100cf tanks

[kelemvor]

Hey Greg, if I may......instead of spending money on tanks, I would suggest investing that money in yourself and take an extreme scuba makeover class. I can almost guarantee you'll increase your comfort in the water, lose a considerable amount of lead off your belt and perfect your trim and buoyancy. All of those things will transfer into a considerable reduction in air consumption. I know it sounds like a sales pitch but it works and it work very well. There's a great shop in Seattle called Frogkick diving.

Frog Kick Diving - FKD

Extreme Scuba Makeover · UTD Scuba Diving

Not that such a class is a bad idea, I agree that it's a great idea. However, I would not give up my big tanks for anything. I went with low pressure 108's instead of steel 100's after doing just a little math, I think they're a far far better tank (for me).

The times I've used 100's it has been rentals and they have been Al100's. AL100's if I recall correctly, have a larger diameter than AL80's. My steel 108's have the same diameter. If so, it will be an issue to deal with on almost every boat ride unless you have your own. Not insurmountable but you have to get used to doing things differently than every other diver if you have 8" tanks.

My point? I think big tanks are a great idea, and I think that @Greg Doyle should do a little tank research before plopping down $500ish dollars. Your dive shop can probably order just about any tank you want. Given the price, get what you want. I put together a little spreadsheet comparing tanks when i was shopping. I have seen a better one that someone else did since then but I have mine, so here it is.
Color legend: Red = >al80 Green = <al80

Those "actual cubuc feet" values account for overfilling. That will only be possible if your local shop is okay with it. Here in Florida, it's not a problem. I get overfills at more than one local shop. I've got them from several shops in the Florida Keys. I've got them from shops near Blue Heron Bridge. Most of the time I don't even have to ask. Your shop may not be willing to do it, so check before you spend money on a tank based on overfull capacities. That said, even with standard fills, a LP108 is a better tank than an HP100 in my opinion. Many shops use "banks" when they do fills. Often the bank pressure is lower than required for a 100% fill of an HP tank so you are stuck with less than a completely full tank. I've never seen a shop that can't put at least 3200 into a scuba tank, though.

When I bought my tanks, I could barely squeeze 30 minutes out of an al80 (east coast fl ~80' dives). Now days I can do much longer. As long as I don't select a boat that has a hard time limit on dives i still love having big tanks. If only my tanks were round, I could play AC/DC every time I got on a dive boat.

 

[halocline]

I'm at about 10 dives so far and I've still got my training wheels on. I find I blow through air much quicker than fellow divers. I had a shop suggest I might try going to 100CF tanks until I get my breathing under control.
My question, I assume this changes the weight I'll need, but not by much as I enter the water, more so as I use the air. Won't a larger tank make me more buoyant toward the end of a dive than an 80CF tank?

any other down side to using a 100cf tank?

Thanks,
G

At 10 dives, I think it's a bit early to worry about air consumption to the point where you are considering a bigger tank. Your consumption will dramatically lower as your diving experience increases and your technique improves.

I suspect your shop is talking about AL100s, which IMO are the worst tanks I've ever had the displeasure of using. They weigh a ton, and somehow manage to be floaty and unstable on your back at the same time. It's a little like a burger that's both too dry and too greasy...

Now if your shop is simply suggesting that you rent a AL100cft tank for an upcoming dive, fine. But don't for a second consider buying one. If the shop is pushing a 100cft steel tank, in particular one of the 3442 PSI special permit tanks, those are excellent tanks that have good resale value. Depending on your buoyancy needs, they can be great to dive with or a bit heavy. For most divers using any sort of wetsuit, they are fine.

 

[boat sju]

"3442 PSI special permit tanks"

halocline,

I've never heard them referred to like that before. What do you mean by "special permit"?

 

[kelemvor]

It's a little like a burger that's both too dry and too greasy...

I may have to commandeer that phrase!

 

[halocline]

"3442 PSI special permit tanks"

halocline,

I've never heard them referred to like that before. What do you mean by "special permit"?

The "standard" engineering DOT specification for steel scuba tanks is 3AA, like the LP steel tanks. Those tanks have a hydro test pressure of 5/3 of their stamped working pressure, and are usually stamped with a "+" to allow 10% overfill on that pressure. They've been around for several decades.

The 3442 PSI tanks like the faber FX series and the worthington/ XS scuba series have a different DOT spec, which gives them a hydro pressure of 1.5 times their working pressure, no 10% overfill. The DOT issues a 'special permit' or exemption for those tanks. They are far lighter and less negatively buoyant than the old 3AA high pressure steel tanks. They're also much more common and popular. But occasionally you do see one of the older 3AA HP tanks, and they are basically anchors-with-valves. The old faber HP100 is about 15lbs negative full.

The pitiful AL100 weighs a whopping 41 lbs (46 for the catalina!) and is still 3 lbs positive empty. The faber FX100 is slightly negative empty and only weighs 34lbs. AND it's much smaller on your back.

 

[boat sju]

Ah, got it. Thanks.

 

[The Chairman]

Steel tanks? Yes! I love mine.

However, if you're chewing through your air, might I suggest a few things.

• Get your attitude right
  • You should be flat, flat, flat!
  • Often referred to as 'trim'.
• Hold your hands together in front of you.
  • Flailing (sculling) wastes energy
  • Sculling ruins trim
  • Sculling scares fish
  • Holding your hands in front of you, actually helps with trim
• SLOW DOWN!
  • It's a big ocean and you're not going to see it all in one dive
    • Why even try?
  • Going slow will allow you to stay down a lot longer!
  • The slower you go, the more you will see.
  • Make your buddy/DM stay back with you, not you up with them!
• Use down lines correctly
  • Pull your self down: DON'T KICK!
  • Pace yourself. Did I mention going slow?
  • If you seem to be panting when you hit the deck, you're doing it wrong.
• Stay out of the current!
  • Usually the closer to the bottom, the better off your are.
  • Hide behind structure whenever possible.
  • Use the rules of Dodge ball...
    • Dodge
    • Dive
    • Dip
    • Duck and...
    • Dodge

 

[Rred]

Under the DOT "special permit" rules, those tanks can be filled for typically five years. And then the DOT re-evaluates whether to extend the permit, based on how the tanks have performed. If the DOT decides not to renew the permit--you've got scrap metal. Judging from how the Faber HP steel tanks have performed so far, that's not going to be a problem, but it is something to be aware of.

Considering that the negative buoyancy of a steel tank usually means you can take 8-10# off your weight belt, leaving you with a total weight (tank+belt) that is the same as when you dive an Alu80, but you're getting 20-25% more air...I'd call the steel tank a no-brainer, other than the extra cost up front. FWIW.

 

[Greg Doyle]

At 10 dives, I think it's a bit early to worry about air consumption to the point where you are considering a bigger tank. Your consumption will dramatically lower as your diving experience increases and your technique improves.

I suspect your shop is talking about AL100s, which IMO are the worst tanks I've ever had the displeasure of using. They weigh a ton, and somehow manage to be floaty and unstable on your back at the same time. It's a little like a burger that's both too dry and too greasy...

Now if your shop is simply suggesting that you rent a AL100cft tank for an upcoming dive, fine. But don't for a second consider buying one. If the shop is pushing a 100cft steel tank, in particular one of the 3442 PSI special permit tanks, those are excellent tanks that have good resale value. Depending on your buoyancy needs, they can be great to dive with or a bit heavy. For most divers using any sort of wetsuit, they are fine.

I'm not considering buying anything for a while. I'm travelling back and forth between Seattle and Miami too much right now for a project.
Maybe next year, but for now, rentals will do just fine.
G

 

[wetb4igetinthewater]

I'm not considering buying anything for a while. I'm travelling back and forth between Seattle and Miami too much right now for a project.
Maybe next year, but for now, rentals will do just fine.
G

Greg,

Have you joined any of the dive clubs in the area? There are a number that are active. Marker Buoy and Moss Bay are two. If you'd like you can borrow one of mine when I dive with recently certified students at EUP. PM me if you are interested.