Understanding deco theory

Abbo

There's a bewildering array of deco models out there. My suspicion is that the hundred years since Haldane's first models have still left us in the province of snake oil salesmen selling software that gets people dangerously bent. There appear to be large grey areas on even dives to 100m, particularly related to IBCD. I want to understand the theory better. What is the best way to read up on this? Do members rate Wienke's Reduced Gradient Bubble Model book? There was an IANTD course on deco modelling at one stage: can I just buy the course materials? Are they a nourishing read? What's the best reading material on deco theory? I'm a lapsed physicist: before the amber nectar and a career in finance killed my brain cells and grew my gut I used to understand some fancy theoretical physics. The grey cells relish a work out...

wedivebc

Weinke will certainly give the grey matter a workout and with you background you will probably understand more of it than I did. If you figure out a way to explain to folks on this side of the intellectual bell curve please let us know.

__________________
Cheers,

Dave....

www.wedivebc.com

Gene_Hobbs

We recently started putting together a "suggested reading list" of materials we have available in the Repository. I do need too spend some more time on the model section so please let me know if you find things I should add.

Hope these help!

diverreb

My 2 cents.....

There is only so much known at this point in time as to why some divers get bent and others don't that reading all the theory in the world won't prevent you from the possibility of getting a hit of some sort. The only way to avoid the risk is stay out of the water, which is obviously not an option for most of us on this board.

What is known is how to reduce the risk by taking various actions. They are fairly common knowledge to most advanced divers.

It goes back to the risk ladder and how high each of us wants to climb.

Why does a diver do the same profile 50 times and gets a hit of some sort on the 51st. Assuming all other things being equal, no one really knows.

Why one diver gets a hit when everyone else followed the same profiles and didn't get bent, again assuming no obvious variation, is still a mystery for the most part.

The variation of run times on a bottom time of :40 at 160' followed by a repetitive dive for :40 at 160' can vary by well over a half hour, depending on which software you use and how you plug in GF's or levels of conservatism. That's a pretty wide variation, suggesting that to an extent, deco theory is all over the place.....

Everyone is different and reacts differently on any given day to most dive scenarios. In the sport we all love we just have to do whatever we can to minimize the level of risk we choose to accept for the rewards we take from the sport.

Hopefully as time goes on, more will become known and we will all be safer in the world's Oceans, Lakes, Rivers, & Quarries.

Safe Diving To All.....

Richie

Mark Chase

My 2p

Its all bollocks.

Deco theory is very very theoretical. In truth the only way to find out what works for you is do a lot of deco diving. Start very conservative and build from there and then make allowances for your own personal condition generally and on the day of the dive.

RGBM as a deco model scares me (and a lot of others) This is deco in a petri dish, at least Buhlman was deco on goats and snakes.

If you want to get a good comparison look at commercial diving deco profiles. They are far less aggressive than we recreational divers take on.

I know good divers who have found they can pull off very quick deco and feel OK. I respect this but i have no respect for people who just copy them on the basis that if they can do it I can.

Personally I have tried to get my feeble brain around VPM and i sort of get it but in the end i keep opting for VPMBE on big (for me) dives and thats just Buhlman with a load of deep stops thrown in for good measure.

I prefer to use Gradient Factor deco profiles, because I can get my head around them and because they seem to have a simple pattern.

For some reading i can offer the following:

ftp://ftp.decompression.org/pub/

VPM Decompression Site

Isobaric Counter Diffusion

Prlonged bubble production by transient isobaric c...[Undersea Biomed Res. 1979] - PubMed Result

For advice on deco i can only offer my opinion which is no one ever got hurt doing too much deco.

ATB

Mark Chase

__________________
See my "Doing It Chasey" video where I'm locked into a padded room, naked, with two ball bearings and within an Hour, I manage to lose one and break the other!!!

Kevin Juergensen 16/11/08
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Gene_Hobbs

PDF of the paper... (and all the other UBR articles)
Rubicon Research Repository: Item 123456789/2840

--Note: our file names are the PubMed ID numbers so if you find one, search for the number in our database.

If the interest is Isobaric Inert Gas Counterdiffusion, the 1979 UHMS workshop is also available.

Lambertson CJ, Bernmann RC, Kent MB (eds). Isobaric Inert Gas Counterdiffusion. 22nd Undersea and Hyperbaric Medical Society Workshop. UHMS Publication Number 54WS(IC)1-11-82. Bethesda: Undersea and Hyperbaric Medical Society; 1979; 182 pages.
Rubicon Research Repository: Item 123456789/4337

diverreb

Mark,

Very well put.... I agree 100%....

Richie

dom

i agree with most of what mark has said, winkes book is tough going but i could understand most bit with my science backround, vpm and RBGM theory is sound but gives run times longer than we know is required so formulas were applied to the sound theory to reduce run times ie tghe models were too conservative so they manupliated them to suit without any evidence or testing of these new times which dont corralate to what started as sound theory, ie it appears to me that these formulas to shave time off these modles were pulled out of someones arse. winkes book suggests this and it covers an explanation of the different models, enough to get an understanding but not too much detail. personally i use proplanner, tried and tested bullhman. the settings i use on the programme are 10/100. with the 100 adding deeper stops and 10% conservativy. my vr3 is set up to reflect this also. from what i can see of vpm BE it has gone towards bullhman and as a result is similarn to a lees tested version of proplanner. proplanner will keep ya in the watwer a little longer but at least your not twisted to shit.

dom

dantheman

If proplanner allows you to add deep stops, it's not tried and tested Buhlmann . . .

I'm not familiar with proplanner, but the 10/100 you reference looks
an awful lot like gradient factors. If it is, you would be right that you
are adding deep stops, but you would be referencing the wrong number.
The 10 is what stops you deep. The 100 would indicate a nominal shallow schedule.

--dan

cramerdn

How were your grades in Physical Chemistry? All the pysics majors at the school I went to loved their quantum class but ran from P-chem like it was the plague.

The cool thing about Wienke is that if you quit diving you still have about 1/2 of a P-chem text book still on your shelf.