steel vs alum

[DA Aquamaster]

Pressed Steel Tank's E7-100 would be my tank of choice. It holds 100 cu ft at 3442 psi and even if you can only get a 3000 psi fill you will still have about 87 cu ft (compared to 77 cu ft in an AL 80 at 3000 psi.)

It is also, to my knowledge, the lightest 100 cu ft tank available and is very comparable to an AL 80 in both overall diameter and weight but is 2 inches shorter. It also has better bouyancy traits, being 2.5 lbs negative when empty. so you can remove about 5 pounds from your weight belt compared to an AL 80.

Of course, the problem is actually finding them.

 

[dbg40]

Aside from the OBVIOUS, (even at 3000 lbs) Steel HP tanks are the hot set up. (ALL the cool kids are diving them) Figure neg. bouy, and I never really seem to have any problem with this, where others say they do. EXTRA AIR! Most times, I hit the water with a 3600 lb tank on me. It's a win win, over fill or not, just for the neg.wt. factor.

 

[Leadking]

Does anybody know just how much more a steel 100 weighs?

A HP steel 100 cylinder weighs a couple of lbs. more than a aluminum 80.

A Worthington steel HP100 cf will be 4 lbs negative vs. 4.4 lbs positive for an alum. 80 cf cylinder (both tanks empty). this would allow you to remove as much as 8 lbs of lead weight.

Lee
www.seapearls.com

 

[dirthead]

I just received my PST E7 100 from DiveRite Express. I cannot tell the weight difference between it and my AL80 Luxfor, just from picking them up. The steel tank does not feel heavier. It is smaller, and since it displaces less water, it will be more negatively bouyant. I haven't had a chance to get it in the water yet, but will try to lose 4-5 pounds off my belt with it. That means with my 7 mil suit/hood/booties/gloves, SS backplate, and HP 100 tank, I will need about 9 pounds of weight in freshwater. SWEET!!!!!!!!!!!!! And if I can remove 8 pounds, as Leadking suggests, I will only need 6 pounds of weight.

 

[spectrum]

Here's an oldie but a goodie...
http://www.scubaboard.com/showpost.php?p=1191538&postcount=16

Pete

 

[billtodive]

Here's an oldie but a goodie...
http://www.scubaboard.com/showpost.php?p=1191538&postcount=16

Pete

Best link I've ever used. Thanks.

PS. wanna buy a couple al80's?

 

[anth]

2. When I go to dive shops, I very rarely get a fill to 3000. Usually it is closer to 2800:wacko:. Is this enough of a difference to complain or am I just being picky? Is there any way to help, um, encourage a fill monkey to kick it up to 3000 without being rude?

2800 psi isn't too shabby. If they're giving you a slow fill to 3000 , it'll cool down to somewhere around 2800 (PV=nRT). Even filled slowly, ~300 psi a minute, they'll still be a tiny bit warm at the end of the fill. Maybe if you ask they'll top it off once its cooled down... Just don't call them monkeys .

DSAO,

Anthony

 

[nwfellah]

so, my next question is, how do AL80s "wear out"?

 

[Monkey Knife-fight]

2800 psi isn't too shabby. If they're giving you a slow fill to 3000 , it'll cool down to somewhere around 2800 (PV=nRT). Even filled slowly, ~300 psi a minute, they'll still be a tiny bit warm at the end of the fill. Maybe if you ask they'll top it off once its cooled down... Just don't call them monkeys .

DSAO,

Anthony

Yeah i'd reccomend just saying something like "I've got time to wait can you give me a nice slow fill?"

Or just drop off the tank overnight or something and if it's low when you pick it up ask them to top em off.

I sometimes go to a shop where they fill my AL80's to something like 3400 hot so it cools to 3100 or so.

 

[spectrum]

so, my next question is, how do AL80s "wear out"?

The cylinder measurably expands and contracts with each fill cycle. Aluminum does not stand up to this activity nearly as well as steel.

The temperature at which the temper of aluminum is disturbed at is much lower and can be reached in agressive filling rates. Remember that the hot tank you feel is air cooled, the inside is hotter.

Stress cracks in the neck usually result.

Pete