DIR Ratio Decompression question

gerstl_ossi · April 6th, 2008, 12:18 AM

Hi DIR guys, i normaly dive with a CCR Rebreather and use a Shearwater Pursuit diving computer or, and a VR3 but would have some help on Ratio Decompressing used by DIR.
Example:
48 Meter 30 Min BT
DECO Min (= BT + 5 Min (as 48= 45 Mt. +3) = Totale Deco 30+5 = 35 Min

80% first Deepstop = ATA 5,8/10 = 0,58x2= 1,16 5,8-1,20 = 4,6 ATA=36M

Deep Time Mix.
48 30 18/45
36 Mt. Deep 1 min
33 Mt. Deep 1 min
30 Mt. Deep 1 min
27 Mt. Deep 1 min
24 Mt. Deep 1 min

18 Min (50% 21-9 Meter)

21 Mt. Deco 3 min on 50/25
18 Mt. Deco 3 min
15 Mt. Deco 4 min
12 Mt. Deco 4 min
9 Mt. Deco 4 min

6 Mt. Deco 18 min on Oxygen

Would that be the decompression You use? Or are there errors in my interpretation?
Thanks a lot
and save diving on Your twinsets
Oswald

DRE · April 6th, 2008, 12:59 AM

Quote: (Originally Posted by gerstl_ossi)

Hi DIR guys, i normaly dive with a CCR Rebreather and use a Shearwater Pursuit diving computer or, and a VR3 but would have some help on Ratio Decompressing used by DIR.
Exampel:
48 Meter 30 Min BT
DECO Min (= BT + 5 Min (as 48= 45 Mt. +3) = Totale Deco 30+5 = 35 Min

80% first Deepstop = ATA 5,8/10 = 0,58x2= 1,16 5,8-1,20 = 4,6 ATA=36M

Deep Time Mix.
48 30 18/45
36 Mt. Deep 1 min
33 Mt. Deep 1 min
30 Mt. Deep 1 min
27 Mt. Deep 1 min
24 Mt. Deep 1 min

18 Min (50% 21-9 Meter)

21 Mt. Deco 3 min on 50/25
18 Mt. Deco 3 min
15 Mt. Deco 4 min
12 Mt. Deco 4 min
9 Mt. Deco 4 min

6 Mt. Deco 18 min on Oxygen

Woud that bee the decompression You would use? Ore are there errors in my interpretation?
Thanks a lot
and save diving on Your twinsets
Oswald

the 6 m deco is done on 50%, not O2; when using O2 you can cut that portion of the deco in half. I would also reshape the curve of the times spent between 21 and 9 meters, and do 30 sec stops 36 and 33 meters rather than 1 minute stops, but overall this is definitely a profile that'll get you out safely.

Anders Knudsen · April 6th, 2008, 11:22 AM

the time is very similar to what I would do.

I am not sure I would bother to bring O2 on a 48m dive, but if you are trying to use it for CCR then count the 6m stop as oxygen.
Deep Time Mix.
48 30 18/45
36 Mt. Deep 1 min
33 Mt. Deep 1 min
30 Mt. Deep 1 min
27 Mt. Deep 1 min
24 Mt. Deep 1 min

this is actually just a 3m/min ascend with no real stops

21 Mt. Deco 5 min on 50/25
18 Mt. Deco 2 min
15 Mt. Deco 3 min
12 Mt. Deco 4 min
9 Mt. Deco 5 min

total time is close to what you did, but I shape my stops in another way.
if I use oxygen i would do the 9m stop on back gas.

6 Mt. Deco 6 min on Oxygen
then 1m/min ascend

if staying on EAN50

6 Mt. Deco 6 min
3 Mt. Deco 12 min
followed by a 1m/min ascend

but this is just what I would do

gerstl_ossi · April 6th, 2008, 12:01 PM

Thanks guys for Your help. I think this kind of decompression would be great also for bailout scenario on eCCR rebreather diving. Now a other question. If deep is more than 60 meter the ratio change to = 2:1, is that correct? That means, 60 Meter 20 Min BT= 40 Min deco? Is the 5 Min+ every 3 meters the same as on 45 Mt. The first Decostop I suppose would move from 21 to 36 Mt as you use a standart deco gas for that deep? Can You make a sample You would dive a 66 Meter BT 25 Min. dive.

Thanks an save diving
Oswald

se2schul · April 6th, 2008, 02:54 PM

Hi Oswald,

This http://www.txfreak.de/ratiodeco.pdf should answer most of your questions.

Personally, I prefer to use either software or my personal tables for dives deeper than 65m.

ku1111 · April 7th, 2008, 09:22 AM

Quote: (Originally Posted by gerstl_ossi)

Hi DIR guys, i normaly dive with a CCR Rebreather and use a Shearwater Pursuit diving computer or, and a VR3 but would have some help on Ratio Decompressing used by DIR.
Example:
48 Meter 30 Min BT
DECO Min (= BT + 5 Min (as 48= 45 Mt. +3) = Totale Deco 30+5 = 35 Min

80% first Deepstop = ATA 5,8/10 = 0,58x2= 1,16 5,8-1,20 = 4,6 ATA=36M

Deep Time Mix.
48 30 18/45
36 Mt. Deep 1 min
33 Mt. Deep 1 min
30 Mt. Deep 1 min
27 Mt. Deep 1 min
24 Mt. Deep 1 min

18 Min (50% 21-9 Meter)

21 Mt. Deco 3 min on 50/25
18 Mt. Deco 3 min
15 Mt. Deco 4 min
12 Mt. Deco 4 min
9 Mt. Deco 4 min

6 Mt. Deco 18 min on Oxygen

Would that be the decompression You use? Or are there errors in my interpretation?

Thanks a lot
and save diving on Your twinsets
Oswald

Not that it would kill you ;-) But from 65% of ATAmax (= 27m) you would double the deepstop time. From 21 to 9 DIR divers often follow a S-curve (read that ratio deco paper from the previous post)

If you want an example for your 60m dive there's an article (in Dutch) on a decompression presentation by Kees Hofwegen for DIR-NL on <click> GAP Decompressie Software </click>. You'll find a table in there comparing several decompression models for a 30 minute dive to 60m with TX18/45 and EAN50 + O2 for decompression.

When I read the ratio deco paper I come to the conclusion that for 30 minutes on 60m you would have 60 minutes deco (ratio 1:2 for 66m) - 10 minutes because you are 2 x 3m shallower then 66m. Total 50 minutes deco. Half you spend in the 21 - 9m segment and half you spend in the 6 - 0 segment. Half of the 21 - 9 (EAN50) segment time is spend in the 36 - 24m segment.

If you do that you get a profile that is close to what is shown in the article.

As you might have guessed by now I'm not (yet) GUE TECH educated so be warned. And I find that GUE TECH educated people often don't give the level of detail that you probably want/need.

Cheers

Marcel

Rubis · April 7th, 2008, 11:54 AM

Quote: (Originally Posted by gerstl_ossi)

21 Mt. Deco 3 min on 50/25
18 Mt. Deco 3 min
15 Mt. Deco 4 min
12 Mt. Deco 4 min
9 Mt. Deco 4 min

Hello Oswald,

looks to me you spent some time with UTR guys... :D

I have just started diving CCR and I am in the process of running a bunch of tables to compare OC vs CCR for ratio deco sakes.
Well, so far for the long dives around 30m I don't find much difference in the run times between running 32% - 30/30 + O2 on OC and having a set point of 1.2 on CCR. (I am so not giving up Ratio deco for a computer).

I think it's a matter of finding the new set points, but ratio deco should be applicable to CCR diving as well.

Cheers

Cris

gerstl_ossi · April 7th, 2008, 08:17 PM

Thanks guys for your answer and links.

Have fun and save diving
Oswald

April 6th, 2008, 12:18 AM	#1 (permalink)
gerstl_ossi(Offline) New Member Join Date: Aug 2007 Location: Italy Posts: 47	DIR Ratio Decompression question Hi DIR guys, i normaly dive with a CCR Rebreather and use a Shearwater Pursuit diving computer or, and a VR3 but would have some help on Ratio Decompressing used by DIR. Example: 48 Meter 30 Min BT DECO Min (= BT + 5 Min (as 48= 45 Mt. +3) = Totale Deco 30+5 = 35 Min 80% first Deepstop = ATA 5,8/10 = 0,58x2= 1,16 5,8-1,20 = 4,6 ATA=36M Deep Time Mix. 48 30 18/45 36 Mt. Deep 1 min 33 Mt. Deep 1 min 30 Mt. Deep 1 min 27 Mt. Deep 1 min 24 Mt. Deep 1 min 18 Min (50% 21-9 Meter) 21 Mt. Deco 3 min on 50/25 18 Mt. Deco 3 min 15 Mt. Deco 4 min 12 Mt. Deco 4 min 9 Mt. Deco 4 min 6 Mt. Deco 18 min on Oxygen Would that be the decompression You use? Or are there errors in my interpretation? Thanks a lot and save diving on Your twinsets Oswald Last edited by gerstl_ossi; April 6th, 2008 at 01:01 AM.

April 6th, 2008, 12:59 AM	#2 (permalink)
DRE(Offline) New Member Join Date: Nov 2005 Location: Mineola, NY Posts: 162	Quote: (Originally Posted by gerstl_ossi) Hi DIR guys, i normaly dive with a CCR Rebreather and use a Shearwater Pursuit diving computer or, and a VR3 but would have some help on Ratio Decompressing used by DIR. Exampel: 48 Meter 30 Min BT DECO Min (= BT + 5 Min (as 48= 45 Mt. +3) = Totale Deco 30+5 = 35 Min 80% first Deepstop = ATA 5,8/10 = 0,58x2= 1,16 5,8-1,20 = 4,6 ATA=36M Deep Time Mix. 48 30 18/45 36 Mt. Deep 1 min 33 Mt. Deep 1 min 30 Mt. Deep 1 min 27 Mt. Deep 1 min 24 Mt. Deep 1 min 18 Min (50% 21-9 Meter) 21 Mt. Deco 3 min on 50/25 18 Mt. Deco 3 min 15 Mt. Deco 4 min 12 Mt. Deco 4 min 9 Mt. Deco 4 min 6 Mt. Deco 18 min on Oxygen Woud that bee the decompression You would use? Ore are there errors in my interpretation? Thanks a lot and save diving on Your twinsets Oswald the 6 m deco is done on 50%, not O2; when using O2 you can cut that portion of the deco in half. I would also reshape the curve of the times spent between 21 and 9 meters, and do 30 sec stops 36 and 33 meters rather than 1 minute stops, but overall this is definitely a profile that'll get you out safely. __________________ www.dirtydiving.com - DIR is not a 4-letter word!

April 6th, 2008, 11:22 AM	#3 (permalink)
Anders Knudsen (Online) Gadevang Underwater Explorers Join Date: Dec 2005 Location: Denmark Posts: 179	the time is very similar to what I would do. I am not sure I would bother to bring O2 on a 48m dive, but if you are trying to use it for CCR then count the 6m stop as oxygen. Deep Time Mix. 48 30 18/45 36 Mt. Deep 1 min 33 Mt. Deep 1 min 30 Mt. Deep 1 min 27 Mt. Deep 1 min 24 Mt. Deep 1 min this is actually just a 3m/min ascend with no real stops 21 Mt. Deco 5 min on 50/25 18 Mt. Deco 2 min 15 Mt. Deco 3 min 12 Mt. Deco 4 min 9 Mt. Deco 5 min total time is close to what you did, but I shape my stops in another way. if I use oxygen i would do the 9m stop on back gas. 6 Mt. Deco 6 min on Oxygen then 1m/min ascend if staying on EAN50 6 Mt. Deco 6 min 3 Mt. Deco 12 min followed by a 1m/min ascend but this is just what I would do __________________ If someone standing on dry land tells you they're safe diving deep on air, give them a wide berth. If they're that stupid at 1 ATA, you know they won't get any smarter at depth

April 7th, 2008, 09:22 AM	#6 (permalink)
ku1111(Offline) New Member Join Date: Jun 2006 Location: Netherlands Posts: 18	Quote: (Originally Posted by gerstl_ossi) Hi DIR guys, i normaly dive with a CCR Rebreather and use a Shearwater Pursuit diving computer or, and a VR3 but would have some help on Ratio Decompressing used by DIR. Example: 48 Meter 30 Min BT DECO Min (= BT + 5 Min (as 48= 45 Mt. +3) = Totale Deco 30+5 = 35 Min 80% first Deepstop = ATA 5,8/10 = 0,58x2= 1,16 5,8-1,20 = 4,6 ATA=36M Deep Time Mix. 48 30 18/45 36 Mt. Deep 1 min 33 Mt. Deep 1 min 30 Mt. Deep 1 min 27 Mt. Deep 1 min 24 Mt. Deep 1 min 18 Min (50% 21-9 Meter) 21 Mt. Deco 3 min on 50/25 18 Mt. Deco 3 min 15 Mt. Deco 4 min 12 Mt. Deco 4 min 9 Mt. Deco 4 min 6 Mt. Deco 18 min on Oxygen Would that be the decompression You use? Or are there errors in my interpretation? Thanks a lot and save diving on Your twinsets Oswald Not that it would kill you ;-) But from 65% of ATAmax (= 27m) you would double the deepstop time. From 21 to 9 DIR divers often follow a S-curve (read that ratio deco paper from the previous post) If you want an example for your 60m dive there's an article (in Dutch) on a decompression presentation by Kees Hofwegen for DIR-NL on <click> GAP Decompressie Software </click>. You'll find a table in there comparing several decompression models for a 30 minute dive to 60m with TX18/45 and EAN50 + O2 for decompression. When I read the ratio deco paper I come to the conclusion that for 30 minutes on 60m you would have 60 minutes deco (ratio 1:2 for 66m) - 10 minutes because you are 2 x 3m shallower then 66m. Total 50 minutes deco. Half you spend in the 21 - 9m segment and half you spend in the 6 - 0 segment. Half of the 21 - 9 (EAN50) segment time is spend in the 36 - 24m segment. If you do that you get a profile that is close to what is shown in the article. As you might have guessed by now I'm not (yet) GUE TECH educated so be warned. And I find that GUE TECH educated people often don't give the level of detail that you probably want/need. Cheers Marcel Last edited by ku1111; April 7th, 2008 at 09:50 AM.

April 7th, 2008, 11:54 AM	#7 (permalink)
Rubis(Offline) cave deprived and Kissed Join Date: Nov 2005 Location: Broadway, (lost in Central NC, USA far far way from Caves SIGH !!!) Posts: 275	Quote: (Originally Posted by gerstl_ossi) 21 Mt. Deco 3 min on 50/25 18 Mt. Deco 3 min 15 Mt. Deco 4 min 12 Mt. Deco 4 min 9 Mt. Deco 4 min Hello Oswald, looks to me you spent some time with UTR guys... :D I have just started diving CCR and I am in the process of running a bunch of tables to compare OC vs CCR for ratio deco sakes. Well, so far for the long dives around 30m I don't find much difference in the run times between running 32% - 30/30 + O2 on OC and having a set point of 1.2 on CCR. (I am so not giving up Ratio deco for a computer). I think it's a matter of finding the new set points, but ratio deco should be applicable to CCR diving as well. Cheers Cris __________________ Petition against M26

April 6th, 2008, 12:01 PM	#4 (permalink)
gerstl_ossi(Offline) New Member Join Date: Aug 2007 Location: Italy Posts: 47	Thanks guys for Your help. I think this kind of decompression would be great also for bailout scenario on eCCR rebreather diving. Now a other question. If deep is more than 60 meter the ratio change to = 2:1, is that correct? That means, 60 Meter 20 Min BT= 40 Min deco? Is the 5 Min+ every 3 meters the same as on 45 Mt. The first Decostop I suppose would move from 21 to 36 Mt as you use a standart deco gas for that deep? Can You make a sample You would dive a 66 Meter BT 25 Min. dive. Thanks an save diving Oswald

April 6th, 2008, 02:54 PM	#5 (permalink)
se2schul(Offline) New Member Join Date: Mar 2007 Location: Ottawa, Canada Posts: 69	Hi Oswald, This http://www.txfreak.de/ratiodeco.pdf should answer most of your questions. Personally, I prefer to use either software or my personal tables for dives deeper than 65m.

April 7th, 2008, 08:17 PM	#8 (permalink)
gerstl_ossi(Offline) New Member Join Date: Aug 2007 Location: Italy Posts: 47	Thanks guys for your answer and links. Have fun and save diving Oswald