[Reeve]

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<font color='#000F22'>Not totally sure what I'm looking here in terms of response but here goes.

What do you do for your deco stops? Do you perform stops on the fly with say your computer, or do you use Pyle, WKPP etc.  Does anybody use the "M values" information other that just a general understanding? (I know some computers now incorporate some of these models)

Haldanian, Workman and Buhlmann all produced M-Value theories, most of which have been tinkered with by Decoplanner etc and there's a whole plethora of papers on RGBM, Doppler testing, does anyone follow and understand. Less than 50 pages of PDF please.

There's been some talk in the last year or so of reduced descent speed, as rapid on gassing has further problems. Thought please.

 

[Mark Chase]

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A vast question but my personal choice is GF's (Gradiant Factors)

Streight Bhulman tables are 100/100 GF and I run 20 / 80GF

So a vast oversimplification

On the first deepest stop I am 20% over the theoretical maximum off gassing depth and at the shallow stop I am at 80% of the minimum off gassing depth (these are bassed on the M values)

It dosent realy work like that but it gives a general view on what your trying to acheive. The lower the first GF the deeper the first stop will be and the lower the second GF the longer the deco comitment on the shallow stops.

50m for 20mins on air 100/100 = 24mins of deco first stop at 9m

50 for 20 on air 20/80 = 55mins deco first stop at 27m

As for ascent rates I use a slow ascent rate 10m /min up to the 12m stop then slow it right down to a slow as 1m /min from 6 to the surface. I do not include the ascent from 6 in the deco. (Some do)


ATB

Mark Chase

 

[And]

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<font color='#000080'>Hi

I dive as GUE Tech1 recommends which is an on the fly method based on a computer model. We plan the dive and work out the deco and if anything changes during the dive we can extrapolate a deco plan by following a few simple rules. This is possible because we use standard gasses.

M Values are theoretical values, based on the Buhlmann model and various computers use various ways to set conservatism. This is just one deco model. Others are based on bubble theory (VPlanner) or a kind of mixture of both (RGBM, of which Mares have a computer model) They are only models and as such all we have is a general understanding based primarily on empirical evidence.

Exactly what is it you want to know?

Andy

PS Regards Gradient Factors look at Eric Bakers stuff on the GUE website in the DPlan section.Deco Documents

 

[Helen F H]

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<font color='#000080'>I do what my computer tells me  

 

[Reeve]

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<font color='#000F22'>Mark thanks, not sure that information even bounced as it passed overhead.

Andy to answer your question, as I gain more knowledge and my skills improve I've found myself wondering if following the computer deco recommendations, (as I do in an almost reverent manner,) is the best approach.

My diving is just getting me to the area of deco, barely touched double digits. But I'd like a little more information rather than blindly accepting what is displayed. This also stems from doing back up info for slate prior to more planned deeper dives. The options given on the two deco software programs I have (V & Z planner) started me thinking. I'm currently diving with a Cochran Commander Nitrox set with no conservatisum, as I see this as the minimum time I need to spend doing deco or can safely exit the water.

thanks

gareth

 

[Andy Phillips]

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Ah,

Best approach, type decompression theory into your favorite search engine, wait, print, then read.

There is a huge amount of info on it, most of it say's the same thing, but it is all worth reading. Start with Haldane and enjoy.

Andrew

 

[Mark Chase]

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Quote[/b] (Reeve @ Feb. 17 2004,19:52)]Mark thanks, not sure that information even bounced as it passed overhead.

My diving is just getting me to the area of deco, barely touched double digits. But I'd like a little more information rather than blindly accepting what is displayed.

I'm currently diving with a Cochran Commander Nitrox set with no conservatisum, as I see this as the minimum time I need to spend doing deco or can safely exit the water.

First we ALL HAVE to trust the theoretical models. The time spent on the bottom using PADI RDP without going into deco is based on exactly the same theoretical model as the deco dive tables. In fact the PADI RDP is quite an aggressive table and a lot of the NO DECO dives on there would be deco dives if I planned them using 20/80GF

Also note the Cochran Commander is a quite aggressive computer so multi day deep dives on 0 are only for the fit and the brave.


OK try this adaptation of the coke bottle analogy for GFs:

The decompression zone has a top and a bottom depth. The sealed coke bottle is representative of the bottom depth. No more gas can get in the bottle but none can get out. The open bottle top is the shallow depth depth your off gassing like mad but you with theoreticly get bent if you go any shallower.

If we go for 100/100 profile the lid would be open to the max to allow the gas out but not enough for the coke to fizz over. This gets the drink in the glass very quickly but there is a big risk of fizzing and getting a stain on the carpet.

If we go for a 20% profile the lid is opened just a crack and the gas escapes very very slowly and there is little or no chance of fizzing up. Unfortunately it will take ages for the gas to get out and you might get very thirsty waiting for your drink.

So we go for a 20/80 profile.

You crack the bottle very slowly to 20% open and then progressively open the lid to a maximum of 80% all the time keeping the escaping gas well under control. Then at the end at 80% open you wait a bit longer for the gas to fully escape before finally opening the bottle and poring the drink.

The carpet is dry and stain free and you got your drink all be it with a modicum of patience.

Some people will acheive this with a very slow ascent rate to a shallow stop. Like very very slowley opening the bottle. Some will open the bottle in multiple stages. Like loads of 1min deep stops prior to the longer hang shallow stops.

ATB

Mark Chase

 

[Rob Evans]

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I just copy my buddy's notes & hope I don't snuff it.  He's PADI trained & signed all the wavers, what have I got to worry about?

PS I demand an apology from Chasey for sounding so much more professional than me.  For that matter, I demand an apology from La-la too.   In fact, I might just demand one from Finles.. Nah, that would be silly.

'Skin of the pants Evans'

 

[Andy Phillips]

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Mark,

Be careful, Coke is a trade name, surely you mean cola, also, what happens to the deco if you prefer lemonade.

Andrew

 

[Dr Stevil]

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Wots a deco stop?

No seriously, I don't get bogged down with the technicalities of it:
1) pre-dive prepared schedule from Bhuelmann (speelin?) tables written on a cuff slate,
2) maybe also compare it with deco software and
3) computer(s) for extra info, I'll follow whatever is most conservative
4) and then probably slow it all down a bit more, especially like to do the last 6m as slow as possible, TDI recommend 1min per metre for the last six metres, not at all easy in the sea but it's worth trying to keep it that slow.

 

[Dr Stevil]

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Quote[/b] (Porg @ Feb. 17 2004,18:54)]I do what my computer tells me  

Yeah

Ask PK what he thinks of that method, he's got some valuable real life data that might interest you, this was ages ago before you joined YD so you wouldn't know about it
Steve

 

[Finless]

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I do the deep(er) stops from Proplanner and then finish off from 9 mtrs upwards as per my computer.

Usually!

Mr Skin of the Pants Evans - I have nothing to apologise for. I stand by my record and having ONLY nearly killed myself once I let my reputation speak for itself. Anyway, anyone who can dive my set up and survive (Jules C - you aint seen nothin yet) deserves much respect and an apology free life.

 

[Mark Chase]

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Quote[/b] (Finless @ Feb. 18 2004,10:55)]I do the deep(er) stops from Proplanner and then finish off from 9 mtrs upwards as per my computer.

Usually!

Mr Skin of the Pants Evans - I have nothing to apologise for. I stand by my record and having ONLY nearly killed myself once I let my reputation speak for itself. Anyway, anyone who can dive my set up and survive (Jules C - you aint seen nothin yet) deserves much respect and an apology free life.

Bloddy hell, only once?

Id better keep quiet then

ATB

Mark Chase

 

[Finless]

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Quote[/b] (Mark Chase @ Feb. 18 2004,12:57)]Bloddy hell, only once?

Id better keep quiet then

ATB

Mark Chase

Yes Mark, only the once BUT it was VERY close - seconds away from making it into the Darwin awards (where I deserved to be for that particular piece of continued stupity).

Rgds
Bryan

 

[kramynot2000]

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I'm just about finished with the DSAT Tec Deep (or is it Deep Tec?) course.  Yeah, yeah, I know... its PADI, but I have to say, the materials are the best I've seen out there and the training is long.

Anyway, our instructor has us planning on a table, then printing out a "too long" table and a "too deep" table.  He also suggest getting a dive computer for if you want to cut the dive short for some reason.  I dive a Vytec which is very conservative and typically has me in deco after all other divers' computers have cleared.

 

[440634]

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<font color='#32CD32'>Air dive with air deco, follow my dive comp but always knowing my deco penalty so that if the comp dies, I'd know how long to stop for using my D-Timer.

If it's Accelerated deco or trimix dive, I always custom cut tables including bailouts.

Juz

 

[Dr Stevil]

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You wanna share the story with us Bryan? It's kinda quiet here today, it's forcing me to get into the lab and work  

 

[Finless]

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Quote[/b] (Steve W @ Feb. 18 2004,14:26)]You wanna share the story with us Bryan? It's kinda quiet here today, it's forcing me to get into the lab and work  

Steve,

Mmmmmm, I'm not sure I really want to share with everyone the depths of stupidity I achieved that day. I honestly believe that I would win any competition on YD under the heading "I did something more stupid than you, Oh no you didn't".

Well - I'll type something up off line and stick it on a bit later. If nothing else it should give everyone a warm "I wouldn't be that dumb" glow.

 

[Digger]

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<font color='#000080'>I bet I've done worse. I'm sure of it. In fact, people I know for making bad decisions have called mine a bad decision. In fact, one of the worst they've ever heard of. Oh, to be a novice all over again...

 

[peter k]

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Quote[/b] (Steve W @ Feb. 18 2004,10:51)]

Quote[/b] (Porg @ Feb. 17 2004,18:54)]I do what my computer tells me  

Yeah

Ask PK what he thinks of that method, he's got some valuable real life data that might interest you, this was ages ago before you joined YD so you wouldn't know about it
Steve

Grrrrrr, fu**ing 'pooters

 Yet I'm still dumb-ass enough to strap one to my wrist. Don't pay a great deal of attention to it, more a fashion statement really.

Stops;
1st stop at bottom of shotline to give my body a chance to get settled down for the ascent,
2nd stop 2/3 max depth
3rd stop 2/3 of second stop
4th stop 2/3 of third stop,
etc,
Stop at 12,
Stop at 9,
Stop at 5 for a looooooooooooooong time watching the world go by. Gives them on board a chance to get my coffee ready.


Peter