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See post #11 Another algorithm question... DSAT maps reasonably well to a GF hi of about 95
Where Is Your GF?
- Thread starter Michael Guerrero
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100days-a-year
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All the way until you get into deco and then it's nowhere even close, with the older ORCA products following what I assume are close to USN deco schedules.Side by side diving with Perdix,VR3,Oceanic,Mares and other modern computers accruing deco far faster and becoming near useless as soon as 3 dives into a day.
I really would like some day to wear a data logger on a trip to see how dead I am.
I really would like some day to wear a data logger on a trip to see how dead I am.
It depends.
"NDL" OW bimbling in warm tropical waters, I run super aggressive. Short deco dives, I get conservative. Longer deco dives are in-between.
"NDL" OW bimbling in warm tropical waters, I run super aggressive. Short deco dives, I get conservative. Longer deco dives are in-between.
Diving rec with a Shearwater Perdix set to 45/95.
50/80 for technical dives, at least for me with two ~160-210ft dives a day with runtimes ranging from 90-150 minutes. It has worked well for me and I feel very good getting out of the water.
I run pretty close to ~60/95-60/90 on recreational dives / NDL dives in warm water.
I run pretty close to ~60/95-60/90 on recreational dives / NDL dives in warm water.
Ken (and macado), maybe my brain isn't in gear today, but what is the logic behind this strategy? It's not the first time I have heard people say they use different GFs for NDL dives and "deco dives." And it made sense to me intuitively--at first blush. But then I think about the old axiom: "ALL dives are deco dives." That is, whether some algorithm says you can safely ascend at a steady rate all the way to the surface, decompressing as you go, or whether the algorithm says you need to stop along the way, each kind of dive still theoretically has built into it some margin of safety--the GF in the case of the Buhlmann algorithm. And if you decrease the GFs on what the algorithm initially said could be safely done without stops, the algorithm might then give you stops. Is there a sort of nonlinearity in the algorithm, such that its accuracy for really aggressive dives (the "edges" of the algorithm, if you will) is not as well known as for dives of more time-tested profiles? So the more aggressive the dive, the more safety margin you may want to have?
You misread what I wrote.
Let me break it down for you:
Warm water vacation dives within "NDL" I'm aggressive on the GF, basically to the point of following the US Navy NDL's (60-60, 70-50, 80-40, 90-30, etc).
For dives that require a mandatory deco schedule of anywhere from 15 minutes up to 360 minutes I use a moderately aggressive GF, very similar to a guy that's 20 years younger than me that posted above. I have found this to GF to work well for me; although my last six hour dive was in April, the day after that dive I had a hard workout session with no problems and yesterday afternoon I did a 30 mile bike ride in 96° weather four hours after doing a 3-hour cave dive (which had 45 minutes of mandatory deco) in the morning.
For a cave dive that barely registers deco based on that programmed GF, we're talking something that calls for less than 5 minutes of staged deco, I do more time. If the computer says "you only need to stay for 3 minutes," I'll likely stay for 6 to 10. I've just found that following that aggressive GF on "short deco" dives leaves me with a little bit of post-dive fatigue.
Like anything, you need to listen to your body and adjust accordingly. No two people are exactly alike and what works for me may not work for you.
Let me break it down for you:
Warm water vacation dives within "NDL" I'm aggressive on the GF, basically to the point of following the US Navy NDL's (60-60, 70-50, 80-40, 90-30, etc).
For dives that require a mandatory deco schedule of anywhere from 15 minutes up to 360 minutes I use a moderately aggressive GF, very similar to a guy that's 20 years younger than me that posted above. I have found this to GF to work well for me; although my last six hour dive was in April, the day after that dive I had a hard workout session with no problems and yesterday afternoon I did a 30 mile bike ride in 96° weather four hours after doing a 3-hour cave dive (which had 45 minutes of mandatory deco) in the morning.
For a cave dive that barely registers deco based on that programmed GF, we're talking something that calls for less than 5 minutes of staged deco, I do more time. If the computer says "you only need to stay for 3 minutes," I'll likely stay for 6 to 10. I've just found that following that aggressive GF on "short deco" dives leaves me with a little bit of post-dive fatigue.
Like anything, you need to listen to your body and adjust accordingly. No two people are exactly alike and what works for me may not work for you.
I can't speak for everyone but for me most of my deco dives (and yes I agree every dive is a deco dive.) are cold water dives where I also might be working a little bit (setting a mooring, dealing with minor current, trying to do a task).
My rationale is in cold water your body is not really efficiently off-gassing (I do use a heated vest for deco, not on the bottom) while in warm water or short recreational dives I am not really getting a cold as I might on a longer dive. You certainly get better blood circulation when you're warm. I have always been told that when your body is cold it slows circulation to extremities which means you're off-gassing less efficiently.
Add to the fact that I'm typically diving a high helium (> 50%) mixture when doing a technical dive vs. air on a pretty coral reef due to 130ft-ish. If you believe in the "helium penalty" or the fact that your tissues can be theoretically much more saturated on a longer decompression dive then that is my reason for running a much more conservative GF for those types of dives. I'm not necessarily a huge believe in large helium penalty but I still believe more deco is needed for those types of dives.
I'm obviously not a decompression scientist/researcher and have no idea if any of this is correct but I did stay at a Holiday Inn Express a few weeks ago so there's that.. I just know that my body feels good with these GF numbers and I am reluctant to really change things too much at this point.
EDIT: If I start doing dives longer than 4-5+ hours like Ken mentioned above or deeper than 250ft+ then I might re-evaluate these but as it stands now it works well for me.
My rationale is in cold water your body is not really efficiently off-gassing (I do use a heated vest for deco, not on the bottom) while in warm water or short recreational dives I am not really getting a cold as I might on a longer dive. You certainly get better blood circulation when you're warm. I have always been told that when your body is cold it slows circulation to extremities which means you're off-gassing less efficiently.
Add to the fact that I'm typically diving a high helium (> 50%) mixture when doing a technical dive vs. air on a pretty coral reef due to 130ft-ish. If you believe in the "helium penalty" or the fact that your tissues can be theoretically much more saturated on a longer decompression dive then that is my reason for running a much more conservative GF for those types of dives. I'm not necessarily a huge believe in large helium penalty but I still believe more deco is needed for those types of dives.
I'm obviously not a decompression scientist/researcher and have no idea if any of this is correct but I did stay at a Holiday Inn Express a few weeks ago so there's that.. I just know that my body feels good with these GF numbers and I am reluctant to really change things too much at this point.
EDIT: If I start doing dives longer than 4-5+ hours like Ken mentioned above or deeper than 250ft+ then I might re-evaluate these but as it stands now it works well for me.
So if I'm understanding correctly, you guys choose different GF settings for different kinds of dives based mostly on how you have felt after the dives and factors like water temperature and exertion.
Kind of. For me I use different GFs for cold water dives / dives with high helium mixes vs. low stress / water warm diving limited to NDLs. How I feel is an added baseline but if I'm super tired, achy, experience any joint pain or muscle pain, suffering from any sort of niggles then I'd likely dial my GF down a bit.
Even on those dives where I may have a high GF set in NDL diving I'm usually purposely padding my 10-20ft "stops" by ~2-5 minutes. Cheap insurance I guess but the number is entirely arbitrary. If i have gas and others are hanging out then I'll hang out too.
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