what size (cuft) of tank to get and new or used

[Bubbletrubble]

How much heavier are the steel 100's than the AL80's? I worry about how heavy they would be to carry?

@chs8084: Umm. You need to take into consideration not only the dry weight of the full tank but the added ballast you'd have to carry when using the AL80 vs. HP100.

See this webpage for tank specs.

A full Worthington X7 HP100 weighs (33 + 7.5) = 40.5 lbs. (These numbers take into consideration only the tank and gas...not the valve.)
A full Catalina S80 AL80 weighs (31.6 + 5.8) = 37.4 lbs.
But you need to wear an additional 6.5 lbs. of lead when using the AL80 based on the following specs:
Catalina S80 empty buoyancy: +4 lbs.
Worthington X7 empty buoyancy: -2.5 lbs.

When you add everything up, you get:
Worthington X7: 40.5 lbs.
Catalina S80: 37.4 + 6.5 = 43.9 lbs.

In the end, essentially you have 25% more gas and carry 3.4 lbs. less with the HP100.

This is what people mean when they say: "I prefer the buoyancy characteristics of the HP100 over the AL80 tank." Most novice divers don't understand this.

*Holy crap! Just felt a ridiculously large earthquake here in San Diego.*

 

[herbdb]

I do most of my diving in cold water, I rented a variety of tanks from my LDS before I bought. I suggest you do the same. The different weight characteristics are something you need to experience to make the right choice.

Of course, if you get a good enough deal on the used tanks you buy, you can always resell them.

 

[spectrum]

madprops

Based on where you are and what you predict for consumption thermal stress should be your limiting factor and a few used AL80 cylinders will get you off to a good start. In a number of ways you will not be prepared to make extended north Atlantic dives out of the gate. You will be a new diver and novice dives are what you need to be making. Don't get intimidated by all of the big cylinder talk. Many of those divers are making several "everyday" dives on a single fill just to keep in practice.

When you get settled and ready to spend serious money on cylinders consider some form of steel cylinder for these reasons. Keep your eyes open for good deals on used steels in the meantime.

Pete

 

[Stu S.]

Choosing the right capacity of a single tank is easy. There are cave and wreck exceptions to this, but here goes:

Does your computer, or tables, tell you "time is up" before your tank gets low? That means you have a plenty big tank. Maybe too big. Or, does a tank run out of gas and the computer says you have extra dive time left? That means more bottom time can be had with a bigger capacity tank.

What material? That is all opinion. Divers vote with their wallets. I see many divers with steel 100's, and only know of one that has aluminum 100's, so that tells us something. Compared to the aluminum 80, the Al 100 is a giant.

 

[madprops]

ok from from what you guys are saying i think ill go for the used AL 80s. i have two that i am looking at and i think i can get them for about 250 after testing. looked into steels more and i think i want two 119 hp steels. i hope to find them used but if i can't find anything in the next 2 months it looks like ill be going back on my all potato diet. i'm also going to check the cost of them at my LDS here in vancouver. with shipping it might just be cheaper to get them from my LDS and i would like to support them since scuba store and leisure pro have got just about all my money up till now.
any buddy know the mark up from the net to a LDS in vancouver/sunshine coast

 

[oldflounder]

now here is the thing i don't know anyone that dives and i'm going to be doing alot of diving this summer so i'm going to have to meet some people off of this board and i don't want them to not dive with me cause i don't have enough gas so am i shooting myself in the foot only getting 100 cuft tanks? maybe i could find i used pony and suck it dry at the start of the dive (this was a joke but does anyone do this?)

I notice no one has responded to this quote above in reference to your joke about sucking off the pony for awhile to extend your gas. I quess everyone writes that if you are going to carry a pony it should only be used in case of emergency. It should not be as part of your gas management plan.

I do adhere to this philosophy but I will occasionally use my pony at the start of a dive in water below 40 when the air is well below freezing. I only do it to give my main tank and regs time to acclimate to the water temp to let parts "warm up" to water temp after being in the frigid air - to hopefully prevent freeflow. I'd rather have the pony freeze up in the shallows if that may be the case. The pony is serving a special purpose and not that of emergency use. They say you shouldn't breath off your tank until you are underwater but I find this to be uncomfortable. I'd rather start sucking air as I am entering and still on the surface in case I have issues with the entrance.

But in your case, if you were to suck your pony dry to extend your underwater time, then you have to drag it around with you and deal with an empty tank the rest of the dive. This may not be a big issue but it is just one more hassle to deal with and distract you.

 

[kanonfodr]

oldflounder,

You are basically talking about staging your pony which is not the intended purpose of tool. A pony is a completely redundant source of breathing gas that you use only when you have a catastrophic failure in either your reg/tank or (worse, IMO) your gas planning. Unless you are carrying a sizeable (30 or 40 cu ft) pony it wouldn't be worth it, IMO, to scrap the benefits of carrying the pony bottle (redundancy, oh crap factor) to just waste it to get a few extra minutes of dive time.

As far as the 100 cf cylinders, that should be plenty. My LP95s don't have their plus rating any more, so they really only hold 87 cf and that's if the guy doing the fills loves me that day. Most of the folks I dive with only use LP72s, and I am just now coming even with them as far as ending pressure. If I had an HP100, I might just now be outrunning one or two, but that's it.

Ultimately, you can carry as much gas as you want or need, but don't forget the most important thing: GO DIVING!!! My Air consumption has improved more just by going diving for the last ten dives than anything else has done. Eventually it just clicks, and if you dive regularly it clicks faster.

Peace,
Greg

 

[elmer fudd]

When I started diving, I bought 2 HP 119's, mainly because I was a lousy diver and I went through air like a shop vac. Having big tanks meant that whoever was unfortunate enough to dive with me got at least half a dive in.

I've never really regretted it. Now that my breathing is a little less frenzied, I often come up with extra air. On a typical dive, I'll have 1000 psi or more left and it's not unusual for me to come up with more than 1500 psi. Not once however, have I ever wished I had less air with me.

My HP119's are still smaller than an AL80 and when you factor in the extra lead, they don't weigh that much more. What's more, as you learn to dive you will inevitably go deeper and as you go deeper having more air is good for a variety of reasons. You're also going to be diving in cold water and that makes a big difference too. Diving in a drysuit, (it's only a matter of time), with thick undergarments means more weight, more drag and more air consumption. If you dive wet, you'll be cold and that will mean higher air consumption as well.

 

[oldflounder]

Kanonfoder - My first paragraph was a quote from Madprops. My note was in response to it. I agree with you, as I wrote, that the pony should not be part of your gas management plan. The pony is not to be only used in an emergency. I use mine all the time in the pool at home and at the Y. I hold it in my hand at the lake or ocean and jump in to check the viz in my bathing suit and no other scuba gear. I find many uses for a small bottle. I have a 19 and 30 and use them all the time for purposes other than redundancy [which is the main reason I bought them, yes.] As I explained, I use it on an entry in very cold air, even when buddy diving [if I find someone fool enough to go with me in water and air that cold.] It can have more than one use.

 

[Mike Boswell]

hey ill be doing all of my diving in vancouver canada (cold water ocean) using a farmer john style 7mm wet suit with another 7 mm long arm sleeve shorty on top (no money for a drysuit) and i would like to know if i should just get AL 80s or Catalina 100 cu ft Compact AL tanks? i was thinking about steel but its just to much money .... I'm going to have to meet some people off of this board and i don't want them to not dive with me cause i don't have enough gas ...cheers
Darcy Hinds

Hi Darcy,

For me, the most basic question is "Do I have enough air to do the dive?". Most of the recreational divers I see here in San Diego (52-55 Degrees F) are using AL80's with no problems. Unless you are a "Hoover", you should be fine with an AL80.

As you gain more experience (and money), you will probably find that you want to change most (or all) of your gear anyway. Buying good quality used tanks and other gear will allow you to recover most of the purchase prices.

If your main concern is whether other divers are going to want to dive with you, I would visit or call a few dive shops and dive boats in the areas you want to dive and ask them what most people are using.

I would also advise you to rent your gear for at least the first few dives. This will give you a much better idea of what you need.

Best of luck.