planning a multi-level dive with a dive table

[the_explorer]

I was wondering if you can apply a dive table for square profiles to planning a multi-level dive.

My thinking was that if I plan a multi-level dive as if I were planning for multiple dives, all I need to do is use 0 minutes as the surface time to calculate my NRT at the end of the first depth. To be conservative, I'd bump myself up to the next pressure group. I'd then repeat the exercise at the end of every level.

Can you actually do this or is there something inherently unsafe to this practice?

 

[Dive the World]

It could get complicated really quickly - depending on how many levels. The more levels you add the more likely you are to make a mistake with the numbers.

Get a computer (with Nitrox) - it will track everything and you will get the most out of your dive. Best investment I ever made.

If you are diving a wall or coral - plan for the deepest as per tables and as you come up slowly you de-gas while still enjoying the views.

That won't happen if you are doing a wreck dive.

 

[DivemasterDennis]

I do this all the time for practice and for scuba refresher courses. There used to be a planner called "The Wheel" that was taught in AOW classes, designed for multilevel dives in particular. But you are right in you method. I am responding without an RDP handy, but assume a dive to 60 feet for 15 minutes, followed by 20 minutes at 40 feet , then 15 minutes at 30 feet. Calculate the pressure group for a 15 minute dive to 60 feet, then determine the rnt for a dive to 40 feet with no surface interval. Add that to the 20 minutes at 40 feet to get the closing pressure group, and then determine rnt for a dive to 30 feet. Add to planned bottom time to determine ending pressure group. You get the idea. But if you have or can get a "wheel," it's a lot faster and simpler once you learn to use the thing.
DivemasterDennis

 

[Pietsweis]

If you are not getting a dive computer I would suggest a ERDPML, electronic tables on which you can plan multi level dives, dive comp is first prize but as far as I am concerned this is the only other option that is very safe

 

[Doc Harry]

PADI says that their dive tables are not to be used for multi-level dive planning.

It may even say that right on the card.

I use my wheel.

 

[Jim Lapenta]

They said that about the erdp as well. It was more bs. All you had to do was put in a 1 minute SI and it worked out the same as tables. You can do multi levels with tables. And I admire someone who has the discipline to do so.

Sent from my DROID X2 using Tapatalk 2

 

[RJP]

I was wondering if you can apply a dive table for square profiles to planning a multi-level dive.

My thinking was that if I plan a multi-level dive as if I were planning for multiple dives, all I need to do is use 0 minutes as the surface time to calculate my NRT at the end of the first depth.

Can you actually do this or is there something inherently unsafe to this practice?

I do this all the time for practice and for scuba refresher courses.

The flaw in the logic is that the Table assumes that you actually SURFACED from the first dive before determining your pressure group - hence the name SURFACE interval. Surfacing from Dive 1 would have you off-gassing longer at shallower depths as you ascended to the surface. So you will actually have a higher nitrogen load in your system than your method considers, even if you assume ZERO surface interval. Further, you will not have a safety stop at the end of your first level where you would offgass even further. Will "being conservative" and adding a pressure group cover this error? There's no way to know...

 

[Paladin]

I have planned multi-level dives using the US Navy tables. When I started diving, that was all we had. As previously mentioned, it can get complicated if you are planning for more than two or three levels. My preference is to plan for the deepest level I intend to reach and plan a square profile. It's simple and conservative. True, it does shorten the bottom time a bit but it is safer.

 

[rhwestfall]

Before computers were "reasonable", I know folks that did that for years. I use(d) my Wheel. Still do ML calculations for the plan unless its a square profile wreck dive. I also still carry "old school" items with me (watch, depth gauge & dive plan based on tables). Yes, the computer gives the "best" result if BT is the concern. Right now, I'm essentially on equal terms between air or NDL limits......

 

[gurnie]

Does PADI still have the wheel? I thought the whole idea of it was to plan multi-level dives?