NDL for DIVE GUIDE

acqua · May 12th, 2006, 09:44 AM

Decompression on the fly is always a main topic , different opinion or methods are easily find around . but what about leading a recreational dive ,let s assume you 're leading a normal recreational dive width
nitrox 32% and you want to stay inside NDL , in a real recreational dive
the square profile are almost impossible , many factor like current nice animals (whale shark last week

) makes very difficult to calculate
underwater and either follow a planned profile , avg depth is a good thing but not so good if there is many up and down ( even if we don't like them )
and so is experience after many and any dives you get the feeling of how much close the deco zone you are , but it possible find a path or a quick way to do it .
we have to dive width computer every time , we need to demonstrate our profile in case of incident , so mine is just a question .. unfortunately

cheers
Richard

jluttichau · May 12th, 2006, 06:01 PM

Quote: (Originally Posted by acqua)

avg depth is a good thing but not so good if there is many up and down ( even if we don't like them )

Are you worried about the formation of bubbles or tissue saturation from doing those ups and downs. I don't think it'll have much influence on your deco obligation if you are of good health etc. Richard Buchaly posted some agressive profiles on some list where they go from 90m to 12m 3 times in a single dive and had no symptoms.
I think that if you have good awareness and practice calculating your average depth that'll give you a good idea of your deco obligation.
As far as i see it your problem is that you have to lead divers that might not be fit to dive per our standards and hence needs a profile with a lot more padding. You could make your profile more conservative, taking into considaration your guests health, fitnesslevel and other factors and you migth end up doing a safer dive then you would using your buhlmann of RGBM algorithm.

Quote: (Originally Posted by acqua)

we have to dive width computer every time , we need to demonstrate our profile in case of incident , so mine is just a question .. unfortunately

I use a computer (in guage mode) and i log my profile. If you have to run your computer in computer mode you can always have a timer on your arm and stick the computer in your pocket. But that might scare some of your guests and label you as one of those cowboy dive instructors

Cheers
Jonas

GoDiva · May 12th, 2006, 06:02 PM

Quote: (Originally Posted by eric)

I don’t think that it would even be possible to get into deco while leading a group of single tank divers on 32%. I guess you need to be more conservative with your dive planning in this case though.

Of course it is, certainly if you do 2 or 3 dives on a day. And if you have "annoying tourists" with low gas consumption ;-). My diving on wrecks in Coron, Philippines, was limited by NDL. I was very happy I combined that trip with a Nitrox course, as this definitely gave me more time to enjoy everything.

GoDiva · May 13th, 2006, 12:54 AM

Quote: (Originally Posted by eric)

I guess it depends on what bottom time you consider NDL.

Well, max depth of 30m, with an average of 25 and this for more than half an hour would get you pretty near anybody's definition of NDL. If you then do a second dive that day, you run a big risk of needing deco.

acqua · May 13th, 2006, 08:51 AM

Tanks everyone form the answers .

"
I don’t think that it would even be possible to get into deco while leading a group of single tank divers on 32%. I guess you need to be more conservative with your dive planning in this case though.Yesterday 11:44 AM
"

this is right , very difficult to get close , but going further assuming 30 meters max depth why not 36 % and say to the people don't worry about
deco you'll never go in width a 12 L thank .
I personally think it's not the best way .

cheers
Richard

Martin Burnard · May 13th, 2006, 02:33 PM

With a SAC of 12 l/min on a easy going dive, a full 230 bar fill to start with, deco is looming and still there is gas in the 12ltr cylinder of 32%.

Square profile dive to 30m on my twin 12 ltr, just avoiding going into deco (40 minute dive) used 70 bar. Water temp 9 degrees, vis 8m, no current.

Hence I can see your concern as a dive guide!

But I guess somebody who has a low SAC is probably an experienced and/or competant diver.

So computer it is, and it covers your ass!!

My 2p worth.

graham_hk · May 13th, 2006, 03:13 PM

If your guiding you will find it difficult to go into real required stops. Most guided divers are not going to have the kind of RMV needed for this to happen on 32% and, futhermore, if your guiding you tell them what to do.

I would keep it to 25min on the bottom and 30m max do a nice slow (atleast 10min) ascent from every dive (perfect if you're on a wall or where the dive permits) and give yourself a decent surface interval. You could do 4 dives and be nowhere near "deco" required stops - suggest you build up to this and see how your feel - your body will tell you when your kicking the ass out of it.

Graham

May 12th, 2006, 09:44 AM	#1 (permalink)
acqua(Offline) New Member Join Date: May 2006 Location: Maldives Posts: 17	NDL for DIVE GUIDE Decompression on the fly is always a main topic , different opinion or methods are easily find around . but what about leading a recreational dive ,let s assume you 're leading a normal recreational dive width nitrox 32% and you want to stay inside NDL , in a real recreational dive the square profile are almost impossible , many factor like current nice animals (whale shark last week ) makes very difficult to calculate underwater and either follow a planned profile , avg depth is a good thing but not so good if there is many up and down ( even if we don't like them ) and so is experience after many and any dives you get the feeling of how much close the deco zone you are , but it possible find a path or a quick way to do it . we have to dive width computer every time , we need to demonstrate our profile in case of incident , so mine is just a question .. unfortunately cheers Richard Last edited by acqua; May 12th, 2006 at 12:15 PM.

May 13th, 2006, 08:51 AM	#5 (permalink)
acqua(Offline) New Member Join Date: May 2006 Location: Maldives Posts: 17	Tanks everyone form the answers . " I don’t think that it would even be possible to get into deco while leading a group of single tank divers on 32%. I guess you need to be more conservative with your dive planning in this case though.Yesterday 11:44 AM " this is right , very difficult to get close , but going further assuming 30 meters max depth why not 36 % and say to the people don't worry about deco you'll never go in width a 12 L thank . I personally think it's not the best way . cheers Richard Last edited by acqua; May 13th, 2006 at 09:09 AM.

May 12th, 2006, 06:01 PM	#2 (permalink)
jluttichau(Offline) Custom User Title Join Date: Nov 2005 Location: Denmark Posts: 437	Quote: (Originally Posted by acqua) avg depth is a good thing but not so good if there is many up and down ( even if we don't like them ) Are you worried about the formation of bubbles or tissue saturation from doing those ups and downs. I don't think it'll have much influence on your deco obligation if you are of good health etc. Richard Buchaly posted some agressive profiles on some list where they go from 90m to 12m 3 times in a single dive and had no symptoms. I think that if you have good awareness and practice calculating your average depth that'll give you a good idea of your deco obligation. As far as i see it your problem is that you have to lead divers that might not be fit to dive per our standards and hence needs a profile with a lot more padding. You could make your profile more conservative, taking into considaration your guests health, fitnesslevel and other factors and you migth end up doing a safer dive then you would using your buhlmann of RGBM algorithm. Quote: (Originally Posted by acqua) we have to dive width computer every time , we need to demonstrate our profile in case of incident , so mine is just a question .. unfortunately I use a computer (in guage mode) and i log my profile. If you have to run your computer in computer mode you can always have a timer on your arm and stick the computer in your pocket. But that might scare some of your guests and label you as one of those cowboy dive instructors Cheers Jonas

May 12th, 2006, 06:02 PM	#3 (permalink)
GoDiva(Offline) New Member Join Date: Dec 2005 Location: Belgium Posts: 540	Quote: (Originally Posted by eric) I don’t think that it would even be possible to get into deco while leading a group of single tank divers on 32%. I guess you need to be more conservative with your dive planning in this case though. Of course it is, certainly if you do 2 or 3 dives on a day. And if you have "annoying tourists" with low gas consumption ;-). My diving on wrecks in Coron, Philippines, was limited by NDL. I was very happy I combined that trip with a Nitrox course, as this definitely gave me more time to enjoy everything.

May 13th, 2006, 12:54 AM	#4 (permalink)
GoDiva(Offline) New Member Join Date: Dec 2005 Location: Belgium Posts: 540	Quote: (Originally Posted by eric) I guess it depends on what bottom time you consider NDL. Well, max depth of 30m, with an average of 25 and this for more than half an hour would get you pretty near anybody's definition of NDL. If you then do a second dive that day, you run a big risk of needing deco.

May 13th, 2006, 02:33 PM	#6 (permalink)
Martin Burnard(Offline) New Member Join Date: Nov 2005 Location: Plymouth, UK Posts: 580	With a SAC of 12 l/min on a easy going dive, a full 230 bar fill to start with, deco is looming and still there is gas in the 12ltr cylinder of 32%. Square profile dive to 30m on my twin 12 ltr, just avoiding going into deco (40 minute dive) used 70 bar. Water temp 9 degrees, vis 8m, no current. Hence I can see your concern as a dive guide! But I guess somebody who has a low SAC is probably an experienced and/or competant diver. So computer it is, and it covers your ass!! My 2p worth.

May 13th, 2006, 03:13 PM	#7 (permalink)
graham_hk(Offline) Pinoy ako pinoy Join Date: Nov 2005 Location: here, there and everywhere Posts: 779	If your guiding you will find it difficult to go into real required stops. Most guided divers are not going to have the kind of RMV needed for this to happen on 32% and, futhermore, if your guiding you tell them what to do. I would keep it to 25min on the bottom and 30m max do a nice slow (atleast 10min) ascent from every dive (perfect if you're on a wall or where the dive permits) and give yourself a decent surface interval. You could do 4 dives and be nowhere near "deco" required stops - suggest you build up to this and see how your feel - your body will tell you when your kicking the ass out of it. Graham