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Go Back   SailNet Community > General Interest > General Discussion (sailing related) > 100 lb of Lead Vs 100 lb of concrete
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Topic Review (Newest First)
04-22-2013 12:17 PM
downeast450
Re: 100 lb of Lead Vs 100 lb of concrete

I am going to have my next keel cast of gold so it doesn't create a bio hazard. It will be a very small boat!

down
04-22-2013 12:10 PM
SlowButSteady
Re: 100 lb of Lead Vs 100 lb of concrete

Quote:
Originally Posted by mad_machine View Post
...

Concrete ships are nothing new. The US was playing with them in WW1. There is the remains of one off of Cape May NJ. ...
There's also one in Capitola, CA (just south of Santa Cruz, CA).
04-22-2013 10:46 AM
Roger Long
Re: 100 lb of Lead Vs 100 lb of concrete

Explanation of all the above and more at:

Stability of Boats and Ships



Buoyancy is imaginary
04-22-2013 10:31 AM
mad_machine
Re: 100 lb of Lead Vs 100 lb of concrete

encapsulated in your keel... lead is not going to hurt you. Sanding it, touching raw lead, or cutting it without proper biohazard precautions would bring about lead poisoning.. and that can take years to get over.

Concrete ships are nothing new. The US was playing with them in WW1. There is the remains of one off of Cape May NJ. The Atlantis. It was mothballed after the war and towed to Cape May to make a ferry terminal. Unfortunately it broke loose in a storm before it could be sunk in place and was blown ashore at Cape May Point where it has slowly deteriorated and sunk deeper into the sand.

Almost 100 years after she was launched, there is not a lot left.. but a lot more than if she had been built of steel
04-22-2013 10:17 AM
zeehag
Re: 100 lb of Lead Vs 100 lb of concrete

you guys are failing to mention th e lead as a biohazard. will raise your lead levels in blood and cause learning curve disorders--and agression increases.

concrete doesnt do that. is easier to obtain as it isnt a biohazard substance and wil not create learning curve dysfunction.

just add stuff to it as did the taiwanese when they made many boats with concrete keels--they added steel, lead chunks, whatever was in the yard that could be added.
04-22-2013 10:06 AM
mad_machine
Re: 100 lb of Lead Vs 100 lb of concrete

right... mass never changes. Even in the Microgravity of earth orbit. You could get a ton of weight moving slowly in orbit by yourself (if you had something to push against or an EVA thruster pack) but it could also crush you very slowly if it trapped you between it and something.
04-22-2013 08:04 AM
Minnewaska
Re: 100 lb of Lead Vs 100 lb of concrete

Cool. If weight = mass x gravity, then an object does not weigh less when buoyed, it just appears to.
04-22-2013 07:40 AM
SlowButSteady
Re: 100 lb of Lead Vs 100 lb of concrete

Quote:
Originally Posted by Minnewaska View Post
Here's one for the engineers.

Does an object really weigh less once submerged? That implies an elimination of mass. It is subject to an opposing force (buoyancy). Does an aircraft weigh less when airborne because of lift?

Having taught deep wreck diving when I was younger, I get the concept being discussed. Just a question of technical clarity on whether something actually weighs less. I don't think so. I think it's really a case of opposing forces that makes the object appear to weigh less.
It all depends on what definition one is using: mass, weight, or apparent weight. Mass is a measure of the inertia of an object. Weight is the force an object exerts in a gravitational field (weight = mass x gravity; we talk about an object "weighing" so many kilograms, but in fact the proper units of weight are newtons). For a body at rest, apparent weight takes buoyancy into account. The buoyancy provided by air is small enough, and gravity is constant enough, that our operational use of apparent weight to estimate mass is sufficient for most applications. However, as this thread demonstrates, there are exceptions.
04-22-2013 07:23 AM
Minnewaska
Re: 100 lb of Lead Vs 100 lb of concrete

Here's one for the engineers.

Does an object really weigh less once submerged? That implies an elimination of mass. It is subject to an opposing force (buoyancy). Does an aircraft weigh less when airborne because of lift?

Having taught deep wreck diving when I was younger, I get the concept being discussed. Just a question of technical clarity on whether something actually weighs less. I don't think so. I think it's really a case of opposing forces that makes the object appear to weigh less.
04-22-2013 02:15 AM
Siamese
Re: 100 lb of Lead Vs 100 lb of concrete

Okay, I'm cancelling my concrete order.
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