Manual calculation for accelerated deco

[chrisch]

I think you mean Ratio Deco. What I really mean is the science behind MultiDeco and such software. In other words, if I want to do all the calculations without any aid of computer software nor Ratio Deco method.

By reducing the N2 you speed up the deco. The calculations are similar to the EAD for backgas. You have less N2 so you have less PPN2 - equivalent to a shallower stop.

To exactly replicate the software you would first need to calculate the on gassing with the same parameters (as the software). Then you could off gas at the reduced PPN2. I don't think this is suitable for mental arithmetic to be fair. The principle is easy enough to understand though.

 

[lowviz]

...//... I don't think this is suitable for mental arithmetic to be fair. ...

Being an engineer myself, I get it. Yes, there are simple approximations to the problem. It is how we wrap our heads around such things, it isn't how we dive. I dive a Petrel 2.

As an example of trying to gain some basic form of insight (a basic feel for how long one can stay down), a constant divided by depth squared can approximate your NDL in minutes on air rather well. If dealing with feet for depth, try 222222 (six 2's) as the constant. You can futz with that by changing the PPN2. You won't find this anywhere, it is just how I approximate how long I can stay at the party...

222222/(60^2) = 1 hour
222222/(130^2) = 13 minutes

 

[chrisch]

Being an engineer myself, I get it. Yes, there are simple approximations to the problem. It is how we wrap our heads around such things, it isn't how we dive. I dive a Petrel 2.

As an example of trying to gain some basic form of insight (a basic feel for how long one can stay down), a constant divided by depth squared can approximate your NDL in minutes on air rather well. If dealing with feet for depth, try 222222 (six 2's) as the constant. You can futz with that by changing the PPN2. You won't find this anywhere, it is just how I approximate how long I can stay at the party...

222222/(60^2) = 1 hour
222222/(130^2) = 13 minutes

Not sure my mental skills are up to that

As feet are what you have on your legs I can see you need 24000 to make it work in metric. Still need to get my phone out to work 24 thousand divided by the square of 35.

 

[Dan_P]

I'd say you're best off taking a class and get answers from someone qualified to teach the material
If you subsequently form an opinion, it'll be your own.

Three organizations teach RD, in various approaches:

UTD teach RD only - and the most recent version. RD was originally structured by the founder of UTD and former Course Director at GUE.
GUE, I believe, still do teach RD in the old format, as a backup, but now use computer and software.
ISE, I believe, teach it too - though I'm not certain how, specifically.

 

[tursiops]

I'd say you're best off taking a class and get answers from someone qualified to teach the material
If you subsequently form an opinion, it'll be your own.

Three organizations teach RD, in various approaches:

UTD teach RD only - and the most recent version. RD was originally structured by the founder of UTD and former Course Director at GUE.
GUE, I believe, still do teach RD in the old format, as a backup, but now use computer and software.
ISE, I believe, teach it too - though I'm not certain how, specifically.

I'd say any posts about RD are off topic in this thread, which is about calculating deco from first principles, not calculating something that looks like deco. Unless I've misunderstood the OP and his later clarification.

 

[rsingler]

I'd say any posts about RD are off topic in this thread, which is about calculating deco from first principles, not calculating something that looks like deco.

 

[bamafan]

Just look up some of Bruce Weinke's books.

 

[JohnnyC]

@hanymamdouh
You may have already gone through all these, but they might be some useful links:

Bühlmann decompression algorithm - Wikipedia (Lots of good references to poke through)
User Manual ~ D-Plan Deco Program ~ New Jersey Scuba Diving (Info from a guy that wrote his own implementation)
Dive-Tech: Decompression theory - Robert Workman and Prof A Buhlmann (Good jumping off point. Follow through the series of articles)
DIY DECOMPRESSION (Some more engineery bits)
Gradient Factors | Dive Rite (Gradient Factors paper. You don't want to run pure Buhlmann)

Hope these get you started.

 

[Red Sea Shadow]

I think you mean Ratio Deco. What I really mean is the science behind MultiDeco and such software. In other words, if I want to do all the calculations without any aid of computer software nor Ratio Deco method.

If you mean decompression simulation and the "internals" of deco algorithms, these topics are discussed in my book Deep Into Deco. Excerpts from the book (in the form of articles) are often published in Tech Diving Mag (free publication; link in the sig line).

 

[hanymamdouh]

I'd say any posts about RD are off topic in this thread, which is about calculating deco from first principles, not calculating something that looks like deco. Unless I've misunderstood the OP and his later clarification.

Yes, it is not related to Ratio Deco, in fact the original deco calculations