Rookie Question about extending bottom time...

[Ber Rabbit]

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.

Never even occurred to me that he was in a wetsuit--that's what happens when cold water divers interact with warm water divers. Around here if you want to stay down that long you wear a drysuit--even 60 degree water gets cold if you're in it long enough.

Walter has a pair of double slim 72's, they look like a really nice set for warm water diving in a wetsuit.

One thing I learned when I went for my doubles dive--put air in that wing before you enter or you're going to the bottom.
Ber :lilbunny:

 

[CBulla]

One thing I learned when I went for my doubles dive--put air in that wing before you enter or you're going to the bottom.
Ber :lilbunny:

Yeah... none of us who dive 2 different rigs are guilty of this. I didn't put enough in on one of my early dives (didn't do my methodical step by step pre-jump check at the platform) and hopped in sans air in the wing.... off I went! 15' of drop I had it under control and laughing to myself but it was a brief moment of harrowing "well, thats a deep step.. thats not going back up!" before I hit that inflator button and gave a little kick to stop.

I saw Walters doubles in the Keys.. pretty much like mine. Great for 2 dives on the keys boats.

 

[TeddyDiver]

One thing I learned when I went for my doubles dive--put air in that wing before you enter or you're going to the bottom.
Ber :lilbunny:

Excuse me, but isn't it allways important? And secondly, your's and Cbulla's messages let me to understand that you were negatively boyant without air in your wings? How much and your doubles chararteristics? Just to check I got you right

 

[victor]

Excuse me, but isn't it allways important? And secondly, your's and Cbulla's messages let me to understand that you were negatively boyant without air in your wings? How much and your doubles chararteristics? Just to check I got you right

You should always be slightly negative at the start of a dive when you enter the water.
You plan to be neutral with a near empty tank at the safety stop on exit. So with doubles you could be 8lbs negative on entry with full tanks.
On a giant stride with a 7mm wet suit to compress and 8lb's negative you will have to put a lot of air into the BC to stop your descent.

Edit Ops feeling stupid, just realised to whom I am replying. :redface:

 

[JimC]

Just a note, you'll need 3 sets of double AL80's to actually increase your bottom time over 3 dives. If one AL80 is not enough for one dive, then your doubles will have less than one full 80's worth each each dive.

You could stage at this point, but your talking even more training and what not. I personally think you'd be better served with 3*100cf single steel tanks. A volume sufficient for most recreational need. Combine this with another 20-30 dives to get your comfort up and SAC rate down and you'll be getting 40-50 minute dives out of them @ 90 feet easily. Best of all, you don't need extra training.

Suggesting a guy with 25 dives buy 3 sets of AL80 doubles? Come on guys, get real.

 

[Ber Rabbit]

Excuse me, but isn't it allways important? And secondly, your's and Cbulla's messages let me to understand that you were negatively boyant without air in your wings? How much and your doubles chararteristics? Just to check I got you right

Let me clarify what I meant, when I dive my AL80 I don't put air in my bc when I enter. I'm weighted for neutral buoyancy without air in the bc and 500psi in the tank and I always pop right back to the surface after a giant stride whether I'm in a wetsuit or drysuit. When my buddy took me out in his doubles they were double 100's with an aluminum backplate and 16lbs of lead in my weight harness (I normally wear 28 lbs with my drysuit and am neutral to just a bit light with an AL80). It occurred to me as I was setting up to enter that the doubles were probably going to make me negatively buoyant with no air in the wing. My buddy did not know at the time that I always enter with an empty bc so it never occurred to him to mention putting a little air in the wing. That was an interesting dive to put it mildly and I haven't had a chance to get out for another lesson--I definitely need it. When I started my descent the tanks flipped me forward into a turtle and since I was only in 20 feet of water the bottom comes quickly even with a slow fall. I sorted it out before hitting the bottom but I have more dives than the original poster and doing two things at once (turtle recovery/getting neutral in unfamiliar gear) isn't always easy for newer divers. I was trying to share things I learned the hard way during my experience as a newbie to doubles.
Ber :lilbunny:

 

[divekraz]

Kevin, I'm assuming you must be on the west coast of Fl. to be going so far off shore for a dive site? I've been diving up and down the east coast and the reefs are all pretty close to shore.

A safety precaution suggestion for your situation might be to buy the uniden voyager VHF radio (or some other radio) for $150 and a otter box for $20. The otter is rated to 100' (have taken it past 100') and the radio is rated 30 minutes at 1 meter depth. This is not to eliminate other safety devices but when your to far for an audio or a visual signal to easily work, the radio can put you in contact with other vessels in the area to let someone know there's a problem. Both my wife and I carry radios and have never had the otter leak on us yet or had to use any of our signaling devices but it only takes that one time.

I've always dove with my wife and she would always come back with 500psi+ more than me until I started making a point of taking slow complete breaths on inhale and exhale to maximize the exchange of co2 in my lungs. Now I often have more air than she does even though I'm twice her weight and at 52, 10yrs her senior.

Don't hesitate to contact me if you have a question.

 

[mislav]

Suggesting a guy with 25 dives buy 3 sets of AL80 doubles? Come on guys, get real.

I agree. I can't believe the direction thist thread has taken.

The OP will get better at air consumption with time and with more experience.

 

[CBulla]

Excuse me, but isn't it allways important? And secondly, your's and Cbulla's messages let me to understand that you were negatively boyant without air in your wings? How much and your doubles chararteristics? Just to check I got you right

Clarification is always key, but to be super clear here, I dive in tropical warm water and don't wear a wetsuit. My single tanks are either neutral AL or steel tanks. In essence, even with a single tank I don't wear weights unless I am diving a bouyant tank, which I add 4# and am groovy.

With the doubled 72's, well, they are steel. I don't wear a wet suit and I already don't need weight.

Regardless of what I dive, single or doubles, I am negative without air in the bladder! If you want to see it in action, come dive with me and I'll show you

 

[mislav]

With the doubled 72's, well, they are steel. I don't wear a wet suit and I already don't need weight.

:lol: Is that with or without that giant cross around your neck?


ps. j/k - I know it's not really you in the avatar.