Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 04-09-2016, 04:37   #1
Registered User
 
Delancey's Avatar

Join Date: Oct 2011
Location: nondum cognita
Boat: sailboat
Posts: 3,061
Sail Flicking

Nicely explained courtesy of ****yeahfluiddynamics.tumblr.com


"If you watch some of the sailing in Rio, you may hear commentators mention sailors being penalized for breaking Rule 42. Broadly speaking, Rule 42 says that sailors canít use their body to propel the boat. While it seems like a little rocking couldnít make much difference, it turns out events have these rules for good reason.

One way to break Rule 42 is to perform sail flicking, demonstrated in the animation above. The sailor uses his or her body weight to roll the boat slightly, which causes the sail to flick. Aerodynamically speaking, weíd call this motion heaving. On the flexible sail, this unsteady motion decreases drag, allowing the boat to go faster. Done with the right frequency and amplitude, sail flicking actually makes the sailís drag become negative, thereby creating thrust!

The bottom image shows a visualization of the wake of a normal sail (left) and a sail being flicked (right). Both sails shed vortices in the downstream direction, but the flicked sail has much stronger vortices, indicated by the darker colors. In addition to giving a sailor an illegal boost, sail flicking creates more difficult, turbulent conditions for any competitors downstream, so itís restricted in many (but not all) sailing events. (Image credits: AP Photos; Reuters; National Solo, source; research and flow diagram credit: R. Schutt and C. Williamson, pdf)"

Tagged "sail flicking" | **** Yeah Fluid Dynamics
Attached Thumbnails
Click image for larger version

Name:	image.png
Views:	53
Size:	249.8 KB
ID:	130577  
__________________

__________________
Delancey is offline   Reply With Quote
Old 04-09-2016, 04:42   #2
Registered User
 
UNCIVILIZED's Avatar

Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Anything entertaining.
Posts: 3,513
Re: Sail Flicking

And this is news since which millenium, BC?
__________________

__________________

The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
UNCIVILIZED is online now   Reply With Quote
Old 04-09-2016, 04:56   #3
Registered User
 
Delancey's Avatar

Join Date: Oct 2011
Location: nondum cognita
Boat: sailboat
Posts: 3,061
Re: Sail Flicking

Quote:
Originally Posted by UNCIVILIZED View Post
And this is news since which millenium, BC?
Yes well, of course you are junkyard da vinci and master of all things sailing aren't you?

Did it ever occur to you that if you don't share information with the uneducated masses they will never learn? Did it ever occur to you that this might be new information to some of our less experienced members? Did it ever occur to you few who come to this forum looking for information about sailing have ever sailed a dinghy let alone raced one?


Seriously, thanks for your constructive contribution mr. know it all. At least your response wasn't TL;DR like they usually are.
__________________
Delancey is offline   Reply With Quote
Old 04-09-2016, 05:16   #4
Registered User
 
UNCIVILIZED's Avatar

Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Anything entertaining.
Posts: 3,513
Re: Sail Flicking

Quote:
Originally Posted by Delancey View Post
Seriously, thanks for your constructive contribution mr. know it all. At least your response wasn't TL;DR like they usually are.
Thanks for the nice judgements on things you've not bothered to read BTW.

And forgive my pre-caffeinated, misguided attempt at humor. I'd thought such propulsion techniques to be sailing 101. Evidently not.

BTW, pumping, or coordinated rocking of even a large boat, by the crew IS an effective means of propulsion, especially when used in conjunction with the rudder to scull. Though on a heavy, full keeled boat it'll work less well than on a fin keeler with a spade rudder. But in a flat calm, it works regardless. Even on a 30t pocket Maxi. Well, once.
Thus it's a handy tool for any & every sailor to learn.

As to the technique, at least when I was first reading about sailing as a kid, it was covered in most basic sailing texts. And on long -25deg F. Midwest winter nights at age 11, you've gotta have a hobby.
__________________

The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
UNCIVILIZED is online now   Reply With Quote
Old 04-09-2016, 05:26   #5
Registered User
 
Delancey's Avatar

Join Date: Oct 2011
Location: nondum cognita
Boat: sailboat
Posts: 3,061
Re: Sail Flicking

You're obviously a smart guy with a wealth of experience. All I am saying is know your audience. You can go a little overboard sometimes.

As far as humor goes, maybe try some of those smiley face things so people don't misunderstand you as being pithy and condescending.
__________________
Delancey is offline   Reply With Quote
Old 04-09-2016, 06:23   #6
Registered User
 
thomm225's Avatar

Join Date: Aug 2011
Location: Hampton Roads
Boat: 1974 Bristol 27
Posts: 2,745
Re: Sail Flicking

Quote:
Originally Posted by UNCIVILIZED View Post
[COLOR=navy]

BTW, pumping, or coordinated rocking of even a large boat, by the crew IS an effective means of propulsion, especially when used in conjunction with the rudder to scull. Though on a heavy, full keeled boat it'll work less well than on a fin keeler with a spade rudder. But in a flat calm, it works regardless. Even on a 30t pocket Maxi. Well, once.
Thus it's a handy tool for any & every sailor to learn.
yeah, the wind dropped on the racing fleet here about a month ago. Some of the smaller boats had left their outboards on the dock thinking the wind would hold long enough after the racing for them to return to their slips.

I was sailing back in also and ended up among them, but having raced/sailed for 15 years or so without and engine I motored in rather than wait.

Near my marina, a J24 could be seen using the method above. They had a hefty crew member on each side of the boat rocking it. Skipper handled the rudder and they enter the marina between docks A and B then made way to their slip which was all the way in and parked the thing.

The wind was about zero in there so their system worked perfectly!
__________________

__________________
thomm225 is offline   Reply With Quote
Reply

Tags
sail

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Sail Guam ? Sail Japan ? Lightfin Meets & Greets 24 14-02-2013 22:01
why is my mains charger flicking on and off? Shanaly Electrical: Batteries, Generators & Solar 2 08-05-2012 08:00
For Sale: Stay sail, Storm Sail, & Head Stay MoonlightSailor Classifieds Archive 1 18-12-2009 11:27
For Sale: Stay sail, storm sail, & head stay MoonlightSailor Classifieds Archive 0 31-10-2009 17:25


Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 10:07.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.