Sunday, March 23, 2014

Re: [Electric Boats] Re: electricboats

 

Speaking as an engineer, sailor, and electric boat owner - your comment is interesting but it is a stretch to make it relevant to the "rule of thumb" type of calculations in this energy per displacement discussion. 
While working to develop a conceptual grasp of energy requirements we have been talking a severalfold difference in thrust energy here - so a ten percent difference in mass units doesn't much matter at this point. 
Once we agree on the concept we can get to the details. That's a useful engineering trick for problem solving.
    Roger L. 
 


On Mar 23, 2014, at 1:51 AM, Kerry Thomas <kjthomas@ihug.co.nz> wrote:



Hi
 
I'm afraid long tons are only used in the US and a couple of other backward countries.
 
The world uses metric tons for ship and boat displacement.
 
Working out stability and other nautical calculations in pounds per cubic foot of seawater and all the other imperial units is long gone.
 
A metric ton is 2206lb
 
 
 
Regards
 
Captain Kerry Thomas
 
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Oftugs@earthlink.net
Sent: Sunday, 23 March 2014 2:41 p.m.
To: electricboats@yahoogroups.com
Subject: [Electric Boats] Re: electricboats
 


Displacement tonnage is measured in long tons, 2240 pounds per ton. It is the international standard as applied to ships and boats by maritime administrations and class societies. It is the measure used when calculating load lines and stability. 

The "short ton" of 2000 pounds is not a nautical measure. 





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