How to setup a Double Tank rig?

[RJP]

i have about 40 dives and im getting nitrox certified and i want more bottom time. simple enough.

"Much to learn, do you have."

 

[Doc Harry]

...theres no way in hell im buying a whole new set of gauges etc...

Want to know how to make a small fortune?

Start with a large fortune and then head down the tech diving pathway.......

 

[DA Aquamaster]

As you've obviously discovered, the majority opinion is that relatively new divers should not dive doubles - and many are not real nice about it. But ironically enough most will make a big deal about a dive with 145-150 cu ft in double AL 80's and not taise an eyebrow at using a single 130. 15-20 cu ft of gas does not really make that much difference as 130 cu ft is already way too much if the concern is getting into deco trouble.

Diving doubles is however not rocket science, if you plan to get involved in tech diving eventually, it makes sense to get comfortable in doubles sooner rather than later, and double 80's are a good choice for starter doubles.

Whether you are ready does not depend strictly on number of dives, but rather on your swimming ability, comfort level in the water, buoyancy control, general skill level and equipment configuration. Some divers are ready at 25 dives, others never get there even after 500. Way back in the day divers even learned in doubles (gasp!!).

It is not rocket science, but it does come with some responsibility as it does provide enough gas to get into serious decompression and decompression involves a whole set of skills and training that are separate from using doubles. Many divers however use a single set of doubles for a two tank boat trip - diving half on dive one and the other half on dive 2. It is a bit more efficient than two separate AL 80s as the reserve left from dive 1 is available on dive 2.

I have written a couple fairly detailed posts for similar divers asking similar questions over the last few months, so use the seach function and avoid more blood letting and arguments in this thread. PM me if you have more questions after reading all the threads that are already out there.

One part of your question is unique - can you dive doubles with one reg? The answer is yes. In the 70's and 80's it was common for divers to dive with a single outlet manifold. This uses one reg on a cental post and is essentially operated like a great big single tank.

It is not ideal for decompression diving as there is no redundnacy and no real way to prevent the loss of all the gas in the event of a regulator, burst disc, or tank neck, o-ring failure, so you are strictly limited to recreational non-deco dives with this system. For any kind of decompression diving (soft overhead environment) or diving in a wreck or cave (hard overhead environment) you need a fully redundant system such as isolator manifolded doubles where two first and second stage (but only 1 SPG) are required.

Single outlet manifolds show up on e-bay on a regular basis and most dives shops have one or two sitting in the basement. You need the manifold (single outlet = $75-$100), a set of bands for 7.25" diamter tanks ($50-$150), and two AL 80s ($100 each used, $180 new).

You also want bands designed to attach to a back plate, not bands with a curved section designed to mount to a cam pack, because you will want to use a back plate and wing - ($80-$100 for an aluminim backplate with basic one piece harness, $200-$400 for a wing).

That is about $600-$1000 total, just for single outlet set of doubles if you are starting from scratch and need a BP/wing. That is one of the stronger arguments to go with dual outlet manifolded doubles. An isolator manifold will not cost you much more, and a second reg suitable for doubles (like a Mk 10 Balanced Adjustable) can be bought used for around $125-$150 ready to dive so an Extra $200-$250 will get you into a far more useful set of doubles.

 

[elan]

Hey everyone, im new to the board but i was jw how do i modify my setup to a 2tank rig? i know you need a manifold, 2 tanks(no shlt lol), wings, 2 regulators, and 2 bands. can someone explain this more thouroughly and give an in depth explaination? or even a link to all the items needed? A price estimate would be greatly appreciated. also, is there anyway to do this with 1 reg, 1 octo, and 1 gauge? theres no way in hell im buying a whole new set of gauges ect. thanks for your help

FYI

im about 6 ft 185

i would use 2 AL 80's. i have about 40 dives and im getting nitrox certified and i want more bottom time. simple enough.

i dive cold water by me (New York). about 55 degrees F with a 7mm single, and 5mm boots gloves and hood. i use about 18lbs

on vacation i dive a full 3mm for protection. i use about 12lbs

please help me out.

You might just want to ask your LDS to have them assembled for you. It should not cost you much.

 

[JDMerk]

As DA said...its not rocket science, and as long as your a competent diver now, you might as well start on the doubles road sooner rather than later. In fact you will learn more about diving and your equipment by setting it up yourself and piecing your rig together...the one caveat being that you should employ someone knowledgeable in doubles to help you with the actual setup and your first few times in the water.

Edit: It will cost you at least $1000 to do it right (no DIR reference intended)

 

[UCFKnightDiver]

I think the problem here is that the OP is trying to get into doubles to increase his bottom time, he didnt say he wanted to go down the path of Tech diving. Rather than become a more expirienced, competant, and relaxed diver underwater he is trying to throw gear at the problem, and new and more advanced gear at that. This is why I would recommend that the op just go out and dive more to get more expirience or maybe get a bigger single tank. Better air consumption will come with time as you get more expirience, and relax more.

 

[pickens_46929]

Given the OP's stated experience, I would strongly suggest that his options for increasing dive duration are....

1. Dive more, get more experience - your air consumption will decrease noticeably and you can do longer dives with your existing AL80.

2. Perfect your weighting, bouyancy, trim, finning technique and relaxation. Again, your air will last longer.

3. Get a dive computer and mulit-level your dives, to extend NDLs and decrease your gas consumption in the shallow portions.

4. Invest in a larger capacity or HP single tank initially....it is less expensive that a double set-up and will compensate with extra air, whilst you gain experience and reduce your air consumption.

5. Take a Twin-Set Familiarization, Fundies or Intro To Tech course BEFORE emptying your bank account on a set of doubles. Some money spent here will bring you new skills, knowledge and help you avoid the mistakes that so many divers make when purchasing doubles.

Don't jump straight into diving a twin-set. There are a host of new problems and dangers you can encounter with this equipment. Whilst a manifolded twin-set is 'safer' than a single cylinder - it is so only if you are capable of operating it correctly.

I pretty much agree with everything that DevonDiver has to say and will add the following:

#1 above -- definitely... dive, dive, dive... before you make the jump

#2 -- I would switch over from diving a typical BCD to plate / wing because overall you will find it much nicer and it will be required for doubles anyways... dive a BP/W with a single tank and get used to it before you make the switch to doubles...

#3 -- a stainless steel backplate will take 6# off your belt and distribute it evenly along your center of gravity... if you go with a "tall" stainless backplate you take off 8# of your belt... plus you can add trim weights to the plate very easily... Deep Sea Supply (Tobin) has a really nice set of weights for his plates bringing the total to something like 16#... keep in mind that if you travel, an 8# metal plate means you have only 42# for other stuff before your at your 50# baggage limit... fyi, in warm water with a single AL80 and 6# backplate, I don't need any additional weights except for that first dive of the trip...

#4 -- start transitioning over to a long hose configuration before you move to doubles... take GUE fundies or intro to tech and learn the new setup with a single tank...

#5 -- if you really must, go with a large single to add volume... AL 100, steel 100, etc.

#6 -- skip using an H-valve on a single tank... don't make the mistake... works for some people but I found it to be a pain...

#7 -- try out some bodies doubles setup in confined water or controlled setting... see how they feel... rent some if you have to... I did... was the best decision I ever made and I got to try out about 3 different setups of doubles... double AL80's, double LP85's and double 104's....

 

[DevonDiver]

As you've obviously discovered, the majority opinion is that relatively new divers should not dive doubles - and many are not real nice about it.....Diving doubles is however not rocket science,....Whether you are ready does not depend strictly on number of dives,..... Way back in the day divers even learned in doubles (gasp!!).

I agree with DA Aquamaster completely. and thought I should add some more - just in case my initial post was misinterpreted....

Twinsets have many benefits over single cylinders - that is why they are used for technical, cave and wreck penetration diving. Greater capacity of gas is one obvious benefit. The second is redundancy.

I see nothing wrong with anyone utilising a twinset -should they require it for a legitimate reason.

However, I do strongly believe that a twinset is sufficiently different from diving single cylinder that it warrants appropriate training.

I also believe that switching to a twinset should not be done to 'solve' problems caused by bad air consumption. A serious diver should tackle the root of the problem (improve their diving, to decrease their SAC) rather than just throwing more tanks onto their back...

DA Aquamaster's advice to switch to a BP&W configuration, with long hose, and single cylinder is very appropriate - if your end goal is to dive twinset. It is a nice progressive step, that will allow equipment familiarity and the development of control, trim and weighting, prior to adding a second cylinder and learning the correct drills for shutdowns and reg switching,

 

[ucfdiver]

I strongly suggest getting double HP130's instead of double AL80's (it's actually what I use). Here's why-

• They allow you to stay down long enough to go into deco, which really helps if you want to get the full benefit of your DAN membership.
• They're a GREAT workout on the surface. I try to jog at least a mile a day in them for peak cardio workouts.
• If your wing fails, you can swim them to the surface, and if you're good at it, you'll learn to survive if you're ever thrown overboard with a cement block tied to your leg by someone trying to kill you as you see on the movies.

 

[UCFKnightDiver]

While were on the subject why not LP120's, I think Faber even has some LP130's now