Computerless Multi-Level dives

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QKRTHNU

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Those of you that do multi-level dives without the use of a computer, could you please share how you calculate your NDLs?

I've seen a few different methods while searching the board.

#1. The Wheel (Sounds like using an abacus)

#2. After diving below 3ata spend at least as much time above 2ata (Uncle Pug's method)

#3. I've seen a lot of references to average depth. I'm not sure if people are calculating average depth and then using tables/120 rule and basing NDLs on that or what.

#4. Use tables and figure a no-surface-interval repetitive dive to calculate the multi-level profile.

#5. Read the tables sideways (When I compared this method with the others it only matched up if I used the next deeper depth column for successive levels, which made it very close to option #4.)

BTW, I do plan on purchasing and using a dive computer. I just would like to be able to do without it if need be. And double check it for my own peace of mind.
 
I hope we get some solid feedback on this for I am pondering the very same thing. I just earned my Advanced Open Water and I have ordered a decent dive computer. However, I dont want to be a brainless diver.

I would like to be able to calculate rather straight forward multi-level-dive-plan using the PADI RDP. I KNOW it can be done. It was demonstrated to me months ago but, at that time I was not prepared to take in the procedure.

My ideal is to able to create a simple multi-level dive plan -Example: 90ft-60ft-40ft lets say 15 min at each? Can this be done..can anyone explain using PADI RDP how you can evaluate this and how long you need to spend at 20-15 ft?..Show me the money baby...:think: :cheer:
 
QKRTHNU once bubbled...
Those of you that do multi-level dives without the use of a computer, could you please share how you calculate your NDLs?

I've seen a few different methods while searching the board.

#1. The Wheel (Sounds like using an abacus)

#2. After diving below 3ata spend at least as much time above 2ata (Uncle Pug's method)

#3. I've seen a lot of references to average depth. I'm not sure if people are calculating average depth and then using tables/120 rule and basing NDLs on that or what.

#4. Use tables and figure a no-surface-interval repetitive dive to calculate the multi-level profile.

#5. Read the tables sideways (When I compared this method with the others it only matched up if I used the next deeper depth column for successive levels, which made it very close to option #4.)

BTW, I do plan on purchasing and using a dive computer. I just would like to be able to do without it if need be. And double check it for my own peace of mind.

A couple of thoughts:

1) The Wheel is dead easy and it works.

2) If you're thinking of using the Uncle Pug method then you should plug it all into a spreadsheet and verify it. My gut feeling is that this idea would be supported by the Wheel provided you didn't go over your NDL at any point during the dive.

3) I'm not in favour of the average depth method. Even if you had an instrument displaying your average depth (which you don't) and you were sure you didn't go into deco at any point during the dive (which you aren't) then you *still* won't know your average depth for the *whole* dive until you surface at the end of the dive. In other words you can't hang any kind of dive plan on this method. If you're going to do this then it quickly reduces to diving with a computer and just doing what it says.

4) Method 4 probably gives you the same results as the Wheel. The table form of the RDP takes your ascent into acount in the calculation too so you might need to use the next higher group to start calculation on the repetative dive. Seeing if it would work would take a little verification. Also, if you know the wheel you know you can't just tack any two repetative depths into a multi-level dive. The depths need to be in a certain range and you'd have to use those ranges with the RDP too if you want similar results.

I've never seen method 5 used. How do you do that?

R..
 
Method 4 and 5 are the same thing.
 
I think the best and more reliable method would be the wheel, wich I agree looks odd, but it´s really simple, even easier than tables once you know it.
 
Method 4 and 5 are the same thing.
Seems like it would be, but you end up with different results since table 3 isn't used in method #5.

For example:
USN tables
90ft - 20min Follow by 40ft.

Method #4 would give remaining ND time of 139min @ 40ft
Method #5 would give remaining ND time of 150min @ 40ft

I'm guessing diving method #5 would not be wise.

I'm not in favour of the average depth method. Even if you had an instrument displaying your average depth (which you don't) and you were sure you didn't go into deco at any point during the dive (which you aren't) then you *still* won't know your average depth for the *whole* dive until you surface at the end of the dive.
The only part of the dive you wouldn't know is the final ascent time. If you calculated average depth without that it would simply be conservative because it would show a deeper average.
 
QKRTHNU once bubbled...

<snip>

The only part of the dive you wouldn't know is the final ascent time. If you calculated average depth without that it would simply be conservative because it would show a deeper average.

You don't get it. Say you start you dive by descending to 150ft. What will your average depth be?

R..
 
Diver0001 once bubbled...


You don't get it. Say you start you dive by descending to 150ft. What will your average depth be?

R..
I see what you're saying.

Obviously we can't fortell the future but we can plan the dive ahead of time and then follow that plan as well as possible.

You would have to make sure you never go past NDL for whatever depth you're at. The first depth is easy, just look at the table. Then once you've changed depth you can start figuring averages.
 
QKRTHNU once bubbled...

I see what you're saying.

Obviously we can't fortell the future but we can plan the dive ahead of time and then follow that plan as well as possible.

You would have to make sure you never go past NDL for whatever depth you're at. The first depth is easy, just look at the table. Then once you've changed depth you can start figuring averages.

Exactly. That's exactly what a computer does. That's why I said that the average depth method reduces down to just following your computer. You can't do this stuff on the fly in your head. It's too much work. Trying doing it narced and you'll be lost beyond hope.

R..
 
Diver0001 once bubbled...


Exactly. That's exactly what a computer does. That's why I said that the average depth method reduces down to just following your computer. You can't do this stuff on the fly in your head. It's too much work. Trying doing it narced and you'll be lost beyond hope.

R..
Like I said, I plan on using a computer. I just want to be able to double check it.

This isn't really "exactly what a computer does". Since the computer monitors each compartment separately.

Has anyone out there compared what the table says NDL is for your true average depth to what a computer gives you for NDL?

Obviously the computer should be more true to actual Nitrogen loading but I'm curious how much of a variance there is.
 

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