Rig weight change when changing tank

[Dann-Oh]

Hey all,

My current rig setup is a 5mm wetsuit, SMS75 BCD and PST LP72 cylinders, with this kit I need 8lbs of lead. I am looking to change over to Faber LP50 (already have the tanks but haven't dove them yet). I'm not too sure what my weight change would be, would anyone be able to help me with the buoyance characteristics of theLP72 and LP50 tanks?

Thanks in advance.

 

[MT_Shadow]

Could weigh the tanks in the water with a hand scale full and empty and have a real life look at the characteristics. I saw a few videos about it on the sidemount youtube channel with the math on a whiteboard was interesting.

 

[inquis]

Best bet is to just measure them both empty in a hot tub, pool, or trash can full of water using a luggage scale. The difference is the adjustment to make.

However, I found the PST 72 (2250+ psi) specced at neutral empty and Faber LP50 at +1.25 lb empty.

I would guess you should add 2.5 lbs of lead if your weight is good with the 72s.

 

[Jacob BV]

You can work out their buoyancy without weighing it. You know the water capcity, and the weight of steel or aluminium is stamped on the outside so using the right denisty you can work out the litres of metal. Now you have the total displacement and the weight (remember to add the weight of the valve, you can try looking it up or just call it 1kg). This is all easy in metric can't comment how to do it with imperial. Here is a website with a calculater and a selection of known cylinders: UK Scuba - Cylinder Buoyancy Calculation

 

[Celt]

You can do all the sums but your just not going to be happy till you try them in the water, there's no substitute.

 

[Jacob BV]

You can do all the sums but your just not going to be happy till you try them in the water, there's no substitute.

yeah totally. But for what to try first this will give the OP the ballpark of what to try first.

 

[rx7diver]

Hey all,

My current rig setup is a 5mm wetsuit, SMS75 BCD and PST LP72 cylinders, with this kit I need 8lbs of lead. I am looking to change over to Faber LP50 (already have the tanks but haven't dove them yet). I'm not too sure what my weight change would be, would anyone be able to help me with the buoyance characteristics of theLP72 and LP50 tanks?

Thanks in advance.

Single LP50? Or double (manifolded) LP50's?

If double, then the weight of the manifold, SS doubles bands, bolts, and harness hardware, and the additional regulator is significant.

rx7diver

 

[Dann-Oh]

You can do all the sums but your just not going to be happy till you try them in the water, there's no substitute.

Yeah but would I need to haul all 36lbs of available lead with me to the pool or should I bring an additional 6lbs. That's really why I's asking.

Single LP50? Or double (manifolded) LP50's?

If double, then the weight of the manifold, SS doubles bands, bolts, and harness hardware, and the additional regulator is significant.

rx7diver

Since this is the sidemount forum it would be safe to assume I am asking about a single tank that I would be doubling for true sidemount. I wouldn't need to worry about a manifold and other gear for back mounted doubles.

 

[PR_SMITH]

Here's a handy chart showing empty and full characteristics of most scuba tanks:

SCUBA Cylinder Specifications – Huron Scuba, Snorkel & Adventure Travel Inc. PADI 5 star IDC in Ann Arbor, MI

huronscuba.com

 

[Celt]

Yeah but would I need to haul all 36lbs of available lead with me to the pool or should I bring an additional 6lbs. That's really why I's asking.

If i though I might need 6lbs I'd bring 12 but definitely not 36