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Thread: Rebreather buoyancy comparison

  1. #1
    RBW Member andrespp is on a distinguished road andrespp is on a distinguished road andrespp's Avatar
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    Rebreather buoyancy comparison

    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

  2. #2
    RBW Member EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD's Avatar
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    Re: Rebreather buoyancy comparison

    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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    RBW Member andrespp is on a distinguished road andrespp is on a distinguished road andrespp's Avatar
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    Re: Rebreather buoyancy comparison

    Quote Originally Posted by EngelenD  View Original Post
    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.

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    RBW Member DaleHawerchuck is an unknown quantity at this point DaleHawerchuck's Avatar
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    Re: Rebreather buoyancy comparison

    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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    RBW Member broncobowsher is on a distinguished road broncobowsher is on a distinguished road broncobowsher's Avatar
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    Re: Rebreather buoyancy comparison

    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.

  6. #6
    RBW Member EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD's Avatar
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    Re: Rebreather buoyancy comparison

    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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