Rebreather buoyancy comparison

[andrespp]

hello, I have done a cursory review in rbw about subject matter but found nothing.


noticed that some dive mates that use heavy units as a HammerMeg, despite the initial dry weight of the unit they still need to carry significant amounts of lead (i.e. 8-10 kg on a trilaminate drysuit), meanwhile I only use with the CK and a 4 mm neoprene drysuit about 4 kg of lead.




So my question is, supposing equal conditions (i.e steel standard BP and 3L steel tanks, ), how would be the ccr's rank depending on what units are more or less buoyant.


I think that if weight is a consideration when choosing a unit, the weight to be considered should be the one of the unit ready to dive plus the weight one needs to put on lead.


Probably this is a question for those that have used several units along the years(not my case).


Regards,
Andrespp

[EngelenD]

In a rEvo micro titanium with 3 L steel bottles , dry suit and heavy undergarment and very light fins I have 2 kg on top of my rEvo.


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[andrespp]

In a rEvo micro titanium with 3 L steel bottles , dry suit and heavy undergarment and very light fins I have 2 kg on top of my rEvo.


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The lead you use is just those 2kg?


wow, that would indicate that your unit is really negative.

[DaleHawerchuck]

I think the main factor you need to consider is the unit scrubber can size. This is the main source of lift on a unit that needs to be compensated with lead, considering the diver is capable of diving at CL minimal volume (I used to use more lead when I first started diving CCR).

I use a HH unit with close to 10kg of lead. I also know people who dive rEvos with almost no lead at all. They are are pretty much the two extremes when it comes to can size/capacity. As an approximate rule of thumb I would suggest you to compare units by their maximum scrubber capacities in kg, and I'm guessing your weighting ranking will be close enough.

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[broncobowsher]

I would think it would be rather simple. Archimedes' principle should cover most of it.
How much does it weigh, how much volume does it take? This is where a good design that minimizes volume comes into play.


Simply put, the bigger the displacment of the unit, the more it will have to weigh. Either naturally or with added weights.

[EngelenD]

I guess I don't need much weight because it's a small unit. I also use a whites fusion drysuit so this makes a difference compared to thicker neoprene drysuit's



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