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Posted by Ross-O on March 07, 2004 at 19:56:24:

In Reply to: Solo Dive Ques./ Pony Tank Backup posted by B. Xavier on March 07, 2004 at 18:30:32:

Hi Xavier,

1. What's the deepest you usually dive?
2. What is your SAC or RMV (breathing rate in ft^3/min at the surface)?
3. Do you do deco dives?
4. Would you be willing to share your air with someone else who found themselves in an emergency?
5. How long do you figure it'll take to overcome whatever obstacle used up your back gas or otherwise made it unavailable?

All of these are questions you should consider when sizing your pony bottle. If you do a little math, you'll see that 6 cuft doesn't buy you much time.

I'm not a tech diver or a dive instructor and these are just a few things that come to mind. There are probably many more things to consider.

Maybe you're RMV when you're chillin is 0.5 (this is in the "pretty good" category, expert cave divers are around 0.35, I'm at about 0.6 on beach dives, and big guys are usually closer to 1.0).
Now a giant clam just grabbed you by the ankle and your're scared - you're RMV is probably something like 1.0-1.5 cuft/min. You're at 60ft, therefore you're sucking through your air at 3-4.5 cuft/min. If you're only carrying 6 cuft, you better hope that clam lets you go in less than 45 seconds or so or you're SOL (assuming you like 30 fpm ascents).

Consider sharing the diving experience with someone else. It's like having a giant pony bottle swimming along with you :-) I've carried an AL30 and AL40 on my left side on several dives and found it to be pretty comfortable. I rig mine like this http://dir-diver.com/en/equipment/stagebottle_rigging.html

Dude - that's one heavy weight belt! Are you sure you're not over weighted? Try dumping your tank to 500psi at 15 ft. Now empty all of the air out of your BC. Get horizontal and breath normally for a few mins. Do you sink? If so, time to lighten the weight belt a few lbs.

Cheers,
Ross-O


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