Twin 45's: How Neg or positive in Salt water

[leicamshooter]

Just picked up twin 38's for the DW Mistral that Bryan just overhauled. They are 2015 + PSI bottles, black, 3/4 inch thread, and have a fresh Hydro. Can anyone tell me how negative or positive they float when full, and when empty?

The twins also have a scubapro manifold 8.25 inches from center to center. Does anyone know who can service the manifold, or is it something I might be able to do my self with proper tools... Nothing is wrong with it, just think it should be serviced as it sat unused in a garage for 20 years +. I should add that up till now, I've used a single steel 72.

Kind regards,
Gonzalo.

[1969ivan1]

If they are 2400 PSI they are possibly twin 50s FYI.

[Robohips77]

Sounds like its time for a pool dive to experiment. Dependant on the valve make and model this is something that you may not want to tackle if you have never repaired them before. Start with the catalogues and manuals listed and if it is a USD then you can see the internal works but if not and it is a scubapro or dacor or other manufacturer then I would seek some further guidance. If it has no J valve on it then it should be fairly easy to rebuild. Bryan, I am sure can rebuild it for you and quite frankly he is probably the one to send it to. Reasonably priced and very timely on his service.

[leicamshooter]

Hmmm. They have scubapro boots. And they come with a scubapro backpack and buckles. They are 2400. Do you think they are 50's instead of 38's?

[leicamshooter]

These are the markings on the tank?

DOT-3AA 2015

HM 40292

B74

[time2dive]

My 2015s are 10 pounds more negative than an aluminum 80, I wear 6 pounds of weight, my 1800s are 6 pounds more negative than an aluminum 80. My 1800 psi 45s are about the same as my 1800psi 38s.

[leicamshooter]

Thank for the info! So the volume of your 2015 tank when filled to its operating pressure is about?

Regards
Gonzalo

[luis]

My 2015psi tanks are 45 cu ft with the 10% fill (with the + stamp rating).
That is at 2216 psi.

[leicamshooter]

You are right Luis! I just found the tanks in the Scubapro catalouge of 1976. 19" tall, 22lbs. and they hold 45 cubic feet of air at 2216 psi (2015 psi "working" pressure).

They are galvanized exterior with an epoxy coating. Fresh hydro of 7/11. The diameter on them is 6.75" inches. The manifold has a high pressure port available, and from center to center is 8.25 inches.

They are kinda heavy to get 90 cubic feet of air on your back. Maybe 50lbs when they are filled? Might be tough on my beach dives here in California.

I am thinking they may work with Richard Green's double bands and a harness? I wonder how comfortable that setup might be with these doubles? Anybody have experiece lugging twin 45 around with a harness?

[luis]

I do... IMHO a plain harness is the most comfortable way to use doubles (45, 72, etc). IMO, adding a back-pack or back-plate just moves the tanks away from your back which tends to pull you back. I do mostly shore diving here in Maine and I like my doubles to be as close to my center of gravity as possible.

[Aileron]

I can vouche for the harness instead of a backpack. My triples (30cf) weigh 51 lbs (bare and filled) on land and they don't feel terribly heavy huffing them to the water. My shore dives have no surf though, so it's really a big salt water pool dive. Using the harness snug keeps it close to your back and they stay put. Very comfy. I ditch 6 lbs of weight when I dive these.

Lisa