How Much Weight to Add?

[Oddthomas]

How much Weight do I need to Add?

Set Up: DUI TLS 350 Dry Suit, zeagle escape BC, Steel 119 tank. I have logged about 20 dives with this setup and am getting fairly comfortable with it. I am going to Bonne Terre this weekend and will be using an Al 80 instead of my Steel 119. I normally use 8lbs of lead with my current setup. How much weight am I going to need to add with the Al 80?

Thanks for the Help!

 

[DivemasterDennis]

Others who have dove with the big steel tank will give you a more specific response, but for starters, know that an aluminum 80 will be slightly positive when mostly depleted. Based on my experience going from a steel 72 to 80 AL, I have a differential of about 4 to 5 pounds. Yours may be a little greater than that. Be sure to do a weight check, preferable with an aluminum 80 with about 1000 psi if you can.
DivemasterDennis

 

[cool_hardware52]

How much Weight do I need to Add?

Set Up: DUI TLS 350 Dry Suit, zeagle escape BC, Steel 119 tank. I have logged about 20 dives with this setup and am getting fairly comfortable with it. I am going to Bonne Terre this weekend and will be using an Al 80 instead of my Steel 119. I normally use 8lbs of lead with my current setup. How much weight am I going to need to add with the Al 80?

Thanks for the Help!

*Most* common steel tanks are about -1 ~-2 lbs empty. The Typical al 80 is +4 lbs empty.

Look here Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

If you dive in salt water now you will need less ballast in fresh water.

Fresh water is ~2.5% less dense than saltwater. That means you need to remove 1 lbs of ballast for every 40 lbs of diver and gear (1/40 = .025)

Tobin

 

[flots am]

How much Weight do I need to Add?

Set Up: DUI TLS 350 Dry Suit, zeagle escape BC, Steel 119 tank. I have logged about 20 dives with this setup and am getting fairly comfortable with it. I am going to Bonne Terre this weekend and will be using an Al 80 instead of my Steel 119. I normally use 8lbs of lead with my current setup. How much weight am I going to need to add with the Al 80?

Thanks for the Help!

That depends almost entirely on your drysuit underwear and which steel tank you had and which aluminum tank you're switching to. Tanks from different manufacturers and different models from the same manufacturer can have significantly different buoyancy characteristics. There's about a 2.5% change between salt and fresh water, but changing your tank and underwear will have a much bigger effect.

In cold water with a steel tank and a drysuit, divers can use anywhere from 16 to 40 pounds, depending on the buoyancy of the underwear and the tank.

I don't know of any way for you to come up with a reasonable number except to get in the water with your gear and do an actual buoyancy check.

flots.

 

[TSandM]

I found two brands of 119s -- both are -2 when empty. A Luxfer Al80 (the usual sort) is +4.4. That would mean about a 6 1/2 pound additional weight requirement, just from switching tanks. I would assume that, being in Ohio, you are mostly diving lakes, so there would be no change for salinity. And if you use the same undergarments, the answer is that you should add at least six pounds. Note that Al80's get very butt-light when they are empty, so putting that weight as low down on your body as you can would probably be most helpful.

 

[Teller]

Your undergarmets will play the biggest role. Best thing to do is grab an AL80 and do a weight check prior to you trip.

 

[Oddthomas]

Thanks for the help!