My white 130's.

[Linedog]

OK so I got my buoyancy pretty much dialed in on my HP steel 100's. Then I go and trade them for a pair of HP steel 130's, they have almost the exact same buoyancy. However they weigh 10 pounds more! So could I just drop 10 pounds of lead? I'm planning on dropping 8 to start and go from there. What say you?

 

[VooDooGasMan]

What ever you do make sure you breathe it at like 200 psi, and easier to do if at 500 to start, this way you know you can get down with it. Diving a 130 could get you into deco obligation easier, so my concern would be staying at 10' from 500 to 200 psi.

Now if you know that you will always have a 1000 left you can shed weight and use the tank and air for a weight distribution.

The answer I would say is to take ditchable weights and figure out that way, if 8# is to much you now have to deal with a problem right away.

 

[Reef_Haven]

Might help if you post the manufacturer of each. Sounds like they are both PST. As VDGM points out you need to be concerned with nearly empty buoyancy weight. Since they have almost the exact same buoyancy, you may not be able to drop any weight, unless you plan to end your dives with a lot more air.
This chart may help. Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

 

[Scared Silly]

Then I go and trade my HP steel 100's for a pair of HP steel 130's, they have almost the exact same buoyancy. However they weigh 10 pounds more! So could I just drop 10 pounds of lead? What say you?

What I say? I say you do not know the difference between buoyancy and dry weight. So drop 10lbs of lead and have your friends call you "Bob" cause that is what you will be doing (bobbing at the surface) while they dive.

If the cylinders have almost the same buoyancy then you will not need to make any changes to the amount of lead. Any lead difference will be due to the change in buoyancy. As for the dry weight difference suck it up or buy a hand truck to wheel that monster down to the shore.

 

[Linedog]

OK, both are Worthington's
100's full -10.0 lbs 500 psi -2.5 lbs Dry weight 33.0 lbs
130's full -11.7 lbs 500 psi -2.0 lbs Dry weight 43.0 lbs
So what I'm looking at is a 10 pound weight change.

 

[Cyprian]

Linedog,

What the folks above are trying to tell you is that you only need to be concerned with dry weight on land. In the water you are looking at the difference in buoyancy characteristics. The Worthington 130's are actually more buoyant at 500 psi than the 100's by 0.5 lbs per tank, based on what you just posted (I didn't look at the chart).

So you won't be dropping any weight in the water, you will just be carrying around heavier tanks on land. You might even have to add a pound.

Cyp

 

[TSandM]

Look at the buoyancy when empty -- it isn't different. Buoyancy when empty is the key, because that's what you have to weight yourself for, in order to hold a stop at the end of a dive, when the tanks are nearly empty.

What a tank weighs on land, and what it weighs in the water, will be different, because the tank displaces water and therefore the water "buoys" it up. 130s are physically bigger than 100s, and displace more water, so although they are physically heavier on land, they are NOT heavier in the water WHEN EMPTY, which is what you care about. They are heavier at the beginning of the dive, when full, mostly because they have more pounds of air in them -- but you are going to let that air go out into the water during your dive, so you'll be getting lighter and lighter. At the end of the dive, you'll be just where you were with your 100s.

Do not drop weight. You might find yourself in an actually dangerous situation, where you cannot control your ascent.

 

[Linedog]

OK, with enough people telling me the same thing in 5 different ways I'm finaly getting it. Thank you all for saving me, I just needed to get my head wrapped around the 2 different/separate weights. On land the 130's weigh more but in the water they "float" about like my old 100's. So for now I won't change my weight, as I was just a bit heavy before. Once again thank you all for taking the time to help me get it!