Can you help me learn about: gas management and basic deco therory?

[stangd1909]

subscribing....

 

[terrasmak]

THe Naui Master diver course/book will teach you about it .

 

[lamont]

BTW, the link in my sig isn't working today unfortunately because my DNS/web server crashed last night and I'm at work and can't reboot it...

Fixed.

 

[cerich]

be back on the boat with 500 psi and keep your computer out of the red zone.

What else do you need to know?

 

[Scott in AK]

Great info and links.
So now I have a question for Lamont. Let me start this with the info that I am new to diving, with that said, I went over the " rock bottom" info last night. I am confused about one thing, ( well more than one, but I must start somewhere).
Precise Tables

These tables all use the computationally precise method of determining rockbottom.
Precise tables for different tanks

Source Code
DepthRock BottomHP80Al80LP72HP100LP80Al100HP119LP95HP130LP10410 fsw13.01 cu ft569 psi504 psi500 psi500 psi500 psi500 psi500 psi500 psi500 psi500 psi20 fsw14.59 cu ft638 psi565 psi534 psi510 psi500 psi500 psi500 psi500 psi500 psi500 psi30 fsw16.36 cu ft715 psi634 psi600 psi572 psi540 psi500 psi500 psi500 psi500 psi500 psi40 fsw18.34 cu ft802 psi710 psi672 psi642 psi605 psi550 psi539 psi509 psi500 psi500 psi50 fsw20.53 cu ft897 psi795 psi752 psi718 psi677 psi615 psi603 psi570 psi552 psi521 psi60 fsw22.91 cu ft1002 psi887 psi840 psi801 psi756 psi687 psi673 psi636 psi616 psi581 psi70 fsw25.49 cu ft1115 psi988 psi934 psi892 psi841 psi764 psi749 psi708 psi686 psi647 psi80 fsw28.28 cu ft1237 psi1096 psi1037 psi989 psi933 psi848 psi831 psi785 psi761 psi717 psi90 fsw31.27 cu ft1368 psi1212 psi1146 psi1094 psi1032 psi938 psi919 psi869 psi841 psi793 psi100 fsw34.46 cu ft1507 psi1335 psi1263 psi1206 psi1137 psi1033 psi1013 psi957 psi927 psi874 psi110 fsw37.86 cu ft1656 psi1467 psi1388 psi1325 psi1249 psi1135 psi1113 psi1052 psi1019 psi961 psi120 fsw41.45 cu ft1813 psi1606 psi1519 psi1450 psi1368 psi1243 psi1219 psi1152 psi1116 psi1052 psi130 fsw45.25 cu ft1979 psi1753 psi1659 psi1583 psi1493 psi1357 psi1330 psi1257 psi1218 psi1148 psi

In these tables it shows a higer "rock bottom" psi for a hp130 than a lp104.
I am assuming that a hp130 at 1000psi will have more cf of gas in it that a lp104 at 1000psi. so why is "rock bottom" at 130fsw with a hp130 1218psi and 1148 with a lp104? what am I missing here? Again I am assuming that HP= High pressure and LP= low pressure.

 

[Scott in AK]

Well that chart didnt post well.

 

[dsteding]

In these tables it shows a higer "rock bottom" psi for a hp130 than a lp104.
I am assuming that a hp130 at 1000psi will have more cf of gas in it that a lp104 at 1000psi. so why is "rock bottom" at 130fsw with a hp130 1218psi and 1148 with a lp104? what am I missing here? Again I am assuming that HP= High pressure and LP= low pressure.

A 130 and a 104 have very similar tank factors because they are the same sized tank, however they are not EXACTLY the same. What you are seeing is the slightly smaller tank factor (cubic feet of gas per 100 psi) for the 130, requiring it to have slightly higher RBs.

Tank factor (cubic feet per 100 psi) for a 130 =130/34.42, for a 104=104/26.40.

I don't have a calculator, but if you do the math you'll see they are slightly different numbers (like 3.7 versus 3.9 I think).

 

[lamont]

they're also impossibly computationally precise. whats the real effective difference between 552 and 521 psi? can you actually measure those values on your SPG?

 

[Scott in AK]

OK I think I get it, you have to factor in the physical size of the tank, not just the max psi. The 26cf of "extra" gas is due to the max psi, not a bigger tank.

 

[Spratman]

Hi Leah,

I've been through most of Weinke's papers, his books on decompression theory and other stuff. I took the NAUI Intro to Technical Diving class and it explains a lot and trims you up too. With a good instructor, you can spend time on particulars. Best class I've ever taken, as far as, sorting things out goes.

Good luck!