- Reaction score
- Philadelphia and Boynton Beach
- # of dives
- 1000 - 2499
If I understand correctly (which is by no means certain), setting GF-Low should affect NDL times, either statically for planning or dynamically for reporting during the dive, namely when the corresponding (imaginary) tissue is the controlling one?
Or did I learn nothing in the 15 minutes I invested reading about gradient factors
There are practical fudges in place to ignore GF low for no stop dives. If you take a planner such as MultiDeco and play high low game to find the NDL (ie the longest bottom time for no stops n the ascent) you will find it is impacted by GF low. So for 30m 40/85 is 4 minutes while 85/85 is 12 minutes. For reference a Perdix at 40/85 gives 14 minutes. For widely different GF low/high pairs, once you have a celling based on GF low the change in instant GF as depth decreases is steep and so the ceiling gets shallower quickly and so never actually matters.
It is all about what you call "recreational dives", as on the other side of the Atlantic, the limit of recreational diving is 60m (CMAS 3* Diver)
That is why in Shearwater Rec mode, you can dive with up to 3 gases, including 99% Oxygen.
Indeed, from what I understood of gradient factors, for a no-deco dive, the GF low is impacting the NDL. If you have a small GF low, your NDL will be smaller at depth requesting you to ascend shallower to continue your dive, without mandatory stops.
And for a deco-dive with a short TTS, let's say 10/15 minutes, having a small GF low might make you start your decompression stops deeper than other divers of the group (first stop at 9m while others shall start at 6m, impacting on their decompression)
@tursiops is correct in his post. The GF low plays no role in your computer for no stop dives. The GF high controls the dive by ensuring that you will not exceed the set value, in any tissue compartment, as long as you make an ascent to the surface, before exceeding the NDL, at the designated rate. This topic has been discussed numerous times on SB and can be found with the search function. A specific thread polled users as to whether their computer took GF low into account on not stop dives, none did. There are no deco stops in a no stop dive.
However, @KenGordon is also correct. MultiDeco works differently than dive computers. MultiDeco does not calculate NDL, it only calculates deco. This topic has also been discussed numerous times on SB, I'm not sure I fully understand the issue. Some of the stops, can largely me mitigated by using a 1 sec stop time rather than a longer time, such as 1 min, in the configuration menu.