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Old 16 November 2006, 09:36   #1
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Carrying Diving Air Tanks Aboard

Not being a diver myself, I've not paid any attention to how tanks are safely secured aboard a RIB. What are the important safety concerns? What are some of the options for securing tanks aboard?

I may need to be regularly carrying some small tanks on the Searider, so I'm starting to plan for it. Probably 6 or 13 CF tanks, maybe 2-6 of them. Is this a fabricated it yourself or purchase?

Suggestions? Recommendations?
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Old 16 November 2006, 09:45   #2
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Most dive RIBs I have seen have a bottle rack in the middle made from stainless.

A cheaper solution for just a few would be this ssytem

http://www.hitechplastics.co.nz/imag...ck%20right.jpg
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Old 16 November 2006, 10:50   #3
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Dive tanks are not really all that fragile. You're at more risk of beating the crap out of the rest of the boat with the tanks. That said, you don't want side impact on the tank valves (that would be classified under the "bad stuff" heading.) The cylinders themselves are tough, but constant banging together will drive you nuts in no time.

For my SIB (with limited space), I used to assemble the scuba rig, and lay them in the front of the boat. Spare cylinders were wedged in between the assembled rigs. (In truth, my RIB is using the same method, until I can get the boat into my buddy's shop to finish up with the tank racks.)

Some people use wire "milk crate" racks; I always found that they take up too much room, and are a pain in the butt to use (tank boots and BC's keep snagging on the wire when you don't want them to.)

A couple of people I know stand the rigs up and use a ratchet strap to tie them to the tubes, but I could never get mine to stay put that way.

Just reread your message: 6 or 13 CF tanks? What are you using those for? I hope you're not planning on using those as primary dive tanks.

Those would be a custom job, as most off-the-shelf solutions are sized for standard dive cylinders (7 to 8" diameter) rather than ponies (which are closer to 4 or 5 inches, I'm guessing.)

jky
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Old 16 November 2006, 13:58   #4
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Dive tanks are not really all that fragile. You're at more risk of beating the crap out of the rest of the boat with the tanks. That said, you don't want side impact on the tank valves (that would be classified under the "bad stuff" heading.) The cylinders themselves are tough, but constant banging together will drive you nuts in no time.

Just reread your message: 6 or 13 CF tanks? What are you using those for? I hope you're not planning on using those as primary dive tanks.

Those would be a custom job, as most off-the-shelf solutions are sized for standard dive cylinders (7 to 8" diameter) rather than ponies (which are closer to 4 or 5 inches, I'm guessing.)

jky
Thanks. It's the "bad stuff" that I want to avoid. I keep thinking of the scene at the end of "Jaws", where the Chief uses the diving tank to blow up the shark. Don't need anything like that happening aboard unintentionally! Sounds like I'll be building something myself. Or rather, having an expert woodworker build something for me. Probably best to build something with a lid, so the tanks are fully enclosed and protected?

No, This isn't diving related. It's a top secret project I'm working on. Probably going to wind up using compressed air as a power source for some machinery and will need to carry the tanks on the rib. Waiting for the engineering students at MIT to calculate the forces and capacities before we know what size tanks we need to carry. Probably won't be the full sized tanks though, too big & heavy!

I could tell you more, but then I'd have to kill all of you (or at leat the Brits ). And maybe blow up the rib.net server as well! It's a damned cool project though!!

Hmmm... maybe I can have the carbon fiber fabricator who's building the system make me a really cool looking bottle rack!
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Old 16 November 2006, 14:28   #5
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No, This isn't diving related. It's a top secret project I'm working on. Probably going to wind up using compressed air as a power source for some machinery and will need to carry the tanks on the rib. Waiting for the engineering students at MIT to calculate the forces and capacities before we know what size tanks we need to carry.
Flame thrower for dealing with errant yachties that get in the way?
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Old 16 November 2006, 17:58   #6
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No, This isn't diving related. It's a top secret project I'm working on.
You gonna be running your RIB on Nitrous Oxide?!!! With a big red GO button on the helm! It'll make everything blurry like in the Fast and the Furious!

WMM
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Old 16 November 2006, 18:21   #7
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You gonna be running your RIB on Nitrous Oxide?!!! With a big red GO button on the helm! It'll make everything blurry like in the Fast and the Furious!
I LIKE that idea! Especially after getting slammed on another forum, for asking about tweaking a 75 E-TEC up to a 90.

I'm enjoying the conjecture! Anyone else??
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Old 16 November 2006, 19:19   #8
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You point out that these are 6 and 13 cu ft bottles, right? These are just "pony bottles", so that won't fit in any standard tank racks. I presume that they are aluminum, so you need to be careful not to gouge them. Aluminum is considerably softer than steel of course. I am curious as to their end use, and why you would use a number of small tanks rather than a large one....

As jky pointed out though, it is mainly the valves you need to protect, but they are pretty tough. Also, be careful you don't overfill the tanks and leave them lying about in the sun or you might end up with a burst disk letting go...!
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Old 16 November 2006, 20:22   #9
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Probably going to wind up using compressed air as a power source for some machinery and will need to carry the tanks on the rib.
If the application will take place at above 0 C (32 F) temperatures, why not use CO2 tanks? Much safer and will provide much more energy for a given tank size.

http://www.powertank.com/
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Old 16 November 2006, 23:58   #10
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Like Stoo said, the cylinders aren't really all that fragile.

The exploding cylinder thing is, for the most part, myth (some older aluminum cylinders, made of a more brittle alloy, are in fact prone to cracking and exploding; usually during the fill process.)

Recently manufactured cylinders use a more ductile alloy, which is not as prone to cracking, and when they are punctured, release one hell of a blast of air (and possibly project the cylinder around), but no explosion.

In case you're wondering, an aluminum cylinders' wall is near a half inch thick; not something that an errant gaff is going to hurt.

What you build will depend on how many cylinders you need to carry. Might check out wine racks; they'll be too small, but if you can find one with a decent density of bottle storage, it may give you some ideas.

Personally, I'm of the opinion that a plain box would be simplest, especially if you need in situ access to the valves. Plan on using something to isolate teh cylinders from one another (neoprene works well), or you'll drive yourself batty with clanging.

I, for one, have officially had my curiosity piqued.

jky
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Old 17 November 2006, 20:50   #11
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I've thought of CO2, but with travel, compressed air will be easier to replenish on-site. CO2 would require finding a commercial gas supplier. Anywhere the RIB is, we're likely to be able to find a dive shop to refill air tanks. We'll see what the engineers think

Oh, the machinery won't be aboard the rib, which will function as a support vessel... Small tanks for weight savings aboard the other boat.

I'm surprised no one's making any guesses!
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Old 17 November 2006, 21:50   #12
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They use compressed air to power torpedos!!!
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Old 18 November 2006, 14:36   #13
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I'm surprised no one's making any guesses!
Nautical Paint-ball?
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Old 18 November 2006, 17:46   #14
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They use compressed air to power torpedos!!!

Uhh, no they don't. They expel the fish from the tube with compressed air, but the prop is driven from a small turbine engine (I think.)

jky

Later research on my part shows that there are a number of propulsion systems in use now; ranging from piston engines (US Mk48) to chemical engines (US Mk50 - uses sulphur sprayed onto lithium to generate heat for a steam turbine), to an Ottofuel powered gas turbine (US Mk46, UK Spearfish.) Probably a bunch of battery powered fish, as well.

jky
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Old 18 November 2006, 17:59   #15
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Ok maybe I shoud have said "used" - not just to push it out of the tube but to power it's piston motor. Most WWII types used this system.
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Old 18 November 2006, 18:04   #16
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Uhh, no they don't. They expel the fish from the tube with compressed air, but the prop is driven from a small turbine engine (I think.)

jky

Later research on my part shows that there are a number of propulsion systems in use now; ranging from piston engines (US Mk48) to chemical engines (US Mk50 - uses sulphur sprayed onto lithium to generate heat for a steam turbine), to an Ottofuel powered gas turbine (US Mk46, UK Spearfish.) Probably a bunch of battery powered fish, as well.

jky
I think maybe you are getting a little confused - some of the piston engines are NOT operating in the conventional sense like a car engine. It is operating in the same way as the earlier compressed air torpedo engines - instead of using compressed air though it uses a rapidly expanding gas.
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Old 19 November 2006, 11:51   #17
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I'm surprised no one's making any guesses!
Some sort of high powered air lift?
No, no I know, I know, you are trying to automate expired air resuscitation, but have you thought about all those divers doing balloon impressions, might not look good on the accident forms
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