Doubles w/o manifold...

[jagfish]

I've seen products that are able to hold two independent singles together, and then are able to be attached with bolts to a backplate.

They look like an intersting idea if you wanted to dive doubles at locations that only had single aluminums available.

Anyway, curious who uses these setups and under what circumstances...

 

[msandler]

That's exactly what those setups are for. Independent doubles are fine in a forgivinig environment where the extra air is needed. You must alternate "sides". When diving independents doubles, I still use tank bands (probably cheaper, sturdier and travel easy enough). The cam band devices you refer to look like they will do the job fine.

 

[novadiver]

That's exactly what those setups are for. Independent doubles are fine in a forgivinig environment where the extra air is needed. You must alternate "sides". When diving independents doubles, I still use tank bands (probably cheaper, sturdier and travel easy enough). The cam band devices you refer to look like they will do the job fine.

The most important lesson of independent doubles is " alway leave enough gas to surface in each tank." if you breath one dry and find out the other tank just blew an O-ring than you are truely SOL. With the isolation manifold, you can isolate 50% of the gas remaining.

 

[DA Aquamaster]

Independent doubles work well but they do require attention to gas management and require that you switch regs twice during the dive.

Normally you use 1/3 from 1 tank then switch and use 2/3 rds from the other tank leaving 1/3 in each tank in reserve. Proper planning and management will always leave you with enough air to ascend and meet all deco obligations with the air in either tank. The potential that you may not be able to access the reserve air in one tank or another does require a slightly greater volume of air compared to manifolded doubles but this is not as large a limitation as most peopel think.

Critics claim independent doubles increase task loading, but my thought is that if the minor increase in task loading from two reg switches is really an issue, you are not qualified to be doing whatever you are doing in the first place. Mike's reference to independent doubles being fine in a "forgiving environment" is interesting. Side mount divers tend to dive in some very unforgiving caves so I am not sure that everyone would agree with that assessment as the two systems are functionally identical.

The obvious disadvantage of independent doubles (or sidemounting) is that should a first stage permanently fail, you cannot normally access the gas remaining in that tank. The advantage however over isolator manifolded doubles is that the two tanks are completely independent and you do not have to rely on an isolator valve to prevent the loss of all your air. Most of my diving is in very old water and a freeze flow is the most likely failure mode. So I prefer independent doubles as in the event a freeze flow ever occurs, no action is required to close a valve. It is still a good idea to close the valve and conserve the gas, but if circumstances prevent it you will not lose all your gas.

 

[cool_hardware52]

I've seen products that are able to hold two independent singles together, and then are able to be attached with bolts to a backplate.

They look like an intersting idea if you wanted to dive doubles at locations that only had single aluminums available.

Anyway, curious who uses these setups and under what circumstances...

Hi Jagfish,

Our backplate allows independent "Twins" to mount directly, no adapter required. The two pair of vertical slots about half way from the top to the bottom of the plate are for a single cam band on each tank.

http://www.deepseasupply.com/page7.html

Our 50lb doubles wing has 2 large windows to accomodate the camstraps required.

http://www.deepseasupply.com/page10.html

This may not be the most common setup, but for travel to places without banded doubles, and for operators that require an alternate source it's handy, and requires no extra parts or expense.


Regards,



Tobin

 

[msandler]

Mike's reference to independent doubles being fine in a "forgiving environment" is interesting. Side mount divers tend to dive in some very unforgiving caves so I am not sure that everyone would agree with that assessment as the two systems are functionally identical.

Function wise perhaps but a sidemount dive is a very different set of circumstances than what I interpreted by the question. Sidemounts are dived in caves where restrictions are a serious obstacle and detaching your cylinders is a requirement of the dive, presumeably where a backmount system would be too cumbersome. Cave diving is not forgiving but it is not the question asked either. A forgiving dive, IMO, when when the task loading is minimal! 130' END, no stage tanks, no zero vis, no need to re-find a lost line, no need to deploy a bag for deco, no need to simultaneously manage a light and reel and an unexpected problem (diver stress or panic). Diving independent BACKMOUNTS on a "technical" dive can be done (I have a number of times), its just not recommended.

 

[Hugh]

Jagfish

Diving independent doubles is a great way to go in places like Japan - where I know you are diving. While you were DIRF-ing at YGM I was scootering with my indy doubles.

Gas management needs to be watched - but it is not a drama. If you put a dog-clip 3" from your SPG and then clip onto the LH and RH D-ring on your harness you can check your gages just by dipping your head. Diverite do a great twinning set and there are a couple of other smaller suppliers in the US. I strongly recommend investing in pair - if manifolded doubles are not available I always dive with doubles - even on gentle rec dives. As they say... if you need it, take two. If you don't need it, leave it on the beach.

Hugh

 

[DEEPLOU]

I've seen products that are able to hold two independent singles together, and then are able to be attached with bolts to a backplate.

They look like an intersting idea if you wanted to dive doubles at locations that only had single aluminums available.

Anyway, curious who uses these setups and under what circumstances...

In my area these are called "Berg Bands" after Dan Berg who made and marketed a version under his "Aqua Explorers" label
http://www.aquaexplorers.com/
Others call them "Travel Bands"

The Berg version comes with a Halo so they could even be munted on many hard backed BCs.

Many divers I know use them regularly, often only switching out one tank between dives. Most of these guys I call "living dinosaurs" as they have been diving steadly since the early 50's.

 

[DA Aquamaster]

I agree with Hugh on the lack of drama involved in gas management. I clip the SPG to a D-ring and also clip off the unused second stage. The boltsnaps on the regs are zip tied to suitably sized o-rings in place over the mouth piece on the second stages. This keeps them secure and in place but also makes them immediately available if you need it right now and do not have the time to unclip it. If accessed that way they can also be restowed underwater by inserting the mouthpiece back through the o-ring.

In response to Mike's comments, I routinely used independent doubles below 130 ft in limited viz on deco dives with lights and reels where I will often shoot a lift bag on ascent and am likley to encounter an entanglement. I have never found the additional task loading of checking an spg and swapping regs twice during the dive at the appropriate times/pressures to be a problem.

And, I routinely do what Deeplou describes as I use the same configuration on short/shallow/rec dives as I do on deep/long/technical dives. It allows a great deal of familiarity with your configuration and in my opinion, it is less important what configuration you use as it is that you use the same basic configuration every time you dive. So with independent doubles on a rec dive, I will use one tank with the other along as sort of a super pony and the only difference is in how the gas is managed.

I also use the Aqua Explorers travel bands. They are well made and quite secure. The only suggestion for improvement that I would make would be to replace the plastic cam buckles with metal ones.

 

[jagfish]

Jagfish

Diving independent doubles is a great way to go in places like Japan - where I know you are diving. While you were DIRF-ing at YGM I was scootering with my indy doubles.

Gas management needs to be watched - but it is not a drama. If you put a dog-clip 3" from your SPG and then clip onto the LH and RH D-ring on your harness you can check your gages just by dipping your head. Diverite do a great twinning set and there are a couple of other smaller suppliers in the US. I strongly recommend investing in pair - if manifolded doubles are not available I always dive with doubles - even on gentle rec dives. As they say... if you need it, take two. If you don't need it, leave it on the beach.

Hugh

Hi Hugh
You were one of the people that gave me this idea. Seems like Japan woud be a great place for such an item...

JAG