Logging multilevel dives with tables

[Mr Carcharodon]

So let me ask a followup question:

Is it possible to calculate your pressure group following a multilevel dive some other way than using The Wheel or a dive computer?

Well as Blackwood alluded to in one of the previous posts you can use ratio deco to calculate if you are within NDL, or the deco you need, without a computer or wheel. There are no pressure groups however. RD uses average depths, set points, standard ascent profiles, gasses and other details that it would better to get in a more formal setting. I believe UTD has an online course on RD now.

 

[BoltSnap]

CT Sean,

I am following NAUI's recommendations on SIT less than 10 minutes.

40Fathoms,

If your computer craps out, you sit out for at least 24 hours (or whatever you computer manual says that you have to do). You really can't go back and forth between tables (or Letter Groups) and computers. If you are not comfortable with that still , you should buy a second computer as a backup. What you are trying to do is not reliable, not efficient and highly error prone.

Please note that I am speaking from a "recreational" diving point of view.

Again, get a computer or two. They are dirt cheap these days. Spend your precious time U/W enjoying your dive and still be safer.

 

[RonMurray]

Thanks for the replies, guys. Seems like it is where I thought it would be: it can be done, but should be done with a lot of caution.

So let me ask a followup question:

Is it possible to calculate your pressure group following a multilevel dive some other way than using The Wheel or a dive computer?

@ BurhanMuntasser: It's not that I don't dive with a computer, it's just that I don't want to rely solely on my computer to do the calculating of my dive profiles on a dive trip with multiple dives each day. I prefer logging them with pressure groups based on the tables as well.

This is exactly what the eRDPml is (the 'ml' is multilevel). It's not a computer, but a calculator that vastly simplifies things for the end user. eRDPml is a set of electronic tables that incorporates the standard RDP tables, the standard multivel tables ('the Wheel'), and since electrons are small, it has an increased time resulution (5 min time increments instead of the 10min increments you find on the the printed tables). But it's still just the tables.

If you want to stay with 'tables' and compute multilevel dives, the eRDPml is the exact tool for which you are asking.

 

[knotical]

and/or see this thread:
http://www.scubaboard.com/forums/ask-dr-decompression/78882-flat-wheel.html

 

[DevonDiver]

Thanks for the replies, guys. Seems like it is where I thought it would be: it can be done, but should be done with a lot of caution.

So let me ask a followup question:

Is it possible to calculate your pressure group following a multilevel dive some other way than using The Wheel or a dive computer?

@ BurhanMuntasser: It's not that I don't dive with a computer, it's just that I don't want to rely solely on my computer to do the calculating of my dive profiles on a dive trip with multiple dives each day. I prefer logging them with pressure groups based on the tables as well.

Get some software. You can get dive planners for PC, IPhone or Android nowadays.

The software used for planning recreational dives, will also be suitable for recreational. Im the event of computer failure, and if you can accurately remember your dive, you could even go back and 'plan' that dive on the software...then plan repetitive dives following it.

When I will be diving the same sites a few times (recreational dives), I often print off a few dive plans from V-Planner or GAP...laminate them and take them down with me. They are usually 'just deeper' and 'just longer'... to provide a resource if I suffer computer failure.

 

[rjack321]

There are courses that teach divers how to compute multi-level profiles on the fly. I suggest looking into one of them. I would personally run that as 15m for 30 minutes.

Ditto. And I have not calculated a pressure group nor used a computer in about 6 years.

 

[Paladin]

In this case you would treat them as a single dive add up the dive time for all of them and use the deepest depth in all of them (20 meters in this case) which gets you back to where you started.

I don't know what you mean by saying "old school" but one needs to stay in touch with today's technology for the same reason no one uses double hose regulators these days (even old school).

Somebody needs to do a bit of research. There are lots of us still using double hose regulators (myself included) and a small industry has grown around supplying the needs of vintage equipment divers. In fact, I'm diving a 1959 DA Aqua Master in my avatar. Check out the vintage equipment divers forum right here on SB.

Us "old school" divers used our Navy tables to plan multilevel dives all the time. Yes, we did count the different levels as separate dives with no surface interval and the system worked for decades before the advent of the computer. That said, it was more convenient (and more conservative) to just use the NDL of the deepest point of the dive and plan the dive on a square profile. But if the dive required the most submerged time at multiple levels for some reason, a multilevel dive could, indeed, be planned using the tables.

 

[Paladin]

CT Sean,

I am following NAUI's recommendations on SIT less than 10 minutes.

40Fathoms,

If your computer craps out, you sit out for at least 24 hours (or whatever you computer manual says that you have to do). You really can't go back and forth between tables (or Letter Groups) and computers. If you are not comfortable with that still , you should buy a second computer as a backup. What you are trying to do is not reliable, not efficient and highly error prone.

Please note that I am speaking from a "recreational" diving point of view.

Again, get a computer or two. They are dirt cheap these days. Spend your precious time U/W enjoying your dive and still be safer.

There is no need to "sit it out" for 24 hours if you know how to use the tables. The switch is easy and painless. Just use the info from your previous dive(s) and calculate from there. Computers are a nice convenience, but they are by no means absolutely necessary. I have one, but I do not depend on it as my only source of information, as some divers seem to do.

 

[BoltSnap]

Paladin954,

Most of the time when using a dive computer the profile and Dive Times U/W do not correlate to tables at all. I can do a dive where the deepest point in the dive is 100 feet but because of the "multi-level" nature of the dive, I could have stayed U/W for an hour. If you try to get back to tables (especially after you have made several multi-level dives), it will be very difficult indeed to get the tables to agree with you. It won't be simple nor painless to convert to tables in this case.

It will be totally irresponsible for a diving professional to tell somebody to ignore their computer's instruction manual especially as related to what to do when the diver computer goes down.

At any rate, I am not sure of what your point is but if you are trying to prove a point that we can still use tables, you are absolutely right. However, as technology advances in all aspects of our lives, it would be not so smart to ignore progress technology brings (although we have the freedom to ignore it) especially when it makes life simpler with less errors and would let us enjoy our time U/W much more than table would allow. If you consider how much money we spend on training, equipment and travel for the precious few minutes U/W, it would make very much sense to spend a couple of hundred dollars on something that would allow us to do more of what we love to do with much more accuracy and safety (assuming you follow the instructions).

 

[Paladin]

I'll tell you what, you go ahead and tie yourself to your technology, and I'll continue to enjoy diving the way I have for 45 years. I have a computer, but I don't need it. It's a convenience, nothing more. If it craps out on me during a dive, I can switch over to tables without batting an eye, including the calculations for multilevel dives. But, then, that's where knowledge comes into play, isn't it?