are double 80's dangerous?

[Gary D.]

According to some if you dive them you’re gonna die.

We used to dive doubles the majority of the time and they ranged from twin fire extinguishers, 30’s, 50’s 72’s, 80’s, 90’s and in some cases triples on the back. Guess what? Those of us that did that are still here.

What matters is what you can handle safely. You still need to dive within the limits of the gas you have, be it 20cf or 2000cf. The amount of tanks on your back don’t matter, the volume of gas and your ability does.

Gary D.

 

[Icarusflies]

With one AL 80 and 6-3 mm wet suit I use 6 lb of weight so taking a bigger tank than my HP 100 will mean that I am way overweighted, mostly in summer when diving .5 mm wetsuit, this is not safe. Double AL 80 give me the possibility to have a good trim and be able to swim up in case of problems. As far as the extra weight to carry I can go for V weights and some ditchable for security.....that is what my shaholin kung ** master told me ...

 

[TeddyDiver]

With one AL 80 and 6-3 mm wet suit I use 6 lb of weight so taking a bigger tank than my HP 100 will mean that I am way overweighted, mostly in summer when diving .5 mm wetsuit, this is not safe. Double AL 80 give me the possibility to have a good trim and be able to swim up in case of problems. As far as the extra weight to carry I can go for V weights and some ditchable for security.....that is what my shaholin kung ** master told me ...

Doubles can be great but you have the wrong reason. Please check http://www.scuba.com/shop/product.asp_category_131 The boyancy characteristic of the tanks discussed here:
XS SCUBA HIGH PRESSURE STEEL 100 TANK
Buoyancy Full = -10lbs
Buoyancy Empty = -2.5lbs
XS SCUBA HIGH PRESSURE STEEL 130CF TANK
Buoyancy Full = -11.7lbs
Buoyancy Empty = -2lbs
SHERWOOD ALUMINUM TANK 80CF
Buoyancy Full = -1.9lbs
Buoyancy Empty = 4lbs

So there actually no difference btw hp 100 and hp 130 just bigger swing due more air.

 

[TeddyDiver]

With one AL 80 and 6-3 mm wet suit I use 6 lb of weight

And with Double80 you need 10lbs of lead, with HP130 none, and you are equally boyant with both setups.

 

[ekewaka]

Some would say that the extra gas will cause you to exceed your no deco time, but I disagree. Just because have more gas, doesn't mean you have to say down until it is gone. If you are the type of diver who doesn't watch time, depth, gas supply, then there is a greater risk of being out of gas at depth with a deco obligation, but those divers will be eliminated by natural selection before long anyway. Plan your dive, watch your gas, depth, and time, and the extra gas can't hurt you.

If I am not mistaken, GUE advocates dive planing, even for inexperienced recreational divers, so the instructor must have been talking about something else. Maybe buoyancy or valve drills or something like that.

 

[GreenDiverDown]

And with Double80 you need 10lbs of lead, with HP130 none, and you are equally boyant with both setups.

I don't think you understand double Al80's.

 

[TeddyDiver]

I don't think you understand double Al80's.

Educate me. Actually if you noticed I was commenting OP's last reply, based on the facts he stated, not the original question

 

[GreenDiverDown]

Well... actually... one's weight requirement DECREASES when Al80s are doubled up.

 

[TeddyDiver]

Well... actually... one's weight requirement DECREASES when Al80s are doubled up.

How that might be possible.
SHERWOOD ALUMINUM TANK 80CF
Buoyancy Full = -1.9lbs Times 2 makes -3,8lbs
Buoyancy Empty = 4lbs Times 2 makes 8lbs positive bouyancy (weight req increases)
In this stage the OP is not yet on 1/3's. With doubles he surfaces at 250psi so the tanks are allmost empty.

 

[GreenDiverDown]

Ah... this is what fools most people.

The bands and manifold plus two regs are enough to offset the positive bouyancy of the cylinders. In fact... in fresh water, for example, a set of [nearly empty] banded AL80's with regs attached (but backplate and wing removed) is about 2-4 pounds negative.

A diver who needs 6 pounds for a single Al 80 very likely will need only 2-4 pounds if he twins up.

Many of us don't use any weight with Al80 doubles.

edit: [nearly empty] inserted