Weight Change with new Steel tanks

[seaseadee]

I am a new diver with an equipment question. My current equipment configuration is thus:
1. 3mil Wet Suit
2. back-inflate BCD with 4 lbs in the trim pockets and 6lbs in the integrated weight pockets
3. Rental Aluminum 80 tanks


I live on the Florida coast so all of my diving is in salt water. With this configuration I am very comfortable in the water with what I consider to be good buoyancy control and good trim. I have just purchased a set of Faber Blue Steel LP85's from my LDS. Faber lists the buoyancy characteristics of these as -3.8lbs full and +2.82lbs empty. The folks at the LDS inform me that most people are able to lose 4-6lbs when switching to these tanks. Since my only gear change is going to be these tanks, I am having trouble understanding how I might be able to drop said 4-6lbs. Here is the thought process: The Rental Luxfor AL80's are -1.4lbs full and +4.4 empty. This seems to be a 2lb difference at both ends of the dive. Am I being two simplistic in my calculations? Also, my LDS overfills these to 3000psi to give me the maximum air time. I do not know if this factors into the equation as the larger amount of air would also weigh more.

 

[Superlyte27]

You should be able to drop 4-6lbs of lead. LOL

 

[rongoodman]

Why not start out by taking 2 lb out of either the trim or integrated weight pockets and see how it goes? I can't see losing 4-6 lbs with this switch unless you're too heavy to start with. Even if your LDS gives you a nice overfill, the tanks will still weigh the same at the end of the dive, and you will need enough weight to hold a stop with them nearly empty.

 

[Phil_C]

I am a new diver with an equipment question. My current equipment configuration is thus:
1. 3mil Wet Suit
2. back-inflate BCD with 4 lbs in the trim pockets and 6lbs in the integrated weight pockets
3. Rental Aluminum 80 tanks


I live on the Florida coast so all of my diving is in salt water. With this configuration I am very comfortable in the water with what I consider to be good buoyancy control and good trim. I have just purchased a set of Faber Blue Steel LP85's from my LDS. Faber lists the buoyancy characteristics of these as -3.8lbs full and +2.82lbs empty. The folks at the LDS inform me that most people are able to lose 4-6lbs when switching to these tanks. Since my only gear change is going to be these tanks, I am having trouble understanding how I might be able to drop said 4-6lbs. Here is the thought process: The Rental Luxfor AL80's are -1.4lbs full and +4.4 empty. This seems to be a 2lb difference at both ends of the dive. Am I being two simplistic in my calculations? Also, my LDS overfills these to 3000psi to give me the maximum air time. I do not know if this factors into the equation as the larger amount of air would also weigh more.

I think you have your figures off here and the LDS is wrong, Steels are not positive when empty, they are still negative, so steels start negative and end negative. So I think the figures you are quoting for the Fabers are wrong.

In contrast Ali's are positive empty and negative full so you have a greater buoyancy swing. - I have tried to look up the LP85's and can't see the figures at the moment.

But that will be where the confusion is coming in, I agree you should be able to drop a few pounds. - Phil

 

[tomfcrist]

Remember that it is more important to be neutral at the end of your dive . If you drop 6lbs of lead and dive with an overfilled tank you may find that you are a bit light at the safety stop. I would just start with dropping 4 lbs out of the weight pockets(not the trim ) and do some trial and error on shallower dives. If you are still needing air in your bc at the safety stop with a 500psi tank, drop the other 2 lbs

 

[seaseadee]

Here is what I found on the tank specs:

http://bluesteelllc.com/cylinder-specifications.html

Near as I can tell the L85DVB is the tank I purchased.


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[rongoodman]

The figures for the Fabers look right, the Worthingtons are heavier and stay negative though out.

 

[Phil_C]

Just looked at your link and the buoyancy quoted is for an empty naked tank I.e. No post and valve. You will have to add 1.5-2 lb for the post and valve, and then factor in the 50 bar air you are leaving as your safety limit. I think this will still make this tank negative at the end of the dive. Phil



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[seaseadee]

Just looked at your link and the buoyancy quoted is for an empty naked tank I.e. No post and valve. You will have to add 1.5-2 lb for the post and valve, and then factor in the 50 bar air you are leaving as your safety limit. I think this will still make this tank negative at the end of the dive. Phil



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Ok now that would make sense. If I take the empty buoyancy of +2.8lbs add -2.0 for the post and valve and another -1.0 for my reserve then I would be -0.2lbs at the end of the dive. The luxfor's are +3.4 at 500psi, so I should be able to drop 4lbs and still be neutral at the end of the dive. I will do as someone else suggested and start with dropping 4lbs from my integrated weights and see what happens at my safety stop.

Thanks to everyone for their help.


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[luscioman]

I think most people are thinking of the Faber FX series when going to steel. I did it and in south florida dropped 6lbs of my weight. I think you are going to be correct with dropping 2 pounds.