• Post Reply Bookmark Topic Watch Topic
  • New Topic
programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other Pie Elite all forums
this forum made possible by our volunteer staff, including ...
Marshals:
  • Campbell Ritchie
  • Tim Cooke
  • paul wheaton
  • Jeanne Boyarsky
  • Ron McLeod
Sheriffs:
  • Paul Clapham
  • Liutauras Vilda
  • Devaka Cooray
Saloon Keepers:
  • Tim Holloway
  • Roland Mueller
Bartenders:

How does a sail work?

 
Ranch Hand
Posts: 64
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
During a recent (and first) sailing trip, I was struck with how the sail can be positioned to make the boat travel *upwind*.

Does anyone know the physics of how this works? Some diagrams would be excellent
 
(instanceof Sidekick)
Posts: 8791
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
It is amazing isn't it? I marvel at how such complex physics were developed over time. Here are some pictures:

http://www.phys.unsw.edu.au/~jw/sailing.html
 
Sheriff
Posts: 4313
Android IntelliJ IDE Java
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
this sail trim simulator is REALLY cool.
 
Mani Venkatesan
Ranch Hand
Posts: 64
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator

Originally posted by Jessica Sant:
this sail trim simulator is REALLY cool.



It is indeed really cool!
 
Ranch Hand
Posts: 162
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
How do physsicists think?Do they work on maths and all equations and build or build first and arrive at equations?
Regards
Dharam(Still awake)
 
author
Posts: 4354
45
jQuery Eclipse IDE Java
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator

Originally posted by Dharam Singh:
How do physsicists think?Do they work on maths and all equations and build or build first and arrive at equations?



They build first and ask a mathematician to fill in the missing pieces after they crash a few times.
 
Desperado
Posts: 3226
5
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Real physicists are better than mathematicians. Although I must admit that mathematicians are a close second (only to Physicists). Witness Isaac Newton, God made Man.

After those two, come chemists and then biologists in that order. And then everyone else.

Accountants and used car salesmen come dead last in the Absolute Totem Pole of importance in this Universe.

And God said: "F = mA and E=mc2".
 
Tony Alicea
Desperado
Posts: 3226
5
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
BTW, I have a "diploma" from the Annapolis Sailing School certifying that I took a sailing class that lasted 4 weeks in the summer of 1989 in that great sailing town (the sailing capital of the eastern United States).

To prove ourselves, my brother and I rented a 25' sailboat with no engine whatsoever, and took it out of the dock, sailed into the Chesapeake Bay and then came back to the dock (remember I said no engine) and successfully docked in w/o any problems.

Back to the original question, the instructor, who had sailed all his life and was very good a it, confessed during the first hour of the in-classroom classes that he did not know the physics of (for example) how can you sail into the exact opposite direction of where the wind is blowing from.
 
author
Posts: 23958
142
jQuery Eclipse IDE Firefox Browser VI Editor C++ Chrome Java Linux Windows
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
This is the same physics for an airplane. The shape of the wing causes the airflow across the top and bottom to travel at different speeds, causing a pressure differential.

Henry
 
Ranch Hand
Posts: 126
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
So Dont let the kids miss this one.

[link]

[shortened really long link - Jim]
[ January 15, 2006: Message edited by: Jim Yingst ]
 
Wanderer
Posts: 18671
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
[Henry]: This is the same physics for an airplane. The shape of the wing causes the airflow across the top and bottom to travel at different speeds, causing a pressure differential.

Mmmm, partly, but it sounds like the Bernoulli effect is only part of it - and the article describes this as a secondary effect. The primary issue seems to be that the keel acts to constrain the motion to be in a particular line, and by adjusting the angle of the sail relative to the wind and to the keel direction, a component of the wind force against the sail will be directed in the keel direction. The Bernoulli effect would help this, but I'd think tacking would be possible even if the shape of the ship's sail did not utilize the Bernoulli effect at all.
 
Jim Yingst
Wanderer
Posts: 18671
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
[Dharam]: How do physsicists think?Do they work on maths and all equations and build or build first and arrive at equations?

Some physicists are theoretical physicists, meaning they start with the equations, while others are experimental, meaning they are more likely to build something and see what happens. That's an oversimplification, but probably good enough for this discussion.

In the case of sailing, I imagine most of the techniques were probably worked out by trail and error long before anyone tried applying any equations to explain the results.
 
Do the next thing next. That’s a pretty good rule. Read the tiny ad, that’s a pretty good rule, too.
Smokeless wood heat with a rocket mass heater
https://woodheat.net
reply
    Bookmark Topic Watch Topic
  • New Topic