Displacement - Missing element in calculation

[Derek Warner]

Oli - there appears to be an element missing in the posted file - and that is relative to the total
surface area of the body of water that the hovercraft is acting upon

If we considered a model hovercraft 300mm x 300mm square and placed it in a water tank
400mm x 400mm square, the weight of the model will displace the equivalent weight of water
therefore lowering the vessel in the tank by raising the water level surrounding the model

Think of a 100,000 ton capacity vessel tying up in a port - when 100,000 tonnes are loaded into
the vessel, the vessel displaces that same 100,000 tonnes on the surface of the water, and apart
from any land locked sea, the increased water level would be distributed evenly over the earths
oceans etc

However if the 100,000 tonne capacity ship only had 50 mm of clear water on each side and a berth
deep enough and land locked the ship would be sunk due to the increasing height of water

So from the old adage "that a ship will float as long as the water is deep enough" - is not correct

This is a very interesting subject and have posted a CC to paddleducks for interest - regards Derek

[KC6OLD]

Wait a minute!
I always thought, and was taught that, if you could build a container shaped
just like the hull, (But just a tad larger) that a ship would float in
whatever amount of water it takes to fill the space between the hull and the
container to the "normal" water line! the boat/ship floats because it
displaces an amount of water equal to the weight of the boat/ship!
Dave, Confused in the climatic wonderland

[Derek Warner]

on Sunday, January 20, 2002 Oliver Mertschat wrote

Well, actually the water level is raised by anything dropped in the
water, but if you think twice about your narrow harbour example, how
will you get your 100.000 tonne vessel into it
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Thanks Oliver - I have previously acknowledged that I have zero knowledge with hovercraft,
however my questions and thoughts relate to the basic & fundamental laws of physics for
any water craft

I fully understand that we could not berth a 100,000 tonne capacity vessel with 50mm per,
(Stbd, Port, Fwd & Aft) and place the vessel in a land locked constraint - however if we could
and loaded 100,000 tonnes into the vessel, the displaced (water) would sink the vessel
(again on the premise of sufficient depth of water under the hull and height of containment etc)

regards Derek

[Derek Warner]

So from the old adage "that a ship will float as long as the water is deep
enough" - is not correct
>>>>>>>>>>>>>>>>>
on Monday, January 21, 2002 Gordon McAndrew wrote
>>>>>>>>>>>>>>>>>
Your thought experiment has holes in it

If an item floats it floats no mater where you place it. Closed or open
container makes absolutely no difference. Try that with anything that
floats. If you make the container small enough in relation to the size of
your boat you will see that as you add weight to the boat and the water
level rises you can actually have the boat float higher in relation to the
world as you add weight because the water level is rising.
>>>>>>>>>>>>>>>>>>>>
Sorry Gordon

You are absolutely correct - my only plea is that at the time of writing the original text was post
celebrations of my daughters wedding on Saturday - but judging from the content, it would suggest
something I ate during the wedding breakfast did not agree!

It was not an attempt to right new laws on buoyancy or displacement

regards Derek