Renting/Owning tanks...

[p1p]

First off, this question isnt what you think, so read carefully.

My question, is I'm planning to get steel tanks, just to avoid the buoyancy issues.

But when I travel, I'll be renting tanks.

Are most rentals AL,or steel, or are there choices?

Another related question, should I learn/practice with AL tanks, to learn to control the changing buoyancy? (I'm thinking yes?)

 

[melanie.]

Most places I have been the rentals are always aluminum. However, that is something you could research before going to a particular place and make a decision based on if they have steels.

But....

You have to understand that both steel and aluminum are going to become lighter throughout the dive. That is because regardless of what kind of tank you use, compressed air has a weight and you will still go through (for example) 8 lbs, meaning the tank is (ex) 8 lbs lighter at the end of the dive then at that the start.

The difference between steel and aluminum is that al will (generally) become positively buoyant when it is empty. Steel will be just a little negative or neutral.

So with al you need more lead to counteract that, but the steel tanks you need less because the weight is already in the tank material.

Hopefully this is helpful

 

[Wookie]

Most rentals are aluminum for a number of reasons, but the 2 biggest ones is their forgiveness as far as maintenance issues goes, and the fact that they are way less expensive to ship than steels.

You don't need to practice in aluminum cylinders because of the change in buoyancy, as Melanie. said above, all cylinders change buoyancy during the dive. You need to practice in aluminum cylinders because the trim is different. Additionally, I would expect you to be in a heavy wetsuit/drysuit when diving steels at home, and in a 3 mil or dive skin when diving aluminums in the south Pacific. You'll want to practice in that 3 mil too. <grin>

 

[mike_s]

But when I travel, I'll be renting tanks.

Are most rentals AL,or steel, or are there choices?

I've found that 95% of rental tanks are Aluminum's, for the reasons that Frank stated. Mostly because they are cheaper.



However, if you call ahead, you can typically find a shop/operator that rents Steels. The selection is often limited though.

Also... Typically it's a better chance that a Steel tanks have a convertible DIN/yoke valve also for those that prefer DIN. But most folks who have DIN have learned to take a screw on YOKE adapter also.


Some (but not many) operators are switching over to using all steel tanks in their rental/customer tank fleet and getting rid of AL80's. Bluewater Adventures is, Panama City Dive Charters is... and Ultimate Getaway switched over to LP95's with convertible valves a few years ago.

 

[p1p]

Pretty much the answers I expected, thx!

 

[TMHeimer]

I own both and found there's not a lot of difference. Maybe you tend to rise a bit more when near the surface and low on gas with aluminum. I don't change my trim. I do like my steel a little more. Less weight on the belt and I like the negative buoyancy. When I just owned steel and rented AL there wasn't much to adjust to at all.

 

[g1138]

If you're 5'6" like me, tall tanks like Al 80's and Faber St 72's can change your trim a bit. An ankle weight on the top of the tank could fix this.
If you have a Bp/W then it isn't so much an issue since you can center your tank on your back without having the first stage being gouged in your head.

When switching between St and Al tanks I add 5 pounds and a bit more air in my BC at depth. But other than that you're buoyancy doesn't change. You're still able to do the same things to control it without any added effort.

 

[p1p]

I found locally a pair of AL 80's for 90$ each, thx everyone.

 

[DivemasterDennis]

I'd just like to add that any change in equipment ( type/size of tanks, exposure suit, etc.) or conditions (fresh vs salt water, cold vs warm water, etc.) justify a buoyancy check and proper weighting review. That's why I keep that data in my log book for every dive and can "look up" proper weighting for any dive location and gear set I have already been to (or similar conditions and gear). One other variable- my own body's buoyancy. My weight can vary plus or minus 10 pounds with the season (don't judge- it's true for some of you too.) That can change proper weighting as well. So I also record my body weight in the log book, in code, by noting number of pounds over or under 200. Don't tell anyone.
DivemasterDennis

 

[fnfalman]

First off, this question isnt what you think, so read carefully.

My question, is I'm planning to get steel tanks, just to avoid the buoyancy issues.

But when I travel, I'll be renting tanks.

Are most rentals AL,or steel, or are there choices?

Another related question, should I learn/practice with AL tanks, to learn to control the changing buoyancy? (I'm thinking yes?)

Most places rent aluminum, but a feel do rent out steel. HOWEVER, not all steel tanks have the same buoyancy characteristics, so the point is moot anyway.

Most important is to know your dive weight. That way it doesn't matter what tank you rent, you can add or subtract lead as needed.

Let's say that you live and dive in Hawaii and your current dive weight is 10-lbs of lead with a steel tank from Faber and a 3mm wetsuit. You need to know what the buoyancy characteristics of these steel tanks are by going to the manufacturer's website. Let's say that you currently own a Faber M-series and it has a -6lbs buoyancy characteristics when it's empty.

So now you're at Roatan, and the water temp is about the same so you wear a 3mm wetsuit (rent or brought your own), with your BC/Regulator/flashlight/etc. but you are now renting an aluminum tank. Aluminum tanks are usually +4lbs buoyancy characteristics when empty.

What does that mean? that mean in addition to the 10-lbs of lead you usually need to wear, you will need to add 4-lbs of lead to compensate for the positive buoyancy of the aluminum tank AND another 6lbs of lead to compensate for the -6lbs buoyancy characteristics of your Faber M-series that you use at home in Hawaii. That means you'd have to wear 20-lbs of lead instead the usual 10-lbs of lead.

As far as renting aluminum tank for practice, don't bother. Once you figure out your dive weight and know how to compensate for the aluminum tank with additional lead, then it's a non-issue.