Average depth finder

[CAPTAIN SINBAD]

What about the UTD Table are you planning to test? NDL/NoStop or light deco on backgas or Oxygen?

The minimum-decompression table I posted above. Nitrox 32.

 

[Kevrumbo]

When I was with UTD, I used a Uwatec bottom time and used its average depth feature for those calculations. Near the end of my UTD experience, though, Andrew said that was not the right thing to do, because he said the time descending should not be included in that average. You were supposed to start averaging once you had reached your bottom depth. This was to be done by checking your depth every 5 minutes and maintaining a running average of those 5 minute checks in your head. That was considered to be a far better system than using a computer for calculations, because unlike the human mind, computers are capable of making mathematical errors. I don't know if they are still advocating that system for averaging.

It is a good idea to carry a computer in gauge mode, whether it shows you the average depth or not, so you can later compare what the computer thinks you did on your dive with what you think you did on the dive. You should have seen the case of two friends of mine. The graph of the dive shows them hitting their planned bottom depth and then drifting slowly downward until they did their first 5 minute check and returning to their planned depth. Then they would drift down, check their depth, and go back up. They did that throughout the dive. They later decided that the computer thought they were on average about 8 feet deeper than their calculations. Who knows which was right? (They were, of course, looking at the log to try to figure out why they got bent.)

Was the planned profile on the MDL Table or a RD schedule (or Cascading RD)?

 

[boulderjohn]

It is a part of a dozen or so experimental / test dives I plan on doing this winter. Testing a few profiles generated by conventional US navy tables against depth averaging tables against Buhlmann with gradient factors.

What about the UTD Table are you planning to test? NDL/NoStop or light deco on backgas or Oxygen?

The minimum-decompression table I posted above. Nitrox 32.

How will you test it? What will you learn, and how will you learn it?

 

[boulderjohn]

Was the planned profile on the MDL Table or a RD schedule (or Cascading RD)?

It was an RD schedule. They thought their average depth was 150; the computer had it different. The computer also made a couple other mistakes (i.e., showed a different dive profile than the one they thought they did.)

 

[rhwestfall]

The computer also made a couple other mistakes (i.e., showed a different dive profile than the one they thought they did.)

 

[stuartv]

It was an RD schedule. They thought their average depth was 150; the computer had it different. The computer also made a couple other mistakes (i.e., showed a different dive profile than the one they thought they did.)

Those dang computers! It was probably narc'ed and didn't even know it.

 

[Kevrumbo]

The minimum-decompression table I posted above. Nitrox 32.

Test the repetitive dive paradigm in comparison to the other models: Minimum SIT 60min, recommended 90min; Min Deco 10'/3m per minute ascent starting at 50% max or ave depth and double stop time at 30'/9m, 20'/6m and 10'/3m depths for repetitive dives.

Take a look at this Table and following thread for reference as well:
Printed from DIR-diver.com ⓒ 2002-2014 Peter Steinhoff

"averaging" table NDLs and multi-level diving

 

[CAPTAIN SINBAD]

Those who are saying why not trust a computer and wear another computer for back-up? Depth averaging appeals to those who reject the idea of No Decompression Limits. In other words, they believe that every dive is essentially a decompression dive and must end with staged decompression stops. The concept became popular after Doppler research confirmed the existence of bubbles in people who would be "safe" by computer standards.

Here is the post written by everyone's beloved TsandM (Lynn Flaherty). May her soul rest in peace ...

"The concept of "minimum deco" comes from the idea that there really is no such thing as a "no decompression" dive. ALL dives involve absorption of nitrogen, and offgassing or decompression. "No deco" dives are the ones where the M-value line intersects the surface, and staged decompression dives are the ones where you hit the maximum M-value before you get there. A pure Haldane/Buhlmann dissolved gas approach will drive you shallow very quickly, and have you sit shallow to offgas. "Shallow", for a no-deco dive, is the surface.

Bubble models introduce deeper stops and slower ascents. I believe NAUI is now suggesting that even "no deco" dives should have a brief stop at half maximum depth.

The MDL tables we are given as DIR divers are derived from Decoplanner, for the times that give an ascent profile with one minute stops from half maximum depth. Therefore, our ascents are at 30 fpm to half maximal depth (or half average depth, depending on where the ascent begins) and 10 fpm thereafter. This is often accomplished by a "thirty second move, thirty second stop" strategy, which I suspect is what your buddy was doing. We often also do two minutes from ten feet to the surface, if conditions permit.

Because we have built decompression into our model, we are able to do some depth averaging to determine the total time we can spend at depth. The tables built and taught by other agencies are made with other assumptions, which is why you are taught to take the maximum depth of the dive and run your tables from there. But it has never made a great deal of sense to me (nor is it the way any of my computers has run) to consider the entire dive done to 130 feet, if we went down there for two minutes, and spent the majority of the rest of the dive above 60.

You are not required to accept this approach to diving, but there are a lot of people using it and diving actively around the world with an excellent safety record."

 

[JohnN]

You are not required to accept this approach to diving, but there are a lot of people using it and diving actively around the world with an excellent safety record."

I would suggest there are a lot more people that dive by following their computers with an excellent safety record.

 

[stuartv]

Those who are saying why not trust a computer and wear another computer for back-up? Depth averaging appeals to those who reject the idea of No Decompression Limits. In other words, they believe that every dive is essentially a decompression dive and must end with staged decompression stops. The concept became popular after Doppler research confirmed the existence of bubbles in people who would be "safe" by computer standards.

People are, by and large, "safe" by the only standard that REALLY matters, too, right? They don't get bent. Even the ones doing multi-day repetitive diving. Right?

I've read some posts that RD is supposed to give ascents like using GF 20/85 or something like that, right? So, what is to be gained versus simply using a computer with GF 20/85? And, if you like, when the computer says no deco is required, still doing the very slow ascent (with "stops" - 10fpm, 30 seconds move, 30 seconds stop) as Lynne described?

From what I can tell, there is NOBODY that is trying to make a case that on-gassing or off-gassing is linear. So, doing anything based on an average depth will always boil down to a hack that is like a broken clock, right twice a day. It may get you out unbent every time - in which case it's more conservative than necessary a LOT of the time. Just like using PADI tables. But that's sort of moot, because it doesn't get you out unbent every time - and I know you don't need me to post links to threads where RD divers got bent. Heck, boulderjohn already mentioned on case of it in this thread already. Saying, "well that's not RD's fault. They didn't follow it right" doesn't matter (to me). They got bent because their "computer" (between their ears) didn't work right. And that kind of computer failure is a LOT more common than an electronic computer failure. And near-infinitely more common than having two electronic computers fail on the same dive.