• smfinley
  
  

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  Posted: Jul 07, 2010 - 12:26 PM

  Quote

  VERY SIMPLIFIED 225 lb sitting on the end of an 8' lever yields 225lb x 8' = 1800
  On the wire, lets assume his centre of mass is 4 feet further out, & he keeps the hull just on the water, horizontal for our purpose, we now have:
  225lb x 12' = 2700
  What force would it take on an 8' teeter totter to balance the 225 lb kid sitting 12' out?
  2700/8 = 337.5
  
  And you guys thought math & physics were boring

  
  
  EC your simplified answer looks very similar to mine from earlier yesterday also.
  
  
  

  Quote

  Another explanation, same answer as Steve.
  If you assumed an 8 foot beam, that your center of mass is 4 feet from your feet, and the boat is level..... You could take your weight x current distance from leeward hull / alternate distance from leeward hull. 225*12/8 = 337.5

  
  
  I think the real answer is to many engineers on one forum discussing boats. I am an Electrical Engineer so all these forces are over rated
  
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  Scott,
  ‘92 H18 w/SX wings
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  ‘96/‘01/‘14 Hobie Waves
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• MN3
  
  

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  Posted: Jul 07, 2010 - 12:39 PM

  sailing is easy...
  only 2 directions (upwind and downwind)
  and 2 things to do...sheet (in or out), steer (left or right)
  
  WHY oh WHY do we have to take a beautiful, fun, glorious sport and RUIN it, destroy its simplicity, turn it into something complex (Math) :)
  
  
  

  veryfastsailor

  I'm 6 feet 2 and weight 225 pounds. how much weight on the tramp is needed to have the same affect of me being out on the wire?
  

  
  NOw.. back to his question.. there is no "same affect" because as we know... moving the weight outwards fights the healing motion and therefor increases speed... so there is no "same affect". you might have the same resistance to the wind/sail/heeling motion but by moving your weight out.. you have an affect... more speed - right?
  

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• smfinley
  
  

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  Posted: Jul 07, 2010 - 04:29 PM

  Quote

  NOw.. back to his question.. there is no "same affect" because as we know... moving the weight outwards fights the healing motion and therefor increases speed... so there is no "same affect". you might have the same resistance to the wind/sail/heeling motion but by moving your weight out.. you have an affect... more speed - right?

  
  
  This gets interesting, and the math more complex (thanks for asking Andrew)..... Just for the sake of arguement, if 337lbs on the beam is the same as 225lbs on the wire. How does the extra 100+lbs on the boat impact performance? The two weights would have the same force to keep the boat level, but the extra weight will make it sit lower in the water and therefore more resistance and therefore travel slower.
  
  I think the simple answer to the "same affect" is 337lbs. However lots of assumptions that may or may not be correct. Since if sailing with the hull just out of the water, 225lbs on the wire will have a very similar affect on the angle of the boat as having 337lbs sitting on the beam. But yes Andrew there is no answer for a true "same affect".
  
  --
  Scott,
  ‘92 H18 w/SX wings
  ‘95 Hobie Funseeker 12 (Holder 12)
  ‘96/‘01/‘14 Hobie Waves
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• MN3
  
  

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  Posted: Jul 07, 2010 - 05:53 PM

  so your answer - "the simple answer to the "same affect" is 337lb"
  
  and you conclude that with - "But yes Andrew there is no answer for a true "same affect"
  
  so i am "simply" wrong
  yet "truthfully" correct?
  
  
  
  
  
  ...
  what is the air speed of an unladen swallow?

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• smfinley
  
  

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  Posted: Jul 07, 2010 - 07:05 PM

  I agree there is technically no "same affect" but for different reasoning then you.
  
  But I don't think the new member who started this was looking for a technical or mathematical "same affect" my guess is they wanted the simplied answer of roughly 337 lbs. However they are probably running away scared right now.
  
  --
  Scott,
  ‘92 H18 w/SX wings
  ‘95 Hobie Funseeker 12 (Holder 12)
  ‘96/‘01/‘14 Hobie Waves
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• MN3
  
  

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  Posted: Jul 07, 2010 - 09:27 PM

  i love that sailing is interesting on 1000's of different levels

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• smfinley
  
  

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  Posted: Jul 07, 2010 - 10:25 PM

  When I was in college I had a stranger on the beach come up to me and start explaining how he hadn't really sailed much, but since he was an engineer he knew how sailing worked and started to explain it to me. That was when I decided I wasn't going to be that errogant or annoying when I graduated (maybe it did or didn't succeed at that ....).
  I let him go on for a while until I explained I had been sailing for years and was also about be graduate and become an engineer, so those big words he was using didn't scare or impress me. It kind of shut him up.....
  
  But I completely agree Andrew if you want it to be sailing can be an excercise in mental thought. Or you can just be layed back and cruise, which I love having the option to do either.
  
  --
  Scott,
  ‘92 H18 w/SX wings
  ‘95 Hobie Funseeker 12 (Holder 12)
  ‘96/‘01/‘14 Hobie Waves
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• Edchris177
  
  

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  Posted: Jul 08, 2010 - 06:15 PM

  And all these years I thought electrical engineers were just glorified electricians
  
  after the first year of university light/electricity & magnetism I had so many right hand rules & left hand rules I could barely jack %&f!
  
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• golfdad75
  
  

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  Posted: Jul 08, 2010 - 07:16 PM

  Using Euler's law of trapeze physics you would need 876 lbs. Which is too much butt to carry on a beach cat. Therefore if you are sailing above the equator where the trapeze wire would rotate leeward i would suggest that you see Principal Benoulli and buy a monohull where it doesn't matter about the trap
  
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  Nacra 5.2
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