Question about twin tanks

[alan_lee]

The local GUE shop ran a twin tank workshop yesterday at a local diving pool and I signed up for it cos I intend to dive the comping season as much as I can in twins so that I can get used to it, in preparation for Tech.

After the explanation on land about the whole set-up and drills, we rigged up and took the plunge. The first thing I realised was that staying in a balanced position was not as easy as it was in a single wing. I was diving with the Evolve wing, and I found that I'd be thrown off balance if my body was out of trim. Initially, I was in an over-trimmed position, and I soon found out it was because I'd dropped my head, and therefore the air had rushed to the bottom (or back, depending on your perspective) of the wing. Soon found out that as long as the back of my head was touching the manifold, I'd be in trim. Another problem I had was trying to stay stationary in the pool when performing the valve drills (I've always had problems staying stationary in the pool).

I'm definitely looking to diving in open water with twins soon, but I'm wondering how long it took you guys to adapt to diving with twin tanks, and would definitely appreciate any advice you guys could offer. I'm a real perfectionist and the fact that I'm a slow learner doesn't make an ideal learning situation for me.

 

[Cave Diver]

My first dive in doubles was a nightmare. Did it in a pool, kept shifting forward and backward, rolling side to side. I was using a transpac at the time.

Went to backplate, got the harness adjusted and snug and by the third dive everything was pretty stable.

 

[strazz]

Mine felt pretty natural on my first dive. I had been diving with a single X8-130 for a while, so I just pulled off the STA and bolted on the doubles. The harness was already adjusted perfectly and I was used to it. I felt like I was swimming on rails because the stability is so much better than with a single steel.

 

[PerroneFord]

My first doubles dives were in a pool. And great laughter was had by all. Took about a week of diving them to get comfy. I don't dive singles any more. I find doubles a LOT more stable.

 

[TSandM]

Sometimes it depends on the tanks. I dove a set of LP72s for several months, but I could never get them to balance out correctly. The first dive in my 85s, I was in love.

Getting the harness adjusted correctly really is critical. Unlike with a single tank, where you can afford to be a little sloppy, in doubles you can't afford a loose harness or the tanks are always trying to go somewhere you aren't. In addition, as you found out already, the whole thing about a really disciplined body position for trim comes out of balancing doubles. (You'll find that, if you let your head drop, you'll come up out of trim for two reasons -- One is that, as with the center of gravity drills, you're dropping your weight forward so you have to shorten that forward lever arm to balance, and the other is that, with your head down, you can't see in front of you.)

It's a little more difficult to manage the air bubble in the wing (and dry suit, for us) with doubles, because you begin the dive so much more negative, and therefore have to have a bigger bubble to compensate. It's very important to have your weighting correct, because you really don't want to haul around any more weight than you have to with doubles.

Staying put while doing drills is related to stability. When you can hover perfectly still (without finning) AND reach up for those valves without changing trim, you don't have to fin. If you're not in balance in the tanks, you have to fin constantly to keep from pitching head down, so you can't stay still. And if you're going out of trim to reach the valves, you again have to fin to keep your stability, and you can't stay still.

I actually dove doubles for about a dozen dives or so before I ever attempted a valve drill, because I knew the key was to get basic stability in the rig before taxing myself with any task loading. But then, "perfectionist and slow learner" describes me to a T

 

[Scared Silly]

My first few times using doubles was PDF (pretty damn funny). I got worked as did my wife. As she said we normally have pretty good buoyancy skills but our first few times in doubles was like starting all over again. We are trying to get a descent set up for my wife. It is taking some time. But for me 85 are the ticket right now.

 

[ovarygirl]

I started diving doubles pretty early on and it took a number of dives before I felt comfortable in the water. As a newer diver (~150 dives over 2 years), the whole process has been gradual so you're not alone. Learning to be a better diver takes awhile and you can always throw in more stuff (i.e., task-loading) to make things more difficult again. Changing your gear such as add/switching drysuits, underwear, adding a larger/smaller cannister light etc will put you back a bit in terms of progress but it does become easier as you gain more experience.

 

[Solitude Diver]

You’ll just need to practice and get used to them. Try not to be too hard on yourself or expect too much right off the get go. It takes time to loosen up, and get your body used to them.

I started off with twin HP 130’s which were very heavy and about 18 lbs more negative full than empty. It meant carrying a lot of extra weight to compensate for the loss. I chose to dive those tanks for ALL dives for about 50 dives before starting my tec and wreck diving programs in order to get used to them. It was pretty funny for my buddies to see me showing up for simple shore dives wearing double 130’s ......but it paid off as they became second nature in time.

During valve drills watch your breathing, and your body tensing up and changing positions. The amount of air in your lungs combined with the arms and legs bending in an effort to reach the valves changes trim and buoyancy. Sometimes people are so focused on the shutdowns they are not aware of the other issues going on. Practice in front of a wall or anchor line, etc. and do the drills while staring at one point and trying to keep it in front of you. Caution: When practicing, I wouldn’t recommend actually shutting the valves unless you have a buddy watching. I’ve forgotten to reopen one in my haste to set a world record (ok.... to get under a minute), and ended up with two closed valves at once. It can be a high anxiety moment.

Tip: during all of your dives while just cruising around (and even when just driving in your car, sitting at home, or whatever) practice reaching back and holding your arms where the valves are and stretching. As the muscles and joints get more limber, the effort to do the shutdowns is reduced, the body is more relaxed, and it becomes easier to remain stable when doing the drills. The added stretching time when not diving speeds up the training process. (At least for those of us who have a hard time just touching our toes)…. Ok…. knees.:54:

 

[TSandM]

It was pretty funny for my buddies to see me showing up for simple shore dives wearing double 130’s ......but it paid off as they became second nature in time.

Yeah, you get some funny looks heading into the Edmonds Underwater Park (max depth 35 feet) in doubles. But the instructor for my wreck workshop told me the best thing I could do to get ready for my cave class was dive the doubles exclusively, so that's what I did.

I HIGHLY second the recommendation for not actually doing valve shutdowns unless you have a spotter. EVERYONE I know who's been through this has at some time shut down all their gas. Once you're good and confident at shutdowns, that's not a big issue -- you just turn it back on. But in the beginning, when you're slow, or if it's difficult for you, you're WAY better off having somebody donate and give you time to get yourself sorted out. (And spotters, keep your eyes peeled for which reg the person is breathing, and which post they're shutting down!)

 

[ae3753]

The first thing I realised was that staying in a balanced position was not as easy as it was in a single wing. I was diving with the Evolve wing, and I found that I'd be thrown off balance if my body was out of trim. Initially, I was in an over-trimmed position, and I soon found out it was because I'd dropped my head, and therefore the air had rushed to the bottom (or back, depending on your perspective) of the wing.

Not great at diagnostics via the internet but it sounds like you're head heavy and you're overcompensating with "over-trimmed" body position. When the doubles are trimmed properly, it's much easier to stay in balance than a single tank.

If you're diving an SS plate, consider moving to an AL plate with a v-weight or trim weight on the lowest bolt. Also, consider moving the wing to it's highest position, and play with tank position as well.