J-Vo
Contributor
Back in September I was bent in my shoulder ascending from a 200’ for 30 minutes dive. I was diving two Shearwaters set to GF 50/80 and executed all deco stops as specified. 30 minutes IWR at 20’ on O2 and an hour on O2 at the surface completely relieved my symptoms.
A buddy of mine was recently bent on a benign dive above 100’ for less than 60 minutes total run time.
A recent study showed GF Low needs to be set between 55 & 70 while GF HI needs to be set below 70 for the algorithm to remain inside of Navy safe diving limits.
These things have sparked recent conversations about GF settings inside my small group of dive buddies. I got curious and started running some numbers. I’m not sure why I haven't done this before. Probably because most of my reading on the NEDU study came before I had actually done any serious decompression diving.
The NEDU study shallow stop profile:
The NEDU study deep stop profile:
GF 50/80 Produces:
Given that the NEDU profile was bending the Navy divers I feel much less bewildered by my bend in September. I was also working on the bottom (with my shoulders) and cold during deco, so no surprise.
So, where do I go from here? On top of moving my GF High lower, I'm considering significantly raising my GF Low. I may even go to something like 70/70.
How would this impact the same dive while adding accelerated deco?
GF 50/80 Produces:
In addition, for a while I have thought it may be best to keep GF High and GF Low equal to each other. This preserves the empirically tested deco curve of Bhuelman's ZHL-16c while simultaneously introducing a flat percentage of conservatism to the original M-values.
Thanks for reading and fire away,
A buddy of mine was recently bent on a benign dive above 100’ for less than 60 minutes total run time.
A recent study showed GF Low needs to be set between 55 & 70 while GF HI needs to be set below 70 for the algorithm to remain inside of Navy safe diving limits.
These things have sparked recent conversations about GF settings inside my small group of dive buddies. I got curious and started running some numbers. I’m not sure why I haven't done this before. Probably because most of my reading on the NEDU study came before I had actually done any serious decompression diving.
The NEDU study shallow stop profile:
- 170 FSW for 30 minutes
- 40' first stop
- 174 minutes run time, air decompression
The NEDU study deep stop profile:
- 170 FSW for 30 minutes
- 70' first stop
- 174 minutes run time, air decompression
GF 50/80 Produces:
- 170 FSW for 30 minutes
- 70' first stop
- 134 minute run time, air decompression
Given that the NEDU profile was bending the Navy divers I feel much less bewildered by my bend in September. I was also working on the bottom (with my shoulders) and cold during deco, so no surprise.
So, where do I go from here? On top of moving my GF High lower, I'm considering significantly raising my GF Low. I may even go to something like 70/70.
How would this impact the same dive while adding accelerated deco?
GF 50/80 Produces:
- 170 FSW for 30 min on Air
- 70' first stop
- 71 min run time, 50% and 100% for deco gas
- 170 FSW for 30 min on Air
- 60' first stop (gas switch at 70')
- 73 min run time, 50% and 100% for deco gas
In addition, for a while I have thought it may be best to keep GF High and GF Low equal to each other. This preserves the empirically tested deco curve of Bhuelman's ZHL-16c while simultaneously introducing a flat percentage of conservatism to the original M-values.
Thanks for reading and fire away,