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

[webbah]

My newbie brain is having trouble processing this one. I've requested a 100 cu ft. tank for a boat dive while on Maui to see what it's like since I'm a heavy breather and don't want to be the first one low on air. My question is - will I need an extra pound or so on my weight belt or just the opposite - a pound or two less?

Thanks!

 

[JeffG]

My newbie brain is having trouble processing this one. I've requested a 100 cu ft. tank for a boat dive while on Maui to see what it's like since I'm a heavy breather and don't want to be the first one low on air. My question is - will I need an extra pound or so on my weight belt or just the opposite - a pound or two less?

Thanks!

Depends on what kind of 100 cu ft tank and what you want to compare it against.

 

[webbah]

Sorry - it's an Al100 vs an Al80 which is what I'm used to diving.

 

[JeffG]

Sorry - it's an Al100 vs an Al80 which is what I'm used to diving.

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

 

[Skeeter1097]

Yes you well need to add a couple of lbs. Even thaw the tank well be heaver the bounce of the tank with 500 or less air is more. 8 lbs for a 100 verses 4 to 5 for a 80. A steel tank you would take up to 4 lb off.

 

[Skeeter1097]

I have both but only dive the steel any more.
I looked at the chart and I might be wrong. With some tanks.

 

[ianr33]

Well the link that JeffG posted states that an empty Luxfer 80 is +4.4 and an empty 100 is +3.1 i.e. when empty the 100 is 1.3 pounds less bouyant (heavier)

So you could take off 1 pound. or just leave it the same as 1 pound is neither here nor there

 

[vondo]

Yes you well need to add a couple of lbs. Even thaw the tank well be heaver the bounce of the tank with 500 or less air is more. 8 lbs for a 100 verses 4 to 5 for a 80. A steel tank you would take up to 4 lb off.

That is not necessarily true. You have to look at the empty weight of the two tanks in question and adjust by that amount. There are pairs of AL80/AL100 that have the same buoyancy empty. Look at the Luxfers in that chart. They differ by only about a pound.

 

[spectrum]

Assuming basic Luxfer models you can leave about 1-2 pounds of weight on the boat. See the Empty Buoyancy data.
http://www.huronscuba.com/equipment/scubaCylinderSpecification.html

Pete

 

[Wayward Son]

I dive both tanks, with the 100's my preference. if you weight yourself for a Luxfer 80, you will be slightly overweighted with a Luxfer 100. Not enough to be concerned about for a simple 2 tank trip. if you buy some & dive them regularly you'll want to drop a lb or 2 of lead.