Planning and Training for Cave Course

Hello,

Speaking to my cave instructor for my course in May, he suggested I train rigorously on doubles through to the course. I dive doubles all the time but as I asked more questions the following became clear and this is where I need advice.

I dive on double 12 litre aluminium with 2x 6 litre stage cylinders.

He mentioned that we would be diving 90 cuft to 104 cuft (around that sort of capacity) steels. Am I right in assuming these are equivalent to 15 litre steels?

I tried to find a website for converion but nothing would work for these conversions.

Could anyone advise what an empty steel 15 litre (100 cuft) would weigh empty so I can weight my cylinders accordingly for buoyancy perfection prior to the course?

It has been a while since I dived steels, about 20 months and I don't have the information requested logged properly (only full).

Any help would be very welcome.

kinetic

Air weight 0.0861 pounds per cubic foot. You could figure that double 95s contain about 260 cubic feet with a cave fill (22.386 pounds), but then you have to figure in the weight of the manifold, bands and bolts, ...

I believe 15litre tanks are essentially 104's, if memory serves.

You won't need a weightbelt, that's for sure :)

A simple table to help:

tank----------- internal volume in liters
S80 (Alum)--- 11.23 L
OMS LP85----- 13 L
OMS LP98----- 15 L
OMS LP108---- 17 L
PST HP 100--- 12.73 L
PST HP 120--- 15.17 L

The problem with conversions is that the diving industry in the US name their tanks according to the total volume at the rated pressure (so, 80 cu.ft at 3000 psi) and in other parts of the world they name their tanks according to the internal volume (11.23 L at 1 atm). So, to convert you should either take the internal volume in liters to the final volume (x rated pressure) or you take the final volume in cu.ft to the internal volume (div. by the rated pressure).

Hope this helps. Safe diving,

Jose Ventura.

forgot about buoyancy:

tank----------- buoyancy in Lbs, salt water
full------empty
S80 (Alum)--- (-3.6) (+2.3)
OMS LP85----- (-6.7) (0.0)
OMS LP98----- (-7.73) (0.0)
OMS LP108---- (-7.9) (-1.1)
PST HP 100--- (-8.8) (-1.3)
PST HP 120--- (-10.3) (-1.3)

sorry,don't have the numbers for fresh water.
take care.

Jose ventura.

Found this in the resources section, lots of info on tank specs:

http://diverlink.com/gear/tankspecifications.htm

Thank you...that's a big help, especially the buoyancy info on the OMS steels.

I used the link to Luxfer but was unable to find the buoyancy details for an empty 12 l aluminium tank.....that's the last bit of info I need but I'll contact my local shop to see if they can help.

Many thanks.

kinetic