Sail Flicking

[Delancey]

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 can’t use their body to propel the boat. While it seems like a little rocking couldn’t 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, we’d 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 sail’s 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 it’s 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

[UNCIVILIZED]

And this is news since which millenium, BC?

[Delancey]

Originally Posted by UNCIVILIZED

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.

[UNCIVILIZED]

Originally Posted by Delancey

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.

[Delancey]

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.

[thomm225]

Originally Posted by UNCIVILIZED

[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!