Question Do you adjust weights when switching between 12L and 15L tank?

[darksider]

I discovered that many people adjust weights when switching between 12L steel and 15L. Even my instructor told me to subtract 2kg. I wonder why and if I’m missing something. I don’t do any adjustments because based on charts, at least for Faber steel tanks, the difference in buoyancy is just around 300 grams.

Adjustments would make more sense for aluminum tanks where 11.1L buoyancy @ 500psi is 1.5kg vs 0.4kg for 12.9L. In this case, subtracting 1kg would be justified, I guess.

 

[rjack321]

I don't really dive AL80s as singles ever

But also don't fiddle with my lead from 12L steel vs other sized steel singles. Partly because I'm in a drysuit and cold water and if I a have tiny bit more or less gas in my suit I dont really care. If I were in a wetsuit I'd probably add or subtract a kg

 

[MB NZ]

No

 

[Belzelbub]

For those, probably not.

My 100s are PST and my 120s are Faber. The difference is a bit more pronounced. 2 lbs / 1 kg less with the 100s than the 120s.

 

[MarkA]

It depends. As an example, I used to add 4kg when going from my 15l cylinder to 12l cylinder. That 15l Heiser was a heavy beast compared to the 12l Faber.

Compare the buoyancy characteristics. Each cylinder has its weight stamped on it. For example, if the 12l is 13.4kg and the 15l is 16.6.
12l cylinder. 13.4/7.9=1.7 12+1.7-13.4=+0.3kg
15l cylinder. 16.6/7.9=2.1 15+2.1-16.6=+0.5kg

In this example you can see the 15l is 0.2kg more buoyant. Practically nothing. Just slot your own cylinder weights in the maths to get the result.

 

[happy-diver]

That 15l Heiser was a heavy beast compared to the 12l Faber.

Mate that 15l Heiser is a heavy beast compared to a 15l Faber

When I tried to carry two tanks, you know that stooped shuffle that people do because no one should carry
two tanks, my Heiser arm would stretch and then I would end up walking in circles, and never get anywhere

so now it's one tank only on the shoulder at a time only, and some counterbalancing gear in the other hand

At 110 kilograms I weight like in basic class so the ocean doesn't throw me around and spit me out so much

Keeping in mind there are many different individual diving styles

 

[MarkA]

Mate that 15l Heiser is a heavy beast compared to a 15l Faber

When I tried to carry two tanks, you know that stooped shuffle that people do because no one should carry
two tanks, my Heiser arm would stretch and then I would end up walking in circles, and never get anywhere

so now it's one tank only on the shoulder at a time only, and some counterbalancing gear in the other hand

At 110 kilograms I weight like in basic class so the ocean doesn't throw me around and spit me out so much

Keeping in mind there are many different individual diving styles

Ended up with an Italian spec 200bar 15l faber. A lot lighter than the Heiser.

Sold all the cylinders and replaced them with a bunch of 10l 232bar fabers for independent twins. They weigh 10.8kg so only a tad more than the one Heiser.

 

[happy-diver]

I always wonder why it is so much harder carrying tanks away from the compressor than to it

 

[MarkA]

I always wonder why it is so much harder carrying tanks away from the compressor than to it

It’s the XXXX drunk while waiting

 

[Edward3c]

I dive 300bar 12Lt, but when switching to 232bar 10 or 12Lt cylinders I add 3.5kg.