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When you're diving sidemount, are you always breathing from independent regs? I've read about Armadillo, etc., but is that always the case? I understand the rationale behind being able to switch back and forth between regs, especially if something goes wrong, but is there any setup whereby you can essentially isolate a valve (other than switching off your first stage)? Such questions plague me late at night.
I have seen a high pressure flexible steel cable that is used to create a connection between two dive cylinders. The cable I have seen comes packaged with tanks bands and was designed primarily as a way to connect two independant cylinders in a standard back mounted fashion. I guess you could conceivably use the cable across the chest in a side mount style effectively breathing off both cylinders at the same time. The one problem with this setup though is that the steel cable does not have an an isolator valve. The other problem is that in a side mount configuration the cylinders are always shifting and moving and this may put critical stress on the connecion ends of the flexible cable. With no isolator valve on the steel cable, if one end were to come loose or break off due to movement and stress, well you would loose your ENTIRE GAS SUPPLY. Not good. So, the answer is that you technically can breath off both cylinders but it might ( I don't know the cable specs) be more dangerous in the end. Probably the reason why I've never seen anyone do this. Let's give this rig a new name. The suicide setup.Quote:
Originally Posted by Michelle
Um, sorry I'm not half as a jive and two spools too cool but I think under the man's tank one two and I have one reel shy thirty one oh eye one more I'd walk the plank if my bro yo understated he dont have watcha chacallit undemoted then whatchallit again one time demoted if you weren't lookin at me one time, me just having fun mofo...let your ass out have a good time...oh was this a test? I guess I got carried away. I hate it when that happens.
The side mount freestyler, cool... One reg, two regs, the girl doesn't know, redundancy issues, is her air gonna free flow? haha.Quote:
Originally Posted by Michelle
Rob Parker did this for his 1985 Wookey dive. A pair of Accurex high pressure composite tanks were worn one on each side. Both tanks had Y valves with a HP hose connecting the two worn around the front of the body. I guess that there must have been a way of purging the cross-connect for disassembly. This was a carefully thought out rig.Quote:
Originally Posted by andrebasso
Wow, someone actually has done this...Interesting. More interesting to me though, why don't more divers use the HP composite tanks like they used to. I remember seeing so many photos in the eighties of these 4500-5000psi tanks. I know you can't use them for helium as it leaks out at those pressures (small molecule or something), but if used for just air or enriched air, would'nt those tanks be useful in today's diving?Quote:
Originally Posted by Duncan Price
Two main reasons you don't see HP composite tanks used for scuba
1. The buoyancy characteristics of those tanks is not go. They get very buoyant empty.
2. The material will absorb moister over a period of time and affect the strength of the composite.
They work great for fire dept scba since they are lighter and they don't soak in water all the time.
That's putting it mildly, 007.Quote:
Originally Posted by curtschu
I had someone leave some 4500s for fills (I believe it was a textile mill that does periodic fire drills). A customer picked one up and asked why we didn't use these instead. I tossed one into the pool and it floated like a cork.
Russell
Hey guys, I did a little research on the net. What about the 4350psi "s106w" by Luxfer, they market it as a scuba cylinder and apparently it's only 3 lbs positive when totally empty in saltwater. Any thoughts why more divers don't use this one? Look like it could be perfect as a stage cylinder, small and compact but gives you 106cft of air with somewhat favorable bouyancy characteristics for cave diving. (with 2/3's of the air depleted it would be almost neutral in fresh water.)
I think pretty well any expedition Bill Stone had a hand in back then used the Acurex tanks.Wakulla,Huatla and Pena Colorada,I think some of the stuff in Australia utilized these as well.Luxfer makes hoop wrap composite tanks now.Some of the sump divers up here were looking at them but they don't trust the durability and inabilty to see damage under the carbon fibre wrap.Nice and light for the sherpa with lead being easy to cache for any bouyancy problems.Maybe one day they will be deemed durable enough?
I read that he had used that system and he stopped later on.Do you know why he did not try to utilize the manifold for other dives?
I wonder how difficult it would be to have dual y/h valves with quick connects.Attach a flexible hydraulic hose in between that you could carry strapped to a tank for stuff hitting the fan moments.Don't any one get any ideas ,I am just thinking out loud 8)the more i thought about this later, the bigger cluster f is seemed.
The biggest drawback to connecting your sidemount tanks together, as far as I can see, is that it would then be impossible to remove a tank if you needed to. Also it would limit the amount that the tanks would move around, which would make it much more dificult to navigate the tight spaces that the configuration is designed to allow access to.
I like the fact that the tanks are not connected, it's safer. The valves are right where you can see and reach them so there's no need for it. As other posters said, you should be able to take the tanks on and off easily, I myself don't want any hoses going behind my head for that reason
I don't see any need to connect SM tanks together. It defeats the purpose. It may be necessary for some very specific applications, but not as a general thing.
I am having a hard time attempting to envision where this sort of set up would prove useful. It just seems like it would defeat the whole idea of sm'ing cylinders from the get go.Quote:
Originally Posted by Jay
It seems something like that might be useful if you were rigging up a multi tank setup with >2 tanks. Or perhaps if you needed to fit into some tight spots and the water quality was such you didn't want to have to switch regs.
The fiber wrap tanks are more expensive and less durable. But they are very very light for the amount of gas they're rated for. I seem to remember there were some problems that if you scratched the epoxy, water could get into the fiber wrapping at depth and cause it to delaminate.
Haul tanks for any distance through most caves and they start to sound very attractive though.
Some further comments:
The HP cross-connect between tanks was also used on the Wakulla 1 trip. I'm guessing that the hose could be depressurised so that the cylinders could be carried seperately. Sadly Rob is not with us anymore so i can't ask him why it was not used more widely. The '85 Wookey dive was the first trimix cave dive in the UK and a bit of a one-off. Also, things have moved on over how we set up our tanks - in the bad old days of this era the cylinders were worn on a belt around your waist. You threaded all your tanks on to your harness, would then lie on your back to do it up and had to be hauled to a standing position. There's footage of this on Gavin's Wookey DVD from '85. With this sidemount rig removing a cylinder underwater was almost a non-starter unless you put them on separate belts. From about '94 onwards we moved over to the dual point attachment that US sidemounters use and it became possible to don/doff your gear in the water
The Accurex composite tanks that were imported by Bill Stone and got employed on the '85 Wookey dive were used in other sump dives in the UK. Testing of composite tanks is not straightforward. Other UK sump divers have used composites (especially as firefighters use them in breathing sets) - they must be wrapped up with inner tube to protect the composite outer. Otherwise they are easy to carry down dry caves. Buoyancy is not a problem since lead can (and is) cached in caves by sumps - better than carrying the weight in and out.
For spring diving I can't see any advantage for composites.