CCR buoyancy explained

hi guys Tony from dive tech in Grand Cayman today we're going to talk about rebreather buoyancy many people think buoyancy on a rebreather is very difficult it's not difficult but it's different to what you've known untraditional open circuit the biggest difficulty for most is that you need to unlearn all of the muscle memory you've developed over your years of open circuit diving the more experience you have the harder it may be to unlearn it so let's take a look at why rebreather buoyancy is different and what to do about it when we dive traditional open circuit we have two basic bladders of gas with us our lungs and our BCD of course we all know that on open circuit we can fine-tune our buoyancy with our lung as we breathe in from our scuba tank our lung volume expands we become more buoyant and we begin to rise up as we breathe out into the water column our long volume decreases we become less plant and we begin to descend now let's take a look at this on a rebreather we still have our same two bladders of gas with us but the difference is we are no longer breathing in from a compressed tank and out into the water we are breathing in and out of a bag known as a counter lung this means as we breathe in and out as long as we are at a constant depth our overall volume does not change as we inhale our body's lungs still expand but we are inhaling from our rebreather counterlungs which gets smaller as we exhale the inverse happens our lungs get smaller but we exhale into these same counter lungs our total volume stays the same so the fine-tuning of buoyancy we used to use on open circuit can no longer be controlled with our breathing cycle after I've explained this concept the question I get next is so how do we maintain buoyancy and the answer is simply this by swimming we swim up and down rebreathers light constant depth and the easiest way is to pick a depth and stay there as best you can I call it a target depth let's say our target depth is 60 feet we swim down to 60 feet and then we add gas to our counter lungs so we have enough volume to breathe then we add gas to our wing to make us neutral for 60 feet as we conduct the dive we want to stay as close to 60 feet as we can if we find ourselves at 61 feet we swim back up if we find ourselves at 59 feet we swim back down now of course this is an overly simplified explanation and to be clear my 60 foot depth example is arbitrary we can do this of course for any depth and we can select as many target depths as we want we can do multilevel profiles up down or both but my suggestion is try to avoid the needless up-and-down movements your profile on an open-circuit dive might look something like this when you're diving a rebreather what you should be looking for is a profile that looks like this what you don't want to do is add invent gas with every little depth change the only time you want a vent or add gas is if you plan to stay at this new target depth some tricks to help you instead of going up and over an obstacle underwater go around it if you can proper weighting is key you want to have your rebreather as close to neutrally buoyant as you can the more negative it is the more air you need to have in a wing to compensate which simply means more volume of air to expand and contract as you go up and down exacerbating the issue a properly trimmed rebreather is much easier take the time to rig your configuration so you can be perfectly trimmed out without having to fin to keep yourself level as you get more experience on a rebreather reading the nuances of the loop will become easier and so will your buoyancy that's it thanks for watching we hope to see you diving with us soon

Channel: Divetech Grand Cayman

Views: 12,886

Keywords: ccr, rebreather, closed circuit, trim, buoyancy, tips, tricks, explained, divetech

Id: RHaKZc5IK6M

Length: 3min 45sec (225 seconds)

Published: Fri Nov 15 2019