What tanks???

[jonnythan]

Are you sure about that? An HP 80 is 26 pounds, and negatively buoyant when empty. This is much lighter than an aluminum 80, which is not only heavier, but it requires about 4-5 pounds more weight to sink. You're about ten pounds heavier getting into the water with an Al 80 than an HP 80.

 

[alemaozinho]

I know it would be easier to just get an aluminum 80 and forget about it, but there are other options out there and I want everyone's opinion on them. It seems like there are definite benefits to a steel tank, such as bouyancy and a good selection of tank volumes.

By the way, for right now I am limiting myself to single tank diving.

Anyway, what does everyone recommend? Should I stick with an AL80? Does a steel 85cft or a 98cft tank make more sense for single tank diving?

it all depends on your dive profile and your average dive depth,in my opinion it,s never wrong to have additional air with you.peace

 

[alemaozinho]

What is the big advantage of negative buoyancy with a low steel tank? Although you can take weight off your weight belt you are carrying more weight on your back. Esentially you are carrying the same weight, just in a different place. What is wrong with my thinking here?

put an alum. tank 80cf beside a 80cf steel and you,ll see that the steel tank is considerably shorter and lighter and will therefore displace less water and be more negative.a 80cf al is not necessarily lighter as his 80cf counterpart,check out a tank spec list and you,ll be able to compare.peace

 

[mjhlaw]

What is the big advantage of negative buoyancy with a low steel tank? Although you can take weight off your weight belt you are carrying more weight on your back. Esentially you are carrying the same weight, just in a different place. What is wrong with my thinking here?

I don't think there is an advantage to extra neg weight in steel over aluminum except when near empty. Aluminum tanks are positive at that point. Low steel is near neutral. High steels, because of the higher density when full (I think), change in weight significantly more than low steel. The swing and positive bouyancy is what throws me off.

 

[DA Aquamaster]

What is the big advantage of negative buoyancy with a low steel tank? Although you can take weight off your weight belt you are carrying more weight on your back. Esentially you are carrying the same weight, just in a different place. What is wrong with my thinking here?

It depends on the tanks you are comparing. For example a steel 72 is about 4 pounds lighter than an AL 80 and is about 4 pounds less bouyant. So you are saving 4 pounds in tank weight plus you can leave 4 pounds of lead in the boat for a total of 8 less pounds in total equipment weight that you have to haul up the ladder.

A 3000 psi steel Faber 71.4 will weight about the same as an AL 80 but is much shorter and smaller in diameter and is still 6 pounds negative when empty. This means you get a very compact size plus a nearly 8 pound weight advantage when you consider the lead you can remove.

Not all tanks compare as well to an AL 80 but for the most part the steel tanks that are heavier than an AL 80 will normally provide more air capacity and will for the most part be substantially negatively bouyant meaning less weight is required on the belt which minimizes the difference in tank weight.

The downside of a large and heavy steel tank can, in some cases with some bc's, be a loss of stability. Diving with a nearly empty AL 80 or even better a set of double AL 80's is like floating around under a blimp as all the bouyancy is above your center of gravity making things very stable.

 

[BIGSAGE136]

What is the big advantage of negative buoyancy with a low steel tank? Although you can take weight off your weight belt you are carrying more weight on your back. Esentially you are carrying the same weight, just in a different place. What is wrong with my thinking here?

Trim!

 

[Mverick]

High steels, because of the higher density when full (I think), change in weight significantly more than low steel. The swing and positive bouyancy is what throws me off.

This isn't true. 80cf of air weigh's the same. No matter what pressure it's at.

Aluminum tanks are thicker. So more mass to displace water. One reason for increased bouyancy.
If you can pack 80cf in a smaller package. You're displacing less water. Which means you have less inherant bouyancy. But the GAS still weighs the same. And it will swing the same.

The difference is in how the tanks are weighted. Not the pressure of the gas.

Steel is more dense then AL.