7 Dives A Day

[DiveNav]

Very impressive - I'm interested in your dive planning products......

Thank You

.....If I understand you correctly, you are saying the OP should be okay with his original dive plan, as laid out in posts #1 and #4, assuming "typical multilevel profiles with 3 minutes safety stops"....

NO!
What I said was that I plugged-in the OP 24 dives in divePAL using "Square Root" shaped profiles that I made up (descend at 60ft/min to the max depth, stay there few minutes, then ascend to the surface at 30ft/min - stopping here and there for a bit (like a recreational diver would do) - and then make the final safety stop at 15ft for 3 minutes). No one knows if the OP will actually follow those profiles or not.

Based on the profiles I made up, the level of slowest compartment at the end of the 24 dives sequence was ~75% (again, if you change the shape of the profiles a tiny bit, all the bets are off).

.......My question is, does he need to completely desaturate before boarding an airplane? If not, how long would he have to wait in order to board an airplane?.....

I don't know. I am not a doctor. I just like to crunch numbers

Alberto (aka eDiver)

 

[DevonDiver]

No one knows if the OP will actually follow those profiles or not.

That's my concern.

It's easy to get caught up in the theoretical number crunching of whether it's possible to do, or whether the OP would sufficiently desaturate in time to fly home.

With the high loading on those slow tissues towards the end of the series, there also a big issue in the potential tolerances involved with any underwater mishaps. The OP is an inexperienced diver - and, therefore, more likely to misjudge his ascent rate or have buoyancy problems. The tissue loading of his planned series of dives makes the implications of a fast ascent quite serious.

Personally, I'd recommend that the OP recognises that his planned dive series would leave little to no margin for error. He should judge that against an honest evaluation of his own capabilities. Should he decide to go ahead with the dive series, it should be with full awareness that there could be serious health consequences if he messes up.

 

[DiveNav]

......My question is, does he need to completely desaturate before boarding an airplane? If not, how long would he have to wait in order to board an airplane?.....

You - and the OP - might want to read this post

 

[Mike Boswell]

Thank You


NO!
What I said was that I plugged-in the OP 24 dives in divePAL using "Square Root" shaped profiles that I made up (descend at 60ft/min to the max depth, stay there few minutes, then ascend to the surface at 30ft/min - stopping here and there for a bit (like a recreational diver would do) - and then make the final safety stop at 15ft for 3 minutes). No one knows if the OP will actually follow those profiles or not.

Based on the profiles I made up, the level of slowest compartment at the end of the 24 dives sequence was ~75% (again, if you change the shape of the profiles a tiny bit, all the bets are off).


I don't know. I am not a doctor. I just like to crunch numbers

Alberto (aka eDiver)

Me, too.

Without knowing the OP's intentions or the area, I would have assumed square profiles because they are more conservative and photographers tend to sit on the bottom. Would square profiles with safety stops put him outside NDLs?

 

[Thalassamania]

Me, too.

Without knowing the OP's intentions or the area, I would have assumed square profiles because they are more conservative and photographers tend to sit on the bottom. Would square profiles with safety stops put him outside NDLs?

I suspect that they would.

 

[DivemasterDennis]

I just want to respond briefly to Thalasmania regarding my reference to rdp and the wheel. First, you can in fact use them to predict ndl times on these kinds of dives and to get a result after the dive if you note time at depth, and do a multilevel profile accordingly. Of course a computer model is more accurate, and easier, but as far as planning way out in the future, I find the rdp and wheel to be a good "rule of thumb." I also use computer models, but hey everyone, predicting ndl's and fly times is never more than "rule of thumb," unless of course each dive goes off exactly as planned, with the exact depths and durations and surface intervals used at input for your planning models. That has never actually happened for me nor, I dare say, for anyone else (except perhaps for well planned and followed technical dives. My point was that the OP needed to consider residual nitrogen loading on repetitive dives over repetitive days, and that the OP's planning is likely too aggressive. That is something that some (but not all) of the computer modelers who posted have confirmed. I like the comment about quality versus quantity. And I appreciate this thread, as I have learned alot about dive planning. I will continue to be a bit conservative in my planning, as a nearly 60 year old diver who enjoys diving, and who has been diving and plans to continue diving for a long time.
DivemasterDennis

 

[Thalassamania]

DD: you misunderstand what I am telling you. The PADI wheel and/or RDP use a 60 (or possibly 40 according to Boulderjohn) minute halftime as opposed to the 120 minute half time of the USN tables. This makes them singularly unsuitable outside of the narrow window they were designed for which is basicly no-D diving, shallower than 100 feet, no more than 3 dives per day.

When cutting a table you need to calculate post dive residual nitrogen. Then, for repetitive diving, you must be able to relate the amount of nitrogen that was absorbed in a previous dive to the amount of time that it would have taken to absorb that amount of nitrogen at a different depth, after a given surface interval. To perform this slight of hand, a critical assumption must be made as to what the controlling tissue at the end of the initial dive was. The USN tables assume that it was the 120 minute tissue, and this is good for longer dives and more dives in a running sequence. The PADI tables assume it was the 60 (40?) minute tissue, and this assumption results in both shorter required surface intervals and longer second dives when compared to the USN 120 minute halftime repetitive diver tables given the same initial dive and surface interval. However, since there is no free lunch, the PADI model breaks down with more aggressive pressure exposures and/or longer dive sequences like those proposed here.

 

[sheeper]

personally, I NEVER fly (high altitude, pressurized cabin, etc) within 24 (and in practice i wait 36-48) hours of any logged/real dive.

the greater safety margin and time spent is well worth any possibility of DCS. no single dive is worth the risk when it is so easy to avoid.

 

[DivemasterDennis]

I did understand you, Thalassmania, and I appreciate very much your knowledge of the physics and science implicated by the original post. I am well aware of the limits of the RDP and wheel. That's why I own several computers. I think you stated very clearly that all tables (including computer tables and navy tables) are based on their own parochial assumptions. Moreover, none can incorporate individual metabolic differences. I think, however, that the science of diving has had sufficient years to acquire, analyze and utilize statistical data so that we can dive safely. I wonder what you would tell the OP about his 7 dive a day plan, given your own assumptions. But more importantly, I am sure you will agree that his dive planning in the implementation phase ( actual diving) needs to be based upon where he actually is following each dive, consistent with what his computers, or what you would call appropriate tables, tells him at the outset of each dive.
DivemasterDennis

 

[DiveNav]

......Would square profiles with safety stops put him outside NDLs?

I entered into divePAL-Tech the "plan" indicated by the OP using "U" shaped profiles (plus safety stop).

My analysis shows that the diver will go straigth to the chamber after dive 6 of day 3 as he will be surfacing breaking the ceiling (lead is the slowest compartment).

​

Alberto (aka eDiver)