If you have been following my material on scuba diving you know I have been writing about diving, diving dry suits and diving back inflate BCDs (buoyancy compensation device) a natural follow-on is diving what are known as backplate with wing type BCDs and the configuration of tanks, regulators and hoses known as the DIR (Doing It Right) configuration. The main purpose of double tanks is to extend the amount of time one can remain underwater and to provide for redundancies in your air supply.
Usually the right hand tank valve has the main primary regulator attached, the main primary has the primary-secondary stage (the one you breath through, normally called the primary) and the fill line for the wing. On the left tank valve (or “post” you attach the secondary-primary regulator you attach the backup secondary regulator (taking the place of the octopus) however now it is simply called the backup. On this left hand regulator you also have (in a “pure” configuration) a single, small SPG (usually what is known as a brass and glass SPG) and the fill line for your dry suit, if needed, since actually in a “pure” setup you would have a small bottle of compressed argon with its own regulator that would fill your dry suit.
Let me explain about this backplate and wing I keep talking about. The backplate is just what its name implies, an aluminum or stainless steel (I guess there may some titanium ones out there, but I haven’t seen any) plate that is specially drilled and milled to hold a single continuous length of nylon webbing that forms the shoulder straps and waist belt. This continuous piece of nylon webbing makes for a simple, easy to maintain, method of wearing the backplate for a diver. Being a continuous piece of webbing this eliminates points of failure present in standard BCDs. There is usually a second strap, called the crotch strap, coming off of the bottom of the backplate. The crotch strap prevents the backplate from riding up and provides a point of attachment for a pull line from a scooter, relieving your arms from having to provide not only steering control but a grip on the scooter itself.
A wing is a flotation bladder with an inflation hose (called a “corrugated hose”) and usually a dump valve (on the back side of the one pictured below.) The buoyancy bladder is encased in a protective covering usually of a rugged nylon fabric. Some wings, Like the Oxycheq Signature 50 pound, have a double layer of fabric for added protection of the inner bladder.
As its name implies a set of doubles consists of two air tanks connected through a manifold assembly and rigidly mounted to each other through a set of stainless steel tank bands. The tank bands have the attachment fasteners (bolts) that attach the tanks to the backplate and are usually mounted on the tanks with 11 inch centers to allow mounting to the standard backplate.. Using an STA when using a single tank allows for rapid conversion between diving a single tank and diving a set of doubles as it only requires removing two wing or butterfly nuts and swapping out the doubles for a single tank mounted to an STA.
Meanwhile I purchased two Oceanic Alpha 8 PX3 Piston Regulators, a seven foot hose for my primary and a set of inflator hoses and a Sherwood Compact Navigational 3 Gauge Console with Compass from http://www.leisurepro.com/. I realize that a three gauge console with a SPG, depth gauge and compass is not true DIR but I like it simple and having the three in one place makes it easier for me. I then configured the dual regulators as shown on the GUE website.