Is it worthwhile to convert twins to singles?

[lock_washer]

I wanted ask this question and get some feedback.

I was given for free a set of US Divers Twin Mark II 50 cubic inch aluminum tanks in a twin setup with the dual manifold j value setup, and double tank bands attached to an old Seatec Back Inflation BC. The tanks still has some air in it, but the bc is shot.

I was thinking of taking them in to get hydro testing, and if they pass...separate them into singles and buy values for each of them.

However a friend of mine pointed out that I should keep them in double configuration and have a "100 cu inch" tank. I do have a new DUI BC, that I can attach a backplate to and use it with the double tanks.

But what I am wondering is these old tanks get bouyant when they get empty? How much more weight would I have to add to my belt to compensate if they are in single or double configuration?

Any help would be appreciated,

Lock Washer

 

[dannobee]

I wanted ask this question and get some feedback.

I was given for free a set of US Divers Twin Mark II 50 cubic inch aluminum tanks in a twin setup with the dual manifold j value setup, and double tank bands attached to an old Seatec Back Inflation BC. The tanks still has some air in it, but the bc is shot.

I was thinking of taking them in to get hydro testing, and if they pass...separate them into singles and buy values for each of them.

However a friend of mine pointed out that I should keep them in double configuration and have a "100 cu inch" tank. I do have a new DUI BC, that I can attach a backplate to and use it with the double tanks.

But what I am wondering is these old tanks get bouyant when they get empty? How much more weight would I have to add to my belt to compensate if they are in single or double configuration?

Any help would be appreciated,

Lock Washer

Does that manifold have one outlet or two? How about an isolator valve, is there one between the two tanks? That would tell if it's going to be more of a vintage setup than a modern day doubles arrangement.

Here's a spec sheet for cylinders to see the buoyancy characteristics.

TECHDIVINGLIMITED.COM

50 cubic foot tanks are useful for training dives (pools and shallow water), but generally aren't big enough for most people's everyday type of diving. They simply aren't big enough. Sure, if you're tiny and sip air, they *might* work for you, but for the vast majority of divers, they're too small.

Doubled up they'd be ok if the manifold has two outlets and an isolator.

 

[DA Aquamaster]

I am not sure who made the USD Mk II 50 cu ft tanks. The contenders would be:

1. A Catalina S45, 3000 psi, 45 cu ft, 6.89" in dia, 17.7" tall, 20.3 weight when empty, 1.3 lbs bouyant when empty and -2 lbs bouyant when full.

2. Luxfer 50 3000 psi 48.4 cu ft, 6.89" in dia, 19" tall, 21.2lbs weight when empty, 1.3 lbs bouyant when empty, -2.4 lbs bouyant when full.

3. Catalina S53 3000 psi, 53 cu ft, 7.25" in dia, 19.2" tall, 25.6 lbs weight when empty, -0.2 lbs bouyant when empty, -4.1 lbs bouyant when full.

Measuring the height and diameter will tell you which one you have. If it is 17.7" tall it is an S45. If it is 19" tall and 6.89" in diamater (21.6" in circumference) it is a Luxfer 50. If it is 19" tall and 7.25' in diameter (22 2/4" in circumference), it is an S53.

Twin S45's and Luxfer 50's would be about neutral when empty when you add the weight of the bands and manifold. Twin S53's would be 2-3 lbs negative when empty with bands and manifold attached.

An AL 80 in comparison is about -2 lbs bouyant when full and +4 lb bouyant when empty.

Single 50's work very well for kids and for small adults (usually women) who do not use as much gas and who do not desire to carry a long and heavy tank on dives where they will not use all of an AL 80.

Twin 50's have a great deal of vintage appeal and offer a bit more gas for deeper/longer dives and or for a diver who comes up a bit short compared to his or her buddies using AL 80's. The single outlet manifold is not adequate for technical diving, but for recreational diving it works fine. The only downside is that twin 50's are a bit heavy (about 10 lbs more) compared to a E or X series 100 cu ft tank. They are however almost identical in weight to a 100 cu ft aluminum tank with the advantage of being much shorter and having better trim under water so don't be too quick to break them up.

 

[Stu S.]

Depending where you live, it may be difficult to get cylinders that old filled. This is a trend that many of us despise, yet recognize. Keeping the whole set together may have more value to collectors or vintage enthusiast.

A lot of Florida dive boats have tank holders set up for single cylinders only. That's one reason why we use HP-100's.

Have fun with it.

 

[oxyhacker]

the other downside, over a similarly sized single tank, is that you will pay double for your gas, visuals and hydros. And, as others have pointed out, 50 is a bit small to be of much use as a single.

If it was me I'd sell or trade them to a collector or someone who will enjoy diving with classic small doubles, and get a reasonably sized single tank. too small to be of much use as DIR doubles, too, so I definately wouldn't go for a newer manifold.

 

[herman]

Another alternative is to sell them as a set and put the money into new tanks. There are a lot of us (me) who would like a set of old 50's to go along with our vintage regs.