232 bar vs 300bar

[Subcooled]

Well I am going to start sidemount diving

Welcome to the sidemount community!

and I am looking at squba tanks I am moving to sidemount because I am 15 years old and not that strong to carry 2 12 liters on my back so I coche sidemount.

You want two 7 liter 232 bar steel tanks for cold water drysuit diving.
That is a lovely and light configuration for sidemount diving in drysuit.
Please add 7 to 9 kg of lead depending on situation (BMI and salinity).

if I shuld go with 7 liter 300bars or 10 liter 300bar

No. It is probably a bad idea. Those cylinders are heavy in water.
Instead, you want some weight on you belt.

Get 7 liters 232 bar steels (1600L of gas x2) . They are lovely. Add the recommended amount of lead; probably 7-8 kg on your belt/harness.

Some people do prefer the physically smaller 5 liters and 300 bars.
Due to limited compressibility of air though, these are only 5x270 liters (1350L of gas x2).

It is apparent that the 7L cylinders have more gas, but the 5L cylinders are smaller in size.

You can always add a 7L 200 bar (not 232) cylinder. That does not weigh a thing in the water.
An aluminum AL80 would be another option for extra gas.
But do start with two SM cylinders alone.

My worry is trim

Keep your back bent.

7 liter 232 bar is not that much

It is good for many things. It is not good for extended 100ft deep dives, though. You will want 2x12/232 for those.
Add a 7/200 or an aluminum 80 cuft tank to your 2x7/232 set when needed.
It is said above, that some people dive with 2x7/300. I do not have experience in that.

So is it a good ider with 300bar to have as muche as possebel. (we have a 300bar pump at my culb no problem there) so all I need to know is do 300bar wheig more and how much more do they weigh. And are they balanced or do one part flot and one doesn't.

Please do remember that 300 actually means 270, because pressure increases faster than amount of air.

I really hope u can read this since I am dislexcic and English is not my first language.

OK!

 

[gerj]

Please do remember that 300 actually means 270, because pressure increases faster than amount of air.

Can you explain what you mean by this? Pressure is, by definition, the amount of gas in a given volume (at constant temperature).

 

[inquis]

Pressure is, by definition, the amount of gas in a given volume (at constant temperature).

That's true for an ideal gas where molecules take up zero volume and do not collide or influence each other. In the real world, the higher the pressure, the more deviation from the ideal calculation. Google "compressibility" or "z factor". One good summary is here:

Calculating SCUBA Cylinder Capacity | Dive Gear Express®

Or why does my Aluminum 80 SCUBA tank only hold 77 cubic feet of air? ©2018-2020 by Mark Derrick, Gas Blending Instructor at Dive Gear Express ...

www.divegearexpress.com

 

[gerj]

I see, at 300bar Z=1.1 for air, giving you 10900mol/l, which would be 269bar for an ideal gas, which is what SAC calculations are based on. Thanks.