I've read 30 pages on this thread

[Wayward Son]

given that you have back problems & wt is a real issue, you just have to pick the tanks that work for you.

 

[coldwaterdufus]

Wayward Son I'm diving at altitude and cold water. The calc EOD for a depth of a 75Ft dive = 100 to 110 ft deep . I don't have my tables with me , so I'm trying to remember my log book numbers. But, for me anyway, these are fairly deep dives by the time you add all the conversions. I think I still need the extra air even thought they are only shore dives.

 

[Wayward Son]

that makes the 100's look a lot better. If an AL80 doesn't bother you, they won't. keep in mind you drop about 5 lbs of lead with them

 

[Wayward Son]

Good charts of tanks specs here:

Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

 

[Wayward Son]

it doesn't have all of the newest tanks, like the Faber FX-100, but it does have most of the older ones & can provide info that's been removed elsewhere.

 

[scubaskipper]

Can't go wrong with HP 100's.

 

[Puffer Fish]

I've got all the numbers , so I thought I'd share. Following are tank#, air and 34 lead ( for me )
Pre Dive Post Dive zero air
AL 80 71.8 65.5
X7 100 68.3 60.0
FX 100 71.6 63.3
X 8 119 79.2 69.6
Fx 117 78.1 68.7
X7 120 75.2 65.5
FX 120 77.9 68.2
X8 130 81.1 70.6

Worthington's are the X series, Faber are the FX. Calc Pre dive numbers are after dropping the appropriate weight differences re: buoyancy. I'm 90% sold on the Steel 100's, but I'd be into the steel 120's if they weren't so long, ( or I wasn't so short ) Compare the colored areas. Mr Carcharodon, I'm in a dive club so buddies vary a lot. I just need to try to keep up...

Excellent...you've got it...so now that you feel comfortable with those numbers...you only need to know one more thing... most of them are not right. Sorry, but it seems that tank mfg's are not very good at weights or math or both.

I actually don't have a clue why they cannot get the numbers correct, but for starters... air compressed to 3442 psi would weigh a specific amount per cubic ft..

Best I can figure, that would be roughly .08 lbs per square ft.. but notice that the gas weight in the 100 is .083...and the gas in the al 80 (which is not really 80 cubic ft) should weigh less, as it is not compressed as high.

I have weighed most of the tanks listed about at one time or another...but what always strikes me as odd is they never match. First I thought it was the boot (as that is not inclued), but even removing that, they typically are several lbs off.

Three weeks ago, while loading some FX 117' and FX 120's.... the weight difference was really obvious... with the FX 120 being 3 lbs heavier... but the boot is slightly lighter...do not have a clue why this is...but it does make it a bit harder.

 

[coldwaterdufus]

Done: I'm going to buy the Worthington 100 steel tanks. Lighter before and after the dive than the AL 80's,. As Randy said before, these probably won't be my only tanks. I think I'll buy 2 100's and somehow try out bigger tanks before I buy one more. Thanks to everyone on SB for all the help. Merry Xmas
Puffer Fish, I was using .0807 # / cubic ft weight for air for all calculations My understanding is the weight / cubic ft doesn't change under different pressures, just the volume

 

[Randy43068]

Done: I'm going to buy the Worthington 100 steel tanks. Lighter before and after the dive than the AL 80's,. As Randy said before, these probably won't be my only tanks. I think I'll buy 2 100's and somehow try out bigger tanks before I buy one more. Thanks to everyone on SB for all the help. Merry Xmas
Puffer Fish, I was using .0807 # / cubic ft weight for air for all calculations My understanding is the weight / cubic ft doesn't change under different pressures, just the volume

the volume stays the same no matter what, but your air consumption rate changes because of the different depths you dive. Remember air is delivered to you at the same pressure as the depth you dive. So, the deeper you dive, more air will be delivered to you. The tank and whats in it will remain the same.

 

[Puffer Fish]

Done: I'm going to buy the Worthington 100 steel tanks. Lighter before and after the dive than the AL 80's,. As Randy said before, these probably won't be my only tanks. I think I'll buy 2 100's and somehow try out bigger tanks before I buy one more. Thanks to everyone on SB for all the help. Merry Xmas
Puffer Fish, I was using .0807 # / cubic ft weight for air for all calculations My understanding is the weight / cubic ft doesn't change under different pressures, just the volume

Excellent choice Coldwater. Everyone I know that has them likes them.

I would agree (after checking) that your .0807 is the correct value... where the others are getting their numbers is unknown. The difference between .083 and .080 for 133 cubic ft tank is over half a lb, and one would think they would want to show the weight as low as possible.