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Author Topic:   The Ark - materials, construction and seaworthness
Member (Idle past 2454 days)
Posts: 663
Joined: 11-17-2005

Message 127 of 231 (328682)
07-03-2006 8:38 PM
Reply to: Message 123 by iano
07-03-2006 4:09 PM

Re: Whatever floats your boat
semi-solid sludge from animal waste - this is far easier to pump than water

I don't understand, if it's not a water pump what kind of pump is it? Like a bicycle pump, something that turns force into air-pressure? That's insane, the substances that the components have to made out of weren't even invented, the damned dinosaurs the substances are derived from wouldn't even have drowned yet. Reeds and pitch and some kind of notched ramrod wont do it, you just end up with tarry shrapnel everywhere. Air pressure is much MUCH harder to manage than water pressure.

The whole reason the standard water-pump got invented in the first place is that water has a strict obvious compression limit. When you push it hard enough it suddenly pushes back even harder. This is the same principle that causes soda cans in the freezer to bust open. It's how a plunger works! So we can vaguely allow that the primitive mind might have some understanding of these principles. It's the sort of thing that people with even exceptionally low IQs can learn in special ed and eventually make a career out of as say, a plumber's helper.

So why can't you get it yourself? How old are you? Are you saying that low-flow toilets work better than the old standard flush? Are you saying that it's easier to siphon fresh dung than gasoline? I have to assume you have never had a fish tank even.


Anyway, those of you of the 4004 inclination who have been optimistically supporting this travesty because anything is better than no answer, obviously the real trick will have to be the gopher wood. It's called that because it has visible holes in it, it's a very large porous wood, something like grass only towering tree size, maybe a super-bamboo with extra-spongey qualities and possibly some trick action such as has been known to develop among other water-sensitive plants. Even among normal modern porous plants you get this basic effect, the pores let water in but as the wood gets soaked it expands and closes the pores. Only with the gopher wood this will have to be a whole primary specialization, it will have to be a big pump tree basically.

You cut the wood and build your boat so that the outer barky part is facing out and the inner livewood part is facing in. You seal the places where it joins with your pitch and nevermind the leaks. There's going to be water running down and pooling up in the bottom of your boat continually. Even though the pores close when they are wet a certain amount of water gets through, don't worry about it. It pools up at the bottom of the boat along with all the flotsam and jetsam you care to include in the stream. Dung will be fine.

Anyway periodically at the sides and even the bottom, as a result of the differences in the motion of the individual points comprising a floating, rocking rolling object, there will be points where the water pressure will suddenly rapidly decrease for individual pores. Imagining being a little downward-leaning pore on the side of the boat when the part you are at is moving rapidly upward compared to the water, at the top of each arc. Anyway if there is water pooling up there in a trough on that side of the boat, there might even be a point where the pressure inside is actually greater than the pressure outside.

At this moment the magic gopher wood pore bursts back open to full size briefly, releasing as much liquid and particles as it can, before slamming shut again as the stuff resoaks the pore from the inside out. Down at the very bottom this will happen even more often, it wont depend on slant and kinds of linear motion, every time the boat rocks back and forth with this ever-moving bog sloshing around in it, there will be points where individual pores reverse briefly due to greater pressure within than without.

Sadly, all the gopher wood in existence had to be used to make the boat. And that's why gophers don't live in trees like the other squirrels.


This train is a dead end for you

If there's anyone of a scientific bent still looking longingly at wave-power for a free-floating object, here's the deal. Any number of patents have been applied for and received using this principle. They always work fine for the scale model. My favorite is a dealie called the "water-wings" that flap up and down on each side of the little boat and thereby generate enough power to turn a little prop in the back that will send the model faster and faster across any public pond until it either gets to the other side, tears itself apart, or else reaches a maximum speed arranged by the designer with some sort of auto-brake.

Sadly, all the little model wave-driven engines of every kind (including the neat rocking-pack generator recently developed to help our students in the extended financial-aid program there keep their little flashlights charged while they run screaming through the desert) they all depend on using a given amount of surface to affect a given amount of mass. That means that, like people and animals, they dont scale properly.

Let's look at the water-wings again. We don't need a big closed zoological battleship to start with, a rowboat will be fine. Our scale model is 3 feet by 2 feet by 1 foot high. The wings on each side are 1 foot by 1 foot. And it works fine! We will allow that such a thing could pump itself out in good weather. We will ignore the actual functioning of the pump itself entirely, it can be a very modern bicycle pump. The generator that transfers the energy from the wings to the little boat can be a bicycle wheel. It doesn't matter. We will allow that the 1 square foot surface of these wings gets from the water enough force to keep 6 cubic feet of little boat tolerably dry inside. We will allow the 1 square inch surface of the plunger in the bicycle pump is sufficient to properly apply this force to the water and get it completely out of the boat. Whichever details we start with, this happens to us.

When we make our little boat twice as big, it is now 6 feet long, 4 feet wide, 2 feet high. We could get in and row! our wings are 4 square feet, our pumpbit is 4 square inches, but our volume is now 48 cubic feet. If our boat weighed ten pounds before, it now weighs not 20 pounds, not 40 pounds, but 80 pounds! In order for our wings to parlay the power to do the pumping they need to be not just 4 square feet but 8! They will have to be twice as long again, instead of flat square things they are long rectangular things sticking out the side. And the pump itself has to be bigger again also so that total surface will make 8 square inches, to push the water, the 48 cubic feet of water there in the 80 pound boat trying to thrash around harder and harder to keep dry. With the wings sticking out there our width is actually greater than our length, and we have only doubled once so far.

Let's make it 12 feet long, 8 feet wide, 4 feet high! Now we need 64 square feet of surface for our wings, 64 square inches of push in our pump, and our boat, separate from the long floaty wings and the enormous throbbing pump, weighs 640 pounds.

What it comes down to is that if your floaty-motor gets to be much bigger than a breadbox it gets out of scale to perform whatever its function is.

This message is a reply to:
 Message 123 by iano, posted 07-03-2006 4:09 PM iano has not yet responded

Replies to this message:
 Message 129 by Coragyps, posted 07-04-2006 5:53 PM Iblis has not yet responded

Member (Idle past 2454 days)
Posts: 663
Joined: 11-17-2005

Message 163 of 231 (330645)
07-10-2006 10:05 PM
Reply to: Message 147 by johnfolton
07-09-2006 9:08 PM

This link was a lot of fun!


In the ancient Roman Empire boiling birch bark and extracting the resins yielded a glue-like tar. This resin was used to glue together broken ceramic pots.

Birch bark tar chewing gum was also used thousands of years ago in the Neolithic times as a cleaner for teeth ...

This ancient “super­glue” was detected on remnants of two tools that were unearthed in Germany. The site called Koenigsaue, in the foothill of the Harz Mountains revealed the technical abilities of the people that produced the glue. The glue had been used to secure flint implements to wooden handles.

One of the finds showed an impression of a fingerprint on the surface of the pitch, which was prepared by heating birch bark to between 340-400°C. Lower temperatures would not allow the resin in the wood to melt and be extracted. If the temperatures were too high this would burn the tar that had been extracted from the birch and render it unusable. This required a large amount of intellectual and technical know­ledge.

“The very fact that birch bark pitch was identified [in the artifacts] already proclaims the intellectual and technical abilities of the Neander­thals.

Neanderthals used it for chewin' gum!
That's how they proved they weren't dumb!
(gopherwood, gopherwood)
The Romans used burnt birch to make it!
And bugs in amber kinda fake it!
(gopherwood, gopherwood!)
Think steel is strong? Well this is stronger!
Think your boat's long? Well mine is longer!
(gopherwood, gopherwood!)
Too much water? It can pump it!
Polyploidal species? It can hump it!
(gopherwood, gopherwood) ...

riVeRraT writes:

But if someone makes a scale model of the ark, and applies sclae forces to it, and it survives, doesn't that just say that it was possible?

Nope, not at all, I sort of covered this already though not in so many words. Boats use surface to support mass. When you double the size of something, that's 8 times as much mass but only 4 times as much surface. No matter how nice it floated originally, you double it a couple of more times and it will sink for sure.

Larger ships use a whole different strategy to float involving distribution of density. Take a little scale model of the Nimitz made of comparable materials and put it in the water. It sinks like a rock. It isn't big enough for the amount of air / empty space / whats left when we throw ballast out / empty air to offset the weight of the metal. *Anyone who actually understands buoyancy and wants to improve on my gross overgenuflections, step right up!

Basically if your scale model works really great your boat is never going to be anything except a blueprint that's obviously been scaled all wrong.

This message is a reply to:
 Message 147 by johnfolton, posted 07-09-2006 9:08 PM johnfolton has responded

Replies to this message:
 Message 164 by johnfolton, posted 07-11-2006 12:27 AM Iblis has not yet responded

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