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Discussion of diving methods and equipment available prior to the development of BCDs beyond the horse collar. This forum is dedicated to the pre-1970 diving.
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SurfLung
Master Diver
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Joined: Sat Jan 01, 2011 2:03 pm
First Name: Eben
Location: Alexandria, MN
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New 63 Equals Vintage 72?

Thu Jan 18, 2024 5:25 pm

New 63 Equals Vintage 72?
Generally speaking... It's my understanding that the original steel "72" was really about 65 cf at 2250 psi and reached 72 psi at 10% over or 2475 psi. The reason I mention this is because the present day aluminum "63" is said to have almost the same buoyancy characteristics as the original steel 72 (aka 65). And, you can rent a present day aluminum 63 from most dive operators.

Here's a USD 72 Description from the 1963 catalog...
Image
"Should sink slowly when full. +1.7 lbs positive when empty will float".

And, I looked up the buoyancy of an aluminum 63...
Full is -2.4 lbs (sinks slowly?)
500 psi + 1.7 lbs (floats)

I downloaded the 1963 USD catalog from the Vintage Double Hose website, courtesy of the late Bryan Pennington.
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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ScubaLawyer
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First Name: Mark
Location: Laguna Beach, CA

Re: New 63 Equals Vintage 72?

Thu Jan 18, 2024 11:48 pm

That's interesting Eb. I always found steel 71.2 tanks to be neutral at 500 psi. I guess it makes sense that they could be slightly positive at 0 psi.

M
"The diver who collects specimens of underwater life has fun and becomes a keen underwater observer. .. seek slow-moving or attached organisms such as corals, starfish, or shelled creatures." (Golden Guide to Scuba Diving, 1968) :D

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SurfLung
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First Name: Eben
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Re: New 63 Equals Vintage 72?

Mon Jan 22, 2024 10:11 am

Yes and I think it's also been shown that not all tanks were made the same. Among my 38s, 42s, and 50 there is quite a difference in buoyancy. The 1800 psi USD 38 tanks have thinner steel and are more floaty than the 1880 psi Sportsways 42 tanks. And my 2250 psi Voit 50 tank is absolutely HEAVY. After I posted the above, I saw some other data from the Basic Scuba book that didn't agree with it. I heard that bit about the aluminum 63s being similar to the steel 72s and I've found the 63s to be comfortable diving tanks.
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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rhwestfall
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First Name: Robert
Location: "La Grande Ile"

Re: New 63 Equals Vintage 72?

Wed Jan 24, 2024 2:58 pm

What I like about the AL63 is the length. Using it with a DH, I can wear the reg in the correct place, and have nothing even remotely close to my legs. Also, unlike the HP80 steel, they do not make me overly head heavy.

I have a pair of 63's on a solid bar military manifold.
Bob

No Longer Awaiting my Kraken.....

rx7diver
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First Name: Ronald
Location: Columbia MO

Re: New 63 Equals Vintage 72?

Sat Jul 06, 2024 11:38 pm

rhwestfall wrote:
Wed Jan 24, 2024 2:58 pm
What I like about the AL63 is the length. Using it with a DH, I can wear the reg in the correct place, and have nothing even remotely close to my legs. ...
I have been using an OMS/Faber LP 66 (21" length, 7" OD, -1.67# full, -5.15# full) with my DRAM and "Vintage DH Flat Plate" and J-valve). Works very well for me for MO/AR freshwater diving. Recently acquired and switched in a pillar J-valve.

rx7diver

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