Just ditched the computer......some hints on min deco limits etc wanted.

Little Pete · February 24th, 2006, 08:48 PM

Righto, I'm dive computerless as of monday. Following my (very cold) stint in Gildy, I surfaced to mention in passing to Rich Walker that my bottom timer seemed a lot easier to read than the computer....nice and uncluttered etc etc. Needless to say he just grinned, saying nothing.
Student costs (usually liquid based), a very lovely (albeit somewhat expensive) girlfriend and lack of time/enthusiasm for a job meant that I decided to sell of my computer for a reasonable price to one of the dive club bods here.

The result is that now I'm back onto table diving or the like. What I'm looking for is some suggestions on the ways people would suggest running 'min-deco' single gas (nitrox 32 usually) dives.

I've had it suggested (as a rough guide) to use the EAD of 32% (approx 80% of depth), add it to your bottom time and if they come out as 50 or less you are still in no/min deco 'limits'. This makes sense to me and I would tend to fly things a little with regards to ascents and stops/pauses etc. Any suggestions for the 'best' way to add stops into the profile should I feel I've gone over any limits (eg. start deep, add them at 6m/3m etc?).

Any suggestions much appreciated.

Pete

*Brian Allen* · February 24th, 2006, 09:14 PM

Quote: (Originally Posted by Little Pete)

Any suggestions much appreciated.

Pete

Pimp the girlfriend out... make 600 pound, and do it properly by signing up to tech 1 with me :D

Davey Willo · February 24th, 2006, 10:49 PM

Pete

Just make your self a set of air tables using Decoplanner with a 30/90 Gradient Factor, knock 20% of the depth because you're using 32% and away you go... So if you were doing a 30m dive on a fine ol'wreck, just use the 24m tables

This is what most of us have copied into our wetnotes, infact I have an excel spreadsheet with it all on, courtesy of that fine young Mr Kerslake..

PM me your email address and I'll send it off to you

Dave

Little Pete · February 25th, 2006, 01:28 AM

Thanks Dave, pm sent.

Brian......well for your own sake I shall not let her see that message

Wish I could join you on Tech 1 though....never mind

StephenT · February 25th, 2006, 01:57 AM

I too have moved onto diving without my computer. This ofcourse wasn't strictly due to me moving to a more DIR style. It was because those sneeky fish in capernwray stole it GRRRRR.

DAMN THOSE FISH

graham_hk · February 25th, 2006, 09:21 AM

30s rule. 30min on 30% at 30m for 30 year olds :D

You can add 5min for every 3m shallower or take off 5 for 3m deeper.

It is more conservative than other methods but is very easy to remember

*David Martin* · February 25th, 2006, 02:29 PM

Quote: (Originally Posted by Davey Willo)

Just make your self a set of air tables using Decoplanner with a 30/90 Gradient Factor, knock 20% of the depth because you're using 32% and away you go... So if you were doing a 30m dive on a fine ol'wreck, just use the 24m tables

Pete, to add to what Davey Willo has said:

cut the tables including a 3m stop
"swap" the 3m and 6m stop times ie
do the time given for the 3m stop at 6m
then do the time given for the 6m stop as the ascent time from 6m to the surface.
I'd probably increase the time taken from 6m to surface on the dive/plan but not in the tables.

Lastly, don't clutter your tables with anything with less than the longest min deco. It's just unneccessary columns.

David

Moz · February 25th, 2006, 02:38 PM

http://dir-diver.com/pdf/minimum-dec...h_metric_A.pdf
How about this?

David

davy · February 27th, 2006, 11:46 AM

There are many options for accomplishing this.
And it's best to think about it yourself, run many profiles, analyze them and look for patterns...

To give some pointers;
What I usually do is this... it will also come in handy when you progress to tech1 since it can be almost directly applied there too... :-)

Learn the US navy no deco air times by heart...
I choose the US navy air tables because they are very easy to remember. that's all.
When you look at them you'll notice a pattern...

18m 60mins
21m 50mins
24m 40mins
27m 30mins
30m 25mins
33m 20mins
36m 15mins

So learn the pattern and it's very easy to remember the numbers later.
Now in the beginning you can use it like this with 32% until you feel comfortable with this method.
Notice that the US navy tables are quite aggressive so I only use them for remembering my base line (which are the no deco times for recreational diving.)
Thus you should always incorporate a nice ascent.

For example:
doing 1min deep stops or a 3m/min ascent from 75% your depth.
do a "safety stop" at 6m of lets say 3min and do a slow ascent to the surface from there.

Once you are comfortable with this you can scale it towards the use of 32%.
One way of many to accomplish this is by EAD of just taking 20% or 6m off you depth.

so for example your min. deco time at 30m with 32% is the no deco air time at 24m of the navy tables which is 40mins.
do remember to make a min. ascent here since there isn't as much play anymore as when you didn't scale it towards the use of 32%...

Now you can start looking at what happens when you break the min. deco times... and how your ascent will look like...
run a lot of profiles and again look for patterns.

Even later you can look at what happens for multi level diving and figure out how that changes your ascent and if your rules still apply to those profiles.
It's a long way, but it's better to understand what's going on then to blindly use some rules you found on the internet.
The above rules are all good for starters and to cross check your math, so start from there.
Try to get together with a more experienced person and learn from him/her while you dive...

Also in the beginning it is a good idea to be conservative... When in doubt... be conservative...

*peter_steinhoff* · February 27th, 2006, 12:15 PM

Using US Navy air limits and applying EAD on that for nitrox is not the most straightforward way of doing it. Starting from the beginning it's much easier to just learn the limits for 32% nitrox. Most likely that is how GUE will approach this in the near future.

To get the "limits" how long you can stay I use my own table which in it's metric version has 30m => 35min, 25m => 50min, 20m => 80 min etc.

Keep track of your average depth during the dive and compare to the "limits" above and you can easily plan your dive on the fly. In most cases using a single tank the gas will run out before exceeding the maximum times.

Best,
Peter

February 24th, 2006, 08:48 PM	#1 (permalink)
Little Pete(Offline) New Member Join Date: Nov 2005 Location: UK Posts: 509	Just ditched the computer......some hints on min deco limits etc wanted. Righto, I'm dive computerless as of monday. Following my (very cold) stint in Gildy, I surfaced to mention in passing to Rich Walker that my bottom timer seemed a lot easier to read than the computer....nice and uncluttered etc etc. Needless to say he just grinned, saying nothing. Student costs (usually liquid based), a very lovely (albeit somewhat expensive) girlfriend and lack of time/enthusiasm for a job meant that I decided to sell of my computer for a reasonable price to one of the dive club bods here. The result is that now I'm back onto table diving or the like. What I'm looking for is some suggestions on the ways people would suggest running 'min-deco' single gas (nitrox 32 usually) dives. I've had it suggested (as a rough guide) to use the EAD of 32% (approx 80% of depth), add it to your bottom time and if they come out as 50 or less you are still in no/min deco 'limits'. This makes sense to me and I would tend to fly things a little with regards to ascents and stops/pauses etc. Any suggestions for the 'best' way to add stops into the profile should I feel I've gone over any limits (eg. start deep, add them at 6m/3m etc?). Any suggestions much appreciated. Pete

February 24th, 2006, 09:14 PM	#2 (permalink)
Brian Allen(Offline) GUE Instructor Join Date: Nov 2005 Location: London & Plymouth Posts: 593	Quote: (Originally Posted by Little Pete) Any suggestions much appreciated. Pete Pimp the girlfriend out... make 600 pound, and do it properly by signing up to tech 1 with me :D __________________ ...dive planning again ... GUE fundamentals and Halcyon Equipment Online www.ocean-explorers.co.uk

February 27th, 2006, 12:15 PM	#10 (permalink)
peter_steinhoff(Offline) Instructor candidate Join Date: Dec 2005 Location: Sweden & Florida Posts: 205	Using US Navy air limits and applying EAD on that for nitrox is not the most straightforward way of doing it. Starting from the beginning it's much easier to just learn the limits for 32% nitrox. Most likely that is how GUE will approach this in the near future. To get the "limits" how long you can stay I use my own table which in it's metric version has 30m => 35min, 25m => 50min, 20m => 80 min etc. Keep track of your average depth during the dive and compare to the "limits" above and you can easily plan your dive on the fly. In most cases using a single tank the gas will run out before exceeding the maximum times. Best, Peter __________________ Peter Steinhoff GUE DIR-F, Tech1, Tech2, Cave1, Cave2, Cave3, RB80-1&2, DIR-F/Cave Instructor Candidate. NAUI Tec Instructor (Trimix, Technical DPV, Technical Wreck Penenetration etc) WKPP Support Diver, Halcyon Product Development Team, Gavinscooter Representative. Various IANTD, NSS-CDS, NACD, PADI & NAUI. ---------------------------------------------- http://dir-diver.com http://peter.steinhoff.se (swedish only) Last edited by peter_steinhoff; February 27th, 2006 at 12:24 PM.

February 24th, 2006, 10:49 PM	#3 (permalink)
Davey Willo(Offline) New Member Join Date: Nov 2005 Location: Cleveland Posts: 197	Pete Just make your self a set of air tables using Decoplanner with a 30/90 Gradient Factor, knock 20% of the depth because you're using 32% and away you go... So if you were doing a 30m dive on a fine ol'wreck, just use the 24m tables This is what most of us have copied into our wetnotes, infact I have an excel spreadsheet with it all on, courtesy of that fine young Mr Kerslake.. PM me your email address and I'll send it off to you Dave

February 25th, 2006, 01:28 AM	#4 (permalink)
Little Pete(Offline) New Member Join Date: Nov 2005 Location: UK Posts: 509	Thanks Dave, pm sent. Brian......well for your own sake I shall not let her see that message Wish I could join you on Tech 1 though....never mind

February 25th, 2006, 01:57 AM	#5 (permalink)
StephenT(Offline) New Member Join Date: Jan 2006 Location: Tynemouth Posts: 108	I too have moved onto diving without my computer. This ofcourse wasn't strictly due to me moving to a more DIR style. It was because those sneeky fish in capernwray stole it GRRRRR. DAMN THOSE FISH

February 25th, 2006, 09:21 AM	#6 (permalink)
graham_hk(Offline) Pinoy ako pinoy Join Date: Nov 2005 Location: here, there and everywhere Posts: 779	30s rule. 30min on 30% at 30m for 30 year olds :D You can add 5min for every 3m shallower or take off 5 for 3m deeper. It is more conservative than other methods but is very easy to remember

February 25th, 2006, 02:29 PM	#7 (permalink)
David Martin(Offline) Instructor candidate Join Date: Jan 2006 Location: London, E11 Posts: 419	Quote: (Originally Posted by Davey Willo) Just make your self a set of air tables using Decoplanner with a 30/90 Gradient Factor, knock 20% of the depth because you're using 32% and away you go... So if you were doing a 30m dive on a fine ol'wreck, just use the 24m tables Pete, to add to what Davey Willo has said: cut the tables including a 3m stop "swap" the 3m and 6m stop times ie do the time given for the 3m stop at 6m then do the time given for the 6m stop as the ascent time from 6m to the surface. I'd probably increase the time taken from 6m to surface on the dive/plan but not in the tables. Lastly, don't clutter your tables with anything with less than the longest min deco. It's just unneccessary columns. David

February 25th, 2006, 02:38 PM	#8 (permalink)
Moz(Offline) New Member Join Date: Dec 2005 Location: Gateshead Posts: 205	http://dir-diver.com/pdf/minimum-dec...h_metric_A.pdf How about this? David

February 27th, 2006, 11:46 AM	#9 (permalink)
davy(Offline) DIveR Join Date: Nov 2005 Location: Belgium Posts: 274	There are many options for accomplishing this. And it's best to think about it yourself, run many profiles, analyze them and look for patterns... To give some pointers; What I usually do is this... it will also come in handy when you progress to tech1 since it can be almost directly applied there too... :-) Learn the US navy no deco air times by heart... I choose the US navy air tables because they are very easy to remember. that's all. When you look at them you'll notice a pattern... 18m 60mins 21m 50mins 24m 40mins 27m 30mins 30m 25mins 33m 20mins 36m 15mins So learn the pattern and it's very easy to remember the numbers later. Now in the beginning you can use it like this with 32% until you feel comfortable with this method. Notice that the US navy tables are quite aggressive so I only use them for remembering my base line (which are the no deco times for recreational diving.) Thus you should always incorporate a nice ascent. For example: doing 1min deep stops or a 3m/min ascent from 75% your depth. do a "safety stop" at 6m of lets say 3min and do a slow ascent to the surface from there. Once you are comfortable with this you can scale it towards the use of 32%. One way of many to accomplish this is by EAD of just taking 20% or 6m off you depth. so for example your min. deco time at 30m with 32% is the no deco air time at 24m of the navy tables which is 40mins. do remember to make a min. ascent here since there isn't as much play anymore as when you didn't scale it towards the use of 32%... Now you can start looking at what happens when you break the min. deco times... and how your ascent will look like... run a lot of profiles and again look for patterns. Even later you can look at what happens for multi level diving and figure out how that changes your ascent and if your rules still apply to those profiles. It's a long way, but it's better to understand what's going on then to blindly use some rules you found on the internet. The above rules are all good for starters and to cross check your math, so start from there. Try to get together with a more experienced person and learn from him/her while you dive... Also in the beginning it is a good idea to be conservative... When in doubt... be conservative...