weighting question

I currently use 31 lbs of weight diving in a drysuit with a 400 gram undergarment with twin Al80's. The 31 lbs includes the 6 lb backplate a 12 lb v-weight and the rest in pouches/tailweight. I am making a switch to steel HP 100's. Can someone help me out with how this will impact my weighting. I dive in fresh water.

Assuming you are neutral with 31 lbs, changing from AL80s (+5) to steels (-5) you should drop about 10 lbs.
To be more exact, check the specs of old and new tanks, do a balanced rig calc and then buoyancy check in water. I'd start with 23-25 lbs of total neg weight and see from there.


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decompression:

Assuming you are neutral with 31 lbs, changing from AL80s (+5) to steels (-5) you should drop about 10 lbs.

Click to expand...

Go to a chart like Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan and look at the empty weights (what you want to be weighted for, just in case). AL80s are positive 2.3 to 4.4 pounds, depending one what kind of tank, each. So call the pair 8 pounds positive, empty. The HP100 steels (PST 3500psi) are negative 1.3 pounds each, so 2.6 total. The difference is 10.6 pounds, but could be as little as 6.6 and as much as 24 pounds, depending on exactly which tanks you are talking about. And then note that when your 100s are full, that will add 15 pounds of gas to your overall weight....so you really do need to trim out neutral with empty tanks, or else with full tanks and add another 15 pounds.

I dropped 6#s when switching from alum 80s to Faber HP 100s. Hope this helps you.