What's the most popular tank size?

[CompuDude]

That 3200 psi in the al80 isn't really an issue. Many of the shops I've been to give a hot 3200 in AL tanks which cools to 2900-3100. Its not until you go into the gross overfill category (3400+ or so) that you have real issues. *MAJOR DISCLAIMER*. I do not advocate overfilling AL tanks. The better method is to do a hot 3000, let it cool and top off to 3000 again.

Hot fills are just that: Hot fills. By the time it cools down (i.e., the time you breathe it) you have the appropriate amount of air. So would never use the hot gas pressure in any meaningful calculations. So again, 3200psi in an Al.80 should really be the most you never see, and hopefully that's a hot fill that will soon cool to a more appropriate pressure for the tank.

There is a long history of overfilling some LP steel tanks with generally good results (few failed hydros etc). That said, overfilling does reduce tank life. In this day an age, if you can get basically the same tank as HP as LP (true for many LP tanks), the HP is the better choice. There are LP tanks out there that do not have a HP equivalent and in those cases, LP is your only choice.

I agree. There are a few specific LP models that seem to do very well with overfilling... if (a) you have the right tank (faber, usually) and (b) live in cave country where you have shops ready, willing and able to do a good "cave fill". (That same shop would have no problem giving you a proper fill on an HP tank, too.) And the HP tank will still ALWAYS be smaller and lighter (on land) than the LP tank. And anyway you look at it, you are OVERFILLING your tank beyond manufacturer recommendations. And for some reason that just doesn't sit well with me... especially, coming back on point, given the all-around great characteristics of the HP100 for the majority of normal diving needs as outlined in my earlier post.

I'm not sure I follow what you mean re LP tanks with no HP equivalent... do you mean small tanks, like 72s? Biggest LP tank I can think of is the LP120, which has less gas (barring an overfill) than the HP130. If you need the monster amount of gas of dual LP120s, overpumped, then I can see your point (Although Faber does make a HP149!). But I don't really see that need in the OPs immediate future...

 

[PerroneFord]

Haven't seen anyone recommend the LP 108...is there a reason why everyone is steering clear of the LP tanks? I know the HP gives you the less size/weight issue, is that the main reason why most are recommending the HP? My LDS told me to avoid the HP because of the "getting full fills" issue.

I prefer the LP108s. for a number of reasons, and have mentioned them. I prefer their buoyancy characteristics.

 

[in_cavediver]

too.) I'm not sure I follow what you mean re LP tanks with no HP equivalent... do you mean small tanks, like 72s? Biggest LP tank I can think of is the LP120, which has less gas (barring an overfill) than the HP130. If you need the monster amount of gas of dual LP120s, overpumped, then I can see your point (Although Faber does make a HP149!). But I don't really see that need in the OPs immediate future...

Here are a few LP tanks that do not have the HP equivalant: LP95, LP108, LP112, LP131 and some LP104's. Some of these are close to the HP variants but when it comes to trim and bouyancy characteristics, there can be significant differences.

For single tanks use, the LP85/HP100 looks like a great balance for a tank. I read on another thread about a steel 77 that's price competive to AL80's. That might also be a good choice.

 

[RS]

The most popular size seems to be "BIGGER". That's what everyone is always asking for...

The AL80 is popular for many reasons and makes a good tank. I see you have gotten a piece of advice to purchase a steel HP80. At 6' tall, that little thing will stand you on your head, or you'll have to put it so low on your back you can't reach the valve. You're going to want a tank about 24-27" long at your height.

I see you also got some advice about not buying a tank unless you're diving a lot. Gotta agree with that. For most divers, renting is a better deal. I don't know the break even point for you, or maybe you're like me and simply don't care. I just wanted my own tanks and bought them. I didn't know I'd be doing 75+ dives a year.

Best of luck.

PerroneFord: this is the most right on comment I've heard this year! Great advice.

I never realized my size made me different, but at 6'4", and using the normal-folk size gear, I'm feet-up and can't reach the valves all the time.

I finally got my trim right w/ a bpw. You're advice made so much sense I had to say something!

Now, I'm starting to think about doubles. What's your advice there for a large size diver w/ a comparable SAC?

BTW, I only have 15 dives now, so the advice about get more dives is already noted. If anyone has that advice suffice to post the smiley they feel is most appropriate.

 

[PerroneFord]

Glad to be of some help. You just have to think things trough as you start to buy gear to keep from making mistakes.

In regards to diving doubles, there are SO many factors to consider.

There is the factor of whether you'd diving wet or dry. If we are assuming you're in a wetsuit, I'd recommend either going for a set of AL80 doubles or a set of LP-85s. Both have nice buoyancy characteristics. The problem is that both will put a lot of their negative buoyancy up on your back, which won't help you balance. If you use them with an AL BP that will reduce the weight bias on your top half, but will give you less weight overall. So you'll have to make it up somehow.

If you are diving dry, then you could look to some longer tanks. LP121s are long, as are HP120s. LP121's are BIG tanks. And you'll get a workout with them. If you're diving off a boat, or have a long surface walk, I wouldn't recommend them.

Another option is something like a set of 104s or 108s, with a tailweight. This will put a few pounds near your butt and help your trim. What fins do you have? A set of Jetfins or other negative fin with spring straps on them will help floaty feet. A set of dense rubber soled booties will also help with floaty feet.

Everything is a bit of a compromise. If you can't get your weight down below your center if gravity, exaggerate lift in the top part of your body. It's like a teeter-totter. Just work the balance points. The problem is that unless you have a lot of gear to try out, you're likely to make some mistakes getting to where you want to be. I wish I had a magic forumla for you, but I don't. You'll note that a great many cave divers trade gear frequently...

I finally got my trim right w/ a bpw. You're advice made so much sense I had to say something!

Now, I'm starting to think about doubles. What's your advice there for a large size diver w/ a comparable SAC?

BTW, I only have 15 dives now, so the advice about get more dives is already noted. If anyone has that advice suffice to post the smiley they feel is most appropriate.

 

[Bob Vincent]

I do not own AL tanks any longer they have been replaced with steel. I'm a rather big guy and I like the steel's staying neg during the dive. For most diving I use Steel 80 2400 lp's. With overfill around 2800 to 3000 you have a huge amount of bottom time and are very compresser friendly.

When you need more air than that the HP 130's are the ticket when max is needed.
And being tall you do want to look at lenghts more closely.

 

[mark G]

here's a point to think about "resale value" you can always sell steel tanks quick and recoup a lot of your initial investment, I know it's not something most think about going in
but still something to consider.

 

[rdw_nc]

There is another current thread that states that PST is still in business and plans to start shipping in June. They also plan to renew their exemption.
When I went through the painful process of selecting my tanks I new that I would be doing some deco, cavern and wreck diving. I ended up with the PST E8-119. They are nearly identical to the Faber LP 95s. I had borrowed a some 95s on several occasions from a friend and found that the size, weigth and bouyancy characteristics were perfect for me. 5'10' 185 lbs. I can dive a 7-5mil westsuit in salt water without any lead. (OK, that has something to do with the pony bottle and lights). I've never had to cut a dive short due to low air or felt it float off my back on ascents. I can't say that about aluminum 80s. I've also rented AL 100s for wreck diving. They were comfortable to dive with but they are a few pounds heavier and a few inches taller than the 119. For me, that extra height puts them in the 'bonk me in the head' range.
A few years ago I found a spreadsheet that had about 20-30 different tanks with their dimensions, capacities and bouyancy characteristics. It was a big help in narrowing my search.

 

[rdw_nc]

If only I had a spell ckecker...
I found the spreadsheet and I hope that pasting it works. If not, I apologize. I added the PS info at the bottom. As I recall, the last three columns are cubic feet at 2650, 3000 and 3442 psi.

Manu Material CU FT Pressure Diam length Weight Empty Buoyancy Full Buoyancy Empty Real weight

Catalina Cylinders Abysmal no valve
C100 A 100 3300 8 27.3 46.1 -7.5 0 46.1
C60 A 60 3300 7.25 19.9 27.3 -4.9 -0.4 26.9
C80 A 77.4 3300 7.25 25.1 35 -5.8 0 35
S40 A 40 3000 5.25 24.9 15.9 -2.6 1.7 17.6
S53 A 53 3000 7.25 19 25.6 -4 0 25.6
S63 A 63 3000 7.25 21.6 27.2 -2.5 2.3 29.5
S80 A 77.4 3000 7.25 25.8 31.6 -1.7 4.1 35.7

Faber Cylinders
#24045 S 45 2400+ 5.5 23 17.6 -2.4 0.8 18.4
#24065 S 65 2400+ 7 21.1 25.6 -4.5 0.1 25.7
#24080 S 78 2400+ 7.25 23.2 30 -4.7 0.7 30.7 250
#24095 S 95 2400+ 8 23.8 37.3 -4.4 2.4 39.7 283 242
#24108 S 108 2400+ 8 26.8 41 -4.4 3.3 44.3
#24120 S 120 2400+ 8 29.3 45 -4.5 4.3 49.3
#30060 S 60 3000+ 6 22 22.9 -6.8 -2.8 20.1
#30072 S 72 3000+ 6.75 20.5 28.7 -8.4 -3.7 25
#31080 S 80 3180+ 7.25 20.1 32.4 -13.2 -7.3 25.1 272
#31100 S 100 3180+ 7.25 24.2 38.8 -14.8 -7.5 31.3
#31120 S 120 3180+ 7.25 28.6 45.4 -16.6 -7.7 37.7

Scubapro/Faber S 95.1 2640 8.02 23.8 37.6 -8.5 -1.2
ST100 S 100 3500 7.3 25.2 36.4 -11.5 -4 32.4
ST120 S 120 3500 7.3 28.9 41.5 -11.8 -3.1 38.4
ST80 S 80 3500 7.3 20.9 30.9 -10.9 -5 25.9

Luxfer
50 A 48.4 3000 6.9 19 21.2 -2.4 12 22.4
63 A 63 3000 7.3 21.9 26.9 -2.1 2.6 29.5
72 A 72 3000 6.9 26 28.5 -1.6 3.5 32
S040 A 40 3000 5.3 24.8 15.3 -0.9 2.1 17.4
S080 A 77.7 3000 7.3 26.1 31.7 -1.9 4 35.7
S092 A 89.8 3200 8 24.8 37.5 -2.7 4.1 41.6
S100 A 100 3300 8 26.2 40.2 -3.9 3.5 43.7
S808 A 80 3000 8 22.9 35.2 -3.8 2.2 37.4
S80N A 77.4 3300 7.3 25.8 35.2 -5.8 0 35.2

Pressed Steel
LP-80 S 80 2400 7.25 24 32 -6.3 0.5 31.5
HP-100 S 100 3500 7.25 23.94 31 -8.9 -1.4 29.6
HP-120 S 120 3500 7.25 27.87 36 -9.4 -0.4 35.6
HP-65 S 65 3500 7.25 16.75 24 -6.4 -1.5 22.5
HP-80 S 80 3500 7.25 19.75 26 -8.3 -2.5 23.5
LP-104 S 104 2400+ 8 26.19 45 -8.2 -0.7 44.3
LP-120 S 120 2400+ 8 29.4 50 -9.4 -0.4 49.6
LP-95 S 95 2400+ 8 24.75 42 -8 -1.2 40.8
CU FT Pressure Diam length Buoyancy Empty Buoyancy Full Weight CU FT CU FT CU FT
E7-65 E-9791 3442 psi 7.3 16.75 -1.5 -6.4 3/4-14 23.2 52cf 58cf 65cf
E7-80 E-9791 3442 psi 7.3 19.75 -1.5 -7.5 3/4-14 26.0 64cf 72cf 80cf
E7-100 E-9791 3442 psi 7.3 24.00 -1.3 -8.8 3/4-14 32.0 80cf 90cf 100cf
E7-120 E-9791 3442 psi 7.3 28.00 -1.3 -10.3 3/4-14 36.6 96cf 107cf 120cf
E8-119 E-9791 3442 psi 8.0 24.00 -0.5 -9.5 3/4-14 39.3 95cf 106cf 119cf
E8-130 E-9791 3442 psi 8.0 25.56 -1.8 -11.55 3/4-14 42.2 104cf 119cf 130cf
E8-149 E-9791 3442 psi 8.0 29.37 -1.8 -12.9 3/4-14 47.5 119cf 133cf 149cf

 

[HybridDiver]

Bigger is not always better, The only way to get better BT is to dive more. Bigger tanks are not the way to go, You should watch DIR 3 and learn lots about diving. I have been diving for 3 years and Im doing GUE Fundies and Tech 1 in summer. Watching the DIR 3 video made me rethink all my gear, Dont by stuff if you dont need it. Only buy the stuff you need, Zeagle tech bcd all that no need. So ask your self, Is it worth having a tank? 1st off how tall are you, If your small like me nothing over my steels 100. 100 fits me perfect and I get better BT from my buddie who dives a steel 120 because I dive pretty much everyday. Dont spend lots of money if your not going to use it alot.
Thats my .02
Chris