bizzard Posted August 3, 2012 Report Posted August 3, 2012 There, you said it again Almost perfect or even perhaps perfect neutral bouyancy can be attained in fully controlled laboratory conditions. Fish are cleverer than all of us on this subject, the masters of trim. I watched a big Pike lying in wait for its lunch yesterday, it didn't appear to budge at all in any direction.
jelunga Posted August 3, 2012 Report Posted August 3, 2012 Er.... more bollocks If you can't change the volume of the air, you can't change the bouyancy. That's why bouyancy tanks have great big holes in them. To add for clarification, at the bottom
ditchcrawler Posted August 3, 2012 Report Posted August 3, 2012 And what about the bends as you rise and the pressure reduces
jelunga Posted August 3, 2012 Report Posted August 3, 2012 So therefore as the submarine descends the air in the ballast tanks compress giving smaller volume and therefore less buoyancy. Almost perfect or even perhaps perfect neutral bouyancy can be attained in fully controlled laboratory conditions. Fish are cleverer than all of us on this subject, the masters of trim. I watched a big Pike lying in wait for its lunch yesterday, it didn't appear to budge at all in any direction. Dont tell him Pike. But his fins were moving to maintain position and depth along with his swim bladder
Pretty Funked Up Posted August 3, 2012 Report Posted August 3, 2012 They have to watch out if they cruise into a sea water/ fresh water mix. While moving the can adjust their planes to accomodate the different densities, but if they want to sit still they have to get the neutral bouyancy calculation thing pretty spot on. Is it home time yet?
Gibbo Posted August 3, 2012 Report Posted August 3, 2012 Almost perfect or even perhaps perfect neutral bouyancy can be attained in fully controlled laboratory conditions. Actually it can't Not even theoretically. I watched a big Pike lying in wait for its lunch yesterday, it didn't appear to budge at all in any direction. Cut all its fins off and I guarantee it will go up or down.
bizzard Posted August 3, 2012 Report Posted August 3, 2012 (edited) Actually it can't Not even theoretically. Cut all its fins off and I guarantee it will go up or down. A bit of wheeze this, but its perfectly true. I once made a model shark from a plastic washing up liquid bottle and stuck a cardboard dorsal fin on top painter black. I carefully ballasted it for erm neutral bouyancy and stability with bits of metal inside finishing up with tiny amounts of metal filings and pulling it along with a bit of string in the bath to test it. I can't remember how long it remained at the just submerged depth but it was a long time, it also took a long time to make the very minute adjustments. Anyhow the purpose of this shark was to have a laugh with my people under sailing instruction by towing it on a string amongst them behind the guard boat and it worked admirably. I had drinks bought for me after the lesson for breaking the boredom, it was a flat calm that evening. Edited August 3, 2012 by bizzard
Gibbo Posted August 3, 2012 Report Posted August 3, 2012 I've really tried to wind you up and it isn't working. You don't bite
nb Innisfree Posted August 3, 2012 Report Posted August 3, 2012 (edited) This is like aeroplanes which as we all know become weightless at takeoff speed, everything in and on that aircraft also becomes weightless, you could even unbolt the engines and they would stay there, bolts are there for when the plane is on the ground. Why don't passengers float around I hear you ask? Well, the answer is simple, air is pumped from the ceiling and through ducts under the floor to push people down, to enable astronauts to practice weightlessness in aircraft the air pumps are turned off. If a vertical tube could be fixed to the underside of an aeroplane then passengers could float down to the ground and step off (if it wasn't travelling at high speed that is). Experiments are already being carried out with rescue helicopters to replace the winch with a telescopic tube allowing the rescuer to float down to the casualty. ETA: Bizzard and Gibbo will confirm all this. ETA further: Gibbo have you made any progress with your zoomable 3D Smartgauge display? Edited August 3, 2012 by nb Innisfree
Iain_S Posted August 3, 2012 Report Posted August 3, 2012 (edited) Cut all its fins off and I guarantee it will go up or down. Possibly not. Can a fish vary the size of its swim bladder (and therefore itself) by muscular contraction, thus adjusting its bouyancy? (Unlike a submarine, which adjusts its weight, rather than bouyancy) Iain Edit to add : Bit like a Sea Otter Edited August 3, 2012 by Iain_S
Gibbo Posted August 3, 2012 Report Posted August 3, 2012 (edited) This is like aeroplanes which as we all know become weightless at takeoff speed, everything in and on that aircraft also becomes weightless, you could even unbolt the engines and they would stay there, bolts are there for when the plane is on the ground. Why don't passengers float around I hear you ask? Well, the answer is simple, air is pumped from the ceiling and through ducts under the floor to push people down, to enable astronauts to practice weightlessness in aircraft the air pumps are turned off. If a vertical tube could be fixed to the underside of an aeroplane then passengers could float down to the ground and step off (if it wasn't travelling at high speed that is). Experiments are already being carried out with rescue helicopters to replace the winch with a telescopic tube allowing the rescuer to float down to the casualty. ETA: Bizzard and Gibbo will confirm all this. ETA further: Gibbo have you made any progress with your zoomable 3D Smartgauge display? But surely they have to move the vents around when the plane is upside down? Possibly not. Can a fish vary the size of its swim bladder (and therefore itself) by muscular contraction, thus adjusting its bouyancy? Yes that's exactly how they work. They compress the gas thus reducing the volume. But my statement stands. As a young child my sister cut all the fins off a goldfish. Sure enough, in the morning it was floating on the surface thus proving that they can't control bouyancy without them. Edited August 3, 2012 by Gibbo
nb Innisfree Posted August 3, 2012 Report Posted August 3, 2012 (edited) But surely they have to move the vents around when the plane is upside down? Yes that's exactly how they work. They compress the gas thus reducing the volume. But my statement stands. As a young child my sister cut all the fins off a goldfish. Sure enough, in the morning it was floating on the surface thus proving that they can't control bouyancy without them. Just reverse the fan motors This sister of yours is she free to roam the streets? Edited August 3, 2012 by nb Innisfree
Gibbo Posted August 3, 2012 Report Posted August 3, 2012 This sister of yours is she free to roam the streets? She's a midwife
dove Posted August 3, 2012 Report Posted August 3, 2012 Thank you for this LMAO Put a bottle in a bowl of water, let it fill with water, stand the bottle up side down keeping the kneck under water then try and lift the bottle up. That's how I thought of it. The Sea Otter has a vent at the top of the hollow stem bar conected to the tank, when launching and recovering this should be opened. Andrew (ex- Sea Otter prototype designer and builder) 1
jelunga Posted August 3, 2012 Report Posted August 3, 2012 A bit of wheeze this, but its perfectly true. I once made a model shark from a plastic washing up liquid bottle and stuck a cardboard dorsal fin on top painter black. I carefully ballasted it for erm neutral bouyancy and stability with bits of metal inside finishing up with tiny amounts of metal filings and pulling it along with a bit of string in the bath to test it. I can't remember how long it remained at the just submerged depth but it was a long time, it also took a long time to make the very minute adjustments. Anyhow the purpose of this shark was to have a laugh with my people under sailing instruction by towing it on a string amongst them behind the guard boat and it worked admirably. I had drinks bought for me after the lesson for breaking the boredom, it was a flat calm that evening. I was a bus driver during the floods in Lewes in East Sussex some while ago. There were guys in the pub on the street I was paddling my bus down who had an inflatable shark on a string and were floating it down the street. Quite funny.
Iain_S Posted August 3, 2012 Report Posted August 3, 2012 But my statement stands. As a young child my sister cut all the fins off a goldfish. Sure enough, in the morning it was floating on the surface thus proving that they can't control bouyancy without them. Reminds me of the chap who proved a dog's ears are actually located in its legs.... Iain
Gibbo Posted August 3, 2012 Report Posted August 3, 2012 Reminds me of the chap who proved a dog's ears are actually located in its legs.... No, that was grasshoppers not dogs. But I think it's actually true in their case
Pretty Funked Up Posted August 3, 2012 Report Posted August 3, 2012 (edited) Thank you for this LMAO Put a bottle in a bowl of water, let it fill with water, stand the bottle up side down keeping the kneck under water then try and lift the bottle up. That's how I thought of it. The Sea Otter has a vent at the top of the hollow stem bar conected to the tank, when launching and recovering this should be opened. Andrew (ex- Sea Otter prototype designer and builder) C'mon please tell 'How does it work?' Another thing thats been playing on my mind it the 1kg of water statements. If under any gravitational influence 1kg of water will always weigh 1kg whether youre in a hot air ballon or on the sea bed. What will change is the volume of water required to achieve 1kg! Thats even true in space without gravity but your scales wont work. HA! Water in water is NOT weightless its merely neutrally bouyant. I think Edited August 3, 2012 by Pretty Funked Up
mattlad Posted August 3, 2012 Report Posted August 3, 2012 This is like aeroplanes which as we all know become weightless at takeoff speed, everything in and on that aircraft also becomes weightless, you could even unbolt the engines and they would stay there, bolts are there for when the plane is on the ground. Why don't passengers float around I hear you ask? Well, the answer is simple, air is pumped from the ceiling and through ducts under the floor to push people down, to enable astronauts to practice weightlessness in aircraft the air pumps are turned off. If a vertical tube could be fixed to the underside of an aeroplane then passengers could float down to the ground and step off (if it wasn't travelling at high speed that is). Experiments are already being carried out with rescue helicopters to replace the winch with a telescopic tube allowing the rescuer to float down to the casualty. That's not how an aeroplane flies! Everyone knows it is the pilot's muscle power pulling back on the stick that makes it fly!
RLWP Posted August 3, 2012 Report Posted August 3, 2012 That's not how an aeroplane flies! Everyone knows it is the pilot's muscle power pulling back on the stick that makes it fly! Naahh, it's aesthetics, isn't it. Aeroplanes only look beautiful when flying, and so they reject the uncouth and untidy ground in favour of the grace and elegance of the clouds. Aeroplanes fly because it is a more beautiful solution, truth is beauty. Richard
Harpic Posted August 5, 2012 Report Posted August 5, 2012 Pretty Funked Up, perhaps I haven't caught the physics of your argument, but did you say that the volume of water required to achieve 1kg would change? You'd be pretty hard pressed to change the volume of ANY amount of water (or any other liquid) other than by changing its temperature. Otherwise, all hydraulic machinery in the universe simply wouldn't work. BTW, Andrew's explanation of the Sea Otter's water "ballast" with the simple experiment using a bottle hits the nail on the head for most of those sea Otter boats that have a vent valve set in the stem bar. At the risk of setting off another fascinating discussion, I would just add that my 51 ft Sea Otter has no such vent- the water "ballast" enters via the usual hole in the bottom of the V tank all on its own, and drains out in similar fashion when the boat is lifted out. All this without having to stop up or release any valve. There must be a vent somewhere, but I've never found it.......
nb Innisfree Posted August 5, 2012 Report Posted August 5, 2012 This valve, if fitted, could be used in rough water to power a turbine to charge batts or maybe inflate party balloons, or something....
Pretty Funked Up Posted August 5, 2012 Report Posted August 5, 2012 Pretty Funked Up, perhaps I haven't caught the physics of your argument, but did you say that the volume of water required to achieve 1kg would change? You'd be pretty hard pressed to change the volume of ANY amount of water (or any other liquid) other than by changing its temperature. Otherwise, all hydraulic machinery in the universe simply wouldn't work. BTW, Andrew's explanation of the Sea Otter's water "ballast" with the simple experiment using a bottle hits the nail on the head for most of those sea Otter boats that have a vent valve set in the stem bar. At the risk of setting off another fascinating discussion, I would just add that my 51 ft Sea Otter has no such vent- the water "ballast" enters via the usual hole in the bottom of the V tank all on its own, and drains out in similar fashion when the boat is lifted out. All this without having to stop up or release any valve. There must be a vent somewhere, but I've never found it....... Theres only 2 things to catch really. All liquids can be compressed and there is no such thing as temperature. Then it'll be obvious. The upside down bottle is a great example BTW n1
blackrose Posted August 5, 2012 Report Posted August 5, 2012 Theres only 2 things to catch really. All liquids can be compressed and there is no such thing as temperature. Then it'll be obvious. The upside down bottle is a great example BTW n1 I'll have some of what he's having.
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