100 cu ft. tank - need more or less weight?

[ClayJar]

I dive Luxfer AL80s and AL100s. The former were cheap, and the latter are borrowed.

I've found it best for me to just ignore the 1.3 pound empty buoyancy difference. Why? Well, I'm trimmed left/right just how I like myself to be, which leaves me with one three-pound weight on my right hip. If I were to take half that away, I'd either end up listing to the left, or I'd have to change my gear placement. Staying in trim is worth managing 0.02 cubic feet of additional air.

 

[diverdown247]

If they are both Luxfers, then you won't need to change your weighting.

Here's a page that will tell you the difference between tanks. Just look at the buoyancy empty column

http://www.techdivinglimited.com/pub/tanks.html

Well, just being a luxfer doesn't mean that you will or won't need extra weight. You absolutely must pay attention to the classification on the tanks. Luxfer has an AL80N and an AL80S. The N class is slightly negative when empty where the S class is near neutral when empty.

This is a factor that you'll need to look at when going to a 100 as well if using aluminum and not steel.

 

[plot]

There's always a thousand variables to look at, but I think this guy is looking for a general answer.

Drop a lb, keep a lb on, I doubt it'll make a huge difference for the day. If it's a 2 dive trip, keep it on the first dive then at the end when your tank is around 500lbs or less, depending on whatever it's at when you get back, try losing a pound or two and see what happens then you'll definatly know how much lead you need on the next dive.

 

[webbah]

There's always a thousand variables to look at, but I think this guy is looking for a general answer.

Drop a lb, keep a lb on, I doubt it'll make a huge difference for the day. If it's a 2 dive trip, keep it on the first dive then at the end when your tank is around 500lbs or less, depending on whatever it's at when you get back, try losing a pound or two and see what happens then you'll definatly know how much lead you need on the next dive.

lol - yes - the general answer is what I was looking for - hence the reason I posted in the Newbie forum. But thanks everyone for their replies - I enjoy learning more of the technical side of things!

 

[kidspot]

fwiw - when I've been out with B&B here on Maui they don't change the weighting when going between 80's & 100's as they are close enough that it makes little difference. They oft' times will warn folks that appear to be overweighted as that doesn't help you enjoy the dive.

Aloha, Tim

P.S. who ya' diving with?

 

[ams511]

Well, just being a luxfer doesn't mean that you will or won't need extra weight. You absolutely must pay attention to the classification on the tanks. Luxfer has an AL80N and an AL80S. The N class is slightly negative when empty where the S class is near neutral when empty.

This is a factor that you'll need to look at when going to a 100 as well if using aluminum and not steel.

Most dive boats I have been on use the plain jane 80's. However you are right in pointing out that there are at least 3 models of Luxfer Al-80's out there and they do not seem to vary much in size and shape, so you need to look at the writing on the tanks. If you are diving an 80 N or S, you may need to add weight if switching to an AL 100.