Studying for nitrox class- please help

[Anti-Hero]

Yeah, just call me Hoover.

I used to know a diver named Jim. I haven't seen him in the water in years. :shocked2:

I saw him recently

 

[mikemill]

= Use Depth + 33 / 33 to see how many atmospheres of pressure you're at:

<pedantic>
Might want to watch how you write those equations. I read that and see "Depth + 1" (since 33/33 = 1).

Even meaning it how you meant it I would think that: Depth / 33 + 1 [Or if you want to be even clearer: (Depth / 33) + 1] makes a lot more sense. Who wants to go to the trouble of adding 33?
</pedantic>

 

[Guy Alcala]

Maybe this will help you:

How many ATM is 60 feet?
= Use (Depth + 33) / 33 to see how many atmospheres of pressure you're at:
= (60 + 33) = 93, divided by 33 = 2.818 ATM

(A quick check - we know 66' is 3 atmospheres, so just under that = 2.818 for 60 feet)

If your air lasts 90 minutes on the surface at 1 ATM, you will consume it at a rate 2.818 faster at 60 feet, so...

90 divided by 2.818 = 31.93 minutes

[(PSI / Minutes) x 33] / (depth +33)

Thanks for the help, I'll do something like that about 5 more times and it should be securely learned.

You can also do the above calculation for ATA as follows:

(Depth / 33) +1 or

(90 / 33) + 1 = 1.818 +1 = 2.818

Some people find one method easier, some the other. Of course, if we stubborn Americans would just switch to metric it becomes childishly simple to do in our heads - even a caveman could do it (tm).

(Depth in meters / 10) +1

All you have to do is move the decimal in the depth one place to the left and add one:

(18.2m / 10m) +1= 1.82 + 1 = 2.82 ATA.

Have fun (or not, as the case may be )

Guy

 

[blue steal]

Hey pacificgal.........see you at Laguna........don't think you'll need nitrox there as it is <40' for the most part. (128+33)/33=4.88 round up to 5. 90/5=18.

 

[mselenaous]

I'd love a lecture that includes gestures, lol. "You have this much air" (hands spread wide) and when you descend, the air gets compacted (hands getting closer together) by x amount, the number of molecules doesn't change, but they get squished closer togther..."
I need visuals!

That's how I teach this topic. Very animated makes it come to life.
Come see me in SoCal (soon or in SoFL)...

 

[Divenomad]

That's how I teach this topic. Very animated makes it come to life.
Come see me in SoCal (soon or in SoFL)...

Hah, I showed it this way once too. Except I added the molecules go "squishy". I was speaking to a bunch of biology PhD's. I got four blank looks and hysterical giggles from the fifth. Later, my boss sent an email that said:

Squishy?

That was a good day.

 

[Jim Ernst]

Yeah, just call me Hoover.

I used to know a diver named Jim. I haven't seen him in the water in years. :shocked2:

Ya I haven't been down there in a couple Months now, But I will be on the 23-24 of this month!

 

[Chuck Tribolet]

Some people find one method easier, some the other. Of course, if we stubborn Americans would just switch to metric it becomes childishly simple to do in our heads - even a caveman could do it (tm).

(Depth in meters / 10) +1

All you have to do is move the decimal in the depth one place to the left and add one:

(18.2m / 10m) +1= 1.82 + 1 = 2.82 ATA.

That's blind stupid luck on the part of the metric system. There's
no physical relationship between atm. and meters of sea water.

Now, don't get me wrong: I think the metric system is better, and
can do rough metric conversions in my head. But that's just blind
stupid luck, not something that's inherently better in metric.

 

[zf2nt]

You got it. Of course, you'll need to factor in a possible increased air consumption rate based on cold, exertion, and leave a safe amount of air for surfacing plus a contingency amount. But that's the gist of it.

This brings an interesting question to mind. I have calculated my SAC rate over hundreds of dives in Monterey and it is an invariant 0.45 cu.ft./min. I've also calculated it over several hundred dives in the Caribbean (Little Cayman, to be exact). Down there, I consume just slightly under 0.30 cu.ft./min. That says I use 50% more air here in Monterey than I do in tropical waters, and to me that's an astounding difference. I wonder if anybody else has measured anything similar?

I'm going back down to Little Cayman for a month starting next week and will be doing lots more measurements. This time I'm taking a heart rate monitor and will be very curious to see if the heart beat rate is noticeably lower than when diving cold water.

Bruce

 

[Chuck Tribolet]

You need to burn more fuel to stay warm, and your dry suit probably has
more drag. And are you using the same BC?