Thoughts on setting up backmounted independent doubles

[tbone1004]

It looks like you can do it either way. The point of the bars in the end of these particular spacer blocks is to keep everything aligned when using one long cam band to hold both tanks. As the accompanying text says (in not-great English):

Used with two cam bands or ... for extra-long band and block as a set... The key to the system is an interlocking. A quick-release tank band passes through each component.

I suspect two sets of bands would be much more stable if your backplate has the necessary 4 slots.

the ones that I have mount to the backplate like a set of doubles and are like the one in the image you posted. I've never seen the style that you linked to for the spacer blocks. Looks like those are more in line with pony bottles than trying to use them for doubles.

 

[jale]

Hi
When I used to dive independent double, I had this homemade system

 

[divezonescuba]

So, I received a plate which has the double slots. This is what it looks like. The tanks are closer together than they would be with a manifold. The bend in the plate allows each tank to be very securely attach the tank with the two tank bands. Other than the extra two tank bands, no additional mounting hardware is needed. I suppose you could mount the tanks with only one band each, at the cost of some rigidity.

Since I am considering the lowest common denominator, they are set up on non-modular valves like you can get anywhere. Obviously, the left tank is rotated backwards to allow the valve handle to approximate a twin set left tank so that the valves can be accessed easily.

Depending on your first stage design, you may only need to change the side the spg comes off of the left post first stage. Since I normally use a transmitter on my right post, nothing needs to change there.

 

[-JD-]

@divezonescuba Is that a DR Classic (new cruciform style center) like this?:

 

[divezonescuba]

It’s a Diverite rec 45 pound lift model.

I did not know that they made the classic like that. I just received one a couple of months ago and it had the nylon panel, not the webbing.

 

[-JD-]

Wow! The Rec seems huge on there (I'm mentally interpolating the cylinder outlines) Looks about as wide (I guess not as thick) as my OxyCheq 57.

I'm not sure what the deal is with the solid vs. webbing center panel on the DR Classics. I'm finding different versions and lift capacities depending on where I look.

 

[tbone1004]

@-JD- the gap between the tanks is near 0 where on a "normal" set of doubles, they'd have at least an inch. Doesn't seem like a lot, but it looks about right for narrow space doubles

 

[divezonescuba]

In case anyone is interested, here is a video that I made on this subject.

 

[-JD-]

In case anyone is interested, here is a video that I made on this subject.]

Thanks for the video!

What is the dry-weight of the Ti plate?
Do you happen to have a purchase link for it?

I'm gathering for next season and trying to decide between plates. I can get ID-compatible plates in 304SS (4.8-5.2 lbs) or AL (1.6-2 lbs). AL is more travel friendly, but I wouldn't mind some better corrosion resistance - so maybe Ti, if not insanely expensive.

 

[blatter]

Hi jale - those spacers look exactly like the ones I got from Diverite Express (now Dive Gear Express) years ago. They are pretty good and I still use them a lot with independent doubles. It is a shame that these are no longer readily available. A friend I dive with is an engineer saw mine and made an improved version that was deeper and looks to be a bit more stable.

The soft bands make for easier and allow the use of cylinders with different diameters.

I think that independent doubles are great. Easier to transport and truly redundant, compared to manifold systems. If you dive them correctly (use around 30% in the first cylinder then swap and so on) then even if there is a failure and you can't reach the failing side then you should still have lots of gas left to ascend. I think manifolds give a false sense of security. If a low pressure hose goes and you are holding on to an anchor line in a current with one hand and a camera in the other then you may lose a lot of gas before you can turn off the isolator valve or the failing side and may lose too much gas to allow for a safe ascent. I often do long deco solo dives and this is a consideration if there is no buddy to provide gas.

If dived correctly, independent doubles would likely need at least two major failures (equipment or mental) before you are out of gas.

For serious deep dives I use a rebreather and mixed gas, but independent doubles and maybe some O2 or rich nitrox for deco are ideal for a lot of the diving I do.