Doubles with straps and redundant bladder

[SLE0999]

Couple questions for those with experience.

1. Diving with twin tanks. I understand doubles are usually attached to the backplate or bc with the bolts off the tank bands. Is there any reason why they shouldn't be attached with two straps encircling the double tanks instead of the bolts? I can't find any information on this, and I haven't seen this done in civilian diving.

"The long length of { 52 in | 132.1 cm } will encircle a set of doubles."

Dive Rite Tank Strap w/SS Roller Cam Buckle

The Dive Rite Tank Strap w/SS Roller Cam Buckle is easier to close than most cam buckles

www.divegearexpress.com

I'm currently an active duty navy diver ~13 yrs and all our twin tanks (usually twin 80s) are always attached with straps. I'm wondering why we differ from most other forms of diving.

2.
Straight to the point, why the hate on redundant bladders? For example diving twin 100hps in wetsuit (1-3mm, warm water) and redundant bladder in wing. I thought it was nice to have when spearfishing solo with heavy steel doubles on my back around 70-80 feet. I needed a way to be self sufficient when diving alone and buddy is on boat above so I built a set of 100hp doubles manifolded together with the standard isolation valve and single regulator on each tank. This is also different from work. Our doubles at work are manifolded together but do not have an isolation manifold and are dove with a single 1st stage.

Thanks

 

[-JD-]

1.
Assuming your are talking about manifolded, hard-banded doubles/twins, my guess is it may be somewhat historical, but I can see how there may be a couple advantages to strapping rather than bolting in a military context..

• Straps can be theoretically cut in the case of major entanglement, if it is valuable to keep the rest of the rig with you, where bolts require rig-removal to release.
• Straps could be used on a soft backpack system that would not support a centrally bolted attachment.

2.
I have found the deprecation confusing as well. I use dual-bladder wings for doubles and cold-water singles. For me it is good peace of mind and gives me another option and usually allows for 2 "failures". The arguments seem to be ...

• An uncommanded inflation of the reserve bladder can't be discriminated and you will be uncontrollably buoyant. ( I don't use the power inflator on the reserve currently.)
• (Mostly from the DIR/GUE/etc. system divers) Your drysuit is your reserve buoyancy. (You can't oral inflate a drysuit, but that is a - 2nd level failure argument)
• If you dive a "balanced rig" you can just swim it up. (That is nice, if you actually can make it work at the edge cases, but I doesn't do squat for you at the surface.)

 

[DogDiver]

Flexible webbing bands may not support the manifold correctly and cause a failure.
I used a dual bladder Nomad for years cave diving in a wetsuit. I never kept the redundant bladder attached to a low pressure hose. I made sure my primary inflator hose was long enough to reach the redundant bladder. Now I cave dive in a drysuit so redundant bladder isn’t needed.

 

[Sevenrider860]

Scubapro used to describe an "adjustable belt system" to rig doubles on the Classic BCD in their BCD user manuals. I think Apeks/Aqualung supported a similar configuration with the Black Diamond / Black Ice BCD.

 

[Nick_Radov]

Use of negatively buoyant steel doubles with a wetsuit is not recommended. Even with a redundant wing, if you have a wing failure at the beginning of the dive when the tanks are full then you're going to have a bad time.
Instead of setting yourself up for failure, it's better to dive a balanced rig. In a wetsuit that means double aluminum 80's with an aluminum or carbon fiber backplate. Those tanks are only a few pounds negative when full so if you have a wing failure it's easy to swim them up, and in the worst-case scenario you can always ditch your weight belt to get positive.
Need more gas? Bring an extra stage tank, which can also be ditched in an emergency.
It's not that we "hate" redundant bladders. It's that they're a symptom of not thinking things through and introducing unnecessary convolutions in an attempt to solve a problem which shouldn't exist in the first place.

 

[Trace Malinowski]

I'm surprised the navy hasn't gone with the most non-magnetic equipment possible such as aluminum cylinders instead of steel, brass where metal is needed, and plastic for just about everything else.

Most tank bands are stainless steel which is why I thought the military wouldn't be a fan.

 

[Nick_Radov]

I'm surprised the navy hasn't gone with the most non-magnetic equipment possible such as aluminum cylinders instead of steel, brass where metal is needed, and plastic for just about everything else.

Most tank bands are stainless steel which is why I thought the military wouldn't be a fan.

The Navy uses non-magnetic metals in rebreathers such as the Mk16 issued to mine clearance divers. But for routine inspection, construction, and salvage work it just doesn't matter.

Most stainless steel alloys are non-magnetic. Although I haven't actually tried putting a magnet on a bare set of tank bands.

 

[SubseaSports]

I did a quick search looking for what you are using and didnt find much as far as detailed pics.
Are the Navy manifolds solid ( one piece)? This could be why you are able to use a tank strap safely.
I also beleive you use a soft mounting system.
Anyone please feel free to enlighten me and or post pictures.

I don't use doubles for spearing, but use larger tanks with backmount bailout. I have recently aquired a DR dual bladder as the price was right and it will fit the bill for redundant buoyancy when solo, or whenever.
I used a lift bag prior to this for this purpose, but will keep it for sending fish if necessary. Using a horseshoe wing is ideal for me when backmounting bailout because I keep the pony inverted (my original wing blew out). A donut air cell interferes with this setup.
Curious, are you using your doubles as ID's? (more hate).