Overshooting NDL and mandatory deco stops

[tursiops]

I agree and that is the problem. You can not wear two different computers and have one sat ndl is 12 min and the other say 8 min. and have so much as a clue which one is right. In that case neither one is a useful tool.

LOL. I'm sorry the world is not as black-and-white as you'd like it to be!

 

[Bob DBF]

If we look across the pond it seems reasonable to me that NEDU could be given access to any dive logs held by the USN, for a similar analysis. But then I'm a naïve European...

I wouldn't be supprised if a copy of every log on diving is sent to them as a matter of course. This may well be one of the reasons the Navy tables have changed over the years, if not directly, by showing a scientific study is needed to answer questions that arise from the data.

The NEDU was started to make divers safer and more able to do work necessary for the USN, which it continues to do, and will into the future.


Bob

 

[taimen]

The probability and severity of decompression sickness

A model which calculates DCS risk limits (2% for mild DCS, 0.1-0.2% for serious DCS) for different NDL times. USN2008 and French Navy tables plotted along the risk limits.
Comparing Buhlmann profiles with different GF:s to this model would be very interesting and relevant for recreational divers.

 

[NAM001]

LOL. I'm sorry the world is not as black-and-white as you'd like it to be!

its not a problem with me. but for so many they have no clue what low med or high conservatism means. and worse yet they cant comprehend why one hits end of ndl before another does. it would be a great piece of info to reconcile teh differences.

 

[tursiops]

its not a problem with me. but for so many they have no clue what low med or high conservatism means. and worse yet they cant comprehend why one hits end of ndl before another does. it would be a great piece of info to reconcile teh differences.

Ha! It would also be nice if everybody had the same SAC rate. One less complication! But that is not likely either.

 

[leadduck]

NDL diving and deco diving are different because of the safety stop.

For calculating NDL in rec diving, a GF of 85~95 is usual in dive computers and it's OK, because the 3min@5m safety stop has a big impact. Say you set GF=90 and use the 13min NDL time at 30m. (PZ+ for example gives you 16min NDL time at 30m, so you see they are really not conservative in the NDL.) But then of course you don't shoot to the surface, but as a good NDL diver diligently do your 3min@5m stop. Your effective GF when surfacing after the safety stop is only 70 (!)

Whereas a decompression diver follows the calculated decompression stops, and GFhigh=90 means really surfacing with GF90. I'd never go so high for deco diving, but use 80 and in cold water 75~70. Best way to reduce deco time is a Nitrox stage, but not increasing GF.

So you should really decide before the dive: if you want to stay inside NDL limits and do your safety stop, then GF=90 is OK. But you really shouldn't exceed NDL time then, because then you'll be on a very aggressive deco dive. For a planned deco dive, set a smaller GF value before the dive.

 

[NAM001]

NDL diving and deco diving are different because of the safety stop.

For calculating NDL in rec diving, a GF of 85~95 is usual in dive computers and it's OK, because the 3min@5m safety stop has a big impact. Say you set GF=90 and use the 13min NDL time at 30m. (PZ+ for example gives you 16min NDL time at 30m, so you see they are really not conservative in the NDL.) But then of course you don't shoot to the surface, but as a good NDL diver diligently do your 3min@5m stop. Your effective GF when surfacing after the safety stop is only 70 (!)

Whereas a decompression diver follows the calculated decompression stops, and GFhigh=90 means really surfacing with GF90. I'd never go so high for deco diving, but use 80 and in cold water 75~70. Best way to reduce deco time is a Nitrox stage, but not increasing GF.

So you should really decide before the dive: if you want to stay inside NDL limits and do your safety stop, then GF=90 is OK. But you really shouldn't exceed NDL time then, because then you'll be on a very aggressive deco dive. For a planned deco dive, set a smaller GF value before the dive.

All I will guess is a very good exlaination, but for the technical minded. the techs have no problem with one computer saying 18 min ndl andf another saying something different. It is the rec divers that think rec not tech. If you put yourself in teh rec mind how do youanswer the question of WHICH PUTER IS CORRECT ON ITS NDL CALCULATION. In the rec mind bot hare equal macines and should give teh equal answer ,,,, and they dont. what is the resolution for this. mind would be the most liberal setting on the ric side would be equal to the navy tables. liberal meaning the conservative setting that gives the most time and or longest NDL.

 

[NAM001]

Ha! It would also be nice if everybody had the same SAC rate. One less complication! But that is not likely either.

aincw you brought it up how much does sac change NDL. if it doesnt then it is a moot factor where NDL is concerned.

 

[tursiops]

aincw you brought it up how much does sac change NDL. if it doesnt then it is a moot factor where NDL is concerned.

Ignore

 

[Saboteur]

it doesnt change the fact that its navigation is clunky and difficult to use. I know I speak for most humans that touch the zoop. maybe 99 percent.

That's quite an assumption.