Decompression Question (Gradient Factors) from a newbie

[jj1987]

OK, I got bored tonight and decided to play around with some programming. In the interest of full disclosure my only deco class has been what's covered in full cave so this could very easily be a stupid question, and my apologies if it is...I have plans to take a deco class sometime in the near future, just not sure of good instructors to take it with.

I've been writing a php script, and think I have it so that tissue loading is calculated properly. The script can be seen here-
http://jamesg.net/temp/deco_schedule...60&o2=21&he=35

You can modify the variables by changing depth=100 to depth=90, or swap gas mixes by changing &o2=21&he=35 to &o2=18&he=45 for 18/45...that's not really relevant, but feel free to test it and let me know if you see anything odd. Currently the ascent ceiling is calculated improperly because I don't have the He/n2 a&b values in my database.

OK, now for the stupid question(s)....
is the "Low GF" nothing more than something to change the first mvalue?
- For instance, if the ascent ceiling is at .5 bar, and my GF Low is .5, would the new mvalue be .25?

Once we know the low gf depth as derived from the mvalue*lowgf, can we then calculate the ascent ceiling as follows, and then make sure that no tissue ever exceeds (GF For Specific Depth * Mvalue)?-
(Image taken from RBW Gradient Factors tutorial)


Here's what I'm currently thinking...mvalue=100ft (whatever that is in bar), GFLOW=.35 GFHIGH=.85
Let's say our first stop is at 150ft with the gf adjustment
Then-
GF__ft deep (obviously in bar) = (.85-.35)/(150-100)*CurrentDepthInBar + .85

Thanks in advance for any help. I've been using JpGraph for some things at work (http://www.aditus.nu/jpgraph/), and the goal here is (aside from the fact I'm graduating and making portfolio material ) to show graphs of how deco increases over time, as well as have optional gear failures (such as a dpv or lost deco bottle) that demonstrate how a few gear failures can really cut things close... it's an attempt to make dive plans appear more visual than just numbers on a paper.

The final plan is to overlay graphs of Ratio Deco and compare them to Buhl with GF's to debunk the myth that Ratio Deco is extremely aggressive, and maybe overlay VPM-B Buhl and Ratio Deco for easy comparison on a per-dive basis if I get real ambitious...the gas graphs will come first, since I already have the rock bottom functions written for ratio deco and most of that code can be reused for buhl,

[Skybluewater]

Tease your brain with this info:

http://www.ncdivers.com/phpBB2/viewtopic.php?f=7&t=4489

[jj1987]

Tease your brain with this info:

http://www.ncdivers.com/phpBB2/viewtopic.php?f=7&t=4489

I'm not a huge fan of IWR. I'd have to be a LONG way from home to attempt that. I would rather delay treatment an hour or so, because puking or passing out at the hospital seem a LOT better than underwater. Good knowledge however, if I were doing remote dives, I would read up on it before the trip. Plus, I don't think most of us carry enough o2 with us to make IWR even an option, I know I usually have 1.5x the required deco gas and that's it.

I will say this. When I was reading up on deco algorithms I was floored at how "simple" they've reduced the human body to. I have no doubts that the real word does not mirror the formulas exactly, but when you consider the complications of researching (budget, test subjects, etc) I think we've got it pretty darn good.

[Superlyte27]

I have a copy of Sheck's DR. X. If you want to look at what he did you can use that.

[DA Aquamaster]

I'm not a huge fan of IWR. I'd have to be a LONG way from home to attempt that. I would rather delay treatment an hour or so, because puking or passing out at the hospital seem a LOT better than underwater.

I'm not sure it applies to everywhere along the Atlantic coast, but farther north, the average is more like five hours from the surface to a chamber.

It's something different to go back in the water with DCS symptoms already apparent, but if I missed significant deco and was symptom free over a very short surface interval to get more gas, I'd certainly go back in to do a missed deco procedure rather sit on deck waiting to get hit and then wait hours to get to a chamber.

Practically speaking, I try hard to avoid the whole issue by being very conservative on my deco and my gas planning.

[jj1987]

I have a copy of Sheck's DR. X. If you want to look at what he did you can use that.

If you wouldn't mind, my email is james (at) jamesg.net . Do you have the source code or just the executable?

[Superlyte27]

I have it all. I might have to burn it to a disc and mail you the disc. I can't get Gmail to send an .exe file.

As far as inwater deco goes. Somewhere in my commercial diving book there is an outline for inwater treatment. I'll have to see where I can find it. It was kinda "if all hell breaks loose, and there isn't going to be a chamber available, here's how you can do a table 6 in the water."

I live in Central Florida, within 35 miles, there's at least a dozen chambers near me.



****Edit****
Also, when we're working at depth and have decompression in a chamber, we've got 5 minutes from the time we reach the surface until the time we are back down to a decompression depth. So, lets say we've spent 90 minutes at 200'. Our dive is over, the tender pulls us up, we've got to get out of our hat, drysuit, (take a quick piss if necessary), get into dry clothes, hop in the chamber, dog the hatch and get back down to our deco pressure in less than 5 minutes. You better hope your ears clear.

I would think if you get interrupted because of a shark or loss of air or something, and you can make it to the boat or surface for more Oxygen or Air then descend to finish your IWD you'll probably be ok.

[FW]

... I can't get Gmail to send an .exe file.....

Change the extension, and he can change it back on his end.

[jj1987]

I have it all. I might have to burn it to a disc and mail you the disc. I can't get Gmail to send an .exe file.

Might be easier to upload it here and send me the link-
http://rapidshare.com/

thanks!

[fno]

James, you might just want to get it from the horses mouth, in a manner of speaking. Erik Baker is the guy who originally did most of this work, including your ratio overlays (he was advising and monitoring WKPP for a long time) He has backed away from most of his deco work on account of his work responsibilities. If you would like, I will cut and paste your original post and email it to him along with your email address. That way if he is interested, he can contact you directly. Let me know, Frank Ohidy.