Rookie Question about extending bottom time...

[Kevin K]

Hello to the Collective, I can dive locally with my own boat for the least amount of money. The diving is 70 to 90 fsw mostly. I took the nitrox class to be able to get more bottom time. Problem is I run out of air/nitrox at the same time- about 20-25 minutes at 85 fsw. How can I extend my time? Bring more volume with me! I could get a steel 120. Can I use double aluminum 80's??? That would be about 150 cuft. Maybe double steel 100's or steel 80's? With nitrox 36 I can stay at 90 for 46 mins-1hr SI- 41 mins-1hr SI- 36 mins if I remember my tables correctly.( It might be for 80 fsw) I would appreciate anyone who would like to help me in the right direction. I have 25 dives under my belt, mostly to 90 fsw, am 6'5", 210 lbs. Temp at depth is about 60 degrees. Since it is a 26 mile ride to the dive spot I would like to maximize my bottom time. I don't want to do anything stupid and am researching best I can. I am going to get a thicker wet suit and I pay attn to my breathing best I can. Advise me, please. kk

 

[Ber Rabbit]

You breathe the same volume of air (approx 4 liters) with every breath you take no matter what gas you are using. The volume of gas in the tank is going to decrease with depth (Boyle's Law) no matter what gas you are using. You need to take more gas with you if you want to significantly increase the time you spend at 85 feet. Get some training in doubles if you don't want to go with the steel 120. I don't think I would double the aluminum 80's simply because of their buoyancy characteristics, I enjoyed the steel 100's an instructor friend let me try.
Ber :lilbunny:

 

[Kevin K]

Thanks for the comeback. Where do I get training for doubles, please.

 

[Ber Rabbit]

That answer I don't have. I would guess you could contact any of the places that train cavern/cave divers, that would probably be your best bet for Florida.
Ber :lilbunny:

 

[H2Andy]

ideally, find an instructor in your area who dives doubles and tell them you want to do a couple of dives with them to familiarize yourself with doubles.

in the alternative, find an experienced buddy who dives doubles and do the same thing.

diving double's isn't particularly difficult. there is no formal "class" per se. most people do a few dives under supervision, learn how to fix a turtle, and go off on their own.

for deeper dives, i would suggest doubles rather than a single tank. the redundancy of doubles is excellent. you can isolate them in case of a major gas
loss, and that way you'll keep half your gas for the ascent.

one last thing, and probably the most important, is to learn how to plan your dives
based on gas. with doubles, you can do longer dives, but you can also get yourself into more trouble. make sure you learn how to plan your dives on gas,
know your rock bottom or turn-around point, and otherwise don't go into decompression unless planned.

 

[PerroneFord]

Doubles without gas planning is like a sports car without brakes. You can get yourself into trouble before you know it. And you can get hurt.

If you are diving with a wetsuit, I'd STRONGLY suggest you go with Aluminum tanks for doubles versus steels.

And please, get some training.

 

[Tollie]

Hello Kevin,

A couple of other responders sent up several red flags and I wonder what your response to them will be?

FWIW here are a couple of others. Boat diving is wonderful provided you pay attention. Dives to the depths you are contemplating are not trivial dives I hope you have team members who are diving with you and who are diving similar gas and have similar goals for the dives. One other thing. Please have someone keep the boat while you and your team are down. 26 miles out is “Real Ocean” and things can change very quickly. Also attend to the rest of your kit including SMB and an audible signal.

Diving the limits of the table or computer is pressing it. You leave little margin if the dive plan goes south.

Many newish divers find that air consumption improves with experience... and with sounder technique including stronger control of boyency and trim.

Dive safe.

What is out there and down there that is so compelling?

 

[Kevin K]

By getting into trouble you mean having more gas on my back than I have NDL time, correct? I"m 50, I'm cautious, I read a lot here and in other places. This won't happen this week but I am investigating and I am listening to what other more experienced divers have to say. What is a turtle please? Tanks down and can't roll over? kk

 

[H2Andy]

turtle is when your tanks flip you over and you end up face up at the bottom.

it's easy to get out of (just twist your body fast and flip yourself) but can be disconcerting at first.

as for the gas planning, yeah... make sure you know your NDL limits at depth,
and more importantly, make sure you don't go deeper with the extra gas unless you
plan for it.

 

[Kevin K]

Sometimes I get ahead of myself. I dive with my wife who comes up with 1500+ when I have 300psi. She is competent. We plan the dive but could do better and will. You make a good point about diving to the limits, I don't need to be anywhere near the limits-just thinking to the limits( excited rookie) Just started looking at sub-ducks the other day now that you mention it. Is that a reasonable communication device? Got an SMB, have never deployed it, need to do that. We have a small boat and are comfortable on it where we go. 15 years as a commercial fisherman-offshore-30 days at a time. We go on good days when it is less than 2-3 ft. We have aborted one dive because of current. Couldn't get to the anchor line to go down with out working hard so aborted dive and went somewhere else. Just like diving and would like to become proficient. Easiest is to go here at home and gain experience. Good hunting place. I appreciate the input. kk