Logging multilevel dives with tables

[40Fathoms]

I recently spent a week on a dive trip with a bunch of other divers. There, naturally, we discussed a lot diving. One of the topics of discussion was logging multilevel dives and figuring out your profile and pressure group in appropriate tables (PADI, NAUI, you pick).

Since PADI apparently has more or less given up on The Wheel, one diver there suggested that you could log your multilevel dives by treating them as separate dives without surface intervals, e.g.:

A dive goes to 20 meters for 10 minutes.
Then ascends to 15 meters for 10 minutes.
Then ascends to 10 meters for 10 minutes.
Then goes to safety stop and surfaces.

This could be then be logged as one dive to 20 meters for 10 minutes, followed by a dive (with no surface interval) to 15 meters for 10 meters, followed by a final dive (with no surface interval) to 10 meters for 10 minutes. Then you have your final pressure group.

Is this a viable option? I've seen discussions on this around Scubaboard, but haven't been able to find a real conclusion to it.

And I know that there are many of you out there who would just say "stuff the tables, dive with computer only", but I'm old school, as are many of my dive buddies, and we prefer logging our dives and figuring them out using the tables. So while I respect your opinion on tables vs. computers, that isn't the discussion I'm looking for.

 

[DevonDiver]

If it was viable, to the point of being liability free, then why would PADI have spent so much time and effort designed the 'Wheel'?

If you have a wheel... plan some dives both ways... and see whether they correspond...

I was shown how to do this ad-hoc once before. There were enough discrepancies that I never passed it on to students.

 

[BoltSnap]

Since PADI apparently has more or less given up on The Wheel, one diver there suggested that you could log your multilevel dives by treating them as separate dives without surface intervals, e.g.:

A dive goes to 20 meters for 10 minutes.
Then ascends to 15 meters for 10 minutes.
Then ascends to 10 meters for 10 minutes.
Then goes to safety stop and surfaces.

This could be then be logged as one dive to 20 meters for 10 minutes, followed by a dive (with no surface interval) to 15 meters for 10 meters, followed by a final dive (with no surface interval) to 10 meters for 10 minutes. Then you have your final pressure group.

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).

 

[CT Sean]

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.

Are you sure about that? a 30 minute dive to 20 meters should give a vastly different pressure group than either an increasingly shallow multi level dive or 3 individual dives to increasingly shallow depths

 

[Jim Lapenta]

I have done this before using the rdp. My dm instructor had me do it. It works as long as you don't push the ndl's . Get close and things start to go hinky. You can also do it on the erdp by using a 1 minute surface interval between levels. It comes out very close to the wheel. We lie to our computer at work to set cut speeds in the cnc. Doing the same with the erdp. On tables you do start the next level at the end of the previous one and go from there. The problem is having the discipline to stay with the plan to the minute. Go over at any level and you can get into trouble quickly. I haven't looked at this in awhile. Need to go back to my dm notes and find the exact steps. Do not try this at home unless you have been shown the exact steps. I may have left something out in the procedure. I use square profiles for ow students and for myself it is them, v planner, then my dive comp.

 

[Blackwood]

Just a brief word of caution: the surface interval/repet table is predicated on you returning to the surface between dives.

In the example profile, the table would be tracking decompression which isn't actually occuring (i.e. during ascents from 20m to the surface and 15m to the surface). Is it enough to bite you? Probably not, but maybe.

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. YMMV.

 

[oly5050user]

I recently spent a week on a dive trip with a bunch of other divers. There, naturally, we discussed a lot diving. One of the topics of discussion was logging multilevel dives and figuring out your profile and pressure group in appropriate tables (PADI, NAUI, you pick).

Since PADI apparently has more or less given up on The Wheel, one diver there suggested that you could log your multilevel dives by treating them as separate dives without surface intervals, e.g.:

A dive goes to 20 meters for 10 minutes.
Then ascends to 15 meters for 10 minutes.
Then ascends to 10 meters for 10 minutes.
Then goes to safety stop and surfaces.

This could be then be logged as one dive to 20 meters for 10 minutes, followed by a dive (with no surface interval) to 15 meters for 10 meters, followed by a final dive (with no surface interval) to 10 meters for 10 minutes. Then you have your final pressure group.

Is this a viable option? I've seen discussions on this around Scubaboard, but haven't been able to find a real conclusion to it.

And I know that there are many of you out there who would just say "stuff the tables, dive with computer only", but I'm old school, as are many of my dive buddies, and we prefer logging our dives and figuring them out using the tables. So while I respect your opinion on tables vs. computers, that isn't the discussion I'm looking for.

Not a good idea ..RDP table version not designed or tested to be worked that way.Not woorth the risk.You will not get the proper answers as compared to when you use the proper tool for the job.Wheel is discontinued ,but the ERDPml is available. Just use a computer as the rest of the world does.It is cheaper to buy a computer today,prices have dropped drastically, than to buy a watch and depth gauge.

 

[40Fathoms]

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.

 

[40Fathoms]

There are courses that teach divers how to compute multi-level profiles on the fly. I suggest looking into one of them.

Do you know the names of any of these?

 

[Blackwood]

Do you know the names of any of these?

Ratio Deco - Unified Team Diving

, but there will be no pressure groups to log so that may not fit your bill.