Can I nominate Gludy . . .

Searush

Searush

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. . . for an award for services to Archimedes? Check this out - waterbuoy thread.

Bless him for his patience, sorely tried in explaining what was wrong in 100 different ways to those who believe the stuff they see on the telly!
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Well done mate, although I did, from time to time, notice a trickle of blood from the corner of your mouth when typing (caused by biting your tongue, to prevent an angry response).

Do you think there is a problem with physics teaching in our schools? Or is it that people just don't listen/ think for themselves? Congratulations, mate, a most entertaining thread!
 
Many years ago as a young water resourcea engineer I was the water resources engineer to Cornwall River Authority.
We had steering committee meeting with Devon and Somerset to coordinate water resource planning. Devon was a much bigger richer department than mine and had produced a huge set of documents based on decades of man years looking at all sorts of reservoir plans.
When I took this report home to begin to digest I quickly realised the whole report was based on a false premise - they had direct supply reservoirs yielding more water for supply than on average flowed into them. The average flow in was less than the average flow out. They had simply done a computer simulation until the reservoir began to rise and stopped at that point to determine yield. This was of course nonsense as all that had happened was that winter had come and more water flowed in that day than flowed out.
Anyway at the next meeting I had to announce this error – it would mean the scrapping of man decades of work. After announcing it there was a stunned silence after I explained you cannot on average get more out of a direct supply reservoir than you put in! Then someone said “that is an interesting concept there Paul.”

The work all had to be scrapped and that was the start of a life where time after time I have had to fight such things from the simply monumental in costs where billions were due to be spent without need (government project) to small things like major international corporations getting basic physics wrong with their products.
These things just head my way … or maybe its that I simply cannot let them pass me by!
I saw red watching the manner in which this kilo weoght was dealt with on Dragons Den but was satisfied to vent my spleen with SWMBO but when this thread appeared ...... I was once again hooked. /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif
 
lol. I concur with Searush on the Dragon's Den thread being most entertaining.

Thank you for that Gludy.

(I have only just finished watching all the DD episodes on the BBC website thanks to your post /forums/images/graemlins/smile.gif )

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Ahh - Now I understand the Ocean Deep saga a little better! /forums/images/graemlins/wink.gif Very good! /forums/images/graemlins/smile.gif
 
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Ahh - Now I understand the Ocean Deep saga a little better! Very good!

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You now have it, whilst Archi himself did not state that a boat without stern will sink, I once again applied his good old principles and found out that whilst it would float when it had air inside, the loss of the stern may cause it to fill with water and hence achieve negative buoyancy!
The claims that the fenders would keep it afloat were rejected by me. /forums/images/graemlins/laugh.gif
 
The man done well. Although he was almost in danger of becoming obsessed. It turned out to be a better thread than the "floating your boat in a teacup of water" one. Personally I think that a small float that deploys an attached strong light line, so you can haul your keys or whatever up is a better way to go. But that's another thread.
 
A perfect example of how a 'debate' should be: no sniping, no name calling, just a very patient, polite statement of the position and of the flaws in the thinking of those who disagree.

Could Gludy run a training course for Gordon and David?
 
Just read the thread and I have to agree, Gludy has the tenacity of a very tenacious thing.

Well done /forums/images/graemlins/smirk.gif
 
Gludy is absolutely correct - it is simple Archimedes, very basic physics - yet many folk on here have difficulty in grasping what he has tried to explain in a dozen different ways.

If the buoyancy of the lifting bag is greater than the IMMERSED mass of the object to be lifted, then it will go up. If not, it will go sink. Simple.
Note I said immersed mass, not the mass of the object in air.

An analogy could be : Which is more effective for a mooring, a concrete weight weighing 1 tonne, or a steel weight weighing 1 tonne, all else being equal?
The density of the steel is much greater than the density of the concrete, hence the steel will be 'heavier' underwater - and thus it should be more effective as a mooring.

That tiny key ring lifter would probably bring a 100 kg human to the surface quite happily if the immersed weight of the human was only slightly more than the weight of the volume of water said human displaces.

May I commend to all the cynics to carry out some buoyancy trials on themselves next time they are in a swimming pool. Breathe in deeply, and you go up, breathe out, and you go down.

Eureka!
 
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Just read the thread and I have to agree, Gludy has the tenacity of a very tenacious thing.

Well done /forums/images/graemlins/smirk.gif

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Thank you, Baldrick, do you now have a cunning plan to get us all on (rather than in or under) the water this weekend?
 
Paul. You really have a lot of patience. Your theory explains the need for the plimsol line on ships indicating that more cargo can be carried in salt water than in fresh. I didnt notice if there were plimsol lines on boats in the Dead Sea when i was there earlier this year. They are probably too small to warrant one. It is a theory that some large tankers have instantly sunk and the crew lost without trace when a gas field has exploder underneath. The bouyancy ratio of the gas filled water becomes sudenly much less dense and the ship sinks like a stone. This can apparently happen from an eruption from an underwater volcano.
 
yep, that was one of the more plausible bermuda triangle explanations - for missing boats anyway. I forget how they said it affected aircraft now.
 
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Thats true - a bubbling water has a very low SG and so cannot support what was otherwise floating in it - drops to the bottom like a stone.

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Yes we had that problem at our sailing club.
The club is at Datchet on the Queen Mother Reservoir (about 480 acres of water 100 feet deep) and Thames Water recently installed a special airation system to improve the quality of the water. As a sailing club, we had to be very careful about people capsizing etc near where the bubbles form. It turns out that a person wearing a buoyancy aid stays safely on the surface but someone unconcous without a lifejacked would probably sink. The club has stringent rules about personal buoyancy - wetsuits alone arent enough etc... and the club enforces its rules well.

Just goes to show your point about bubblling water - with all that air bubbling to the surface some would naturally think that the bubbles would push one upwards but in fact the water is less dense and the opposite effect happens.
 
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