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EHowe
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Thoughts on twin 50's

Sun Oct 19, 2014 9:50 pm

I've seen twin 50's using low pressure faber steel tanks advertised in a couple of places. Looks like it could be a hot setup using VDH plate and wing. I picked up an older dual outlet Sherwood manifold with a center port and an 8 1/2" spread that I thought might work nicely after I clean it up and go through it. Anyone have experience with anything similar?

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9fingers
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Re: Thoughts on twin 50's

Mon Oct 20, 2014 3:09 pm

I've been working out a similar setup with Faber/OMS LP 45's, same diameter but a little shorter than the 50's. I have had a hard time finding bands and manifolds, I have a Sherwood manifold like yours (and several others with similar spreads) and made up some DIY/made-at-home temporary bands from plumbing pipe straps and plywood. The tanks are wider than I prefer, and I'm currently working out a way to get a closer spread with some modern Blue Steel rebreather tank valves in DIN and an old Drager center bar also in DIN and then converting the DIN to yoke with the appropriate USDivers Conshelf adaptor I got from Bryan some time ago...all for use with my DAAM HPR Phoenix or Argonaut Kraken. The hardest part is that I'm having a hard time finding someone to make custom bands.

PM me if you have any further questions. Tim H, IAFF local #46 retired PM/current FF :D

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rhwestfall
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Re: Thoughts on twin 50's

Mon Oct 20, 2014 7:16 pm

I did a somewhat "blur the lines" between old and new, using 2xAL63's, a solid post Aqualung "military" manifold w/ j-valve, and an oddball set of bands that worked for the 7.25" tanks. Loving it! I like the 63's as I can lower them on my back for reg performance, and not have them in the way of my legs.
Bob

No Longer Awaiting my Kraken.....

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ScubaLawyer
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Re: Thoughts on twin 50's

Mon Oct 20, 2014 9:23 pm

EHowe wrote:I've seen twin 50's using low pressure faber steel tanks advertised in a couple of places. Looks like it could be a hot setup using VDH plate and wing. I picked up an older dual outlet Sherwood manifold with a center port and an 8 1/2" spread that I thought might work nicely after I clean it up and go through it. Anyone have experience with anything similar?
I looked into the Faber 50s as a twin set. My biggest objection was that the tanks are over 25 inches long (not including the valve). That is about the length of an aluminum 80. I’m afraid they would hit my legs as I swam with a double hose positioned correctly on my back. They are 5.5 inch in diameter and require special bands. You can find 5.5-inch diameter bands to use with the Faber steel LP50's at the following:

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

A Sherwood manifold with a standard 8.5-inch center to center manifold spacing should work just fine with those bands. Good luck. Mark.
"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

mfascuba
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Re: Thoughts on twin 50's

Fri Mar 04, 2016 3:31 pm

I have a set of double LP45's, as well as a third LP45.. My autocad has drawn up some goofy stuff, but the center tank valve/yoke outlet/fits between standard double manifold isolator parts thing has got to be my goofiest idea yet. Imagine a doubles manifold but with two isolators, one on each side, and in the center between the isolators, my goofy center piece. I drew it to accept a tank on the bottom (the elusive triples), and to have an old style post yoke valve on top to use with a double hose reg. The side branches of this abomination would be machined to thread the isolators into it - one left thread, one right thread. This allows triples, isolation, a center-mounted double hose, and the redundancy of a cave rig. I might just have to have one piece made....

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captain
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Re: Thoughts on twin 50's

Sat Mar 05, 2016 12:28 pm

Depends on the tanks, consider the buoyancy, positive or negative. I had some steel Voit 50's that were 4 pounds more negative than twin 72's.
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crimediver
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Re: Thoughts on twin 50's

Tue May 17, 2016 11:09 am

I had been eyeballing a steel PST SCBA tank I had lying around that was given to me. I never got around to actually calculating the cubic feet but I guesstimated it at approximately 38 CF. As I recall the PSI is 2216. I thought it would makes a sweet set of doubles so I scrounged another similar tank. Many fire depts. have some old ones from the 70's lying around you can probably get for nothing as they all use wrapped cylinders now.

The trick is finding a manifold. The cylinders are valved for a 1/2" straight thread. I got a Sportsways 1/2" manifold, 8 1/2" center and it appears that it will work just fine.

The diameter of the tank is about 6.8 inches and I took a set of 6.9 bands and just cut a thick rubber strip under the band to fill the space. I have just been playing with it on and off as I have time. I have a canvas harness to complete it. Once I get a hydro and a paint job I think I will be set.

As easy as it is to get these cylinders you can build a nice set of doubles without breaking the bank. I got the tanks for free, I got the bands and harness for twenty and the manifold for another 20. I figure 40 more for hydro. I am certified to do my own visuals so I will be way under a hundred bucks after buying some bolts, paint and decals.

Until 6 months ago I was able to get a hydro for ten bucks. I have a lead from a LDS that can connect me to a facility to get a tank done for 20 bucks now. That is considered cheap by most standards. I can remember getting them for 6 bucks about 15 years ago.

There is something about the small doubles that warm my heart. The cool factor is there but they dive nicely too. The drawback is that the hydro cost twice as much as just diving a larger tank but it is worth it.

I will have to wait until I finish it up and fill it up to see what the weight swing is with this set-up. Hopefully I can dive it without a horse collar.

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antique diver
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Re: Thoughts on twin 50's

Tue May 17, 2016 3:37 pm

Crimediver, I hope that you have the Sportsways valves with oring sealed straight threads... not the similar in appearance tapered pipe threads.

BTW, I am using a set of those for doubles using the Sportsways valves, and love them.
The older I get the better I was.

crimediver
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Re: Thoughts on twin 50's

Tue May 17, 2016 8:39 pm

My manifold is 1/2" straight thread.

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antique diver
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Re: Thoughts on twin 50's

Tue May 17, 2016 9:28 pm

The ones I have are rated for 2015 psi, and while being shaped and sized like the old 1800 psi 38's, they are just a little heavier. The extra weight is an advantage for me in the water. I am guessing their volume at about 42' if filled to 2200-2250.
The older I get the better I was.

DAAquamaster
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Re: Thoughts on twin 50's

Mon Aug 08, 2016 10:44 pm

I started diving with a set of the 2015 45's, and later got another set of the 1800 psi 38's. I liked how both of them swam.

They both had abad habit of getting filled to 3000 psi as the tank monkeys just assumed they were double AL 50s. Given that the test pressure on a 3AA 1800 psi tank was 3000 psi, it was a cave fill before cave fills were cool.

I currently dive side mount with LP 45s in smaller caves, for recreational dives and I'll carry a single LP 45 as bailout on recreational side mount rebreather dives. They hold 56 cu ft at 3300 psi and 60 cu ft at 3600 psi.

I've certainly considered doubling them up for back mount double hose diving, but the closest I've got a suitable manifold is a single outlet manifold designed for double AL 30s.

----

The Faber LP 45s are a lot lighter in the water than the galvanized Worthington LP 45s. The Worthingtons are a few pounds more negative full or empty than a set of steel 72's.

rx7diver
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Re: Thoughts on twin 50's

Wed Aug 10, 2016 11:44 am

DAAquamaster wrote:I currently dive side mount with LP 45s in smaller caves, for recreational dives and I'll carry a single LP 45 as bailout on recreational side mount rebreather dives. They hold 56 cu ft at 3300 psi and 60 cu ft at 3600 psi.

I've certainly considered doubling them up for back mount double hose diving, but the closest I've got a suitable manifold is a single outlet manifold designed for double AL 30s.

----

The Faber LP 45s are a lot lighter in the water than the galvanized Worthington LP 45s. The Worthingtons are a few pounds more negative full or empty than a set of steel 72's.
DAAquamaster,

I own a pair of OMS (Faber) LP 46's with bespoke OMS bands and non-isolation manifold bar (all purchased new c. 1996). I've wondered how these "mini-doubles" would dive with my PRAM on one post and a single hose reg on the other. Since these OMS bands place the tanks relatively close to each other, the PRAM wouldn't be too far to one side of my spine to cause serious performance issues, I would think--a bit lopsided, but not too lopsided, probably.

Have you thought about doing things this way? I seem to recall that the Cousteau divers dove a triple-tank configurations with a DH reg sitting off to one side.

A couple of potential considerations, though: I would probably need to wear a conventional doubles plate, rather than either my VDH plate or my Freedom plate. And I would probably need to wear a wing of some sort, since 92 cu ft of air weighs about 10 lbs, which would result in too big a buoyancy swing for me to account for with my lungs only. Finally, the two double hose reg hoses ideally would need to be different lengths; however, I'm thinking that the standard-length hoses should work okay.

Any thoughts?

Safe Diving,

rx7diver

DAAquamaster
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Re: Thoughts on twin 50's

Wed Aug 10, 2016 9:03 pm

The Faber 46's are notably less negative in the water than the galavanized Worthington 45s/46s. A par of the Worthingtons are more negative than a set of steel 72s by a fair margin and they'll max out the lift capacity on my 22 pound wing in SM cave diving configuration (can light, reels, etc)

People underestimate how much a galvanized coating weighs as zinc is heavy stuff. I have a very heavy can of ZRC cold galvanizing compound in my garage that is going to get applied to a non galvanized steel 72 that I get tired of repainting, and when it's done it should also stop being the floaty tank when I dive it side mount.

I don't think the lateral placement of the can will make any difference at all, unless perhaps you roll to one side or the other, where you may find the inhalation effort to be slightly higher or lower depending on the side.

With a side mount rebreather and the side mounted counter lung, I'll notice a difference rolled to one side versus the other, but that's a large difference - on the order of 15"-16" off my lateral axis. A few inches off center won't be that big a deal.

With a 2460 psi fill and 96 cu ft, the swing weight will be 6.3 pounds, with a 500 psi reserve. That's really pushing what you can manage with lung volume, and it's more than you can probably manage efficiently. In comparison, the swing weight on a steel 72 from 2475 psi to 500 psi is 4.6 pounds.

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EHowe
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Re: Thoughts on twin 50's

Sun Aug 14, 2016 12:11 pm

The OP is about two years old. I went ahead and bought a set or faber LP 45's. and I have not dove with a single tank in 2 years. I set them up with a sel-pac manifold I found on ebay with center and off set outlets and a VDH plate and wing. I have use a Conshelf 1st stage with an R109 second on a necklace off the side outlet that also runs my spg and inflator. With the + rating fill pressure is 2640. I pump em up to 3000 for 114 cu'. Wearing a 7mm wet-suit I'm using only 8 lbs on my belt.
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I have since bought a couple MI-flex hoses rerouted them to be more streamlined
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