Is there a new tank close to the old steel 72 in buoyancy shifts and weight?

[danvolker]

I want to start doing my recreational dives in an ultra-slick configuration, with a "no buoyancy wetsuit", with no wing, and no extra hoses or other sources of drag. Clearly I will want a J valve or equivalent, if possible also.

Anyone have any tank suggestions that are better for this than an Al 80 ? Something that would have the lowest buoyancy shift of any tank over 70 cu ft....

If I could find a few old 72's, I would consider them if I can determine that the fatigue level on them has not compromised the safety of using them over the next few years.....if an old steel 72 was never abused, my understanding is that it should be safe for use for many decades to come....But this understanding comes from Internet opinions, and may have no relation to actual facts...another reason for this post


[video=youtube_share;AmT-KwGtri0]http://youtu.be/AmT-KwGtri0[/video]

I plan to use the ultra-slick gear and tank with either one of these Dol-Fins, or with big DiveR freedive fins...either will allow movement in the water that takes you to a category far beyond what typical scuba divers are capable of, given the high drag gear concepts most popular today.

 

[Basking Ridge Diver]

I am not sure what the old 72 characteristics are - but this is close to comparing to Alum 72s...

Cylinder	Brand†	Service	Diameter	Height*	Weight	Buoyancy
Pressure	(inches)	(inches)	Empty	Full : Empty
(psi)			(pounds)	(pounds)
Aluminum 72	Catalina	3000	6.9	26.2	27.7	- 0.6 : + 3.5
Aluminum 72	Worthington	3000	6.89	26	27.8	- 1.7 : + 2.8
Cylinder	Brand†	Rated	Dimensions	Weight	Buoyancy +
Pressure	diameter	height	empty	full	empty
psi	inches	inches	lbs	lbs	lbs
Steel 85	OMS* 85	2640	7	26	31	-6.7	0

 

[kwinter]

You shouldn't have any trouble finding old steel 72s. And concern about the fatigue level is exactly what hydro testing is for. I'd be more concerned about whether they are lined or not. That can prevent a clean bill of health on VIP.

 

[rhwestfall]

LP85 goes from -7 to -0.3 - Worthington/XS has ceased production, and there are supposedly some remaining stock (dwindling daily). DRIS was selling them at $275 and $30 to ship them - I grabbed 4 at Christmas. Very close to the 77, IIRC. Faber is making a similar tank but it goes from -3.8 to +2.3 (yuck! - that's about as nasty as an AL80)....

 

[Eric Sedletzky]

I have 5 steel 72's that I protect like my children.
I was running a steel 72 "rescue center" giving old and abandoned 72's a home.
Something tells me that there are probably more 72's on the west coast than anywhere else. I have sources to get many if I want them.
Perhaps I need to consider aquiring them and getting them out the the East coast some how. I didn't realize people wanted them out that way.
As far as I know, there isn't anytning like the 72 produced now. The walls are thinner on the 72, hence the 2250 PSI working pressure (2475 with 10% overfill) which also allowed them to become perfectly neutral when empty with the combination of airspace and amount of steel used.
Plus they were skinny, 6.9" diameter and they were a tad shorter than an AL80. "Cave filled" to 3000 they become an 86.
Everything produced now is going to have thicker walls to allow for 3442, or higher than 2250 anyway.
The worst I hear are those little HP 80's (bowling balls).
The thing about any of those old tanks is that if they are kept in shape and any rust is jumped on and neutralized right away they will last forever, so there really isn't anything old about them as far as life span. A tank is a tank regardless how old it is.
Slap some new valves on them so you can use DIN and you're good to go!

 

[Keith.M]

I am not sure what the old 72 characteristics are - but this is close to comparing to Alum 72s...

Cylinder	Brand†	Service	Diameter	Height*	Weight	Buoyancy
Pressure	(inches)	(inches)	Empty	Full : Empty
(psi)			(pounds)	(pounds)
Aluminum 72	Catalina	3000	6.9	26.2	27.7	- 0.6 : + 3.5
Aluminum 72	Worthington	3000	6.89	26	27.8	- 1.7 : + 2.8
Cylinder	Brand†	Rated	Dimensions	Weight	Buoyancy +
Pressure	diameter	height	empty	full	empty
psi	inches	inches	lbs	lbs	lbs
Steel 85	OMS* 85	2640	7	26	31	-6.7	0

These buoyancy swing calculations on tanks always confuses me.

Looking at the chart and the AL 72s. They are roughly the exact same size, granted a small variation.

But the buoyancy swing on one is 4.1 lbs while the swing on the other is 4.5 lbs.

Now granted that is not a huge difference, but the only thing that is changing is the amount of air in the tank and the air weighs the same thing in both of them.

As far as steel 72s, I can find them out here all day on Craig's List.

 

[Scared Silly]

LP85 goes from -7 to -0.3 - Worthington/XS has ceased production, and there are supposedly some remaining stock (dwindling daily). DRIS was selling them at $275 and $30 to ship them - I grabbed 4 at Christmas. Very close to the 77, IIRC. Faber is making a similar tank but it goes from -3.8 to +2.3 (yuck! - that's about as nasty as an AL80)....

Not all buoyancy characteristics are the same. Worthington are with a valve whereas Faber are not. Once the valve is accounted for the buoyancy characteristics are similar.

Read the fine print:

XS Scuba Worthington Steel Cylinder Specifications

Blue Steel Scuba - Cylinder Specs


Dan, I'd look for some steel 72s - great cylinders.

 

[Akimbo]

Another option to consider given the poor reliability and availability of lever reserve J-valves is double aluminum 40s that are only 5¼" in diameter. You can easily add lead to make them neutral at the pressure you want.

You can then use the narrow 190mm isolation manifold and Progressive Equalization for a reliable hard reserve. You can use a single regulator by using a DIN plug on one post.

Baby doubles allow using a harness like the old-school Mike Nelson rigs since they ride nicely on your back. An expensive but very cool and compact solution would be to use the Interspiro Divator Lite rigs. Their steel cylinders would be way too negative buoyant. Here is an image of the same single-regulator manifold on my steel Divator 324s.

 

[danvolker]

Another option to consider given the poor reliability and availability of lever reserve J-valves is double aluminum 40s that are only 5¼" in diameter. You can easily add lead to make them neutral at the pressure you want.

You can then use the narrow 190mm isolation manifold and Progressive Equalization for a reliable hard reserve. You can use a single regulator by using a DIN plug on one post.

Baby doubles allow using a harness like the old-school Mike Nelson rigs since they ride nicely on your back. An expensive but very cool and compact solution would be to use the Interspiro Divator Lite rigs. Their steel cylinders would be way too negative buoyant. Here is an image of the same single-regulator manifold on my steel Divator 324s.

Thanks for this..
2 questions
1. I used J valves from 1972 to the early 80's...don't recall any failures...though I had heard of a few divers that forgot to pull the J up prior to the dive...so there was no reserve when they wanted one.....Is this the sort of problem you refer to , or was it something else?
2. How much drag would this twin tank set up have on your back? I was assuming that a long narrow hull ( like racing surf ski) is faster than a wider boat....and that with tanks, a long narrow tank is faster in the water ( or is pulled easier) than two tanks....I see each is narrower than a steel 72, but now you have the surface area of 2 tanks..... If I get the chance to demo something like this--to see how well kick and glide works with it with the Dol-Fin system or big DiveR blades, , I will jump at it

 

[rhwestfall]

a little more "mainstream" would be 50-dubs....

https://www.divegearexpress.com/gas/faber.shtml