Doubles w/o manifold...

[wedivebc]

bit of an old post, but could you describe your hose routing with your independent doubles?

Sure, 2 apeks din regs left side has spg,wing inflator, short hose. Right side has spg, long hose and ds inflator. I used to have a poseidon reg that came from the left side but I didn't care for the reg. I now use an aqualung 2nd stage that converts to left hand hose position. That makes it easier sorting out which reg belongs to which tank. Because my right side has the long hose I start my dive using it and switch at 1/3. That leaves the most gas available to the long hose for the longest time.

 

[DA Aquamaster]

I use the same set up (but with Mk 20 D400's) with the long hose on the right and short hose on the left and inflator on the left and dry suit on the right and an SPG on each. But I use a normal right handed second stage on the short hose and route it around the right side as well.

I also have the left tank mounted with the reg facing backwards. It's a little odd but this places the valve knob on the outside where it is more accessible and quicker/easier to turn off if needed. With the Mk 20, it poses no detrimental hose routing issues.

I also use the same approach to air management with regard to leaving 2/3rds in the right tank (long hose) for the majority of the dive.

 

[wedivebc]

I use the same set up (but with Mk 20 D400's) with the long hose on the right and short hose on the left and inflator on the left and dry suit on the right and an SPG on each. But I use a normal right handed second stage on the short hose and route it around the right side as well.

I also have the left tank mounted with the reg facing backwards. It's a little odd but this places the valve knob on the outside where it is more accessible and quicker/easier to turn off if needed. With the Mk 20, it poses no detrimental hose routing issues.

I also use the same approach to air management with regard to leaving 2/3rds in the right tank (long hose) for the majority of the dive.

Just curious, where did you learn this technique? My tech/nitrox/trimix instructor was a caver from way-back and had been teaching this method for years.

 

[Scubaroo]

Neat - this follows what I had envisaged pretty closely. Actually I'm looking at taking DIR configured regs and putting them on independent doubles this weekend - the main difference to what you guys are doing will be that my wing will be running off my right post.

Ditto on the breathing down 1/3rds - I will be using independents for back-to-back dives for now, but it makes sense to me for bigger dives to breath down 1/3 of the right tank (long hose), switch to the left tank (short hose) for 2/3 of it, then switch back to the right tank (long hose) at the end of the dive. Neatly breaks the dive up and you end the dive with a third remaining in each tank, and for 3/4 of your bottom time, you have 2/3 a full tank available to the long hose.

cheers

 

[ianr33]

Neat - this follows what I had envisaged pretty closely. Actually I'm looking at taking DIR configured regs and putting them on independent doubles this weekend - the main difference to what you guys are doing will be that my wing will be running off my right post.

Ditto on the breathing down 1/3rds - I will be using independents for back-to-back dives for now, but it makes sense to me for bigger dives to breath down 1/3 of the right tank (long hose), switch to the left tank (short hose) for 2/3 of it, then switch back to the right tank (long hose) at the end of the dive. Neatly breaks the dive up and you end the dive with a third remaining in each tank, and for 3/4 of your bottom time, you have 2/3 a full tank available to the long hose.

cheers

I have been known to dive independants :11: The regs are the same setup I use on manifolded doubles,except for the addition of another SPG (Short hose+SPG from left ,long hose+wing inflator + extra SPG from right)
I do make sure that my long hose has a breakaway connection on it so that if a buddy has an OOA when my long hose is clipped off to the right D ring the reg can still be instantly donated

 

[DA Aquamaster]

Just curious, where did you learn this technique? My tech/nitrox/trimix instructor was a caver from way-back and had been teaching this method for years.

It was one of those evolutionary self discoveries. After diving independents for awhile and struggling with reaching the valve on the left, it became obvious that the problem would go away if the valve were on the outside like on a manifold.

Since it looks odd and emulates a frequent mistake by newby single tank divers, I often have to explain it to people. I have found that finding an instructor who is ok with independent doubles is a problem. Finding one who actually understands them and teaches independe doubless techniques would be a real luxury.

 

[wedivebc]

It was one of those evolutionary self discoveries. After diving independents for awhile and struggling with reaching the valve on the left, it became obvious that the problem would go away if the valve were on the outside like on a manifold.

Since it looks odd and emulates a frequent mistake by newby single tank divers, I often have to explain it to people. I have found that finding an instructor who is ok with independent doubles is a problem. Finding one who actually understands them and teaches independe doubless techniques would be a real luxury.

I know what you mean. I teach this method to my students and encourage them to choose their own technique as experience dictates. I have had several students complain that they get questioned by well meaning divers who don't understand. One 'tech' diver told a student of mine his system was very dangerous and he would lose most of his reserve in an emergency. Fortunately by the time they complete the course they are able to give a credible explanation, should they choose to the 'experts' they encounter.
BTW , I now dive with a manifold usually but the isolator is shut so the effect is the same. I am teaching a deco procedures course starting this wednesday and I am going to try your backwards tank idea. Thanks.

 

[Soggy]

BTW , I now dive with a manifold usually but the isolator is shut so the effect is the same.

Why? It seems like that brings you all the potential drawbacks to an isolator, but none of the benefits.

 

[wedivebc]

Why? It seems like that brings you all the potential drawbacks to an isolator, but none of the benefits.

Well, I do lots of wreck diving, sometimes solo. If I were to experience a gas failure I need to know I have enough gas to exit the wreck. Let's say Murphy is my dive buddy today and the gas failure happens at my turnpoint I need to find my guideline, and start my exit. With my iso closed I can choose to ignore the gas problem should I find myself in a less than desirable spot. If I am able to do a timely shutdown then I can use whatever gas I have saved but if I don't I would still have 2/3rds in both tanks before the failure at the turnpoint so it's no biggie.

 

[DA Aquamaster]

I agree with you Dave. Ideally you will always be able to find the valve to the offending reg and shut it off or, if need be, close the isolator valve. But as a practical matter, if you are in a confined space shutting the valve(s) may not be an immediate option.

With a closed isolator or independent doubles and proper air planning/management you are always going to have enough air in either tank to surface or, at a minimum, to extricate yourself from the wreck and get ascend normally to the first deco stop that allows you to use your deco gas. So, although it's still highly desireable to close the valve on the freeflowing reg, it is not a live or die situation to be able to close the valve as you will always have an adequate gas supply isolated from the problem tank/reg.