why not doubles on AL?

[jonnythan]

FIXXERVI6 once bubbled...
well, I think I've picked out my BC, fine for singles, and doubles.

Now my question is If I were to do double 80's, do I need double everything!?

like, two pressure gauges, two first stages, two primary second stages!??

Reason I ask is because the manifold has the isolator valve, if you crank it, you have to switch to the other side, witch means, two of everything, including pressure gauges, or am I off base?

Before anyone answers this, let me say that assembling and diving some doubles based on some info from SB and a couple of pictures is a very bad idea. It looks like it would be very easy... get a couple of tanks, some bands, a manifold... put them together, toss on a couple of first stages, bolt to a bp and go diving. Get some instruction of some sort from someone who knows what they're doing.

That being said, you'd have two first stages but one of everything else. Off of one first stage you'd run your primary regulator and BC inflator hose, then off the other first stage you'd have your SPG, drysuit inflator hose (if you have one), and backup regulator. I think this is how it's normally done

 

[ElectricZombie]

You might want to do some more research before buying anything, it sounds like you're not familiar with how doubles work.

With doubles you will need two 1st stages, two 2nd stages, one pressure gague and one inflator hose.

What BCs did you choose?

 

[FIXXERVI6]

I'm not familiar with doubles, thats why I am asking

The zeagle ranger, the standard bladder is not overkill for my single neutral 80, but also a good BC to use on double neutral 80's when I get to that point.

Tried on on, liked the fit/features/price, and even if I never make it to doubles, still a good BC.

I plan on taking advanced nitrox and decompression diving classes before I make investments into manifolds and such, especially seeing how I dont' think there is a lot of good 2 tank deco dives in TX

 

[Don Burke]

Aluminum 80s are really good for starting out with doubles since they work well with a wetsuit and you can dive them dry if need be. If you change your mind, you can sell them or break them down. AL 80s can always be used for something in diving and you can sell the bands and manifold.

I tried my AL 80s with a drysuit and immediately went looking for some small steel tanks. The amount of surface weight required with aluminum and a drysuit was more than I was willing to deal with. Your mileage may vary.

Basically, there are two problems you need to be able to deal with:

1. You jump in the water, snag something on the way in, and your BC inflator hose is ripped to shreds. How much weight do you need to ditch to stay on the surface?

2. You get problem 1 fixed and try the dive again. At the bottom, you immediately snag something and your BC inflator hose is ripped to shreds. How much weight do you need to ditch to get to the surface?

With my wetsuit and full 80s, the answer to #1 is about eight pounds due to the weight of the gas in the tanks minus a little extra bouyancy from the wetsuit at the surface.

The answer to #2 (assuming 100 feet) is about twenty pounds due to the weight of the gas in the tanks plus some missing bouyancy due to wetsuit compression at depth.

With AL80s and a steel backplate, I wear twenty-four pounds on a belt with my wetsuit. That gives me enough ditchable weight.

With my steel 72s and a steel backplate, I would only need about twelve pounds on a belt with the wetsuit. The smaller gas capacity makes the answer to #1 about seven pounds and the answer to #2 twenty-three pounds. If I switch to an aluminum backplate (or jacket BC for that matter), I'll end up with seventeen pounds on the belt, still not enough for my taste. I'd have to swim up at least three pounds, more if I take weight off the belt to allow for a dive light or tools.

Perhaps there are steel tank combinations that makes sense with a wetsuit. I haven't seen one.

 

[FIXXERVI6]

as far as ditchable weight, that wouldn't be very much with double neutrals.

No wet suit I wore 4lbs on my neutral 80, and in testing I can sink with no weight, and 900 psi in the tank, so I may tweak this back to 2lbs on my next dive.

doubles, I would assume I would wear no weight, or 2 to 4lbs with a 3 mil on, because of the low weight would considering standard 80's be better to have more ditchable weight?

 

[c_a_otoole]

A good way to try out various tank set ups before commiting to either AL80s PST tanks ect is to set up your BC and then rent the tanks and go with indapendent (no manafold) doubles. It can be a pain in the ass switching every 5mins/500 PSI or whatever you decide, but it does give you a chance to feel what it is like to dive the various types of tanks. This is also a option for people that are renting tanks.
That being said after about two dives of doing this you will invest in the manafold and never look back. Just my two cents, because I have been diving indapendent doubles because I am only going to be here in Guam for another few weeks and I cant justify buying more tanks.

Chris

 

[Don Burke]

If you're wearing a wetsuit, standard AL doubles are the way to go. You're going to need that buoyancy on a BC failure. Steel tanks are actually lighter on the boat, but don't give enough ditchable weight. Neutral 80s are even heavier than standard 80s and give about the same ditchable weight as steel. The only use I'd have for a Neutral 80 would be singles diving and I have steel tanks that work much better for that.

My first time in the water with doubles was also my first time with harness/backplate/wing system. I just went ahead and took the plunge with the manifold and bands. It was quite a leap of faith, although I expected to at least end up with a set of tanks for digging on shallow wrecks. It turned out I like doubles better than singles and I bought a couple of sets of steel 72s for the drysuit.

I'm way the heck over here in Chesapeake, Virginia (near Norfolk) or I'd offer to loan you a set of doubles so you could try them out. Perhaps you can find someone nearby to loan you a set for a "fly before buy".

Watch your weight distribution (ditchable vs non-ditchable) and don't start thinking you have infinite backgas and you'll be fine.

 

[scubatexastony]

ElectricZombie once bubbled...


With doubles you will need two 1st stages, two 2nd stages, one pressure gague and one inflator hose.

Mine seem to work fine with one 1st.....go figure!

 

[FIXXERVI6]

how?

Do you not have an isolator valve?

 

[scubatexastony]

old scubapro manifold....2250/72s

tony