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Pirates of the Caribbean - Underwater boat logical or not?

The stunt they pulled is possible... but.. the boat should have been heavier then the water displacement, this would have also ment that the boat wouldnt float.. kina nasty aint it. they tought me all about it at school with ships stability classes.. btw.. its good to be back.. now i hope there's anyone remembering me LOL <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/icon_wink.gif" style="vertical-align:middle" emoid=";)" border="0" alt="icon_wink.gif" />
 
Saw dis same stunt done last night watchin' de ol' 1952 movie, Crimson Pirate! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/icon_wink.gif" style="vertical-align:middle" emoid=";)" border="0" alt="icon_wink.gif" />
 
<img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/w00t.gif" style="vertical-align:middle" emoid=":woot" border="0" alt="w00t.gif" /> AHHH, Burt Lancaster! Great old movie, wish I'd caught it. I'd forgotten about that scene, LOL! Good spotting, Fred Bob! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/keith.gif" style="vertical-align:middle" emoid=":keith" border="0" alt="keith.gif" />
 
Still i doubt the whole thing, keeping a boat underwater?
even if you would fill it all up with water and tip it it would still float.
as I said before, the weight of the water displaced can not match up to the weight of the boat! If the boat would indeed be havier then the displaced water it would sink anyway... tipped or not. and than the whole concept of any boat is kina gone I think. AND! who ever saw anyone walk underwater.. I tried it lots of times and its inposible as we do float is some kind of way. and keeping the boat underwater would be faaaar to impossible if you cant even keep yer own body down. <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/dunno.gif" style="vertical-align:middle" emoid=":shrug" border="0" alt="dunno.gif" />
 
As I said before, negative buoyancy is the key. Otherwise, yes, the boat and all would float... But I've seen plenty of boats on the ocean floor to know that even if they DO float, they CAN sink! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/boom.gif" style="vertical-align:middle" emoid=":boom" border="0" alt="boom.gif" /> <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/laugh.gif" style="vertical-align:middle" emoid="xD:" border="0" alt="laugh.gif" />

I was in on a `ship-building` project while I lived in Chicago, and they were making the hull out of FerroCement - And of course the question on everyone's lips was, "Will it float?" Yep... Boats can be incredibly heavy and still float... <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/yes.gif" style="vertical-align:middle" emoid=":yes" border="0" alt="yes.gif" /> <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/par-ty.gif" style="vertical-align:middle" emoid=":cheers" border="0" alt="par-ty.gif" />
 
I think I saw that on Letterman, Lady Cat. <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/yes.gif" style="vertical-align:middle" emoid=":yes" border="0" alt="yes.gif" />
I guessed wrong too! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/oops3.gif" style="vertical-align:middle" emoid=":eek:ops2" border="0" alt="oops3.gif" />
 
<!--quoteo--><div class='quotetop'>QUOTE</div><div class='quotemain'><!--quotec-->they were making the hull out of FerroCement  <!--QuoteEnd--></div><!--QuoteEEnd-->
Isn´t there an island off Baltimore near which old ships from the First World War that were made of cement have been abandoned? I think I read about it once.
 
What Jack & Will did was theoreticaly possible but physically impossible.
The Diving Bell is a good example & works on exactly the same principle. If the air can't get out, then the water cant get in. The deeper the diving bell goes, the higher the water pressure gets, so the smaller the air pocket gets as the air compresses. Turn a seaworthy boat `upside-down` so that air is trapped inside & it will float, (no matter what it is made of).
However, If you take an empty 20litre/`4-5` gallon drum & try to hold it under water (sealed), you can't do it by yourself. Remember, the drum is made of steel, not the most unsinkable of materials. The same sort of principle keeps 200,000 tonne Ore Carriers afloat. Now take a piece of dead wood & throw it into a pond/creek/`what-ever`. 99 times out of 100 it will float.
A wooden ship wasn't easy to "sink" in the terms we think of. Naval battles in the days of the ancient Greeks & Romans were won & lost on the point of a Sword or a Pike & the ship taken. The ships of the day didn't have the weight of iron in guns, & copper sheathing etc. to "sink" them. Imagine swimming around above a sunken 3 decker when one of her spars breaks loose at 100 fathoms.
There's no way 2 men could hold that vollume of air under water no matter what the boat weighed. They just couldn't get it under water, with or without a crab pot on one foot.
It works in Hollywood!

Cheers, Dusty.
 
<img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/mybad.gif" style="vertical-align:middle" emoid=":facepalm" border="0" alt="mybad.gif" /> Neutral (not negative, really) buoyancy! It's how submarines work!

<!--quoteo--><div class='quotetop'>QUOTE</div><div class='quotemain'><!--quotec-->Buoyancy is the force which tends to keep an object afloat in water or any other liquid. When an object is immersed in a liquid, the liquid exerts pressure from all directions on the external surface of the object. The deeper the object is immersed in the liquid, the greater is the pressure exerted against its surface. Also, the upward pressure exerted by the liquid against the lower surface of the object is greater than the downward pressure against its top. If the immersed object weighs more than the liquid it displaces, it is said to have negative buoyancy. Such an object sinks. If the object weighs less than the liquid it displaces, the object is said to have positive buoyancy. Such an object floats, or if it is thrust under the surface of the liquid, it rises. When both the object and the liquid it displaces weigh the same, the object is said to have neutral buoyancy. If such an object is submerged, it remains submerged unless it is acted upon by an outside force.<!--QuoteEnd--></div><!--QuoteEEnd--> (from a site on submarines)

Combined weight of Jack and Will, plus weight of boat, minus the pressure of air pushing boat up and TEMPERED by the fact that the boat was not *quite* full of air and perhaps also tempered by the extra molecular buoyancy of salt water, and the boat might have been made out of green wood rather than dead wood or made of a type of wood that is QUITE heavy - well, there are a lot of factors - but it IS possible! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/yes.gif" style="vertical-align:middle" emoid=":yes" border="0" alt="yes.gif" />

Here also is something on boat buoyancy:
<a href="http://www.`glen-l`.com/weblettr/`webletters-7`/`wl55-flotation`.html" target="_blank">http://www.`glen-l`.com/weblettr/w...-flotation.html</a> <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/par-ty.gif" style="vertical-align:middle" emoid=":cheers" border="0" alt="par-ty.gif" />

Yes, it's Hollywood. But I firmly believe it is possible! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/bookish.gif" style="vertical-align:middle" emoid=":mm" border="0" alt="bookish.gif" />
 
De scientist in <b><i>Crimson Pirate </i></b>explains it purty well! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/icon_mrgreen1.gif" style="vertical-align:middle" emoid=":cheeky" border="0" alt="icon_mrgreen1.gif" /> Ye must have jus' de right amount o' trapped air, not too much an' not too little! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/yes.gif" style="vertical-align:middle" emoid=":yes" border="0" alt="yes.gif" /> Ye actually want de capsized boat tew be heavy enough such dat de men only has tew lift it a little an' push it along! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/icon_wink.gif" style="vertical-align:middle" emoid=";)" border="0" alt="icon_wink.gif" /> But it might only have a couple o' minutes o' breathable air! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/ohmy.gif" style="vertical-align:middle" emoid=":eek:" border="0" alt="ohmy.gif" />
 
I still don't get it...

How was the air trapped under the boat if the boat was not touching the ground? The way I imagine it is with a cup. When you stick a tissue at the bottom of a cup, flip it over and stick it in water, the tissue will not get wet if you make the cup touch the ground trapping the air. What they were doing was carrying the boat over their heads, I don't see how the air would get trapped?
<img src="http://overlee.com/boat.jpg" border="0" class="linked-image" />

this is the image I see.. how would air get trapped? Looks like there's a huge opening for the air to get out an water to get in

Cup example where air would in fact get trapped

<img src="http://overlee.com/cup.jpg" border="0" class="linked-image" />

Some water does get in the cup, but air is trapped on top, because cup prevents water from getting in + air from getting out

I Just need some clarification, I guess.
 
Dis be a pro'lem in hydrostatics, matey! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/unsure.gif" style="vertical-align:middle" emoid=":?" border="0" alt="unsure.gif" /> At de bottom edge o' de boat (or bottom edge o' de cup) de pressure on de outside must equal de pressure on de inside:

Pressure Outside = Density o' Water x Depth o' Water Outside x A Constant

Pressure Inside = (Density o' Water x Depth o' Water Inside x A Constant) + (Density o' Air x Depth o' Air Inside x A Constant)

Onct ye turn yer boat o'er (or yer cup), water will enter de boat (or de cup) from beneath until de pressure on de outside an' de pressure on de inside, right at de lower edge, become balanced! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/icon_mrgreen1.gif" style="vertical-align:middle" emoid=":cheeky" border="0" alt="icon_mrgreen1.gif" />
 
Aye, CapitainDams! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/icon_mrgreen1.gif" style="vertical-align:middle" emoid=":cheeky" border="0" alt="icon_mrgreen1.gif" /> Just a few minutes o' good breathin' air perhaps! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/unsure.gif" style="vertical-align:middle" emoid=":?" border="0" alt="unsure.gif" />
 
<!--QuoteBegin-coeus+May 2 2005, 12:47 AM--><div class='quotetop'>QUOTE(coeus @ May 2 2005, 12:47 AM)</div><div class='quotemain'><!--QuoteEBegin-->I still don't get it...

How was the air trapped under the boat if the boat was not touching the ground? The way I imagine it is with a cup. When you stick a tissue at the bottom of a cup, flip it over and stick it in water, the tissue will not get wet if you make the cup touch the ground trapping the air. What they were doing was carrying the boat over their heads, I don't see how the air would get trapped?<!--QuoteEnd--></div><!--QuoteEEnd-->

Air gets trapped because it cannot get away. It is lighter than water and wants to rise upwards, but that's where the bottom of the boat blocks it.

You CAN trap air into a cup even if it doesn't touch the bottom. In fact, that's how many small (low depth) exploration subs work - they have a hatch on the bottom of the vessel that is open to the sea/ocean and through which the divers can just pop in and out as they want (with no necessity to open and close the hatch every time.
 
Maybe Jack Sparrow, or Will, were familiar with the work done by Cornelius Drebbel and William Bourne! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/bookish.gif" style="vertical-align:middle" emoid=":mm" border="0" alt="bookish.gif" />

<a href="http://www.dutchsubmarines.com/specials/special_drebbel.htm" target="_blank">http://www.dutchsubmarines.com/specials/special_drebbel.htm</a>

It's not clear to me how they steered... <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/keith.gif" style="vertical-align:middle" emoid=":keith" border="0" alt="keith.gif" />
 
Yeah, like was said before, next time you're washing the dishes, turn a glass upside-down and push it under water. You will notice the air stays trapped there whether it's touching the botom of the sink or not.

Actually the first underwater "submarine" or "scuba gear" was a diving bell, basically a heavy bell turned upside-down like the glass in the dish sink.
<img src="http://www.adventurediveandsnorkel.com/3e9c2ce0.jpg" border="0" class="linked-image" />

Of course the boat in POTC would have to weigh more than the bouyancy of the air trapped underneath, and that is where it wouldn't have actually worked. The upside-down boat would have probably floated to the surface because I doubt the wood was haevier than the bouyancy.


Still, ya, it's just a movie, like are the skelletons logical? <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/laugh.gif" style="vertical-align:middle" emoid="xD:" border="0" alt="laugh.gif" />
 
<!--QuoteBegin-Admiral8Q+May 3 2005, 08:42 PM--><div class='quotetop'>QUOTE(Admiral8Q @ May 3 2005, 08:42 PM)</div><div class='quotemain'><!--QuoteEBegin-->Yeah, like was said before, next time you're washing the dishes,<!--QuoteEnd--></div><!--QuoteEEnd--> <img src="http://www.ganotherapyusa.com/extras/pink.gif" border="0" class="linked-image" />

I can just SEE a buncha scurvy pirates like us WASHING THE DISHES! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/laugh.gif" style="vertical-align:middle" emoid="xD:" border="0" alt="laugh.gif" />

<!--QuoteBegin-Admiral8Q+--><div class='quotetop'>QUOTE(Admiral8Q)</div><div class='quotemain'><!--QuoteEBegin-->The upside-down boat would have probably floated to the surface because I doubt the wood was haevier than the bouyancy.<!--QuoteEnd--></div><!--QuoteEEnd-->And that's where the art of filling the boat with air comes in - the weight of the men, coupled with the weight of the boat (even "buoyant" wood will sink, especially if it's green wood or a dugout like what that boat appeared to be).

I can't believe we're still discussing this! <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/mybad.gif" style="vertical-align:middle" emoid=":facepalm" border="0" alt="mybad.gif" /> <img src="http://www.piratesahoy.com/forum/style_emoticons/<#EMO_DIR#>/laugh.gif" style="vertical-align:middle" emoid="xD:" border="0" alt="laugh.gif" />
 
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