Moving to doubles....

[Firediver32]

Lets say you had, tanks, regs and bands. Would there be any harm in banding them as independant doubles, getting use to trim, bouancy, weighting, etc, for a little while until money can be saved for the manifold, viz, installation etc. Again assume you had everything but the manifold and extra money. This would only be for shallow, NDL, practice dives for getting the feel of doubles. NOT for deco dives, deep etc. Would this develop bad habits as you progress into manifolded tanks? My thinking is, I could get used to the feel, trim, etc than work up to valves, etc after comfortabe with the basic feel. (and after he extra cash is saved). Just a thought.

 

[DA Aquamaster]

Many tech divers end up going the other way - diving manifolded doubles at home and then having to use independent doubles when traveling.

Proper gas management is vital and a second SPG is needed. You use 1/3 of the first tank (left post usually) then 2/3rds of the other tank, then switch back to the first tank to use the 2nd third from it. (1/3rd is left in each tacnk as a reserve).

This approach helps ensure that at the point of maximum penetration (where you have used 1/3rd from each tank) the contents of either tank (both having 2/3rds left in them) will be enough to get you back to your exit or first deco stop in the event you lose access to the contents of either tank.

The upside is that being unable to access a valve will not result in loss of all your gas. The downside is that for half the dive you are breathing off the short hose reg, which creates a small hitch in the otherwise smooth "donate the long hose primary" OOA drill as you have to unclip and hand off the long hose if you are already breathing the short hose. My preferred way to deal with this is to clip the long hose off on the right shoulder D-ring when it is not in use with the bolt snapo secured to the second stage by using a large o-ring slipped over the mouthpiece. That ensures it can be pulled free by me or the buddy with no need to unclip it.

I route the second SPG (on the right tank) over the shoulder inisde the neoprene shoulder pads I use on my harness. The 1.5" spg exits by the right D-ring where it can be seen without adding major complication to hose routing or streamlining issues.

On the other hand, an extra SPG suitable for tech diving will run you around $80 and used manifolds go for not much more than that at around $100-125, with new ones costing only $170-$225. So it is not that much more expensive to go with manifolded doubles in the first place.

 

[Firediver32]

I Think you missed my point, or maybe I wasn't clear. My long term Goal is manifolded doubles, learning proper gas management, valve drills. etc. In the mean time, Will it hurt my progress later on If i use them as independants for a couple of months while saving money for the manifold. I have all the equipment needed already (tanks, bands, bp/wing, regs, long hose, spg etc) EXCEPT the manifold most of which I've been using for some time. I am not trying to replace the value of manifolded doubles by using independant, just getting used to the feel, trim etc until I can get my tanks manifolded. I'm gonna be diving anyway, thought there may be a befefit to getting used to the weight/feel of doubles. This would likely be a few months

Using the this set up as independant tanks, It would only be for NDL, practice dives, working on skills of trim etc. NOT the full range of valve/manifold training, that would come later....

 

[Jimmer]

Yes I don't think it would be an issue using them to work on trim etc. but I think the point DA was getting at was unless you already have 2 SPG's (which you don't specifically say) then you might want to consider going straight to the manifolded doubles, considering you can easily spend 3/4 or more of the cost of a decent used manifold, just buying a quality brass and glass SPG.

 

[Rainer]

Save up $200.

 

[Firediver32]

Got it. I have another spg I could use, or just use one tank for gas and keep all spg/second stages on that one. Or maybe I'll just wait till I get the manifold. I was not trying to reap the benefits of a redundant air supply by doing this, just experimenting with trim, but may be better off in the long run to wait a few months

 

[TSandM]

Well, having never dived independent doubles, I would think your trim will be somewhat different from putting the weight of the manifold up behind your head, so diving the independents is probably not an ideal way to perfect your trim for diving manifolded doubles. Somebody can correct me if I'm wrong.

 

[DA Aquamaster]

I never noticed any significant trim difference. The difference in terms of manifold versus two valves is the center section/isolator valve and that probably does not add much more than a pound underwater. Slide the tanks an 1/4" lower in the bands would probably have a larger effect.

 

[Colliam7]

Proper gas management is vital and a second SPG is needed. You use 1/3 of the first tank (left post usually) then 2/3rds of the other tank, then switch back to the first tank to use the 2nd third from it. (1/3rd is left in each tacnk as a reserve).

In thinking about this, going with independent doubles may be a helpful method of practicing good gas management. It does encourage you to pay attention throughout the dive. (And, before getting flamed, I am not suggesting that most of us with manifolded doubles don't do that, or that we get lazy or complacent.) This is not unlike flying single engine airplanes with independent fuel tanks, where you switch tanks at prescribed times (30 minutes, then hourly) duing longer flights. Is it ideal? Not necessarily. But, is it manageable, and can it be used as a tool to continue to improve awareness and gas management? Seems like it.

 

[Dive Junky]

I take deep dive vacations quite often and use independent doubles. The travel bands are great. Keep an eye on your gas and manage it well and there is absolutely nothing wrong with your plan Firediver32. Dive safe.