Neutral Buoyancy

[jbd]

and I couldn't agree more about having the time to play around with the bouyancy control stuff. Its one thing I think that all agencies should allow before the signing of the C-card. One of the things that seemed different from my training compared to my daughters training was that her instructor had them spend almost an entire pool session on self exploration of bouyancy control. I was there watching and some caught on quicker than others but even from the surface you could see when the light bulb came on for each of them. My pool instructor was more interested in impressing us with his skills. Another difference we had was my class was 5 pool sessions while my daughter had 8 pool sessions.

I'm sure glad things worked out for your daughter after her trouble spot.

 

[Dryglove]

I found the easiest way for me was to get a AL80(most common tank to rent here) with no more than 500 psi in it and go to 15 feet.I added and subtracted weight tilll i was neutral with no air in my bc.You also have to aware of your breathing as that will affect your bouyancy and remain relaxed while doing this.Have fun!!

 

[ScubyDoo]

Originally posted by scubabunny
The NB aluminum 80 tanks are AWESOME!!! I don't think anyone else uses them but us (Guam). I HATE diving with Standard 80 aluminum. Even if I put extra weight on (for Yap and Bali) I'm still fighting the tank.

Neutral bouyant tanks are just that at 500psi. I think they are .5 positive when completely empty. But they make bouyancy so much easier...I still don't understand why more people don't use them.

I considered getting one, but backed out because I didnt know enough about them. Aren't they basically a standard AL80 with a thicker wall, which makes them about 5lbs heavier? I think they weigh about 35lbs compared to 29-30lbs. for a std. AL80

I'll probably wind up getting one eventually.

 

[Jasey]

Having just finished my OW I must say that buoyancy control seemed to be one of the most important aspects to learning scuba. My enjoyment/confidence(these seem to go hand in hand) increased tenfold when I clicked to how to control it.
I don't know much about tanks, but the aluminium one I had did not appear to give me extra buoyancy as it got lighter...but will be something I will remain aware of.

 

[stingray3]

You'll find with experience that the way you breath will compensate you for the ligher tank at the end of your dive, without having to put on extra weight.

 

[old guy]

Drew Sailbum got it right...

80 cubic feet of dry air weighs 5.9lbs. It doesn't matter what kind of tank you put it in. Boyancy will change as you release the air.

A neutral bouyancy tank can only be neutral at one pressure. It can't be neutral empty and full.

 

[scubatexastony]

All the talk of stl vrs al and "neutral tanks"! Volume used is directly proportionate to weight lost. stl just puts less weight on your belt and more on your back, which to most is more comfortable.... go figure. JETBLAST has the answer, have enough to hang at your safety w/ 500 or so in your tank(s). JMO

tony

 

[scubabunny]

Originally posted by ScubyDoo



I considered getting one, but backed out because I didnt know enough about them. Aren't they basically a standard AL80 with a thicker wall, which makes them about 5lbs heavier? I think they weigh about 35lbs compared to 29-30lbs. for a std. AL80

I'll probably wind up getting one eventually.

The NB80s are heavier than the standard AL80s. Empty with valve they are 37lbs. (I know this by heart because we mail enough of them..valves seperate of course). The main advantage is they are rated at 3300 psi, instead of 3000 psi. So, you have more air without the positive bouyancy at the end of the dive.

There are actually 2 versions of the 3300 psi 80cuft that I know of. One is the compact 80 (Catalina), and the other is the neutral bouyant 80 (Luxfer). The both have basically the same bouyancy characteristics, but the Luxfer tank has the majority of the weight at the base of the tank which is supposed to keep the diver in a more comfortable position (keeping his butt down, I guess). Catalina has the weight up by the neck (helping with a horizontal position). I have used both, and didn't really see any difference.

They are both negitively bouyant when full, although I don't know the exact weight factor right now. I prefer them here in warm water, but I don't know if that is what colder water divers want.

 

[Dryglove]

I own two of the luxfer neutral bouyancy tanks.I prefer them over the regular aluminum 80's.One of the best things about them is that they remain negatively bouyant at the end of the dive.For me i couldnt stand the feeling of a near empty al 80 wanting to float off my back and shifting around.Yea i know there are ways to solve that like tank weights.To me its just more crap to fall off or get hung up.I also dive in a drysuit and the NB 80's have most of the added weight in the bottom which helps keep me level.No need for ankle weights plus its 5 more pounds to take out of my weight pouches.One last positive of the NB 80 is due to the fact most of the weight is in the butt of the tank it helps you to keep an upright position when bobbing in the water with a back inflate bc. So for me it was a no lose deal and helps keep my gear streamlined and simple


service pressure NB80 3300 AL80 3000

weight empty NB80 36.7 AL80 33.2
w/valve

salt water NB80 -7.3 AL80 -3.4
bouyancy full

salt water NB80 -1.5* AL80 +2.5
bouyancy empty

height NB80 28.81 AL80 29.06

This is the information on these tanks as provided by diversdirect.

 

[savant]

Can't argue against all the comments made except to add that the first couple of times I dived, I used way too much weights and was in fact suffocating me. Reduced it and found it a lot more comfortable. Then the more I dived, I realised that as my neutral buoyancy skills improved (also by 'playing' around in the water), I need even lesser weights. Right now, the number of weights I used are fixed but I expect that to change soon as I have new equipment and will take a while to get used to them (new wetsuit, BCD etc etc.)