[AndyA]

With my 15L (17.4 kg) cylinder, SS backplate, drysuit etc I needed 3kg in fresh water to hold a stop.
Im now switching to twin 300 bar 7s (11.4 kg each) so wondering if there is any formula to work out how much lead I am going to need.

I am planning to do a proper weight check at the end of the days diving when the cylinders are low but just looking for a rough idea what to jump in with.

 

[Soup]

Just a guess....

The table here Diving cylinder - Wikipedia, the free encyclopedia gives the buoyancy of a range of cylinders.

It looks to me that the difference in buoyancy between the two cylinder configurations would require a bit less weight with the twins but only about 0.6kg less. However, once you consider the added weight of the manifold and the twinning bands and two sets of regs you might consider getting rid of 1-2kg.

 

[nigelH]

With my 15L (17.4 kg) cylinder, SS backplate, drysuit etc I needed 3kg in fresh water to hold a stop.
Im now switching to twin 300 bar 7s (11.4 kg each) so wondering if there is any formula to work out how much lead I am going to need.

You're loosing a litre of displacement and gaining 6Kgs of steel.
I'd dump the whole belt and consider some extra thermals.

 

[mad major]

Try this site for calculations
UK Scuba - Cylinder Buoyancy Calculation

 

[AndyA]

You're loosing a litre of displacement and gaining 6Kgs of steel.
I'd dump the whole belt and consider some extra thermals.

Seems the ideal time to ditch the belt and try my new Sub Xero suit, which I am told will require an extra 3kgs, this will probably work out quite well.

 

[eey_ore_9]

This is the best information you will get bar none..... have a read

Balanced equipment - what does it mean? at Wreck and Cave