Weight question

[scubanut]

Diving steel tanks currently, have a PST 80 and 119.  I scored a couple of Luxfer AL 100's for the right price of free!  Was wondering how to weight myself for the AL tanks, I'm at 16 lbs. with the steel 80 and 14 lbs with the 119.
Looking at the different bouyancy charts for each tank (everyones charts are a little bit different) the empty bouyancy difference between the ST 119 and the AL 100 is roughly 6 lbs positive for the AL!

That tells me that I should be at 20 lbs for the AL 100 right?  Am I going about this correctly, or this a trial and error thing?

I'll be putting a couple of 1 lbs weights on the flag bouy incase I can't get down when I try them the first time!

Chris

[Chris H]

Are you diving wet or dry?
As you’ve already pointed out, the buoyancy swing on the aluminum tanks is much greater than the steel tanks.   To really know what you need, put the tanks on with 500psi in them and have enough weight to comfortably hold a 20ft stop without a wing full of air.  Getting down won’t be the problem, staying down with tanks that are nearly empty will be. 

I don’t remember for sure, but I think I only wear my SS BP for weight and possibly a 4 or 5 lb tail weight when I wore Steel 50’s, 80’s, 95’s, and 130’s with a trilam drysuit and Weezle Extreme + insulation.   I know that is the case for the 50’s because I used them a week or so ago.

I made the assumption you were talking about doubles.  However the same situation will happen with a single tank too.

[jasondbaker]

I dive steel 85's and aluminum 80's.  When going from steel to aluminum I add about 3lbs.

Funny story.  A couple weeks ago I did my first local dive of the year.  I got geared up in my dry suit, aluminum tank, grabbed my camera, and waded into the water.  I had a bit of difficulty getting down.  I had taken some weight out of my belt the night before and just assumed that I took too much out.  I struggled with my buoyancy throughout the dive (which wasn't deeper than 25ft).  After about 30 minutes I ended the dive and walked up the shore.  As I was removing my gear I noticed my dry weight belt sitting on the tarp.  The lesson: maybe proper weighting is just a state of mind.  <Don't try this at home>. 

[scubanut]

Thanks for the replies, Chris I'm talking about single tanks, soory should have clarified, and diving a wet suit (7mm) full.  The only thing that will change is my tank.  I looked up bouyancy figures online, and as I stated, every chart you look at is alittle different.  I came up with Luxfer AL-100 Full -3.9, empty +3.5, PST E8-119 Full -10.5, empty -2 lbs.  The difference in empty bouyancy is "roughly" 5.5 lbs.  I use 14 lbs with my 119, so I should be at 19.5-20 with my AL100.

I'll give it a shot tomarrow, I'll have a bunch of extra weight along in case I can't get dialed in with my figurin'!  Let you all know how it turns out..

Thanks again
Chris