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SurfLung
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Quick and Dirty Doubles

Thu May 12, 2016 10:09 am

Quick and Dirty Double 72s...
- My dive buddy Rich runs out of air a little too soon on deeper dives like Fortune Pond. We've tried larger capacity tanks: He's got a couple of Faber 95s an dives them singly... But still runs out a little too soon. We talked about doubling some tanks but just never seem to get around to it. Last weekend as we were returning from another trip to Fortune Pond, I realized I have everything I need to double my steel 72s.
Image
- The Sportsways Bands, Back Pack, and harness came off my Twin 42s that were converted to Sea Hunt style bands and harness. The extra double bands are from a lot of 3 sets I bought on eBay awhile back. And the Dacor connector bar is something I bought on eBay a few years ago and never used. The only extra expense I had for this set up was in new nuts and bolts.
- We're heading to Wazee May 20-21 and will give this set-up a shake-down cruise. :)
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

swimjim
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Re: Quick and Dirty Doubles

Thu May 12, 2016 7:05 pm

Nothing like the good ole suicide manifold. Lol. I didn't make that up, that's what they are called. Nothing to worry about Eb, that manifold will work just fine.

Jim

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rhwestfall
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Re: Quick and Dirty Doubles

Fri May 13, 2016 1:49 pm

actually, "cheater bar" around here....
Bob

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SurfLung
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Re: Quick and Dirty Doubles

Fri May 13, 2016 3:58 pm

I'm kind of pleased with the old Sportways backpack and bands. They mount the tanks almost directly to your back. We strapped these on last night and they are a load but not too bad. The darned waste strap is too short... Divers must have been skinnier in the old days.
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

swimjim
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Re: Quick and Dirty Doubles

Fri May 13, 2016 6:50 pm

Around the end of WWII the average height of a man was 5'7". Now that's the average girth around the beer gut. Yep, things have changed :lol: :lol:

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rhwestfall
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Re: Quick and Dirty Doubles

Fri May 13, 2016 8:03 pm

I inherited some "vintage" stuff from a shirt-tail-relative. I'm 6'-7" and he was much more "the norm"..... it's comical....
Bob

No Longer Awaiting my Kraken.....

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Ron
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Re: Quick and Dirty Doubles

Mon May 23, 2016 11:18 pm

I like suicide manifolds for rigging up double 72s on short notice. They also make a cheap fill whip in a pinch to equalize singles to each other. I ran my doubles like this for a while before I found a USD doubles manifold and it works well. It actually makes the right tank valve easier to reach as well.


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sitkadiver
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Re: Quick and Dirty Doubles

Tue May 24, 2016 2:33 am

slonda828 wrote: It actually makes the right tank valve easier to reach as well.


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just out of curiosity... Are you cascading?
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Ron
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Re: Quick and Dirty Doubles

Thu May 26, 2016 2:14 am

Not while diving. I cannot really think of a point to shut down a valve under normal operation. Is there one?


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luis
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Re: Quick and Dirty Doubles

Thu May 26, 2016 6:37 am

You can use one cylinder as a reserve (that was Cousteau preference).

With doubles, you equalize the cylinders when air is needed and close the valve again. Every time you do that, you know how much air is left (half as much). So you go from 1/2, to 1/4, to 1/8, of what you started.

This is a very reliable method of keeping track of how much air you have left in a zero visibility condition, where you can not see a pressure gauge.

It is also a much more reliable and much more practical reserve than a "J" valve. It actually provides a reasonable volume of reserve, not just enough air to reach the surface above.

This method is sometimes used by commercial divers in zero visibility condition and as I mentioned, it was used by the Calypso divers.

I also remember discussing it (in the 70's) as a better alternative to a "J" valve, but at the time very few manifolds were designed to operate this way. I can only think of White Stag (maybe Healtways had one also), and my Poseidon and Drager double cylinders could also be operated in this form (but I never did).

Note: this method works best with the valves on the bottom where they are much easier to reach. In Europe and Australia that has been tried a lot more than here. I think some of their valves were also intended for this method of reserve.
Luis

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antique diver
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Re: Quick and Dirty Doubles

Thu May 26, 2016 8:02 am

One of our friends from down under called that "Decanting", others have referred to it as "Cascading".

It's how I dive with my Siebe Gorman doubles (circa 1955) that have the valves down. A convenient way to have a close approximation of your remaining air when diving without a gauge. Love those tanks.
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luis
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Re: Quick and Dirty Doubles

Thu May 26, 2016 5:12 pm

Yes, I have also heard it called as “decanting” and I was using that term when I started writing my post, but I before posting I looked the definition of decanting and in all the definitions it specifically talked about liquid (not fluid). So at that moment, I decided not to use the term decanting unless I could verify that is was commonly used (or should I say miss-used).

I do like the term for this application even if it is not totally accurate.
Luis

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antique diver
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Re: Quick and Dirty Doubles

Thu May 26, 2016 7:55 pm

luis wrote:Yes, I have also heard it called as “decanting” and I was using that term when I started writing my post, but I before posting I looked the definition of decanting and in all the definitions it specifically talked about liquid (not fluid). So at that moment, I decided not to use the term decanting unless I could verify that is was commonly used (or should I say miss-used).

I do like the term for this application even if it is not totally accurate.
I agree.
I first heard the term from YankDownUnder, and believe it to have been commonly used in Australia in the vintage diving era. So I think we are ok with it too.

Even though it appears to generally refer to pouring out liquid, air cylinders/tanks were (and still are in some fire departments) often referred to as "bottles"... a term also generally associated with liquid containers. So it's not too far off to see "decanting" used to describe pouring air from one air bottle into another. I like the term, and also find it a fun way to manage air.
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captain
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Re: Quick and Dirty Doubles

Fri May 27, 2016 9:06 am

In the chemical industry the term decanter and decanting is used to describe a vessel where one liquid is removed from another such as decanting oil and water. The water is removed from the bottom leaving only oil.
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Ron
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Re: Quick and Dirty Doubles

Fri May 27, 2016 10:07 am

That's really interesting. I'd never thought of that, but it makes sense.


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