Would like to add that the ratio between the ditchable and non-ditchable weights is important and should be part of balanced rig concept. I see lots of divers with 8 kg or more on the belt, with 5/7 mil neoprene wetsuit. This is extremely dangerous. The ditchable weight should be minimal, only to allow a safe accent with an empty BCD.
It's funny you're speaking about people being over weighted. I recently went diving with a few guys and they all were extremely over weighted. By the end of the day i had them diving with half the weight they began with. All of them where shocked on how much easier it was to control their buoyancy and how much less gas consumption they used... None of them where trained correctly or educated on how to figure out what they actually need for themselves then with gear and tank.
Just a question about the tanks and their potential downlift. 10l tank wont be displace 10l of water cause of the wall thickness of the steel/alu. Is there a rule of thumb where I can try to get close to balanced rig? For today I just do try and error but I want to get faster near to my sweet spot.
its possible to do that a numbernof different ways, you can literally hang it from a luggage scale and then lower it into water, quick and easy if you have access to a drum full of water
My 8.5l bottle weighs 10.4kg. Steel has a density of 7.8kg/l. So the Volume of the steel is 10.4/7.8=1.3l plus 8.5l tank volume = 9.8l = lift. 10.4kg-9.8kg = -0.6kg when the bottle is empty. with 50bars left in the 8.5kg tank it equals ruffly around -1.1kg.
Look at manufacturers website for buoyancy charicteristics. 10l steel tank is roughly 4-5kg negative when full and about 2-3kg negative when empty. An AL80 is 1kg neg when full and 1kg positive when empty
not really, each litre of air (assuming itnis air, and not nitrox or trimix etc) weighs around 1.28g so the buoyancy of a tank willbalter as it is depleted.
cant be that hard to figure it out for sidemount: take the two bottles of your balanced rig which are on your back, get rid of the connections and put them on your side. I dont think you can unbalance a rig by just moving the bottles from your back to your side.
I blame a lot on these instructors that they pump out. I watch them teach the class and instead of relaxin a student and putting them in proper exposure gear for the conditions. They just add weight to get them to the platform. This weekend i witnessed a girl probaly all of a 100lbs in a 3mm suit no hood or gloves on her cheque out dives water temp was 63°f at 20 ft. She was shivering at the surface and breathing heavely befor the dive and could not get down with 12# on. So the instructor's solution was add more weight i watched 6 more pounds added. On the platform the instructor had all his students standing. It looked like a f%#&€=g disco dance. I gusee they learned 1 thing i call it the ( rote tiller ) it was not hard to find them out of the water they were muddy. So i think the system needs a overhauled
I understand weight is an easy term for people to use when talking about a tank but its not very useful when we are talking about buoyancy. An aluminum tank will weigh more than a steel tank but because the metal is less dense, a will be more buoyant than the lighter steel tank.
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I always like your videos. You cut to the bottom line without the BS and I trust your opinion.
Very important concept, well explained
It will be an interesting video about a sidemount concept and some demonstrations of sidemount drills in ISE.
Artur Shakirov very informative thank you
Would like to add that the ratio between the ditchable and non-ditchable weights is important and should be part of balanced rig concept. I see lots of divers with 8 kg or more on the belt, with 5/7 mil neoprene wetsuit. This is extremely dangerous. The ditchable weight should be minimal, only to allow a safe accent with an empty BCD.
Question is about emergency ascent. If you have 7 mm wetsuit and 15 ltr steel tank 80% full and your bcd fails at 40 mtr, will you be able to surface?
It's funny you're speaking about people being over weighted. I recently went diving with a few guys and they all were extremely over weighted. By the end of the day i had them diving with half the weight they began with. All of them where shocked on how much easier it was to control their buoyancy and how much less gas consumption they used... None of them where trained correctly or educated on how to figure out what they actually need for themselves then with gear and tank.
Just a question about the tanks and their potential downlift. 10l tank wont be displace 10l of water cause of the wall thickness of the steel/alu. Is there a rule of thumb where I can try to get close to balanced rig? For today I just do try and error but I want to get faster near to my sweet spot.
its possible to do that a numbernof different ways, you can literally hang it from a luggage scale and then lower it into water, quick and easy if you have access to a drum full of water
My 8.5l bottle weighs 10.4kg. Steel has a density of 7.8kg/l. So the Volume of the steel is 10.4/7.8=1.3l plus 8.5l tank volume = 9.8l = lift. 10.4kg-9.8kg = -0.6kg when the bottle is empty. with 50bars left in the 8.5kg tank it equals ruffly around -1.1kg.
Look at manufacturers website for buoyancy charicteristics. 10l steel tank is roughly 4-5kg negative when full and about 2-3kg negative when empty. An AL80 is 1kg neg when full and 1kg positive when empty
Tank buoyancy is based on volume of the tank, not based on the volume of the air inside the tank right?
not really, each litre of air (assuming itnis air, and not nitrox or trimix etc) weighs around 1.28g so the buoyancy of a tank willbalter as it is depleted.
You're basically right Kevin, but the tanks "outside" volume is not that much different to the inside volume i guess so maybe its just a rough guess
cant be that hard to figure it out for sidemount: take the two bottles of your balanced rig which are on your back, get rid of the connections and put them on your side. I dont think you can unbalance a rig by just moving the bottles from your back to your side.
I basically agree - but what can be seen regularly in the water shows something else. Lets maybe discuss this in an upcoming live video.
I blame a lot on these instructors that they pump out. I watch them teach the class and instead of relaxin a student and putting them in proper exposure gear for the conditions. They just add weight to get them to the platform. This weekend i witnessed a girl probaly all of a 100lbs in a 3mm suit no hood or gloves on her cheque out dives water temp was 63°f at 20 ft. She was shivering at the surface and breathing heavely befor the dive and could not get down with 12# on. So the instructor's solution was add more weight i watched 6 more pounds added. On the platform the instructor had all his students standing. It looked like a f%#&€=g disco dance. I gusee they learned 1 thing i call it the ( rote tiller ) it was not hard to find them out of the water they were muddy. So i think the system needs a overhauled
I understand weight is an easy term for people to use when talking about a tank but its not very useful when we are talking about buoyancy. An aluminum tank will weigh more than a steel tank but because the metal is less dense, a will be more buoyant than the lighter steel tank.