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New tank and weights

PostPosted: Sun Feb 27, 2011 11:01 pm
by Frosty
Sorry to keep bugging you guys.
I did a shore dive at goat island today. the vis wasn't bad at all around the actual island but rubbish in by the shore.
The whole point of the dive was to have a splash with my gear.
Trouble was for the first time I felt totally uncomfortable with the gear.
-Its a airis wing type weight integrated BC and a 15l steel tank
I did a dive last week in lake pupuke with the same gear except I had a borrowed ally 11.5l tank carrying 6kg on my hips and felt great.
Today it for the first time felt alien. I was carrying 6kg again but on advice I put an extra 2kg in pockets right beside the tank.
Does a 15l tank make a big difference or is it just a matter of getting used to it?

Re: New tank and weights

PostPosted: Mon Feb 28, 2011 5:54 am
by GoatFish
Frosty wrote:Sorry to keep bugging you guys.
I did a shore dive at goat island today. the vis wasn't bad at all around the actual island but rubbish in by the shore.
The whole point of the dive was to have a splash with my gear.
Trouble was for the first time I felt totally uncomfortable with the gear.
-Its a airis wing type weight integrated BC and a 15l steel tank
I did a dive last week in lake pupuke with the same gear except I had a borrowed ally 11.5l tank carrying 6kg on my hips and felt great.
Today it for the first time felt alien. I was carrying 6kg again but on advice I put an extra 2kg in pockets right beside the tank.
Does a 15l tank make a big difference or is it just a matter of getting used to it?


Hehe a 15l steel compared to a 11.5l ally is a big difference... in terms of weight that is... I'll let the other more experienced divers give you advice on what to do...

Re: New tank and weights

PostPosted: Mon Feb 28, 2011 8:58 am
by Andy
I agree with the Goat, it's a big difference!

Not just actual weight, but also size and shape - 15L steels tend to be quite dumpy in comparison with aluminium tanks so the weight distribution is completely different.

It's not a dire situation, though! You will find the right way to put your weights.

The best option is to get the tank near empty (35 bar or so) and go somewhere (in salt water) where you can do a buoyancy check. A buoyancy check with near empty tank will tell you how much weight you really need (certainly my guess is that 9kgs is probably too much). After that, you can work out where to put it.

Re: New tank and weights

PostPosted: Mon Feb 28, 2011 9:08 am
by ChuckyBob
15L steels are much more negative buoyant than ali 11.5's
Salt water is more dense than fresh but no so much that it would make up for the change in tank buoyancy.
If anything you should probably had taken off 2 KG's of lead not added it.
This is the great advantage of steel over lead. You will have a bit more weight on your back because of a larger capacity tank but you will require less lead on your belt.

Re: New tank and weights

PostPosted: Mon Feb 28, 2011 2:45 pm
by Frosty
Thanks guys--that answers the question loud n clear. I thought it was all in my head.
I refilled my tank already so I guess ill reset the weights the way they were and see how things feel.
It seems sometime what you think is the sensible choice sometimes aint

Re: New tank and weights

PostPosted: Mon Feb 28, 2011 3:26 pm
by ChuckyBob
You can do a buoyancy check with a full tank.
If fact I would go as far as to say its a better way to do it.

:idea: Kit up and jump in the water,
:idea: empty your BC,
:idea: Add or subtract lead until you become neutrally buoyant
:idea: Next work out the weight of your air that is in your tank.
Air weights about 1.3 grams per litre.
If you have a 15Litre tank and 200 bar in it then its 15x200*1.3 grams= 3900grams or about 4 KG's

The reason I think its a better way to do it is because it really demonstrates the buoyancy shift from a full tank to empty

Re: New tank and weights

PostPosted: Sun Mar 06, 2011 9:47 pm
by Frosty
Hey thanks guys --as per the other post I think I've got it sorted. I had the gear setup all wrong for me

Re: New tank and weights

PostPosted: Sat Jul 02, 2011 12:16 pm
by Frosty
funny how time and practice changes things. We did a 2 tank dive a week or two back. First with the 15 then followed by one with a 12l steel.
Barely noticed the difference--it was great