Long stops

[Wreckie]

Have been playing around with v planner and deco planner but i have a feeling they are set to mega safe, im after some more realistic settings.

I've already set v planner (i think) to zero conservatism and have run the following dive: 51m 20 minutes on air.

BSAC 88 tables get me out of the water in 10 minutes

Now both the above programs, deco ing on 80% have me doing more than double the stops, am i missing something?

Please no 'you shouldnt be doing that on air anyway' there are other and more complex reasons for that profile that i cant do anything about.

thanks

Mike

 

[MikeFerrara]

What are your decompression goals? Is there a reason to get our of the water in a hurry?

There are distinct differences between the models used by the tables and softwares you mentioned. How did you choose them?

What gradient factors did you use with decoplanner and why?

I never looked at the BSAC tables but my guess is that the VPM and decoplanner schedules started decompression deeper. Which is more in line with your own decompression strategies?

I don't mean to cut the answer short but it sounds like you're missing a great deal. There's a lot more to it than total decompression time.

 

[MikeFerrara]

BTW, Ross Hemmingway maintains a web page and discussion board for vplanner. He also has a database of dive results. I haven't watched it lately but prior to some changes I think some divers had less than optimal results using nominal conservatism settings.

None of this stuff is mega safe. VPM is free. I doubt you'd have much luck taking Ross to court and I don't think he has the software fudged to keep you in the water all day so it's impossible to get bent.

If you're looking for a magic answer on preprinted tables or in a software package you won't find it. It's just a tool. We have to do the thinking.

 

[Wreckie]

No reason to get out of the water in a hurry, i have nothing against hanging around, having 'unbent' a few people in my time i have no wish to trade places with them.

The software i was lent to play around with (which is what i was doing), the tables were chosen because they happened to be laying around, i could equaly have chosen USN or any of the derivatives, but they would have had me out of the water faster again.

Yes the software stops deeper, bsac at 9 and 6m. first stop for the software was, from memory 27m, however they almost double the 6 m stops (which is what eats up the time).

I realise that time isnt the be all and end all, but the main point i was after is, why over twice as longe with a rich deco mix?

Now gradient factors, i used the default settings, this could be why the discrepency, where can i find out what settings i can use?

Mike

 

[Waterlover]

Maybe take some training from a knowledgable instructor ..........

 

[DeepScuba]

Nice one waterlover!!.........Kick him in the (sorry Mike F!!) again!!

Ya see Mike, I'm learning!!!

"Proper Instruction" as you say, in this area is basically, "be safe".

Well thanks, but it doesn't help much in the particulars.

I think his questions are valid, and I for one am waiting to see the possible reasons for them myself!

I have fooled with the software vs. tables myself, and have found measurable differences, with the software being much more conservative.

 

[MikeFerrara]

I can't address the BSAC tables but...

decoplanner uses buhlmann with the addition of gradient factors. For a complete explaination of gradient factors check out E. Bakers paper. I don't remember the title but you can find it on the GAP software web site.

In briefe though the lower gradient factor specifies how close to the leading compartments critical tension or "M" value you can get. The default for that software is 30%. This has the effect of starting stops deeper. The upper gradient factor controls the same thing at the shallowest stop and the gradient factores used inbetween fall on a linear scale between the two. The default upper gradient factor is, I believe 85% which has the effect of keeping you in the water longer. If both gradients are set to 100 you're diving streight Buhlmann (16-B I think).

The overall effect on the profile is that the stops start deeper and the large gradient between the bottom and the first stop is reduced and the curve is smoothed overall.

Starting stops deeper is thought to prevent initial bubble formation/growth. Gradient factors are an attempt to address gas in the free phase without any free phase gas math in an absorbed gas model.

Also see "Technical Diving in Depth" and "Understanding Deep Stops" (also on the GAP site)

Stop over to the Vplanner discussion board and direct questions to Ross who wrote Vplanner.

 

[Waterlover]

DeepScuba once bubbled...
Nice one waterlover!!.........Kick him in the (sorry Mike F!!) again!!

I knew someone would like it

 

[DeepScuba]

I love this place.

 

[100days-a-year]

USN had that at 160' 20 min 20' stop 3min and 10' stop 11min.VPMB at 0 conservation gave me 19 minutes less deco with 80%.The chances that you match the empirical dataset criteria for the USN tables are slim and I feel the tables you quoted are even less conservative.The guys who were used as guinea pigs for the USN were 18-25 and in peak conditioning.Keep playing with the software and please get some deco training if you haven't already.