Thunderbird aln80 (neutral buoyancy)?

[napaheck]

Thunderbird aln80 (neutral buoyancy)?

Has anyone used the new Thunderbird aln80 neutral buoyancy cylinders from xs scuba? Seems like a good way to go. Tanks are a little heavier than normal aluminum 80s but at about 4lb negatieve full and only .7 positive when empty that is a big improvement over 6-7lb positive when empty for the normal aluminum 80s.

given I am planing on storing these tanks on the rail of my boat I would much rather go with aluminum.

thanks all,
Christian
Sv Sojourner
I apologize for the grammar and spelling errors. I am a product of 70’s public education.

 

[inquis]

only .7 positive when empty that is a big improvement over 6-7lb positive when empty for the normal aluminum 80s.

My "normal aluminum" Luxfer AL80 is +1.4 lb empty in fresh water with valve & 1st stage (measured directly). Add 0.8 lb for salt water.

I don't think the neutral AL80s are a good choice, especially for single-tank, wetsuit diving. (No idea if that's your scenario, just speaking generally.) The additional mass down low will exacerbate any foot-heavy tendency.

 

[sea_ledford]

I have some of the older neutral 80's, I would imagine they are exactly the same as the new ones. They are just a couple pounds heavier than a standard 80, so they are not positive when empty but are more negative when full.

The buoyancy shift from empty to full is exactly the same, just changes where the starting point is. This is true for all tanks. If a steel 80 held the exact same volume of air as an al80, they would both have the same buoyancy shift.

I very much dislike neutral 80's. Add a couple lbs to your bc, it's easier than moving that weight every time you move a tank.

 

[rjack321]

They are basically just heavier Al80s for 1) the same amount of gas and 2) you can move that weight around as its fixed on the tank bottom. Use a weight pouch on the cam bands to accomplish the same thing and also give you options to move it around to optimize trim

 

[napaheck]

maybe i should added this is California diving at the moment 48f bottom temp on my last dive in Monterey... so 7mm wet suits + extras like vests and socks so at the moment I am diving with 36lb in lead... with a al80 and 32lb of lead with a steal tank.

wile i have been loosing weight my self it is SLOW painful process at my age... and wile it is possible we may end up in dry suits at some point I am not counting on it as we are hoping to make it to warm waters next year.


thanks all,
Christian
Sv Sojourner
I apologize for the grammar and spelling errors. I am a product of 70’s public education.

 

[inquis]

Aluminum is a pretty inefficient source of negative buoyancy. I would much rather have a standard AL & a bit of lead or steel than a neutral AL80. You will be heavier climbing the boat ladder with the neutral tank.

 

[OMyMyOHellYes]

I don't recall ever hearing an experienced diver endorse the "neutral" bottles. Had an opportunity to pick one up but opted to pass based on that.

 

[gmerick]

There is a small difference in buoyancy swing of a neutral 80 (Thunderbird or Catalina), as compared to a "standard" AL80. The "neutral" tanks have a working pressure of 3300psi vs 3000psi. This shaves ~.5 lb off the buoyancy swing.
This is quite evident on sidemount, as the cylinder tail doesn't get quite so light when empty. Evidently much of the extra aluminum in the neutral design is in the base of the tank.

 

[inquis]

This shaves ~.5 lb off the buoyancy swing.

Air weighs what it weighs. The only way the buoyancy swing is less is if you don't consume as much.

 

[gmerick]

The only way the buoyancy swing is less is if you don't consume as much.

For the math and physics majors out there, yes, you are correct. And it holds absolutely true until I sling the tank and dive with it.

Also for the math and physics majors.
A 10.3 l tank at 228 bar holds 2348.4 l air when full, and 505 l @50 bar, 1843.4 l consumed.
A 11.1 l tank at 207 bar holds 2297.7 l air when full and 555 l @50 bar, 1742.2l consumed.
This would also indicate a 130 g larger buoyancy swing (weight of 101.2 l air) in the "neutral" tank. (again, until I sling it and dive).