bigplik(Offline)

Hi Folks,
I have finished my Fundies few months ago and since that time I use minimum deco formula to plan and control my dives but I can't remember how to calculate residual nitrogen time to plan second or third dive during same day when using standard EAN32.
Is any GUE formula for that? I found minimum deco table on DIR-diver.com Peter Stainhoff's website but heard from one of GUE instructor that I should have reserve to this table and what I understood that minimum deco formula is better to plan the dives. Ok, even if it is, but from this table I can calculate residual nitrogen time and plan next dives. How to do this without table?
best
pawel

TobyFish(Offline)

ooh, that's interesting... I've not been GUE trained so I don't know the answer, but the question peeks my interest.

For max-depth based dive planning, the RNT is the amount of time it would have taken to reach your starting nitrogen load by dving at the maximum depth of the planned repetetive dive.

However, with average-depth based deco calculation, RNT must be the time it would have taken to reach your starting nitrogen load at the AVERAGE depth of the repetetive dive.

Therefore your RNT for max-depth models is SET at the point of descent, whereas the RNT for ave-depth models must vary throughout the dive depending on the exact profile... hmmm... does that make it difficult or does it mean that ave-depth deco uses something other than RNT to allow for pre-existing N2-load

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limeyx(Offline)

this should be covered in the DIR-F/GUE-F class, and if not, I would recommend the original poster contact their instructor for more info.

As a practical matter, I essentially ignore any "RNT" if the surface interval is 90 mins or more, and if 60-90 mins, then increase the shallow stops (doubling to 2 mins for 30,20,10 feet for recreational diving)

60 mins is the min SI I will normally do unless the dives are really shallow.

Generally limit to 2 T1 or T2 dives per day, with no big adjustments for RNT, except that if the last dive of the day is really shallow, then a v.slow ascent is probably in order.

YMMV --- not bent yet, i am not an instructor, following any info in this post may get you bent etc. etc. etc.

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LCF(Offline)

I actually asked this question some time ago of two GUE instructors, and from the answers, it did not appear that there is any standard teaching on the subject. I had been taught in another DIR class that, for SI greater than 45 minutes, minimum deco would again do; for SI less than 45 min, to double the shallow stops. It would be interesting to run some dives through DecoPlanner and find out if the software says the same thing, since minimum deco was reverse engineered from DecoPlanner.

One of the instructors was going to bring this up at the conference -- I'll have to write to him and see if he did, and if so, what he learned.

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limeyx(Offline)

I never heard the 45 mins thing.

I've done 7 dives in a day using my 60 min approach (recreational) some down to 100, some in the 50-60 foot range w/out issues, so it's officially "good enough for me"

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TobyFish(Offline)

doubling the deep stops seems fine, but what about a shallow dive? can you not get bent on them?

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limeyx(Offline)

double shallow stops not deep, since thats where the N2 buildup is more likely to be (in the slower tissues)

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keri.lewis(Offline)

IIRC The Steinhoff tables were reverse engineered from 30/85 GF Buhlmann with 1,1,3,3 stops.. should be pretty close..

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pengwe(Offline)

I was taught the same thing, but for 60min, instead of 45.

lostdiver(Offline)

So do we have a conclusion? I used to dive with a club members on both days of the weekend and do 8-9dives in a weekend. It was an embarassing mainly hit and hope I didn't get bent. I spent the next day at work half alive/awake fizzing at my desk.

I would be really interested to see something clear pointing at an effective not overly conservative table/formula of how to calculate, Dive Intervals and the effects on the next dive.

BEN

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