why not doubles on AL?

[FIXXERVI6]

I've never seen nor heard of doubles using aluminum, my guess is they would be too bouant?

what about neutraly bouant AL80's?

What is the cheapest (cheap, but safe) way to get onto doubles?

edit: just saw a post talking about double al80's, would you need less lift on the BC to handle something like that since al is bouant?

 

[JohnF]

Double al80's are popular with the cave divers in the Akumal area. I suppose because cavers plan to end their dives with a fair amount of gas left in the tanks, the buoyancy issue is moot.

JohnF

 

[DA Aquamaster]

Al tanks displace more water due to a thicker overall wall thickness than a steel tank and this combined with similar weights means the Al tanks are more bouyant than comparable steel tanks. There is however a Super 80 available that offers better bouyancy characteristics.

Double 80's can actually be a bit more stable to dive as the tanks are above your center of gravity and the AL tanks are a bit more bouyant and/or less negative than a steel tank. With a properly sized wing however it really is not an issue one way or the other.

Steel tanks can be excessively negative in some cases and it is not a bad idea to use the more neutrally bouyant AL tanks for stage tanks.

In the end it comes down to your indiviual diving and weight requirements. You need to have enough weight to stay down with a pair of nearly empty AL doubles and if the weight required to achieve that is not excessive, it really is not a problem.

 

[Diver Lori]

Yup...we used AL80's in Akumal. Usually a V-weight or two in between the tanks takes care of any buoyant issues. AL80's due to their buoyancy characteristics make them ideal for wetsuit diving.....no need for redundant floatation. Plus the dives are long, but many times very shallow.....and the AL80's fit perfectly.

 

[Ron Brandt]

Al 80's for wetsuit.

Steel 95's or 103's for drysuit.

Ron

 

[ElectricZombie]

I use double AL 80s since I dive a wetsuit. I'll pick up a set of 104s when I get a drysuit.

 

[Genesis]

steels are a good compromise.

More gas availability, and only SLIGHTLY negative (-1.5 or so) empty.

This means they're quite good with a wetsuit; just about the only rig you'd have trouble with is if you wanted to dive a bathing suit (no exposure protection at all.)

With my steel BP + STA + HP100 (or 120) I need 2lbs of lead on my belt. That's a very nice, low-impact weight belt! If I add a 3 mil hooded vest I add another 4lbs or so to the belt, and I'm cool in that configuration as well.

Diving dry I require 15lbs in my "usual" config (changes somewhat depending on the undergarmets, but that's pretty typical.)

The AL tank requires me to add 4-5lbs to the above weights (rather than diving the HP steel)

An LP tank would be impossibly heavy in a light (3 mil) wetsuit and only marginally "ok" with the hooded vest. It would, however, require less external weight in the drysuit config.

 

[DA Aquamaster]

A standard 2250 psi steel 72 is also a viable alternative to an AL 80 for doubles. They are only a couple pounds more negative and much more bouyant than most other larger capacity LP steel tanks and more bouyant than the faber streel 71.4.

A run of the mill steel 72 has all the advantagves of steel, plus they are normally very affordable on the used market.

 

[Padipro]

Aluminum doubles are popular here in South Florida for the same reasons mentiond earlier. With the warm water here only a light wetsuit is required to stay warm. The added weight of steel tanks is not needed. I use double Catlina AL 90's. Even with a 5mil semi dry in the winter and an AL backplate I'm so negitive that I have to add air to slow my decent. If I used steels I don't think I could get off the bottom.

Scott

 

[FIXXERVI6]

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?