Tips for first time doubles diver

[reubencahn]

Okay, this weekend, I'll be diving doubles for the first time. I plan some pool time Saturday and a couple of shallow dives Sunday. So what are the things you wish you'd been told before your first dive with doubles, those little hints that would have made things so much easier? FWIW: I'll be diving wet with AL80s an SS BP. My singles setup has been an AL plate, light STA and an E7-100, so I figure the weighting should be roughly the same.

 

[JimC]

You'll need 10-14 more LBS with the AL80's, the plate change will make up for 4 of that.

Start in water you can stand up in.

 

[OneBrightGator]

Well, with steel doubles, they control you, instead of vice versa
What I mean is, there's a lot more mass back there then before, so be aware of how you move, generally if I tip myself to one side, between the tanks and the air shifting I'm gonna roll over, wether I like it or not.

Take it slow, stay shallow.

 

[MXGratefulDiver]

I think what Uncle Pug did with me on my first doubles "dive" was helpful.

The plan was just to drop down to about 20 fsw and practice hovering ... to get a feel for the buoyancy differences. We weren't going anywhere, just hover. He asked me to show up with not much gas in the doubles. I took that to mean 1,000 psi ... he meant it to mean about half that.

So just before we dropped down, he asked for my primary second. We dropped down and I hovered while he hoovered ... till we got the cylinders down to about 250 or so. Then we could do a reasonable weight check.

Weighting is an issue ... trim is an even bigger one. Can't speak for what AL doubles do ... but my E8-119's (mounted on a 9-lb backplate) made me feel like a lawn dart. It took every bit of control I could muster to keep from doing a 16-minute headstand. It was even more interesting while doing an air-share the entire time.

... Bob (Grateful Diver)

 

[Soggy]

If you think you are in trim on your first few doubles dives, you're probably at like 30-45 degrees. Have someone with you to help you judge your in-water position as everything will feel strange at first.

 

[FreeFloat]

Well, with steel doubles, they control you, instead of vice versa
What I mean is, there's a lot more mass back there then before, so be aware of how you move, generally if I tip myself to one side, between the tanks and the air shifting I'm gonna roll over, wether I like it or not.

Might I comment that I think that refers to "heavy" steel doubles?

I dive steel 72s - just started diving them regularly - and have no issues whatsoever with being flipped.

However I'll agree with you about larger tanks - I dived (I think they were) PST 120s once, and I can confirm, once the air in the wing goes Slosh, you are going over...........

 

[Henryville]

You'll need 10-14 more LBS with the AL80's, the plate change will make up for 4 of that.

Start in water you can stand up in.

The key will be for you to get comfortable with weighting when the tanks are pretty low. Those double 80s, as JimC says, will get pretty floaty when they are near empty. So during your pool work try to get them pretty low and check it out. Maybe don't get them filled all the way for that session or you will have to breathe or bleed off a lot of gas to get down to the 500 psi or less range. Doing this, get yourself so that you are neutral with an empty BC and nearly empty tanks at 10 feet or more of depth.

Also, make sure that the upper band is pretty high on the tanks. I think most people put it right at the edge of the curve.

I got lucky and never had a real adjustment problem with balance and trim, but from what I have read some other divers have found this to be challenging. As the Gator says, just take it slow. I would want to be diving in some pretty benign conditions for my first few non-pool dives, if I were you.

Have fun and good luck. Post what your experience was like after the weekend.

 

[reubencahn]

You'll need 10-14 more LBS with the AL80's, the plate change will make up for 4 of that.

Start in water you can stand up in.

How are you arriving at that number? The tanks themselves are 4.4 lbs positive when empty, so 8.8 lbs for 2, while the E7-100 is 1 lb negative. So that's a 10 lbs. I figure the bands, manifold and extra first stage have got to be at least 5lbs. What am I missing?

 

[Scuba_Steve]

Don't fall down, as it hurts way more than on singles.

Know how your valves operate (and that you can reach them) so when the day comes when you've managed to pull a 30 min, 100ft dive off, and your pressure guage hasn't moved, you'll know why No you didn't grow gills, no your SAC ain't that good.

Hehehhe

Try it in a pool, get the trim and weighting down, proceed as normal. Have fun.

Steve

 

[FreeFloat]

My little steel doubles trim out all right.... I was surprised to find that with my neoprene drysuit and 250 psi in the tanks, I need no weight to hover at 15'. At 10' I have to breathe a bit different, but it's certainly controllable.

Mind you I have a ss backplate too. If I completely stop finning I'm ever so slightly head heavy and will eventually turn fins-up. I'm toying with the idea of putting an AL backplate on instead and moving the 'extra' 4lb to my weight belt as a trim..... ideas anyone?