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 Boat Design Forums Does displacement scale?

#1
04-02-2010, 08:57 PM
 stonedpirate Senior Member Join Date: Nov 2009 Rep: 21 Posts: 315 Location: Australia
Does displacement scale?

Hello,

If i built a 10 foot boat that can carry 1000lbs, would a 1 foot scale model carry 100lbs?

Thanks
#2
04-02-2010, 09:12 PM
 kerosene Senior Member Join Date: Jul 2006 Rep: 239 Posts: 540 Location: Venice, Ca, USA
what do you think? just try to visualize it in your head...

If you scaled it only along length but came same width and height it would...

Area scales in power of 2 and volume in power of 3.

in your example 1ft boat will displace 1lbs.
#3
04-02-2010, 09:14 PM
 stonedpirate Senior Member Join Date: Nov 2009 Rep: 21 Posts: 315 Location: Australia
of course

Gee i'm dumb

I was trying to imagine a tiny boat with 100lbs of lead in it

Cheers
#4
04-02-2010, 10:02 PM
 pistnbroke I try Join Date: Jan 2009 Rep: 404 Posts: 1,386 Location: Noosa.Australia where god kissed the earth.
australian education system
#5
04-02-2010, 10:05 PM
 stonedpirate Senior Member Join Date: Nov 2009 Rep: 21 Posts: 315 Location: Australia
lol

i'd say mary jane
#6
04-03-2010, 11:50 AM
 messabout Senior Member Join Date: Jan 2006 Rep: 1043 Posts: 1,723 Location: Lakeland Fl USA
Pirate; To scale displacement take the scale ratio. In your example you reduced a 10 foot boat to 0ne foot. That is a 10 to one ratio. Raise the scale ratio to the third power. 10 x 10 x10 =1000 divide the displacement of the full sized boat by the scale ratio cubed...in this case you divided 1000 by 1000 and the quotient is one. Lets take a different case in which the the one thousand number does not occur twice. That is kind of confusing, so think of a ...16 foot rowing or sailing skiff. It might displace 360 pounds when occupied by one person. Let us build a model that is scaled to one and one half inches to the foot. That would be one eighth scale. so.....8 x 8x 8 = 512....divide....360/512 = 0.703 pounds. That is all the model could weigh in order to simulate the 16 footer. If you built the model to 3 inch to the foot scale then that would be a quarter scale or 4 to 1 model 4^3 = 64 .....360/64 = 5.625 pounds. The same rule applies when using the metric system of measurement.
#7
04-03-2010, 10:08 PM
 stonedpirate Senior Member Join Date: Nov 2009 Rep: 21 Posts: 315 Location: Australia
Thanks a lot Mess