Sidemount Cylinders

[h2ojoe]

Like you wrote in your article

"Let’s look at the next mistake often made by newer divers – bigger cylinders will mean more bottom time. This isn’t necessarily true. Often times, bigger cylinders simply mean more drag in the water, which in turn means more effort to move through the water. More effort equates to higher gas consumption."
If your tank is 8" dia what does it matter if it is 20" or 40" long?

I am not saying it has anything to do with trim as long as the tank is level and not creating any extra drag from the sides of the tank not being in the slip stream. Thats why submarines, rockets, and jets are long and skinny.

 

[JamesK]

So which works better with Aluminum 80s - putting a weight on the tank or clipping off to a d-ring?

I prefer clipping them off to a dring. Some prefer weights. It all comes down to what you like to do.

 

[Dive-aholic]

Like you wrote in your article

"Let’s look at the next mistake often made by newer divers – bigger cylinders will mean more bottom time. This isn’t necessarily true. Often times, bigger cylinders simply mean more drag in the water, which in turn means more effort to move through the water. More effort equates to higher gas consumption."
If your tank is 8" dia what does it matter if it is 20" or 40" long?

I am not saying it has anything to do with trim as long as the tank is level and not creating any extra drag from the sides of the tank not being in the slip stream. Thats why submarines, rockets, and jets are long and skinny.

There's a lot more to it than just cylinder diameter. Cylinder diameter actually has very little to do with it. When cylinders are sidemounted properly most of the cylinder mass is "hidden" behind the shoulders. And extra inch in diameter isn't going to make much of a difference. The difference comes from the additional air that will be needed in your wing to compensate for the additional weight. That makes your wing bigger, increasing your mass in the water, and creating more drag. So it really has very little to do with the size of the cylinder and a lot more to do with the size of the wing due to the heavier cylinder.

---------- Post added April 30th, 2012 at 09:40 PM ----------

So which works better with Aluminum 80s - putting a weight on the tank or clipping off to a d-ring?

It's a personal preference. I prefer weights but that's because I usually dive steel cylinders and I like the aluminum cylinders to feel like the steels in terms of weight.

 

[beanojones]

It's a personal preference. I prefer weights but that's because I usually dive steel cylinders and I like the aluminum cylinders to feel like the steels in terms of weight.

SInce you travel alot, what do you get mostly: S80's or Compact 80's?

How do you attach the weight?

 

[scuba127]

My sidemount instructor (who turned out to be a great instructor) was wary of putting weights on aluminum sidemount tanks. He said "what if you have to give up the tank?" My initial thought was good point. After, the class, however, when I started thinking about it some more, I wondered why would I give up the tank when I have a long hose I can donate? Any opinions on this?

 

[beanojones]

Standard 80's are buoyant enough that they themselves need weight. Dontaing tanks in general just create balance issues, that for instance someone added tanks to thie own gear does not.

Separately, donating a tank is something that I would never do even ignoring the ballast issues. Of someone is OOA, they are simply not thinking about anything.

(When I here a lot tech divers talking about OOA, it makes me think they have never been faced with an actual OOA diver, they have just practiced things a 'OOA' drills a bunch. OOA divers might be able to see 3-4 inches past their nose to get a reg., but they certainly do not have the awareness to deal with major gear changes.

OOA divers have managed to run out of air which means they have managed to forget how to use their own gear. Giving them more gear is just putting them in danger.)

 

[Dive-aholic]

SInce you travel alot, what do you get mostly: S80's or Compact 80's?

How do you attach the weight?

S80s. I weave the cam band through the weights and position them opposite the clip.

My sidemount instructor (who turned out to be a great instructor) was wary of putting weights on aluminum sidemount tanks. He said "what if you have to give up the tank?" My initial thought was good point. After, the class, however, when I started thinking about it some more, I wondered why would I give up the tank when I have a long hose I can donate? Any opinions on this?

There is no reason to ever have to donate a tank. I don't know anyone who does this in reality and anyone who suggest this hasn't really thought over the full consequences of doing this.