Question re: doubles

[mathauck0814]

Wait, what? I dive double occasionally, but only when I have to. The added weight, the added drag underwater, and the extra PITA of setting up an extra reg, etc. are all a real drag for me. I have a friend who dives double 120's and we are always waiting for him to lug his gear around, check this, clip that. Even he dreads lugging his doubles from the car to the boat or shoreline.

Of course, I'm the guy who never got into tech diving because to me, less is more, but as Devon Diver said, the task dictates the tools and sometimes my tasks dictate doubles. If it were me, I'd leave your tanks as singles and get yourself a couple of used 80's or 72's to band together just for the weight consideration.

I also agree that they're easier. They trim out better (no weight belt when diving dry is a nice start), you don't have to set up an extra reg - just have your singles reg and your doubles regs. My doubles get set up at home the night before a dive, I throw them up on my shoulders and I'm ready to go in no time. It sounds like your complaints are more derived from your lack of experience in diving this way. It becomes second nature with practice, just like anything else in diving.

 

[lowviz]

....//....- just have your singles reg and your doubles regs.....//.....

Or put an H-valve on each single tank. -then one reg config fits both, safer way to dive singles anyway.

 

[darushin]

I currently do this very thing myself. I am a intro to cave diver and I used doubles for redundancy in the cave and for all dives over 100' in depth. Once you get your BP/W gear properly configured, you will find setting up your gear is as fast or faster then someone doing singles. My one piece of advice is get or borrow a air integrated dive computer that lets you set a DTR warning (Dive Time Remaining Warning) and can handle deco because it is much easier then you think to go into deco (especially at deep depths). This will allow you an added measure of safety until you get use to diving NDL with doubles.

 

[mathauck0814]

I currently do this very thing myself. I am a intro to cave diver and I used doubles for redundancy in the cave and for all dives over 100' in depth. Once you get your BP/W gear properly configured, you will find setting up your gear is as fast or faster then someone doing singles. My one piece of advice is get or borrow a air integrated dive computer that lets you set a DTR warning (Dive Time Remaining Warning) and can handle deco because it is much easier then you think to go into deco (especially at deep depths). This will allow you an added measure of safety until you get use to diving NDL with doubles.

Or... you know... plan your dive...

 

[TSandM]

I wholeheartedly agree with the idea of setting up some doubles and getting some diving done with them before you consider any training with them. Diving doubles IS different -- at least I found that posture was much more critical than it is with a single tank -- and you may have to play with your weights until you get the best balance for the set. Different tanks work better for different people, too; I cannot for the life of me dive our LP72s in real balance (even Bob Sherwood gave up) but the Worthington 85s I have feel like coming home. If you can get access to any sets to borrow, try some different ones before you go to the trouble of twinning up what you have. Used sets of doubles go on the market (at least around here) fairly frequently, and often well below the cost of constructing a set de novo.

Until you can do a valve drill, you will essentially be diving a huge single tank with a lot of failure points, but if you stay within recreational limits, you're not a whole lot worse off than you were before. If you are going to practice valve shutdowns on your own, do it with a mentor; I suspect all of us have, at some point, shut off all our gas doing drills, and it's awfully nice to have someone sitting there with a reg ready, in case you can't quickly turn it back on . . .

Pay close attention to your trim -- the most common thing with people newly diving doubles is to go significantly head-up, because the weight of the tanks, manifold and two regs tends to make you very head-heavy. You rear up to shorten the lever arm that that weight has to work. Do not get stuck with the idea that you need to move weight UP to solve the upright trim issue. (I had the HARDEST time convincing my husband of this!) Almost always, you need to move weight DOWN to balance. If you are diving sufficiently large doubles that you require no additional weight, you may need to switch to an aluminum backplate to use a tail weight or something of that sort. Realize that weight belts are often not very much below your COG, so they may not help.

Anyway, I agree that diving doubles has some lovely advantages in stability, both up and down in the water column, and from side to side. The flip side is that you are not quite as agile. And there is the whole weight-on-land thing . . .

 

[cool_hardware52]

Pay close attention to your trim -- the most common thing with people newly diving doubles is to go significantly head-up, because the weight of the tanks, manifold and two regs tends to make you very head-heavy. You rear up to shorten the lever arm that that weight has to work. Do not get stuck with the idea that you need to move weight UP to solve the upright trim issue. (I had the HARDEST time convincing my husband of this!) Almost always, you need to move weight DOWN to balance. If you are diving sufficiently large doubles that you require no additional weight, you may need to switch to an aluminum backplate to use a tail weight or something of that sort. Realize that weight belts are often not very much below your COG, so they may not help.

All good stuff.

What I recommend: Once you have your ideal weighting dialed in go find a hard, horizontal bottom, big pool, platform etc.

Lay down on the platform and assume the "position" Add little puffs of gas to your wing until lyou just lift of the bottom. If your head / chest is rising and your knees are on the bottom you need to move ballast "north" or the wing south, if your knees are comming off first you need to move ballast "south" and or the wing south.

Pools are great aid for working on trim because they have big horizontal surfaces. If you can hover 6" off the bottom of the pool, and your knees are not dragging you are probably pretty close to horizontal.

Tobin

 

[ScubaSam]

Mike - definitely get started with the doubles. They take some getting used to (can you say TURTLE), but once you figure out the balance, everything gets easy. There are plenty of DNY people that dive doubles (me included) and would be happy to dive with you and talk about things. Getting the tanks situated for the proper trim is key. Otherwise you are constantly fighting for trim.

One thing I definitely recommend is starting to stretch for better ability to reach those valves. Your dry suit will also affect that greatly. I have no problems in my wet suit reaching valves, but in my dry suit I have major problems.

Good luck!

Hi, Mike (doctormike),

I dove doubles for a year locally before I felt comfortable enough to take a cave course in doubles. I definitely credit the mentors in DNY who patiently buddy with me until I felt comfortable enough to venture outside of Dutch in doubles.

As Mike (parzdiver) posted, we'd be happy to dive with and talk about your doubles setup. We can meet up at Dutch and try to sort you out. Mike's recommendation about the stretches will help with valve drills so definitely start those.

 

[smellzlikefish]

I have the buoyancy down and trim out flat without any effort but breathing and have practiced valve drills and doffing/donning underwater. Still, it is the lack of agility that kills me. I guess I got into a habit of keeping an eye on the surface after lots of bluewater diving where the critters tend to come at you from above. The doubles' turtle posture makes this a major pain in the neck. Literally.

As for the reg issue, I keep the backplate bolted onto the doubles to make setup a little more efficient, but can't fathom investing in a pair of dedicated regulators for my doubles when I don't care for diving with doubles to begin with. I guess I might be a little jaded also after having to wait what feels like eons for my buddy who decided to practice using his doubles again.

 

[lowviz]

....//.....I cannot for the life of me dive our LP72s in real balance (even Bob Sherwood gave up) ....//..... the most common thing with people newly diving doubles is to go significantly head-up, because the weight of the tanks, manifold and two regs tends to make you very head-heavy. ...//.....

Not a hijack, just a slight detour on the subject of doubles...

I remember your past posts on this subject.

And I love double 72's. Wondered about this for quite a while... Double 72's are long and light so the regs count for a lot of misplaced weight, -thus your consternation with them?

My homemade bands are over-gauge and use 3/8" SS plates to compress them, and along with heavy bolts, all this counters the reg weight. I also need to wear a weight belt with double 72's.

There is a big gap between the two cylinders as 72's are narrow tanks while the manifolds are standard. Lots of room for a short fat lead "V" weight. Next project is to make a short but heavy tank "V" weight that can be slid up and down for adjusting trim, -losing the need for a weight belt. perfection...

 

[James R]

My mentor told me that she preferred to have two different brands of second stages, for two reasons - (1) so that if one failed due to environmental reasons, both would be less likely to fail for the same reason (admittedly a pretty rare occurrence, especially if I'm not ice diving or anything), and (2) so that it's easy to tell which one you are using by the weight, etc... Again, a relatively minor concern, but I guess I could buy another first and second stage, use that with my doubles set, and then use the Atomic first stage / Z2 for travel...

I can't think of any environmental reason that would cause two second stage regulators, identical or otherwise, to fail at the same time.

I have a SeaCure molded mouthpiece on my primary 2nd stage and a stock (oem or whatever) on my backup. Very easy to tell which I am using. Also, as a side note, I fully disagree with having an inferior backup second stage as well (ie balanced primary, unbalanced secondary).

There are some things in this world I don't think people should ever skimp on. Regulators and toilet paper come to mind here