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EWNichol
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Experience with double 38's

Tue May 05, 2020 2:55 pm

I stopped by my LDS the other day and saw that they had four steel 38's sitting out on the floor. When I asked about them, the owner told me that a pest control company had been using them as SCBA tanks. They brought them in for hydro but went out of business while the tanks were in the shop. The pest company owner doesn't want them back, and they have been sitting untouched for a year. They passed hydro, and look very clean on the inside.

The markings on the tanks show that they were originally sold by US Divers. They were all first hydro tested in the late 40s to early 50s. I let the owner know that I'm interested in picking up a set to use as doubles. I have done some reading about diving vintage doubles but would like like to hear from all of you. I've only used my DAAM on single 72s. Do you find small doubles more or less comfortable than single tanks when diving vintage? Have you ever had trouble getting them filled when on a trip? I am worried since I have gotten some weird looks when asking to rent 72s before.

Thanks for the input!

swimjim
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Re: Experience with double 38's

Tue May 05, 2020 4:40 pm

38's make a sweet set of tanks. Mine are very light. After diving a tech rig with twin LP 108's on my back, the 38's feel like they aren't even there. I do all my filling at home before I leave. Some of the guys bring compressors and some trans fill off of larger tanks. You can always try taking them to an LDS, but I wouldn't bother unless I knew the operation. Most of them would probably look at you like your from a different planet if you brought them 38's to fill. Insert long line of LDS excuses....
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ScubaLawyer
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Re: Experience with double 38's

Tue May 05, 2020 4:51 pm

Twin 38's are wonderful. Best balanced set of twins out there (IMHO).  These are mine. Go for it!

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"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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simonbeans
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Re: Experience with double 38's

Wed May 06, 2020 7:22 am

Of all the tanks I have and have used, the double 38s are my favorite. As you can see I have a few sets:
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They ride on your back perfectly, placing the regulator in the proper place. Just one factor, however, not all 38s are the same bouyancy-wise. My Sportsways are heavier than the USDs. In fact the USDs float at about 500 psi. Something to consider when weighting for a dive.
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captain
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Re: Experience with double 38's

Wed May 06, 2020 10:00 am

Be sure to find out what the valve threads are, some SCBA's have different threads from diving cylinders.
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SurfLung
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Re: Experience with double 38's

Thu May 07, 2020 3:29 pm

I Love Twin 38s...
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- My favorites are the war surplus 1800 psi tanks. They're JUST like Mike Nelson because they are so light, you can wear them with no wet suit and you will still need weights to sink... Most double tanks are VERY sinky.
- Yes they position the double hose regulator perfectly... Flat on its face right at the top of your lungs.
- Yes they are comfortable... It's like a balance thing... They just ride nice. The round bottom tanks are best.
- Here's some fun facts: USD Twin 38s are 1800 psi and they hold 38 cf. Sportsways came out with the same sized tank with a little thicker walls and stamped it 1880 psi. They are actually 38 cf tanks. But their marketing team overfilled them an acceptable 10% to 2068 psi and sold them as Twin 42s. So the next year, USD overfilled THEIR Twin 38s by an acceptable 10% to 1980 psi and sold them as Twin 42s.
- My friend AntiqueDiver supplied me with yet another set of 38s so I now have 4 sets. I love 'em all.
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SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

h2operations
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Re: Experience with double 38's

Thu May 07, 2020 11:07 pm

Guys thank you for sharing but I have been grounded too long. I was mislead by the title about a set of 38's .

As always thank you for sharing. It is nice to see what other people are sporting.

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SurfLung
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Re: Experience with double 38's

Fri May 08, 2020 11:14 am

How to Fill Twin 38s Without a Dive Shop Hassle
- One thing nice about the 38s that are from the 1940s is they are VERY low pressure at 1800 psi. This makes them excellent candidates for cascade filling from standard AL80 scuba tanks... Dive shops LOVE to fill current production AL80s. AND, they're cheap to buy.
- I went to the Sea Hunt Forever show and brought my Twin 38s full along with 5 single tanks to fill from: Two 72s filled to 2500 and Three AL80s filled to 3000 psi. The five single tanks refilled my Twin 38s by cascade for the whole weekend... Ten 30 minute dives.
- Before I got multiple sets, I used to bring cascade tanks to refill my yellow USD 38s on dive trips. I think I posted about this a while back with photos. I'll see if I can find it and link it here.
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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EWNichol
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Re: Experience with double 38's

Sun Jun 07, 2020 10:57 pm

Thanks for the replies everyone!

I picked up a set a few weeks ago. With everything that has been going on, I haven't had a chance to put them in the water yet. I'm hoping to change that tomorrow.

The manifold that the shop put on has a J-valve that they said works. I tested it using a reg with an SPG, but I didn't see any pressure drop on the gauge when breathing with the reserve active. Am I correct to assume that the J-valve is not functional, or does the reserve action only become visible at lower tank pressures? The tanks were full when I tested them (~2000 psi).

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captain
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Re: Experience with double 38's

Mon Jun 08, 2020 11:10 am

You won't see a drop with doubles because the tank with out the J will supply enough air to prevent the drop until you get near the reserve pressure.
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EWNichol
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Re: Experience with double 38's

Mon Jun 29, 2020 10:02 pm

I see a transfill whip and a cheap AL 80 in my future...

I've been to three different shops so far and all have told me two tanks means paying for two fills. I think I'll let them fill my 120s instead.

Thanks again everyone for the pictures and the advice. The tanks have been fantastic in the water!

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antique diver
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Re: Experience with double 38's

Tue Jun 30, 2020 9:35 am

EWNichol wrote:
Mon Jun 29, 2020 10:02 pm
I see a transfill whip and a cheap AL 80 in my future...

I've been to three different shops so far and all have told me two tanks means paying for two fills. I think I'll let them fill my 120s instead.

Makes you wonder what kind of mentality perceives that two 38's require more run time on a compressor and/or more labor time to fill than a single 120. The back-strain factor is probably about the same. :?
The older I get the better I was.

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