quite good, but I'd be more general and say that anyone who can explain M values, and how they are used to develop dive tables would be a good start.
(Although this stuff is covered in the PADI encyclopedia of diving, I'd suggest that most rec instructors have merely learned it, rather than understanding it)
After doing all that so you understand what's happening, buy a computer and follow it. It makes recreational multilevel dives way simpler, so you can spend more time watching the fish swim, or the iron rust (depending on preference)
ciao
Mike
Good reply Se7en,
I was hoping to get a response similar to yours. Ex... I am planning on taking a course (GUE first) and would REALLY like to uunderstand the theory, calculations, and details of diving using tables before I get a computer. This is the first I have heard of "M" values. (more, more...)
I also was told verbally that if one is going to use these tables for mutilevel diving that they should take into account a few rules... like planning multilevels with a change of at least 1 atm (30 feet or 10 meters).
If anyone has any links to good websites with info to this stuff ( NON DECOMPRESSION/recreational diving info) and/or some good NON decompression recreational dive planning software (multi-level) that would be interesting as well.
I am learning.....
I was hoping to get a response similar to yours. Ex... I am planning on taking a course (GUE first) and would REALLY like to uunderstand the theory, calculations, and details of diving using tables before I get a computer. This is the first I have heard of "M" values. (more, more...)
I also was told verbally that if one is going to use these tables for mutilevel diving that they should take into account a few rules... like planning multilevels with a change of at least 1 atm (30 feet or 10 meters).
If anyone has any links to good websites with info to this stuff ( NON DECOMPRESSION/recreational diving info) and/or some good NON decompression recreational dive planning software (multi-level) that would be interesting as well.
I am learning.....
Se7en
Contributor
Thanks, but just remember that you have no idea if I actually know what I'm talking about... so take everything with the proverbial grain of salt.
Basicually the M value of a nominal tissue is the overpressurisation gradient (vs ambient pressure) that the tissue can tolerate before bubbles form. From memory, Haldane thought that all tissues could handle a gradient of 2, but later research has shown that to be wrong, and some tissues are quite low (like 1.1 ish).
It's worth understanding, I think.
What this effectively results in is a conservative profile. The more granular (ie the smaller the multilevel stages) you calculate it on, the less inherant 'square profile' conservatism remains.
From a practical point of view, it's seldom worth the effort of calculating more than a few levels. Example is a recent wreck dive I did - there is a reefy wall that I drop down to about 35m on, the hull of the wreck (sand) is in 25m, and the deck in 18. I plan this with times for 35m, 25m and 20m - Something like;
5min at 35m
15min at 25m
10m at 20m
5m at 5m (doing about 3 knots out through the heads as it happens)
(This is just what I do, please don't blame me if you get picked up in an aerial water bombing plane if you try it...)
And then dive it off my computer as well, but with an idea of what the profile I want to dive will look like.
ciao
Mike
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