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Thanks for the excellent input. Even if the simulator is limited, we have thus far had no guideline whatsoever.
I wonder, would it be totally inappropriate to hope you draft a simple table as a guideline?
For example assuming descent/ascent rate of 60m / min, and bottom time of 10s (typical cwt dive with a little margin) and the common "rule of thumb" of having a recovery time of 2x previous dive time.
List depths in 5 meter increments and on the other axis how many repetitions it would take to be likely to suffer dcs
I think that would cover about 90% of competitive type freediving training. Because such diving is usually very constant and predictable in profile. If you've seen dive proviles of competitive dives, they are for the most part an almost exactly symmetrical "V". Maybe the table could have 2-3 colums for differend speeds below and above 1 m/s.
Such a table would be really valuable for the freediving community
Of course, even more useful would be a similar guideline for repetitive recreational diving, but then you have so many variables, it would basically have to be computed real time to be of any use...(depth, bottom time, ascent/descent rates etc vary greatly with every dive).
So something like:
spd 0.9 m/s 1.0 m/s 1.1 m/s
10m 6 reps 7 reps 8 reps
15m 5 reps 6 reps 7 reps
20m 4 reps 5 reps 6 reps
25m 3 reps 4 reps 5 reps
30m 2 reps 3 reps 4 reps
The table would be read "worst case" type, like in scuba. Meaning if you dove to 30m at 0.9 m/s, the even if the successive dives are shallower, you have a total of 2 dives "allowed" for the session (of course these numbers are completely made up).
Naturally, no liabilities of any kind, but as a completely unofficial "off the record" recommendation, such would be very useful! If nothing else to give people a feel of the ballpark we should be operating in. For making it official there would certainly be commercial and legal aspects to be taken into account.
Thanks again. Nice to have you on board. Can you tell us which Oceanic / Aeris models exactly do have freediving modes including the DCS calculation in those modes?
Something is better than nothing. This "modo" drives the decision to post these tables in this forum.
This table covers depths of 10 to 40 meters and bottom times between 1 and 5 minutes.
Allways use your judgment and knowledge that you acquired on your proper training.
Allthough, I have put some effort to make the tables as conservative as possible, there are considerable areas of uncertainty, hence do not use this table to plan your dives as they can not guarantee DCS free diving!!!
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Dive safely!
Thanks so much for this input, and as you request, I fully understand its experimental and no guarantee nature.
Thanks also for considering the spearos.
Here a question: under what basis did you select your recovery time multipliers? Is it arbitrary? Also, i assume you refer to real "lying flat on the bottom" or aspeto, as bottom time, not dive time (as measured by the suuntos etc). I, and every one I know, uses 2x dive time as a surface interval. Would you say that the x bottom time calculation to be safer?
Thanks so much.
Well, what exactly is official? I think AIDA recommends some minimal recovery times between dives as a function of the last dive depth, but I am not sure if it is available online. Some freediving tables are also linked here: decompression table @ APNEA.czHi,
This is a very interesting and comprehensive thread!
Can anybody recommend an official free-diving decompression table ?
Unfortunately I can't agree at all with the tables posted in this thread. For one thing, the tables show a reduced risk o DCS if the descent is done at 1.3m/s and the ascent at 1.3m/s, compared to 0.7m/s or descent/ascent. In my experience of many 'bends', slow descent and slow ascent has a way less chance of DCS compared to fast descent and fast ascent.
The theory discussed earlier in this thread, actually suspects "squeeze" or better told air embolism on the ascent, just before surfacing. When you pack your lungs before the dive, the air inside is pressured above the ambient pressure. As soon as you start descending both, inner and outer pressure are more or less equal. At big depth, blood shift serves for reducing the lung volume, hence keeping the inner lung pressure in equilibrium with the outside pressure. Now when you ascent, the air in lungs start expanding. Although some oxygen gets consumed, the air volume reduction is smaller than the lung volume reduction due to the blood shift. In consequence, just below the surface, the inner lung volume reaches its maximum that is even higher than it was just after the packing at the beginning of the dive (unless you exhale little bit in the last 2-3 meters)....
Considering frc-diving, lung squeeze should occur much earlier then in “normal” free diving because sub- residual volume volumes are reached much earlier. However, packing might cause micro ruptures even before going down which, in combination with pressure equalization techniques (valsalva), should worsen the risk for air embolism even more.