Good morning posters

I have a problem with ships made of metal... how do they float???

I tried this out the other day and my tiny bit of metal sank. does the metal have to be hollow with loads of air in side or something?? I am having difficulties trying to explain this one to my nephew.

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take care zak

No, they float because of their shape, which means that the volume of the water that they displace weighs more than the ship itself. Or something like that.

None of which explains how aeroplanes can fly? :confused:

Ok.. so if i got a small metal ship and put it in the bath then iot will float??

Um... does it have an engine? Is it a small metal ship that's functionally identical to a normal, life-sized ship - ie a ship - in every way?

no i will ahve to get one.

Ok.. so if i got a small metal ship and put it in the bath then iot will float??

http://org33.zorpia.com/0/2331/14918518.95846d.gif

The metal out'ta be something light like aluminum, so that its all proportional to the size and the weight that of the real ship. okey??... yea....

No, they float because of their shape, which means that the volume of the water that they displace weighs more than the ship itself. Or something like that.

you got it.

http://org33.zorpia.com/0/2331/14918518.95846d.gif

The metal out'ta be something light like aluminum, so that its all proportional to the size and the weight that of the real ship. okey??... yea....

hummmm thanks Draqon, i hope all is wel with you..

i dont know how i will be able to gather and assemble the components needed for such an experiement....

Oh this does put a spanner in the works??!!??!

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take care
zak

Cover the top of an empty beer or soda can with tape. Put it in the bathtub.

You can make a sailboat out of concrete, too. In fact, they add stones or lead to sailboats for ballast, large sailboats need hundreds or thousands of pounds added for stability.

Get a bit of cardboard and cover it in tin foil, same effect.

Or, as spidergoat says, empty cans work well.

Good morning posters

. does the metal have to be hollow with loads of air in side or something??

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take care zak

That would certainly help

Hi spider

thanks for this.

But for the experiement to work, i should be using Steel or whatever they use to make boats. i know that aluminum floats as i see beer cans floating in the river near me..

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take care
zak

What's the difference? A chunk of aluminum sinks as fast as a chunk of steel.

OK, use... a tin (coated steel) can, like a soup can, with the top covered.

Theres no reason steel wont work at that scale, aslong as it is not too think, I suggest you make the boat wide too, because that will increase the volume of water it displaces.

If you really wanted an indepth explaination about "Displacement", then you should probably look to either the works of Archimedes (http://www.bbc.co.uk/history/historic_figures/archimedes.shtml) or someone thats written about his discovery (Archimedes Principle (http://en.wikipedia.org/wiki/Archimedes%27_principle)).

As for the Propellers that Boats use now adays, the discoverer for the correct geometry (the right facial angles and depth etc) was Isambard Kingdom Brunel (http://www.designmuseum.org/design/isambard-kingdom-brunel)

Water is heavy. One square foot weighs about 62 pounds. If you have an object that is one square foot and weighs less than 62 pounds (and no water can enter), it will float, no matter what material it is made from.

What's the difference? A chunk of aluminum sinks as fast as a chunk of steel.

OK, use... a tin (coated steel) can, like a soup can, with the top covered.

Does not.

And the term you were looking for in your next message was "cubic foot" not "square foot."

Correct, cubic foot, not square foot.

You can just make an open-top barge out of aluminum foil. (Or aluminium if you buy it in England.) Fold the sides up carefully so you don't tear it and make sure every part of the edge, even the parts you buried because you were a little clumsy in the folding, are above the water line. Make it a couple of inches deep so it won't be easily swamped by the waves you make with your handling, and it will float in a bathtub. Your craft will be top-heavy because of the multiple layers of folding on the sides. If it's not stable enough carefully load a penny into the bottom, then another, until it is better balanced and settles down.

Airplanes (aeroplanes if you buy them in England) do not fly on the principle of buoyancy. They do not float. They use the Bernoulli Principle (Venturi Effect? I always get them mixed up) to create a partial vacuum on the top side of the wings. The vacuum pulls them up. [Yes guys I know that is a terribly unscientific explanation but it's understandable to laymen.]

Blimps and zeppelins are called "lighter than air" craft precisely because they are filled with helium (or hydrogen if you buy them in Germany and FDR won't allow them to be filled with American helium) which actually is lighter than air. They float because they're buoyant.

Airplanes (aeroplanes if you buy them in England) do not fly on the principle of buoyancy. They do not float. They use the Bernoulli Principle (Venturi Effect? I always get them mixed up) to create a partial vacuum on the top side of the wings. The vacuum pulls them up. [Yes guys I know that is a terribly unscientific explanation but it's understandable to laymen.]

Em... The shape of an aerofoil is simply designed to allow air to flow faster over the upper surface than it does over the underside. It's the build-up of air on the underside which gives lift. With air density reduced on the upper surface the degree of resistance to the plane rising is thus reduced.

Not quite a vacuum, but that's the general idea of the thing.

Em... The shape of an aerofoil is simply designed to allow air to flow faster over the upper surface than it does over the underside. It's the build-up of air on the underside which gives lift. With air density reduced on the upper surface the degree of resistance to the plane rising is thus reduced.

Not quite a vacuum, but that's the general idea of the thing.
Just a minor note so as not to perpetuate a myth. The shape of an airfoil is largely designed to move through the air with minimal turbulence, which creates drag. Conventional wings do generate some lift via bernoulli but most of it is generated simply by the pressure differential created by the angle of attack that the wing presents. Conventional wings are perfectly capable of flying upside down. Aerobatic planes have wings that are symmetrical, top and bottom. They do quite well.

"Evan a plank will lift if you can push it through the air fast enough" - Something I read somewhere by some aeronautical engineer guy.

Also, concerte ships were built and used for transport during metal shortages in WWII. There's the remains of one off of the New Jersy coast. Pretty impressive looking.

There was a plan to make an aircarft carrier out of ice mixed with shredded paper (or maybe sawdust) for WWII. Incredibly dense stuff, extremely bouyant, cheap to make. It was gonna be a huge boat, near indestructable too. Didn't happen because the war ended.

There was a plan to make an aircarft carrier out of ice mixed with shredded paper (or maybe sawdust) for WWII. Incredibly dense stuff, extremely bouyant, cheap to make. It was gonna be a huge boat, near indestructable too. Didn't happen because the war ended.
Ice?!?!? Wowsers...

Just a minor note so as not to perpetuate a myth. The shape of an airfoil is largely designed to move through the air with minimal turbulence, which creates drag. Conventional wings do generate some lift via bernoulli but most of it is generated simply by the pressure differential created by the angle of attack that the wing presents. Conventional wings are perfectly capable of flying upside down. Aerobatic planes have wings that are symmetrical, top and bottom. They do quite well.

"Evan a plank will lift if you can push it through the air fast enough" - Something I read somewhere by some aeronautical engineer guy.

Ah, but of course. My bad.

Ice?!?!? Wowsers...

Ice + sawdust, called Pykrete (http://en.wikipedia.org/wiki/Pykrete). The Brits and Project Habakkuk (http://en.wikipedia.org/wiki/Project_Habakkuk)

They use the Bernoulli Principle (Venturi Effect? I always get them mixed up) to create a partial vacuum on the top side of the wings. The vacuum pulls them up. [Yes guys I know that is a terribly unscientific explanation but it's understandable to laymen.]

This has no intension of correcting you at all Rocker, maybe however it will aid with remembering the difference. From Wiki (http://en.wikipedia.org/wiki/Venturi_effect), Venturi Effect is posed as "A special case of the Bernoulli Principle" so it wouldn't be difficult to actually mix them up.

However a few years ago I had to deal with Venturi Effect systems in regards to Gas combustion, so to me the simplest understanding is that a Venturi Effect is where a flowrate is constricted by the pipe size being restricted, or an orifice restriction.

To aid memory you might want to tap "Venturi" into google and search the "Images" since images are easier to remember than written explainations.