ScubaInChicago
Contributor
I had an argument with a local legend who is also a tech instructor during a DPV class. He stated that by adding foam inside a scooter it would make it more buoyant in the water. I told him that buoyancy has a direct correlation to the volume of water displaced and by adding weight inside, it would actually make it more negative. I finally sucked it up and let him win his argument so I didn't have to hear it anymore.
Later I started thinking about lung volume in the exact same manner and realized that lung volume doesn't cause displacement. It is the expansion of the chest cavity that is displacing that volume of water causing the buoyancy change. The weight of the gas would stay constant on an inhale at it has transferred. If you made an argument based on weight it should be the opposite of what we know to be a fact (i.e. expelling a breath and the weight of that gas not causing you to become more buoyant).
And on to the last point which is more of a question. Counter lungs??? Common enough terminology within rebreather circles. But aren't they countering the displacement of the chest expansion. Is there a perfect 1:1 ratio of chest expansion to the gas volume exhaled into "counter lungs" to keep displacement equal, or is there a slight bit of MICRO adjustment with each breath?
Later I started thinking about lung volume in the exact same manner and realized that lung volume doesn't cause displacement. It is the expansion of the chest cavity that is displacing that volume of water causing the buoyancy change. The weight of the gas would stay constant on an inhale at it has transferred. If you made an argument based on weight it should be the opposite of what we know to be a fact (i.e. expelling a breath and the weight of that gas not causing you to become more buoyant).
And on to the last point which is more of a question. Counter lungs??? Common enough terminology within rebreather circles. But aren't they countering the displacement of the chest expansion. Is there a perfect 1:1 ratio of chest expansion to the gas volume exhaled into "counter lungs" to keep displacement equal, or is there a slight bit of MICRO adjustment with each breath?