GUE (and other non-PADI) Open Water Standards for No-Deco Limits

[eelnoraa]

Arent we talking about open water non-deco dives here?

 

[tursiops]

I hope so, we are in the Basic Scuba forum.

 

[PfcAJ]

I plan a dive to 180 ft for 30 minutes. The average depth is 90 ft. What run time can I use at the average depth to compare the two dives. What's the procedure?

What?

So you hopped in then water expecting 180ft but got 90ft instead?

Pls rephrase your question. At present it doesn’t make sense to me.

 

[Ryan Neely]

I might be wrong, but I think what @EFX is asking is:

If he planned a dive to 180 ft for 30 minutes, a chart for no-decompression limits is going to give one set or readings.

What if that planned dive became more of a multi-level dive where he spent 5 minutes at 180 ft., 10 minutes at 90 ft., and 15 minutes at 45 ft. (or something similar) so that his average depth ends up being 90 ft.

Since it has been suggested that the GUE tables run off an average depth, or that using average depth as a means of calculating no-decompression is perfectly valid, how do these two dive profiles compare? According the graph above, using the average depth of 90 feet for 30 minutes makes you a "G" diver. Surely that isn't the same for the original planned dive.

For what it's worth, if @EFX isn't asking the question, I am. Using an average depth doesn't make a lot of sense. It almost feels like reverting to the old Dive Wheel would be more accurate ... but I'm new so I don't really know anything.

 

[eelnoraa]

I might be wrong, but I think what @EFX is asking is:

If he planned a dive to 180 ft for 30 minutes, a chart for no-decompression limits is going to give one set or readings.

What if that planned dive became more of a multi-level dive where he spent 5 minutes at 180 ft., 10 minutes at 90 ft., and 15 minutes at 45 ft. (or something similar) so that his average depth ends up being 90 ft.

Since it has been suggested that the GUE tables run off an average depth, or that using average depth as a means of calculating no-decompression is perfectly valid, how do these two dive profiles compare? According the graph above, using the average depth of 90 feet for 30 minutes makes you a "G" diver. Surely that isn't the same for the original planned dive.

For what it's worth, if @EFX isn't asking the question, I am. Using an average depth doesn't make a lot of sense. It almost feels like reverting to the old Dive Wheel would be more accurate ... but I'm new so I don't really know anything.

We need to take things in context. GUE min deco dive's definition specify the max depth needs to be within 100ft. Gas need to be 32% or 30/30. With in this constraints, the min deco table specify the average depth and bottom time limit.

To plan a dive to 180ft under GUE teaching, we are taking about a T2 (or T1 plus these days) kind of dive. The gas will be 18/45, min deco table definitely doesn't apply.

 

[elgoog]

You can't apply a table or formula designed for recreational min-deco dives with max depth of 100ft using EAN32 or 30/30 to what is very much a technical dive with mandatory deco going down to 180ft, regardless of what your average depth is.
You've exceeded the parameters of that table's usable range by a significant amount - depth and gases used (hopefully you didn't go to 180ft using EAN32 - that's a ppO2 of 2.1)

Also, using average depth with this table or formula is more aggressive than using max depth - that's explained very clearly when you take Fundies and we went over various dive profiles and discussed what makes sense to use when. How aggressive is it? Considering that the depth and time exposures we're talking about for recreational dives, the difference between the two may not be as significant as for a dive that's planned to be significantly deeper and longer. For me, I've done >200 dives using that exact formula and average depth. If you stay in the range it's intended for .i.e. max depth 100ft, EAN32, it works just fine with average depth.
It does for me anyway - if you find you're not feeling so great using average depth, use max depth. This was also discussed in Fundies.

EDIT: @eelnoraa beat me to it

 

[Storker]

Thinking that dive planning can only be done with printed tables and not software or computers is so last century.

But still quite a bit faster

In my job, an advanced computer program is often the right tool for the job, but sometimes the right tool is a pen and a pad of paper. I prefer using the right tool for the job, no matter if it was invented last year or two thousand years ago.

EDIT and to the OP: I believe that teaching tables still is at least encouraged in our CMAS 1* syllabus. I happen to agree, since I also believe that it's quicker and easier to internalize the NDL trends by working the tables than by pushing buttons on a computer

 

[ChuckP]

Out of curiosity - we’re doing an explorer dive tomorrow, using 32, guessing average bottom depth of 100’, bottom time of 60 minutes - using 80 for deco. I use MultiDeco for planning, what’s GUE tables say I should do?

Before we bang on the 80 bandwagon - there’s reasons for it - limited tanks, transfilling to reduce tank fill costs. This is Cozumel, I can stay deep for whatever time and go shallow to continue the dive - ideally we’d always use 50 to get on early but you can’t transfill that so...... it’s an experiment in progress.

 

[elgoog]

There's no GUE table for 32% with 80% deco - the only full table is the one linked earlier in this thread (MDL, <100ft, 32%).

There used to be tables for Tech 1 and Tech 2 type dives but they were more like expansions of the 1:1 and 2:1 ratio deco formulae from when it was called ratio deco. I doubt they are current any more but someone who has done those classes recently could chime in. I think I have those tables downloaded somewhere, if I find them I'll upload them to this thread.

The GUE approach would be the one you're using - use a deco planning software to cut tables for your exposure and gases used.

 

[barth]

Out of curiosity - we’re doing an explorer dive tomorrow, using 32, guessing average bottom depth of 100’, bottom time of 60 minutes - using 80 for deco. I use MultiDeco for planning, what’s GUE tables say I should do?

No tables, just use multideco. We did the same when we were planning a dive during tech1.