Thoughts on setting up backmounted independent doubles

[divezonescuba]

So, I am curious how people who dive backmounted independent doubles set up their gear.

Rather than dive sidemount in areas where twin sets are not available, I would like to set up a set up independent doubles. The concept is to be able to switch out tanks on a backplate easily. This eliminates the use of traditional stainless steel bands and bolts.

I am aware of the ap diving adapter, but am interested in other alternatives.

My thought is that some plates like the Xsscuba highland and the Ist plates have four upper and four lower tank band slots. The two slots on either side of the plate are cut so that the bend is between them. Would it not be possible to mount a band on either side, top and bottom, for a total of four bands for the two tanks?

Since the band utilizes the bend in the plate, it would seem to lend stability to the mounting not unlike the way a single tank adapter achieves its greater stability.

The regsets could then be mounted on the valves with the appropriate second stages, pressure gauges, and inflators. This could be like a set of doubles regulators with the addition of a pressure gauge for the right side tank. Obviously, since they are not manifolded, you would have to practice sidemount breathing techniques.

Xsscuba is unaware of anyone who has done this before. I would have tried it earlier this year, but their plates are back ordered.

No need to turn this into a manifold versus independent twins discussion.

 

[KenGordon]

I think you would still want the AP blocks. They sit between the cylinders and help a lot. You can do this with three slots, one in the centre line. I think that is how my Spiro BCD is set up.

 

[-JD-]

I've started down this road: Backplates for indepdent BM doubles (and maybe single-tank)

I was going to order a similar plate, but I ran across a set of used adapters at NESS (same concept as the AP ones, but they bolt up to a standard plate) and grabbed them. They will work with any standard double wing, whereas cambands straight to the plate will be picky about wings (newer DiveRite probably) or require modification.

2020 (COVID is only part of it) pretty much skunked me for diving this year, and I haven't gotten around to actually trying it out. Faffing about, setting up a completely new configuration and learning a new dive style will have to wait. (Although in two dive days I've worked up to combine my furthest, deepest, dive with new fins, drysuit, longhose, and manifolded HP100 doubles all at once.)

If I like how the concept dives, I'll probably sell the adapters and move to a plate-wing combination that works with direct cambanding.

 

[tbone1004]

remember that with indy doubles without sided valves that it is highly unlikely you will be able to manipulate the left post while diving. I would consider using a single tank rig with the "right post" of a set of doubles, and then run a left side sidemount tank. You'd use the backmount tank as "primary" and swap that out. You could do opposite and run a right side sidemount tank as primary instead and have your backmount single be the left post, but I've found that more awkward for some reason.

 

[-JD-]

remember that with indy doubles without sided valves that it is highly unlikely you will be able to manipulate the left post while diving. I would consider using a single tank rig with the "right post" of a set of doubles, and then run a left side sidemount tank. You'd use the backmount tank as "primary" and swap that out. You could do opposite and run a right side sidemount tank as primary instead and have your backmount single be the left post, but I've found that more awkward for some reason.

Depends on range of shoulder motion. Reaching "straight" back is hard for me - middle is a little easier. So a standard right valve is a tad easier to reach in the left side position than the right. I was just testing it out after seeing you post and I can pretty much reach the same rectangularish bounding box with either hand - far left with left or right hand and the mirror as well. I'm partially broken, but the warranty has expired.

Without the manifold, there is also the option to apply some (at least subtle) rotation to make the valve handles a little easier to access.

For me at least, I have 4-pairs of sided valves across 10 tanks so I'll generally be running that route with independants for "standardization" purposes.

 

[divezonescuba]

In a non-tec friendly location with only conventional right hand valves, you could face the left tank backwards. That would allow the normal outwards tank valve handle orientation.

Doing this may also require a few port adjustments and/or a longer necklace and gauge hose.

 

[ajtoady]

I dive indy's and they are valve sided for left or right, they also are used in sidemount. As for reaching the valves, I use the independent setup due to shoulder issues. I also band my tanks for simplicity and security on my back.I would not be able to do valve drills on a manifolded set and figure if one tank, reg set goes south in the indy setup, guess what,,Im headed to the surface and will deal with it on top. To me any failure, wether indy's or sidemount, I'm done and headed up. I NEVER take my tanks in any situation down to a level too low to make a safe ascent from the depth I may be at. However,,to each their own as far as setup.

 

[elmo]

remember that with indy doubles without sided valves that it is highly unlikely you will be able to manipulate the left post while diving. I would consider using a single tank rig with the "right post" of a set of doubles, and then run a left side sidemount tank. You'd use the backmount tank as "primary" and swap that out. You could do opposite and run a right side sidemount tank as primary instead and have your backmount single be the left post, but I've found that more awkward for some reason.

Few of us have the shoulder flexibility to operate a right hand valve on a left tank. But if diving indies why would you do that? If your left-side is cactus and you shut it down, you can't use anything from the left post. If you don't shut it down you lose gas and can't use anything from the left post. Either way you need to get home on you right post, or other gas source. You can't reasonably feather the valve to breathe on backmount.
This case illustrates the big advantage of a manifold over indies.

 

[Basking Ridge Diver]

So my preference for Independent doubles is for a different reason but just as important for me.

I can fill my own tanks - but I am a fireman and I am required to fill in a fill station which means fill each tank independently. It is free air for me and I can control the fills as well as mix nitrox in the fill station. To use the fill station I can not use a manifold - it will not allow both tanks in the fill station. So I have found on boats - that I can do a two tank dive and bring three tanks. On my surface interval I change a full tank for one that I have used. I still have doubles and it is very easy for me to use and fill my own tanks. I have had no issues with the way I use independent doubles.
YMMV but I am happy with my decision.

 

[tbone1004]

Few of us have the shoulder flexibility to operate a right hand valve on a left tank. But if diving indies why would you do that? If your left-side is cactus and you shut it down, you can't use anything from the left post. If you don't shut it down you lose gas and can't use anything from the left post. Either way you need to get home on you right post, or other gas source. You can't reasonably feather the valve to breathe on backmount.
This case illustrates the big advantage of a manifold over indies.

I was agreeing that you shouldn't dive a "normal" valve on the left hand side because you can't manipulate. Reasons to manipulate?

You can feather the valve if the second stage is freeflowing, same as we do with sidemount. Whether you agree that it's reasonable or not is a different discussion, but it's possible and it's something that we train when diving doubles and is something that you may need to do if it really hits the fan inside of a cave...
You can shut the bottle down so it doesn't drain all the way and risk water ingress