Tips on starting diving doubles

[njl]

Just wanted to add: If it's an option to do some weight training, this is incredibly helpful for diving doubles. I have been shore diving with doubles in CA for a number of years and previously thought it was not attainable as a small-sized human. Weight training was necessary for me, in my opinion, to do it safely and have fun.

 

[SouthernSharktoothDiver]

@njl I do a decent bit of upper body and legworkouts, and for my build I’m fairly strong. I just know I’ll be more comfortable carrying ~80-90 lbs than ~120. I think I could manage double hp 130’s ok, but if nothing else, I don’t know that my boat could lol

 

[SelfDiver]

I would not go mucking around with yoke regs on a set of independent right handed valve tanks. That's a recipe for a flooded reg at best.

Seems like you are several upgrades away from doubles.

What? Why not?
I made hundreds of dives just like that. Two standard AL80 with right hand valves and yoke. Sometimes I turned the left tank around (180° ish) so it was like the manifold and just had the reg on "backwards".
Sometimes I turned the left one so that the valve is at the base of the neck (CCW 45°ish) and I could operate both valves with my right hand.
Independent doubles does not suck.

 

[SelfDiver]

@Nick_Radov Per my understanding, my rig would be safe so long as I'm positively buoyant, minus any ditchable weight. So, for example, if I'm say, six pounds negative at the start of the dive, neutral at the end, and carrying six pounds of lead, all of which is ditchable, my rig would be safe, correct?

Simplistic example, of course, but the principle holds the same. In practice, I would have more than six pounds of air weight being lost with a twinset, but essentially my point here is that at any point in the dive, I can drop weight to achieve positive buoyancy, and even ignoring that, could in theory swim up just fine even without dropping lead, since the ~12 lbs negative I'd need to be at the start of the dive is manageable by use of fins. This is not even getting into the fact that, in the environment I'm planning to use this system in, I could crawl out if I needed to, or, failing that, drop my whole rig and swim 20-30 feet straight up.

Please let me know if my understanding is flawed here. I've seen several discussions on "balancing" a scuba rig, and many people on here seem to have different opinions of what that term means. I'm not a GUE/DIR/any kind of technical diver myself, I'm just trying to stay at about 30 feet for around two hours at a clip, so some of this stuff is a little above what I'm familiar with. Also worth mentioning I won't be using this in places that don't have a hard bottom (at 30-40 feet, max) which adds to the safety factor. Still, if my understanding is flawed here, do let me know.

@gordonscuba Several other people have already made the point about manifolds. I've said I'm looking into it. Need to put the whole thing together and figure out a few basic issues (such as whether my LP 72's are even appropriately sized for my wing) so that if/when I do buy a manifold, I know the stuff I'm putting it on actually works.

Also, your use of hyperbole doesn't really add to your argument, and in fact makes it less compelling. Independent doubles is not like skydiving with a knitted parachute. Better example, from what I've been told so far, would be to compare it to diving with a parachute made in the 1970's. Not suicidal, or even dangerous, if the thing is well maintained and checked off thoroughly, but perhaps not the wisest course. Also bear in mind, some other people, both in this comment thread and elsewhere on this site that I've seen, would dispute even that, so acting like it's a completely insane idea is rather silly, don't you think?

I acknowledge a manifold would likely be better. I'm just chewing on how best that can be integrated. I'm also, transparently, planning to test independent twins in a safe environment with a buddy nearby. If nothing else, I fail to see the danger of it, and it will be a good learning experience. Not like it'll cost me anything but time, after all.

Dude,
You are overthinking this.
One regular tank on the back and sling a second one as a stage. 1st stage with a single 2nd stage tucked in a bungee.
Easy to set up with a tank strap and a couple of bolt snaps, double enders, swivels or whatever.
Two tanks, double the time.

 

[eightytwenty]

If you're going to dive doubles, buy an isolation manifold and opposing valves, but I wouldn't dive twin 72s wet if you paid me. Been there, done that. Don't bother.

 

[happy-diver]

Don't bother.

Considering twin 72s and wetsuits was the only choice folks had for a number of years
and over those years, they learnt to dive them, according to past diving fashion, styles

Do you think you could have spent some more time with them

 

[Eric Sedletzky]

If you're going to dive doubles, buy an isolation manifold and opposing valves, but I wouldn't dive twin 72s wet if you paid me. Been there, done that. Don't bother.

I have a set of twin 72's and plan whole heartedly to dive them in a wetsuit.
What do you think is the problem?
72's go neutral when down to reserve pressure.
Two 72's that are on reserve pressure = both neutral, add whatever the manifold adds, what a couple lbs at most? Take that off your weightbelt.
The whole unit, you, yourself, at the end of the dive in a wetsuit on reserve pressure in your 72 twinset at your 15' stop with no air in your wing gracefully breathing and safety stopping away until you get the green light.
Please tell me the difference between this and a single 133 or 149 ? Besides one tank vs two?
Why is wet steel ok with a big single but not small twins?
Or is steel completely taboo in a wetsuit period?
Ok then, if I'm using an aluminum 80 diving in a wetsuit but I have to add weight to achieve my perfect buoyancy at my magical "no gas in the bc" 15' stop, please tell me the difference.

 

[eightytwenty]

I have a set of twin 72's and plan whole heartedly to dive them in a wetsuit.
What do you think is the problem?
72's go neutral when down to reserve pressure.
Two 72's that are on reserve pressure = both neutral, add whatever the manifold adds, what a couple lbs at most? Take that off your weightbelt.
The whole unit, you, yourself, at the end of the dive in a wetsuit on reserve pressure in your 72 twinset at your 15' stop with no air in your wing gracefully breathing and safety stopping away until you get the green light.
Please tell me the difference between this and a single 133 or 149 ? Besides one tank vs two?
Why is wet steel ok with a big single but not small twins?
Or is steel completely taboo in a wetsuit period?
Ok then, if I'm using an aluminum 80 diving in a wetsuit but I have to add weight to achieve my perfect buoyancy at my magical "no gas in the bc" 15' stop, please tell me the difference.

Your response shows a lack of understanding when it comes to suit compression and the balanced rig. You can talk about reserve pressures and your 15-foot stop until the cows come home, but you're missing a piece of the puzzle. I encourage you to do a little more reading, although I don't think it'll change your position.

 

[Eric Sedletzky]

Your response shows a lack of understanding when it comes to suit compression and the balanced rig. You can talk about reserve pressures and your 15-foot stop until the cows come home, but you're missing a piece of the puzzle. I encourage you to do a little more reading, although I don't think it'll change your position.

Yeah, I understand more than you think.
You know, I will probably end up diving those double 72's with no BC in a 7 mm wetsuit. And I will be using a single second stage and an SPG only.
You probably wouldn't dive them without a wing and a drysuit. In fact you probably wouldn't dive them at all because they have a single center post manifold with a J valve and not two posts with an isolator. And plus its yoke not DIN.

How is it that I dive a single 120 now with no BC, but somehow I'm going to straight to hell if I put on 140 cf air split between two tanks that end up lighter together than the 120?
I'm diving your definition of a "balanced rig" now with a big single. Although "balanced rig" to me means something entirely different from what you think it means. To me I'm just properly weighted for the type of diving I do.
So, how is the twinset different? 10 more cf of air?
Or maybe not if I get a short fill.

I would like a genuine answer, not "you need to do more reading" and "you have a lack of understanding". I've been doing this a while and probably understand more about weighting and minimum weighting than most people these days.

Did you figure it out on your own or did someone feed this to you?

 

[old frogman]

I had one. Never used it because I saw how effing stupid of a setup it was.

How do you know it's effing stupid if you never used it?