Be a manly man OE2X... go with the double 130s. 
8 inch cylinders - read if you've dove one
- Thread starter dlwalke
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You know with the decrepit disks that I have I should be getting my tanks made from titanium!
Actually with the extra length of the 120's I might be able to do a valve drill without turning into a lawn dart.
Next time you have your 104's double let me try them on for size to see if can work the valves.
Actually with the extra length of the 120's I might be able to do a valve drill without turning into a lawn dart.
Next time you have your 104's double let me try them on for size to see if can work the valves.
Yep - doubled HP120's are heavier than a single E8-130. A lot more drag as well.OE2X:
Ron's double 104's are heavier than my double HP120's. They're actually shorter and wider, but I didn't notice any difference in drag or anything. The valves were a lot easier to work than mine, but that actually has nothing to do with the tanks - it's an issue with the valves themselves.
A single E8-130 is heavier than a single HP120.
I'll let ya know about doubled 130's after I try GratefulBob's...
Leadking
Contributor
reefraff:
The Worthington cylinders coming to market were designed from scratch. Sea Pearls and XS Scuba worked with Worthington's engineering staff in Tilbury Canada to create a line of cylinders that WE wanted. Heiser is ownd by Worthington but is not involved in this project. Please review cylinder spec's at http://www.seapearls.com/tanks-steel.html
FredT
Guest
Leadking:
After some detailed discussion with the folks doing the designing these cylinders may be avilable without the powder coating. This would be a great way to ensure a much more durable outer finish, although not it may not be quite as "cute." Testing is underway at this time...
FT
Fred, how would having the tank without the powder coating increase the finish's durability? Isn't the powder coating normally applied *over* whatever other coating is normally there?
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OE2X:
Well now ... THAT could create some excitement the first time you tried to get a partial-pressure nitrox fill ... :11:
Snowbear:
My doubles are only 119's ...
... Bob (Grateful Diver)
FredT
Guest
jonnythan:
A galvanized or metallic zinc coating functions by creating an electrochemical corrosion cell where the Zinc is the anode or corroding member while the steel of the tank is the cathode or protected member. The cell functions entirely on electrical potential and surface area ratio. Galvanizing works because the exposed surface area on the zinc is many orders of magnitude larger than any exposed steel of a scratch or holiday (pinhole) in the coating. As long as this area ratio is retained the zinc coating will actually heal and coat exposed steel with electro-deposited zinc transferred in solution from the surrounding surface and plated out on the steel surface. In this manner process holidays actually self-heal when galvanized metal is immersed in seawater.
A powder caoting functions as a barrier coating to keep corrosive liquids like seawater away from a metal surface. This is fine unless there is a holiday in the coating, and effectivly all single layer coatings will have many almost microscopic holidays on a surface area the size of a SCUBA tank.
Under the powder coat holiday or scratch the exposed zinc is sacrificed, but since the surrounding "donor" area is effectivly coverd no new zinc is deposited to help heal the scar. Once any exposed zinc at the holiday site is gone the underlying steel starts driving the exposed edge of the zic coating rapidly in to solution thus exposing more steel and driving the remainng zinc into solution even faster. Much like a malignant cancer this starts to encourage any surrounding holidays to join the party and starts a feedback loop that drives the corrosion at exponential rates. Even starting with small holidays once you see it start it's too late to salvage the coating system. If Worthington spends the money they would have spent powder coating on additional zinc the tank life will be extended at least 10X beyond the powder coat over flame spray zinc system originally proposed.
Barrier coat OR galvanize, but don't do both.
FT
Ahh, great info, thanks.
Why are tanks such as Fabers painted over the zinc, then? Just because it looks better, even though it ultimately makes the tank more susceptible to rust?
Why are tanks such as Fabers painted over the zinc, then? Just because it looks better, even though it ultimately makes the tank more susceptible to rust?
boomx5
Contributor
Snowbear:
The double 130's are like diving the 104's but a bit heavier. I thought about getting a set but my 95's have been working just fine.
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