2 days down - 2 days to go ........

[wvjohn]

Congrats
1 Just finished the 2nd night of pool work for the YMCA course in Hagerstown Md. Really looking forward to thurs when we start with the tanks, etc. We have done all the scuba/snorkel stuff and when I got up this morning aftter swimming clearing getting the brick from the bottom of the pool I was seriously stiff!

Thanks again to all the SB members for all the great stuff posted here!

 

[dbulmer]

Pyro,
I bet Nina enjoyed it as well

 

[Pyromaniac]

It was fun db' lots of 'serious' moments for sure, but we all had a laugh along the way, Nina is a good instructor, great in my bad moments and every day ended in smiles and us all joking around.

 

[dbulmer]

Pyro,
"45 minutes long, depth 9m,water temp 17 C and surface temp 31 !! starting pressure 220bar ending pressure 70bar. "

What was your sac rate?

If you don't know the answer to the question ask Nina.

 

[Pyromaniac]

Well as far as i can tell, having googled sac rates........

I found this formulae -

Calculate the litres of air used, during the dive by multiplying the air consumed in BAR by the size of the cylinder:

= 150 x 12 = 1800 litres

Get the average litres per minute by dividing the litres used by the time in minutes:

= 1800 / 45 = 40 litres a minute

Compensate for depth - by dividing the average litres per minute by the depth multiplier (see right hand column in table below).

Depth (M)
Convert to
SAC Rate
Convert From SAC Rate​

0
1
1
3
0.76
1.3
6
0.62
1.6
9
0.52
1.9
10
0.5
2
12
0.45
2.2
15
0.40
2.5
20
0.33
3
25
0.29
3.5
30
0.25
4
35
0.22
4.5
40
0.2
5​

= 40 / 1.9 = 21.05 litres per minute

Good or bad or totally the wrong thing I have no idea !

Nina is in Finland I believe..........

 

[Pyromaniac]

well - the copied table failed miserably !!

the figures i used are
depth 9
Convert to SAC Rate 0.52
Convert From SAC Rate 1.9

= 40 / 1.9 = 21.05 litres per minute

Good or bad or totally the wrong thing I have no idea !

 

[Kat4]

Wow it sounds like you are well on your way. Sounds like your instructors are very tuned in to their students, not always the case. The first time I strapped on a tank and reg, went into the water I felt like I was home. Only been diving 6 times. New diver myself. I live in Central FL so getting somewhere other than a lake is a little time consuming. Sometimes I just want to gear up and hover in the water to unwind and clear the mind.:scubadive

Anyway Pyro, you'll probably be one of those that grow gills:azvatar:

Keep us posted
Kat:kitty:

 

[Quero]

Well done, Pyromaniac! Where and when are you planning to dive next?

 

[dbulmer]

Well done Pyro,
It was right! Now if you were at a bottom depth of 30 metres how long could you stay down at 30 metres (assuming a SAC of 25lpm)? (now you know what the SAC rate is you can move on to applying it!)

BTW Sorry if these questions might seem a bit condescending but had I known these answers when I first qualified I wouldn't have had an OOA at 80feet or so.

Congratulations and the Countess of Erne isn't going anywhere and you'll get plenty of opportunity to dive her - do you think diving is for you yet ?

 

[Pyromaniac]

No problem, its good to try and figure this out, even better when told if right or wrong and why ....................

So - the question, I am going to assume 12l cylinder just filled to 220 bar .........

1st - i will 'lose' 50 bar from my calculations for emergencies/contingencies that might crop up, so will work on 12l @ 170 bar.

12l x 170 bar gives me 2040 litres of air.

At 30m (4 BAR) the air consumption would be 4 (BAR) x 25 (SAC) = 100 litres per minute.

tank litres divided by SAC rate = time in minutes of available air.

2040 / 100 = 20.4 so I have air for 20.4 minutes.

I would round that down to 20 minutes, and continue to 'forget' the 50 bar I reserved, and not use it in any planning. (which incidentally equates to just 6 minutes of contingency air at 30m)

possibly..........




Thanks everyone for the congratulations

I would like to continue diving, but in a 'controlled' way, not meaning a pool and instructor, but with supervision and whatever buddy i got being prepared to put up with hesitancy and the newbie ups and downs and prepared to lose their dive to being a surregate instructor............