Diving with 120's for extended bottom time- OK for newbies?

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FastDen

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Hi y'all-
Question for my more experienced friends and DMs: I'm a semi-newbie (50 dives), and headed back to Coz in November for Thanksgiving week and lots of diving. I've been researching new (to me) dive ops, and see a lot about Living Underwater, Aldora, et al, and how they offer extended bottom times with 120 tanks. What do y'all think- any issues with beginners/advanced beginners taking advantage of them? Thanks in advance for your feedback and advice!
FastDen :rainbow:
 
Sure, use them, with 2 important caveats:

1- That you are physically big and strong enough to handle them (they're heavy)

2- That you know, and keep track of your dive schedule and not exceed the the no-decompression limits due to having the extra air.

Tom
 
I would suggest not using 120's to extend your bottom time. The top two reasons for using120's are : better trim and less weight needed. Bottom time is a distant third. If you want more time, work on your SAC rate. A bigger tank for more bottom time will never push you to become a better diver the way learning to dive more efficiently will.

SAC's can vary from one individual to another, depending on size, sex, conditioning and experience. When I started, my average SAC was .97. I began using HP120's when my average SAC hit .65. My SAC now averages .57. Using 120's at that rate, I make 65fsw dives of over an hour. My girlfriend, OTOH, had an average SAC of only .50 for her first 4 dives! She now has a SAC of around .33. She is now considering using HP100's. IMO, every person needs to improve to the point where steel tanks will help you in ways other than bottom times, or you could find yourself part of Dan's annual injury report.

The best way to more bottom time is:

1 improve your trim

2 improve your bouyancy

3 learn to be efficient- kick only when you need to

4 when you DO kick, kick with the minimum effort required

watch divers who have low SACs. What do they do? Ask questions. Practice, practice, practice. By the time you stretch out your bottom times, you will have the experience to do long dives SAFELY. Plus, it doesn't bother me one bit to dive more often.
 
One question. Are they saying "extended bottom time" because some people go through a tank faster than others, or does that mean they are doing planned deco dives?

If you want to dive with a 120 because you go through air fast, then I think thats fine. Improving your SAC rate and just relaxing will help with the air thing (probably a hard thing to practice on in NYC) but it will come with time.

If they are extending the bottom time past the NDL by using a 120, don't do it until you get more training. I know alot of people have gone into deco without the training and survived with no problem (me included), but it is a scary feeling. You may want to find out exactly what they are advertising before you "take the plunge" so to speak.

Just my .02 worth
 
Please, can you tell me what SAC stands for? I understand it has to do with air consumption but I would like to know how do you measure it.
Thanks,
VV:confused:
 
Surface Air Consumption- it is the measure of how much air you are breathing, if you were breathing at that rate on the surface. Usually measured in cubic feet per minute (cuft/min)
 
https://www.shearwater.com/products/perdix-ai/

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