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Post by SeaRat on Aug 11, 2014 17:22:23 GMT -8
A steel 72 is a better balanced tank from a weight perspective in the water than many of today's tanks. It took a few years to come up with the steel 72, and it became the standard tank for many, many years because of the thought that went into it. Today's high pressure steel tanks have a horrible weight in the water, to the point that a BC is mandatory to dive with them, even without a diving suit (which is why it used to be called "skin" diving).
John
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Post by nikeajax on Aug 11, 2014 17:28:07 GMT -8
John, I keep meaning to ask you: on my AL 72, how much extra weight do I need to counter the positive buoyancy?
Jaybird
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Post by Deleted on Aug 11, 2014 18:18:38 GMT -8
I guess you can do anything you want too to a steel tank on the outside........twenty years ago when I finally bought my first twin 38's, they had that vinyl coating Voit liked to put on their tanks......it had many scrapes and rusty spots so I scrapped off all the vinyl, sanded the tanks clean of rust and then had them "Nickle Plated"......WHAT! you say....are you crazy?........well I saw a chromed one once back then and not affording the chrome I opted for nickle to reduce the rust.............problem was I did not have a mirror surface and the nickle only took to the high spots of the steel, not the valleys where the sanding scratched deeper........ SO I painted them with primer and then refrigerator enamel....and held my breath on sending them for hydro. They passed,....amazing.......with a big + after the date, on the second and third hydros in fact.......they still have the same paint, scuffed bottoms now with some rust but nothing major..You can see the nickle on two horizontial scraps on the left tank in the accompanying photo...I don't hydro now as I have my own compressor.......I hope to use them again after I get finished with all this illness crap....
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Post by tomcatpc on Aug 11, 2014 19:10:56 GMT -8
Is external rust an automatic NO-GO? If so, I can just say that one of the tanks is FUBAR'd already, as it has a few bare spots that have rust. I guess I should not feel too bad as these were free after all LOL! Mark
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Post by tomcatpc on Aug 11, 2014 19:13:25 GMT -8
On the positive side of things, the Scubapro "Offset Jet" Snorkel turned out all right after I let a coating of Silicone Grease soak into the very dry rubber. I think it might be useable after I get a replacement retainer for it. Mark
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Post by surflung on Aug 12, 2014 6:25:49 GMT -8
- I don't view tank testing as part of the cost of a tank. Rather it is a regular expense just like the cost of a fill or gas in your car to drive to the dive site. You have to do the tank testing by DOT law to every tank regardless of whether its new or vintage... It's a regular expense in being a diver. - That being said, I HAVE had tanks that were failed by one tester and passed with flying colors by another tester. I have had tanks come back all scratched up and 2 months late when the LDS used an outside service. - It took some looking around but I found the Minnesota School of Diving in Brainerd MN. They have their own hydrotesting facility on site. They have been doing it since the '60s so they have both experience and thread adaptors for my vintage tanks. And, they will do it while I wait! They even let me watch once. - I forget what they charged me last time but I don't think it's possibly for me to feel ripped off there since I don't know where else I could go to get the good, reliable, service that they do. - Finally, I take pride in my vintage equipment and vintage diving skills. I don't dive crappy nor unsafe equipment and I don't want any modern divers to be justified in looking down their noses at me. - Above left are Sportsways Twin 42s that were initially failed. The O-ring sealed straight 1/2" thread may have been leaking for the first hydrotester. My Brainerd service detected the leak, fixed it and the tanks passed by a wide margin. Above center are USN surplus 1940s tanks that somebody cobbled together. Rusty (but steel) bushings adapted tapered 1/2" threads. Inside was clean and rustless with no pits. Outside was old galvanize... Which initially looked corroded but (as it's supposed to) it was only the zinc galvanize that was corroded. These also passed hydrotesting by a wide margin at Brainerd. Above right are the little tanks I did for my grandsons. These each went thru hell and a two month wait. I repainted the white one which is a converted CO2 fire extinguisher with a tapered 1/2" thread. The yellow one is kind of a collector's item for me... A "Vigo 18" as sold by US Divers in the early '60s. It looked almost new when I got it. The outside hydrotesting facility scratched up the original paint quite a bit. My Brainerd service would not have scratched it. - What I Have Learned: When you find a place that does a job right, don't quibble on the price.
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Post by scubadiverbob on Aug 12, 2014 12:00:41 GMT -8
Sent you a PM on two AL80's (brand new) for sale at $49.97 a piece. You won't find them cheaper than that! Me, I prefer steel 72's ... AL80's require 4 to 6 more pounds of lead on the weight belt ....
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Post by scubadiverbob on Aug 12, 2014 12:02:15 GMT -8
If it was me, I'd take care of the steel 72's ...
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Post by tomcatpc on Aug 12, 2014 13:54:35 GMT -8
I am going to hang onto the Steel tanks I got free. As for buying an Aluminium tank...that might have to wait until I get a better job...right now cash is tight, so even the thought of getting the tanks I do have tested is going to have to wait. I do want to have a modern tank to go along with the modern kit I have...but that can and will have to wait until later.
I was messing around this afternoon and got the boot off one of the tanks, the one I perceive as being the worst of the lot. The boot came off easy with the use of hot water, no problem there. Like I suspected there was a spot of rust on the very bottom, not the entire bottom, just a spot a couple inches wide. Is this a "kiss of death" for a steel tank? Or could this gripe be corrected and have the tank pass still?
Sorry for all these dumb questions...I have no clue what I'm talking about here LOL. Mark
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Post by Deleted on Aug 12, 2014 14:56:55 GMT -8
Depends on how deep the rust goes.....surface rust is not a problem, just sand off, treat with zinc spray and paint or what have you.........
My second twin 38's are USD'rs and still have the vinyl coating....some scratches with light rust that I treat once a year.........got me to thinking........that liquid bed liner for pickup beds might be a good treatment...just an ugly black.....unless they come in colors.......what say y'all?
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Post by tomcatpc on Aug 12, 2014 17:56:51 GMT -8
Yep...the one tank I'm "working on" right now, the worst of the lot (in my novice opinion) has bits and patches of peeling paint/vinyl coating. If I could sand down the rust spots and touch up re-paint the patches with yellow paint...this might no look all that bad. Yes, it will look patchy in places, but some of the dirt is coming off and the J-Valve cleaned up great.
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Post by diverdon on Aug 12, 2014 19:40:38 GMT -8
Pics or it didn't happen;) Check this out. I didn't think to pop the boot off this tank until it came back from hydro. I'm thinking I should fail it myself now that I look at it. It came back with a good stamp but dang! What do others think? These are all on the bottom which I realize is thicker and maybe its merely cosmetic...
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Post by diverdon on Aug 12, 2014 19:42:41 GMT -8
You may recognize the tank from an earlier post of mine. Here's the hydro stamp. Attachments:
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Post by tomcatpc on Aug 12, 2014 19:59:07 GMT -8
All right...maybe mine are not that bad?! LOL I took the boots off of the other two and both are rust free on the bottom!!! The 1960s galvanized tank has the whitish surface substance that looks like it will come off with a bit of scrubbing, but other than that it looks all right. Mark
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Post by SeaRat on Aug 12, 2014 20:49:34 GMT -8
The zinc coating from galvanizing oxidizes to zinc oxide, which is probably the white powder you are seeing. This is how the zinc coating protects the steel.
This is why I like having steel tanks that are galvanized. I do have my set of PJ tanks which are not galvanized, and I have simply painted them with a zinc primer prior to painting with a zinc paint.
John
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