Computerless Multi-Level dives
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I don't think you are following what I am saying. I have control during the dive over what my profile will look like at the end of the dive.
If I decide that my profile is going to be shaped a certain way (more than just average depth) I can make my dive end up looking that way. I'm not special... you probably could too if you thought about it.
As for the 3ATA/2ATA business that is not the Uncle Pug *method*. It is
just what I do.
The answer to your questions about it can be answered by playing with GAP.
I follow what you're saying but I think we disagree about how much control you have. I just don't think you can plan for everthing. I mean, Berman screwed it up....Exley screwed it up....I can just about guarantee that they were both better divers than you or me and they both ran out of air and now they're dead. Procedure fault? Judgement fault? Planning mistake? Equipment problem? Doesn't matter much.
If nothing else these two cases are proof positive to me that "total control" is an illusion. No matter how good your planning is.
R..
A computer will take care of all those worries for you.
Diver0001 is right on when he says that using the PADI Wheel to calculate multi-level dives is "dead easy".
You compare using the Wheel to "using an abacus". Have you in fact ever been taught how to use this RDP? Or actually used it?
Here it is one more time:
The flat RDP tables were designed to calculate only a square profile. The Wheel was designed to calculate a square profile OR a multi-level profile.
Even if you are calculating a square profile, the Wheel is easier and faster to use because you do not have do any calculations... it does it all for you. That's right. No adding in of RNT!
Frankly, I don't understand why you are trying to make this so difficult. There is an RDP for multi-level diving readily available, but you would rather go through some long convoluted calculation process that provides ample opportunity for error.
The RDP Wheel version is a very good tool. It is great for planning dives (square or multi-level) or as a dive PC back up. Whether or not you want to avail yourself of it is entirely up to you.
~SubMariner~
You compare using the Wheel to "using an abacus". Have you in fact ever been taught how to use this RDP? Or actually used it?
Here it is one more time:
The flat RDP tables were designed to calculate only a square profile. The Wheel was designed to calculate a square profile OR a multi-level profile.
Even if you are calculating a square profile, the Wheel is easier and faster to use because you do not have do any calculations... it does it all for you. That's right. No adding in of RNT!
Frankly, I don't understand why you are trying to make this so difficult. There is an RDP for multi-level diving readily available, but you would rather go through some long convoluted calculation process that provides ample opportunity for error.
The RDP Wheel version is a very good tool. It is great for planning dives (square or multi-level) or as a dive PC back up. Whether or not you want to avail yourself of it is entirely up to you.
~SubMariner~
Doof
Contributor
My PADI Wheel and my PADI RDP can't even agree what the the PG is for a dive to 90 feet for 15 minutes is.
The RDP says it's H.
The Wheel says it's I.
Granted, I is more conservative than H, but... maybe I'm only getting I from the wheel because I'm reading it wrong. Maybe that arrow really is piercing rather than just touching. Otherwise, why is there this discrepancy on a square profile when both of these were designed by the same company?
And yet you say the Wheel is easier to use than the flat RDP?
Interesting...
I can calculate a multilevel dive on the RDP using ONLY table 1. I guess that's this "reading the table sideways method" everybody's talking about. I've done it correctly, and very quickly. All it took was a little bit of basic arithmetic. And only addition at that.
In that same amount of time, I am still trying to make sure that the arrow is lined up correctly along the 60' curve. It's not even a question of skill... it's just trying to make sure arrows are still lined up correctly and making sure that the wheel doesn't move while I rotate the pointer around.
The RDP lists the final pressure group in the example above (15@90, 15@60, 15@40) as S. The Wheel lists it as T. One pressure group off. Interesting to note that they started off one pressure group apart before I even moved on to the multilevel part. But again, that could be because I'm reading it wrong.
Which is really the problem, in my mind. Do I really want to trust my dive planning to a planner that's open to interpretation? Or do I prefer a table that's black and white. The numbers are right there, and there is no grey area.
Personally, I think PADI just designed the Wheel as it's multilevel planning tool as a way to make more money. Why teach students that the flat RDP works just as well when you can get another $20-$30 for a Wheel out of them?
The RDP says it's H.
The Wheel says it's I.
Granted, I is more conservative than H, but... maybe I'm only getting I from the wheel because I'm reading it wrong. Maybe that arrow really is piercing rather than just touching. Otherwise, why is there this discrepancy on a square profile when both of these were designed by the same company?
And yet you say the Wheel is easier to use than the flat RDP?
Interesting...
I can calculate a multilevel dive on the RDP using ONLY table 1. I guess that's this "reading the table sideways method" everybody's talking about. I've done it correctly, and very quickly. All it took was a little bit of basic arithmetic. And only addition at that.
In that same amount of time, I am still trying to make sure that the arrow is lined up correctly along the 60' curve. It's not even a question of skill... it's just trying to make sure arrows are still lined up correctly and making sure that the wheel doesn't move while I rotate the pointer around.
The RDP lists the final pressure group in the example above (15@90, 15@60, 15@40) as S. The Wheel lists it as T. One pressure group off. Interesting to note that they started off one pressure group apart before I even moved on to the multilevel part. But again, that could be because I'm reading it wrong.
Which is really the problem, in my mind. Do I really want to trust my dive planning to a planner that's open to interpretation? Or do I prefer a table that's black and white. The numbers are right there, and there is no grey area.
Personally, I think PADI just designed the Wheel as it's multilevel planning tool as a way to make more money. Why teach students that the flat RDP works just as well when you can get another $20-$30 for a Wheel out of them?
grouchyturtle
Contributor
1- Using the PADI table, would I calculate a reverse profile dive the same way? Just as 2 dives with no surface interval?
2- What about your ascent and descent times? For example you start at 25', then go down to 50', back to 25' then surface. Your descent from 25' to 50' and ascent back to 25', I'm sure you would calculate as part of the 50' dive, right? What about your initial descent to 25', final ascent, and safety stop? Could you ad that time to either dive, depending on how conservative you want to be, if not where does it go?
3- Where the table tells you to calculate 10' deeper for cold water, is this a real number, if so what? Or is it more of a comfort level thing? So my buddy, who's been known to put the heat on full blast, driving home from LBI, NJ in the middle of August, could actually be 1 pressure group higher than me after the same dive, since the cold doesnt really bother me that much?
4- How does #3 affect calculating a multi level dive? For example using the dive from above: Would you calculate for a 25 dive, and then a 60 dive, since at 50 youre below the thermo cline and it's much colder?
5- I tried reading the table sideways. It was really tough writing the calculations in my logbook this way, and I got a little lightheaded when I sat back up too quickly. Seriously how do you read the table sideways?
2- What about your ascent and descent times? For example you start at 25', then go down to 50', back to 25' then surface. Your descent from 25' to 50' and ascent back to 25', I'm sure you would calculate as part of the 50' dive, right? What about your initial descent to 25', final ascent, and safety stop? Could you ad that time to either dive, depending on how conservative you want to be, if not where does it go?
3- Where the table tells you to calculate 10' deeper for cold water, is this a real number, if so what? Or is it more of a comfort level thing? So my buddy, who's been known to put the heat on full blast, driving home from LBI, NJ in the middle of August, could actually be 1 pressure group higher than me after the same dive, since the cold doesnt really bother me that much?
4- How does #3 affect calculating a multi level dive? For example using the dive from above: Would you calculate for a 25 dive, and then a 60 dive, since at 50 youre below the thermo cline and it's much colder?
5- I tried reading the table sideways. It was really tough writing the calculations in my logbook this way, and I got a little lightheaded when I sat back up too quickly. Seriously how do you read the table sideways?
The "original" multi level diving method was based on the seriously flawed assumption that an average diver with average air consumption could not get bent on one tank (a steel 72 by default). This as it happens was not true as you could get bent very nicely at depths below 100' on one tank. So the apporach was modified a bit to say an average diver could not exceed the NDL's on the US Navy tables on a single tank for the first dive of the day if he stayed above 90 feet ( but with a BIG qualifier that your air consumption and results may vary).
For deeper diving you what amounted to the same thing as is suggested with spending at least as much time above 2 atm. as you spent below 3atm - sort of a built in deco/saftey stop. But this was still very much overhead diving and a profile that required careful air management to ensure you had the air to complete the profile.
The whole thing was ok in the age of Navy tables and a total lack of multilevel tables IF you were real conservative with it. But it was a pretty intuitive on the fly approach and I personally do not care to go in that direction. I also would strongly recommend that this approach not be used by anyone at any time for any reason given that there are much better tools and much more conservative tables available today. I think the same could and perhaps should be said about some or all of the other methods suggested.
The use of the RDP for multilevel dive planning is interesting but again why would you use an RDP for multilevel diving when you can get a Wheel for another $20-$30? The Wheel is easy to use, and has a proven track record and it is very, very cheap compared to a chamber ride.
The more conservative pressure groups found in comparison to the RDP are the result of an intentionally more conservative model in the Wheel.
When PADI moved from their US Navy based tables to their doppler tables, they went from a 12 hour out gas profile to a 6 hour out gas profile and went to much smaller blocks of time to allow less penalty for going deeper than the cardinal depths. I was never entirely comfortable with this with multiple dives per day over multiple days. I think the saftey margin is in some cases pretty thin even with lower doppler limits given the reduction of some of the traditional fudge factors in the Navy tables combined with the potential for the accumulation of residual nitrogen that is more likely to be ignored by the RDP (and the Wheel for that matter) with it's 6 hour out.
Moving divers up an extra presure group with the Wheel compared to the RDP to accomodate the additional variability and potential for error during multilevel dives is a good idea. I think it is a saftey factor that should not be ignored as it would be when using an RDP for multilevel planning.
It always amazes me that some divers who will go to great lenghts to eliminate relatively small risks in terms of their equipment selection and configuration will often be the same ones who play it fast and loose with dive tables where the risk of getting bent is very real. It's an odd contradiction.
For deeper diving you what amounted to the same thing as is suggested with spending at least as much time above 2 atm. as you spent below 3atm - sort of a built in deco/saftey stop. But this was still very much overhead diving and a profile that required careful air management to ensure you had the air to complete the profile.
The whole thing was ok in the age of Navy tables and a total lack of multilevel tables IF you were real conservative with it. But it was a pretty intuitive on the fly approach and I personally do not care to go in that direction. I also would strongly recommend that this approach not be used by anyone at any time for any reason given that there are much better tools and much more conservative tables available today. I think the same could and perhaps should be said about some or all of the other methods suggested.
The use of the RDP for multilevel dive planning is interesting but again why would you use an RDP for multilevel diving when you can get a Wheel for another $20-$30? The Wheel is easy to use, and has a proven track record and it is very, very cheap compared to a chamber ride.
The more conservative pressure groups found in comparison to the RDP are the result of an intentionally more conservative model in the Wheel.
When PADI moved from their US Navy based tables to their doppler tables, they went from a 12 hour out gas profile to a 6 hour out gas profile and went to much smaller blocks of time to allow less penalty for going deeper than the cardinal depths. I was never entirely comfortable with this with multiple dives per day over multiple days. I think the saftey margin is in some cases pretty thin even with lower doppler limits given the reduction of some of the traditional fudge factors in the Navy tables combined with the potential for the accumulation of residual nitrogen that is more likely to be ignored by the RDP (and the Wheel for that matter) with it's 6 hour out.
Moving divers up an extra presure group with the Wheel compared to the RDP to accomodate the additional variability and potential for error during multilevel dives is a good idea. I think it is a saftey factor that should not be ignored as it would be when using an RDP for multilevel planning.
It always amazes me that some divers who will go to great lenghts to eliminate relatively small risks in terms of their equipment selection and configuration will often be the same ones who play it fast and loose with dive tables where the risk of getting bent is very real. It's an odd contradiction.
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