Info Why are tables not taught in OW classes anymore?

[tursiops]

Is the OP still reading this thread, or has he/she [or whatever] fallen into a coma?
Started off as a good read [and laugh] first few pages, the weird part is I can't stop reading it, back and forth and off topic.
I am going to wean myself off this topic, some here could not agree on the colour of an orange.

I'm the OP. Yeah, I've read all the posts in the thread. And ;posted a bunch of times, too.

 

[Pressurehead]

I'm the OP.

Ok, funny, I thought it was a new diver posting in the "Basic Scuba" area.
So long ago , forgot who the OP was.
Thanks.

 

[Blackcrusader]

On a table all of those dives would have been WAY over the NDL.

I think yes if you took the max depth and said that was a square profile dive. What you cannot see is the actual dive profile. So now I have screenshot the dives and with the lowest NDL showing on these dives. Many of the dives have a quite shallow depth as up on the reef shelfs where a lot of good things to photo and video are.
So not using tables which frankly I do not see anyone doing for NDL dives people just dive using their DC ( or their guide or buddy if they have no DC )

How does seeing the dive profiles now show how DC use in multilevel diving just makes life easier. In my humble opinion you can see I am not pushing NDL limits.

 

[John C. Ratliff]

Blackcrusader,

I like the way you are diving deeper at the first, then tapering it off in shallower waters. One of the things I like about DCs is that you have that graph of the dive. That allows a lot of analysis of the dive.

Now, for all you divers using dive computers (DCs), how much money have you sunk into these instruments? When I started diving in the late 1950s and early 1960s, I was a poor high school student, who had a dive watch that I bought for something like $19.99 and a capillary depth gauge. I earned my money for my first scuba by picking strawberries and beans in the fields near Salem, Oregon. At the time, all you needed was a tank and regulator, mask and fins. You didn’t need certification either, as there were no instructors, so I dove for the first 4 years without certification. I did get a wet suit after freezing on a dive with David Haden, a neighbor, in the North Santiam River, from White Stag when my aunt worked there. My text was Cousteau’s The Silent World, which I think I read about three times.

I don’t think this is a route anymore for entry into diving. But maybe this is why I really like divining in Oregon’s lakes, rivers and estuaries (and sometimes the ocean too), as I’ve always dived these places. A kid cannot afford a tank, regulator, peripherals like LP inflator hose, SPG/Computer, wet suit, and BCD. Tables, a watch and depth gauge are much less expensive than a submersible computer. Kids cannot work picking strawberries anymore, due to concerns about pesticide exposures. So how does a kid get into scuba diving?

SeaRat

 

[jale]

Hi.
We have again this debate about tables
Well at least it keeps SB alive and that is good.
Everybody still insist that table means only square profile even when you have been given examples of tables used for multi-level dive.
Too bad to think that precision means correctness.
Computer like GPS, keyboard and calculator is just a tool and this tool is more than enough for most of the divers.
Now GPS shouldn't give you an excuse for not having a sense of directions, keyboard an excuse for not being able to use a pen and calculator an excuse for not being able to do simple maths in your head.
Computer should then not be an excuse for not being able to do a dve without having a, at least, a 'crude" sense of knowing your position in the "crude" mathematical models in diving.
So tables or DS, it doesn't matter. Just get knowledge and not only information

 

[boulderjohn]

I think, if you'll look at the literature, a very slow ascent can add additional decompression stress, thus increasing the decompression commitment in shallower water. Nitrogen under pressure still is absorbed into the blood stream from the lungs, if at a somewhat slower rate in shallower water.

I used to think that, too, and a search of really old SB threads will show many posts from me stating that with confidence. I now know it is more complicated than that--more complicated, in fact, than anyone really understands.

Four years ago, I wrote an article summarizing current thinking on deep stops in decompression diving. The research on decompression diving says exactly that --slowing the ascent too far by adding deep stops adds to decompression stress on decompression dives. I was aided mightily in my research by Dr. Simon Mitchell. When done, I wanted to write a similar article on NDL diving. Dr. Mitchell said he coiuld not help because it was different, there is not enough good research out there, and he did not have any firm opinions himself. I did all the research I could, and when I was done, I decided not to write the article because it was different, there was not enough good research out there, and I did not have a firm opinion myself.

What I learned was that once you begin an ascent within NDLs, as long as you don't linger deep enough long enough to go into deco, it doesn't seem to make any discernible difference how long you take. When I spoke to an expert at PADI, I was told that when they published the RDP, they wrote that the ascent should be no faster than 60 FPM, which was the commonly used ascent rate at the time. In the RDP research, I was told, they did not find any indication that slower rates were any worse.

In reference to this thread, if you are using a table and begin your ascent, you have absolutely no guidance as to when that lingering crosses the line into a decompression dive. Yes, you can do a multi-level dive, but you will be guessing as to how long you can safely stay at any level. You'll be winging it.

 

[tursiops]

Everybody still insist that table means only square profile even when you have been given examples of tables used for multi-level dive.

The examples of using tables for a multi-level dive are not correct, and it is dangerous to suggest otherwise. You may luck out, but depending on luck is not dive planning or analysis.

Why you can't use the PADI RDP table for Multi-Level dives

The PADI RDP table is designed for square profiles, not multi-level dives. The pressure groups after a dive ASSUME you are going to the surface, and that off-gassing time at a shallower depth is included in the computations. Many, however, have invented a procedure that they think allows them...

scubaboard.com

 

[Vicko]

Dopler readings and blood analyses show less bubbles and less bubble forming sites in the blood of divers who were doing very slow ascents while still well within NDL. It's a shame that safety stops were not included as a lot of people were interested if they helped.
Not sure if the researched ever got published but there was about 10-15 of us in there and they monitored single and repeated dives over a course of few days.
People misunderstand deepstops all the time ignoring the fact that they were created for people who's slow compartments were already fully saturated at their max depth. But even when used the wrong way deepstops at recreational depths are still to shallow to allow any significant tissue loading and in practice help people slow their ascents. Remember that those "recreational" deepstops are usually counted in seconds, not minutes.

 

[boulderjohn]

The examples of using tables for a multi-level are not correct, and it is dangerous to suggest otherwise. You may luck out, but depending on luck is not dive planning or analysis.

Why you can't use the PADI RDP table for Multi-Level dives

The PADI RDP table is designed for square profiles, not multi-level dives. The pressure groups after a dive ASSUME you are going to the surface, and that off-gassing time at a shallower depth is included in the computations. Many, however, have invented a procedure that they think allows them...

scubaboard.com

He didn't get it in the other thread, either. (See post #21.) He thought your post saying you couldn't do it cofirmed that you could.

 

[boulderjohn]

People misunderstand deepstops all the time ignoring the fact that they were created for people who's slow compartments were already fully saturated at their max depth. But even when used the wrong way deepstops at recreational depths are still to shallow to allow any significant tissue loading and in practice help people slow their ascents. Remember that those "recreational" deepstops are usually counted in seconds, not minutes.

Deep stops were not created for people whose slow compartments were already saturated at depth. Your use of the word "slow" first of all confuses the issue because you don't define it. With the exception of saturation divers, people don't ever have the slowest tissues saturated at depth. The theory on deep stops was that they protected the fast tissues from bubble expansion. The problem seems to be that 1) maybe they don't need that protection and 2) while you are protecting those fastest tissues, you are dangerously ongasssing in the midrange tissues that are not saturated.

Many of the people who advocate deep stops for recreational, NDL dives do indeed call from them to be done in minutes, not seconds.