Computer VS. Tables

[boulderjohn]

My bad. 1 minute stop every 10 feet. 10 feet per minute ascend. My mistype. It's this metric/imperial mess. Keep multiplying everything by 3.

In that case, using that Baltic Lite program will get you to the surface faster than V-Planner, if that is what you are looking for.

My quick calculations say that you will need about 33 cubic feet to make that ascent, assuming you used your buddy's pony after yours ran out, you should still have a cubic foot or two of usable air in his pony when you surface.

 

[mrdre]

....
You seem to be saying that you have already achieved all the skills and knowledge taught in beginning technical diving classes, and from everything else in this thread, I gather you did so without the help of any instructor.

....

Now, are you saying that all other recreational divers have achieved this level of skill and knowledge on their own as well? You seemed to be saying that everyone should all follow your lead in not paying attention to NDLs and doing deco dives on their own--or isn't that what you have been advocating?

Well.. with instructor.. But I didn't have much problem. Here is what I'm thinking. I would advocate for anybody to treat every dive as deco dive and do the deco stops as tech divers do. It teaches discipline, it's a good training. I'm NOT advocating crossing NDLs. Whether to cross NDL or not is a personal choice. If the diver isn't crossing NDLs then these deco stops wouldn't hurt, wouldn't they? And it's a good training for buoyancy, air/depth/time monitoring, every OW grad suppose to be able to do, isn't it?

Now here is why I personally think low of NDLs. I know 2 people who developed DCS symptoms who never crossed NDLs, stayed within the recreational diving limits, did "safety stops" etc. With one of them I went on much deeper and challenging dives. I told him "we are gonna ascend as tech divers do, we are gonna use the software, plan it and do it". We did that. We crossed NDL once or twice (I don't remember, but we crossed by couple of minutes), the rest of the dives were within NDLs. He felt perfectly fine. He had another problems after the dives - he didn't have those this time.

So, based on my limited observation, on my reading and understanding, the proper ("tech diver") ascent is much much more important than these pure theoretical NDLs. That's why I personally don't care much about them.

 

[PfcAJ]

Well.. with instructor.. But I didn't have much problem. Here is what I'm thinking. I would advocate for anybody to treat every dive as deco dive and do the deco stops as tech divers do. It teaches discipline, it's a good training. I'm NOT advocating crossing NDLs. Whether to cross NDL or not is a personal choice. If the diver isn't crossing NDLs then these deco stops wouldn't hurt, wouldn't they? And it's a good training for buoyancy, air/depth/time monitoring, every OW grad suppose to be able to do, isn't it?

Now here is why I personally think low of NDLs. I know 2 people who developed DCS symptoms who never crossed NDLs, stayed within the recreational diving limits, did "safety stops" etc. With one of them I went on much deeper and challenging dives. I told him "we are gonna ascend as tech divers do, we are gonna use the software, plan it and do it". We did that. We crossed NDL once or twice (I don't remember, but we crossed by couple of minutes), the rest of the dives were within NDLs. He felt perfectly fine. He had another problems after the dives - he didn't have those this time.

So, based on my limited observation, on my reading and understanding, the proper ("tech diver") ascent is much much more important than these pure theoretical NDLs. That's why I personally don't care much about them.

Wow, 1 anecdote! Such data, very wow.

 

[tursiops]

Wow, 1 anecdote! Such data, very wow.

I'm wondering where his "pure theoretical NDLs" came from. All the ones in the standard tables and computers are highly tested and validated, hardly "theoretical"! He's right, of course, that a good ascent is important, but he seems to not know that the standard 30 ft/min ascent is quite all right.....he's convinced that if he stops every ten feet, whether he needs to or not, he will be better off. Also true, so long as he is doing his short, shallow dives....he tries that on a real tech dive and he'll be on-gassing when he hopes he is off-gassing. Oh well, if he wants to play this way, i don't see any harm, but I do wish he'd take a course and learn what he doesn't yet know.

 

[shoredivr]

mrdre, you are really out of your depth here. Sure, practice all the stops you want to, holding them exactly at 40, 30, 20, 10 ft. In trim. Good
practice.

BUT

don't combine this with actual deco obligations until you get training.

 

[PfcAJ]

mrdre, you are really out of your depth here. Sure, practice all the stops you want to, holding them exactly at 40, 30, 20, 10 ft. In trim. Good
practice.

BUT

don't combine this with actual deco obligations until you get training.

Yup.

You can tell its baloney because he uses terms like "long enough" and "true deco stops" in regards to rec diving. Red flags.

 

[Storker]

From your response you are not using SAC rate to plan a dive but to check a dive you already did.

It may be a language thing (English isn't my native language), but that's wrong. I'm using my SAC rate to check on available bottom time and minimum pressure at different depths, I've made a simple table of min pressure at different depths, and I've compared gas-limited bottom time with NDLs at different depths.

Now, when I'm planning the dive, I know the minimum pressure I need at, say, 30, 25, 20 or 15 meters to stay above rock bottom. I also know that for a simple square profile (or the first, deeper section of a multilevel dive), NDLs, not gas, are limiting my bottom time at any depth from 15-20m and downwards provided my gas consumption is fairly normal.

So I am using my SAC rate to plan a dive, but I do it very simply, using my pre-cut minimum pressure table.

 

[mrdre]

I'm wondering where his "pure theoretical NDLs" came from. All the ones in the standard tables and computers are highly tested and validated, hardly "theoretical"! He's right, of course, that a good ascent is important, but he seems to not know that the standard 30 ft/min ascent is quite all right.....he's convinced that if he stops every ten feet, whether he needs to or not, he will be better off. Also true, so long as he is doing his short, shallow dives....he tries that on a real tech dive and he'll be on-gassing when he hopes he is off-gassing. Oh well, if he wants to play this way, i don't see any harm, but I do wish he'd take a course and learn what he doesn't yet know.

Anything that is not directly measured is purely theoretical. Air in your tank is directly measured. Nitrogen in you - theoretical (albeit backed by statistics and measured on others). I'm not doing tech dives. We were talking about dives within recrational limits. The model was for 100 fsw dive with first stop at 60 fsw.

---------- Post added August 27th, 2014 at 08:19 PM ----------

....

BUT

don't combine this with actual deco obligations until you get training.

I'm not doing tech dives. I was talking about dives with recreational limits, but possibly pushnig NDLs.. And I wanted to hear criticism for that.

---------- Post added August 27th, 2014 at 08:32 PM ----------

...

My quick calculations say that you will need about 33 cubic feet to make that ascent, assuming you used your buddy's pony after yours ran out, you should still have a cubic foot or two of usable air in his pony when you surface.

Correct me if I'm wrong, but this is my calculation:

0.6 * ( ( 60 / 33 + 1 ) + ( 50 / 33 + 1 ) + ( 40 / 33 + 1 ) + ( 30 / 33 + 1 ) + ( 20 / 33 + 1 ) * 9 ) = 14.35 cft. - air required for all the stops.

 

[boulderjohn]

Anything that is not directly measured is purely theoretical. Air in your tank is directly measured. Nitrogen in you - theoretical (albeit backed by statistics and measured on others). I'm not doing tech dives. We were talking about dives within recrational limits. The model was for 100 fsw dive with first stop at 60 fsw.

---------- Post added August 27th, 2014 at 08:19 PM ----------



I'm not doing tech dives. I was talking about dives with recreational limits, but possibly pushnig NDLs.. And I wanted to hear criticism for that.

---------- Post added August 27th, 2014 at 08:32 PM ----------




Correct me if I'm wrong, but this is my calculation:

0.6 * ( ( 60 / 33 + 1 ) + ( 50 / 33 + 1 ) + ( 40 / 33 + 1 ) + ( 30 / 33 + 1 ) + ( 20 / 33 + 1 ) * 9 ) = 14.35 cft. - air required for all the stops.

As I said before, in tech diving we assume it will take you a minute to solve the problem and make the required gas switch at depth. You not only assumed you will make the switch instantaneously, you decided you would arrive at your first stop instantaneously. If you have a catastrophic gas loss at 100 feet, you are not one second later breathing calmly from your pony at 60 feet, as you assume you will be, unless you have the benefit of some kind of unexplained magic. We also assume stress will elevate your SC rate, so we do not assume that you will be breathing at a calm everything-is-wonderful SAC rate--we assume 1.0 per minute. But you have made it clear that you are not interested in training or what people have learned doing this stuff over the last decades. You know more than anyone else in the world of diving, and you will not be deterred. I think you should go on doing what you are doing. I won't bother you any more.

 

[mrdre]

As I said before, in tech diving we assume it will take you a minute to solve the problem and make the required gas switch at depth. You not only assumed you will make the switch instantaneously, you decided you would arrive at your first stop instantaneously. If you have a catastrophic gas loss at 100 feet, you are not one second later breathing calmly from your pony at 60 feet, as you assume you will be, unless you have the benefit of some kind of unexplained magic. We also assume stress will elevate your SC rate, so we do not assume that you will be breathing at a calm everything-is-wonderful SAC rate--we assume 1.0 per minute. But you have made it clear that you are not interested in training or what people have learned doing this stuff over the last decades. You know more than anyone else in the world of diving, and you will not be deterred. I think you should go on doing what you are doing. I won't bother you any more.

Oh... Why so many assumptions? I am interested in learning and training. I don't know more than anyone else, that's why I'm here. If I knew better than anyone else, I'd just do it and wouldn't talk about it. I'd appreciate if you bothered me. You are giving valid points and I want to respond to those.

You mentioned that I need 33 cft and so I'm trying to understand why. The deco stops require 14 cft. I reserved 17 cft for ascend. Plus I planned 17 cft reserve in my tank. Plus I have 19 cft pony. I want to learn where is a mistake in my estimate if I receive so much criticism.

I'm exploring pushing NDLs a little in exchange of doing mandatory stops - I'm not talking about tech diving, I'm not talking about hours of deco obligation. I'm talking about 5-10 minute decos just like in the example we talked about. I'm not looking to convince anybody. I'm not trying to prove anything. I'm just giving arguments and want to hear other arguments against. Maybe I'm doing something wrong. So I'll stop doing it. I want to know what are the risks, is taking those risks worth it, etc. If risks are too high - I won't do it, if low - meh. That's all.