Return to surface air volume

[ccx2]

Thanks for sharing your opinion hh.

 

[ccx2]

Thanks for sharing your opinion hh.

Actually,thank you ALL for your comment and opinions.

 

[Afishianado]

I'm not going to disagree with any of the input so far or target anyone as wrong, I just want to add something to the discussion that I think hasn't received enough attention. Remember that the capacity of the tank you are using plays a huge role here, it is just as important as your Depth and your SAC rate in this exercise.

~Chris

 

[Peter Guy]

Chris -- did you look at the "cheat sheet" I mentioned? That puts a lot of emphasis on the differences in tanks and gives examples.

 

[Afishianado]

Yeah saw it in your cheat sheet,but saw some rules of thumb out there that didn't take it into account.

 

[phillies1224]

cascas, I understand the principle you're trying to convey, but there's a flaw in your formula. If you turn the dive at 1400 and you require 1200 to get back to your entry point, you'll only have 200 remaining in the tank. I think what you meant to say is this:

starting pressure - 5 or 600 psi = usable gas
usable gas / 2 = usable gas 1st half of the dive
Turnpressure = starting pressure - usable gas 1st half of the dive

example:
3000- 600 = 2600
2600/2=1200
You should turn the dive at 3000 - 1200 = 1800 psi to return to your entry point

Also (and I apologize for picking on you), this approach does not account for air consumed during your safety stop(s) on ascent, or air you might need to share with your buddy.

3000-600=2400 (just busting your chops) this formula really helped me understand what you guys are talking about. I am new to all of this and appreciate the info. Sorry if others pointed out the typo too!

 

[cascas]

3000-600=2400 (just busting your chops) this formula really helped me understand what you guys are talking about. I am new to all of this and appreciate the info. Sorry if others pointed out the typo too!

Hmmm I guess I need to polish up my math ... Or stop posting on forums when I should be working. Consider my chops busted

Anyway, I'm glad it helped you in understanding turnpressures. It is not rocket science and easy enough to do on the fly and adaptable to different situations.

Have fun diving !

 

[D_B]

the rule of thumb I mentioned is for my HP100 and takes that into account (also for an AL80) .. in the article it goes over tank sizes (and IIRC adding 400psi instead of 300 would make it closer to that calculated figure for rock bottom) ...ether way it gives (math challenged) me a better handle for my purely OW dives