Multi-level diving

[TMet]

Have a few questions about multi-level dive planning. A little bit of history, I have taken this specialty, so I am familiar with the basics. It's just been a while. I currently dive from a computer when doing multilevel but I would like to be able to plan them before hand for practice. I would also like to take my tables with me as a backup. I don't have a wheel and I'm having trouble finding one. Can I just use the standard tables for planning it with a SI of 0? I tried planning a few and want to see if my math is right and see if its possible to do it this way.

Here is one example I tried.
Hypothetical dive on AIR, Planned depths of 100' (10min) 50' (30min) then 20' (20min).

After the dive at 100 it shows me being a D Diver, ascend to 50' and stay for 30 minutes puts me at an H diver (30 min BT and 29min residual) ascend to 20 feet and stay for 20 minutes. This shows I still get out as an H diver (279 residual and 20 min BT)

Seems to make sense to me, am I way off on this?.
I'm going to continue to dive my computer until I talk to my instructor about doing it this way. But, I would like some input from some of the more experienced divers on here as well .

Thanks,
Terry

 

[Peter Guy]

[I'm sure to be flamed for this response.]

a. If I was that concerned I'd just "ride the 'puter" and accept the results of its algorithm.

b. If I didn't want to "ride the 'puter" I'd depth average and then decide the 20 minutes at 20 feet cleared any "deco obligation" I had so I wouldn't worry about it. Re the depth averaging -- my time weighted depth would be just under 65 feet (I'm averaging the depths at 5 minute intervals, 2 at 100, 6 at 50 which is 500/8=62.5 rounded to 65). I suppose you could then add in the 20 foot segment which would yield a 50 foot average -- but really, the 20 minutes at 20 feet is mostly offgassing.

BTW, I used your number on the eRDPml and Brock's iScubaPlan and the eRDPml tracked with iScubaPlan for the first two segments but then violently diverged with the 20 foot level. The "erpl" had me ending as a "T" with a mandatory SS while iScubaPlan had me ending as a "C" -- I'm sure that is a result of the erpl NOT giving any credit for being at 20 feet and assumes 20 feet is 35 feet.

 

[H2Andy]

one good thing about planning multi-level dives without a computer is that it will force you to "plan your dive and dive your plan"

it is a lot easier with a computer, yes.

what i do (since i am lazy) is that i know what my max depth for the dive is going to be and i know my max time there before diving. at some point prior to reaching that limit, i will begin my ascent, knowing that as i ascend, i am extending my NDL.

at that point, i keep track of my remaining NDL as shown on the computer and adjust the rest of the dive accordingly.

this is frowned upon by people who call it "following the computer blindly" but it is practical and it works for me

(this is for non-deco dives, of course)

 

[TMet]

one good thing about planning multi-level dives without a computer is that it will force you to "plan your dive and dive your plan"

This is my purpose exactly. I plan on doing adv. nitrox/deco in the next 6 months to a year, I want to be used to diving a strict plan long beforehand. My goal is to have the computer as a guideline to catch a mistake mid-dive if I make one. But basically dive from a BT and plan, with tables brought along to do on-the-fly adjustments during the dive.

I'm really comfortable doing the types of dives I regularly do, it's time to add a little more to my dives to keep me on my toes and keep learning.

 

[Kern]

This is my purpose exactly. I plan on doing adv. nitrox/deco in the next 6 months to a year, I want to be used to diving a strict plan long beforehand.

In that case why not get some desk top deco software to plan your no stop multi level dives.

That way you are also going to be in front of the curve when it comes to planing your deco dives in the future.

 

[TMet]

I'm a step ahead of you. I've been using V-planner for the last couple of days to check my hypothetical profiles to make sure I don't run into Deco.

The more I think of my OP I guess I'm just looking some verification that my math and thinking are right so I can be confident that I can make changes on the fly (simulated problems, or just seeing something neat and wanting to spend some more time at my current depth) and use standard tables to make those changes in water for practice instead of relying on the computer.

Anyway, I think I'm on the right track. I'll give it a shot this weekend for real (computer backup of course).

Since we're on the subject anyway, I'd like some opinions if I'm going about my preparations for more advanced diving in the right way. Maybe some other drills that would be beneficial. (Probably should start a new thread in the tech forum for this I guess)

Thank you all for the help!

 

[Doc Harry]

Have a few questions about multi-level dive planning. A little bit of history, I have taken this specialty, so I am familiar with the basics.

If you have taken the specialty and are familiar with the basics then you should already know that you cannot plan multi-level dives using the standard dive tables.

The standard dive tables were never meant for planning or executing multi-level dives.

For planning multi-level dives you need to use "The Wheel" or other dive planning devices that are designed specifically for multi-level dive planning.

Some combinations of multi-level diving are not permitted. For instance, you cannot start out at 140 feet and then ascend to 120 feet, you have to ascend all the way up to at least 90 feet. (I don't have the wheel in front of me so the numbers may be a bit off.)

You would never know that certain combinations were not permitted if you tried to plan a multi-level dive with standard tables. That's why all agencies teach that you cannot use standard dive tables to plan multi-level dives.

 

[TMet]

You cannot plan multi-level dives using the standard dive tables. The standard dive tables were never meant for planning or executing multi-level dives.

That is exactly what I'm looking for. I'll try to find one then. Thank you.

 

[Interceptor121]

Computers only give you the NDL for your next dive, as you will recall from your multilevel specialty course you need the wheel or a computer software to plan multilevel dives, as RDP tables are meant to be used for a single dive non multilevel.
So you have three options:
1. Find a wheel on ebay -- Not recommended
2. Procure a computer software for your PC/PDA/Tablet
3. Buy the PADI eRDP multilevel - this is also available as PC version as training aid and is a cheap alternative to 2 if you take a laptop with you on the boat

 

[halocline]

I like the wheel. One nice thing about it is that you can step on it, toss it in a bucket of water, and it still works. It's worth getting one. Who knows, maybe an EMP bomb will go off during your next surface interval, and unlike your computer/software dependent friends, you can keep on diving.

There are some accuracy issues with some wheels; I think there was a batch that printed just a little off. The end result is that with some problems you can read the wheel perfectly and end up one pressure group lower than the PADI answers in the DM book. IMO that's not a deal breaker, it's still a useful device in a pinch, and in real world situations you are rarely pushing NDLs that closely.