# The Physics of Sailing

Northern California has a storied, 500-year history of sailing. But despite this rich heritage, scientists and boat designers continue to learn more each day about what makes a sail boat move. Contrary to what you might expect, the physics of sailing still present some mysteries to modern sailors.

Learn more about the physics of sailing and this video with the Producer’s Notes.

The Physics of Sailing 12 March,2016

• uri neta

want to start course of sailing physics for 15 age children from poor families and to get them drive sail boats

• Zoobernarf

Great video! Excellent relation to Bernoulli principal that is done much better than other online sources.

• ThisOldSalt

Bernoulli’s principle has far less to do with a sailboat’s ability to move than newton’s 3rd law, and is often the incorrect answer given to describe sailing and flying. If Bernoulli was an appropriate description of the physics of airfoils, it could explain inverted flight and downwind sailing. The familiar curved shape of an airfoil functions to reduce drag. It is the flatter underside of of the wing, an the windward “scoop” of the sail that produces lift.

• digitalclips

Actually you are incorrect. Both Newton’s 3d Law and Bernoulli’s principle are at play. If sailing with the wind then yes, Bernoulli’s principle has little to do with things, however, if you are sailing at an angle then Bernoulli principle is describing the reason for the increase in pressure in the sail because of the reduced pressure over the leading, curved edge, this with the rudder creating an equal and opposite vector the resultant vector is forward. If you think of an airplane wing for a moment, there is no ‘wind’ pushing the plain up, it is the forward motion producing the lift due to Bernoulli’ principle. The video is extremely well done and very clear on all these points.

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• Ormond Otvos

Only spent two decades talking about sailboat physics with a NASA airfoil engineer, so I might still have this wrong, but he always finalized his explanation by emphasizing the change in momentum of the air particles induced by the foil. Worked really well for winning races by mentally integrating the foil underwater with the foils in the air. The video is exceptionally poor using streaming hydraulics in an incompressible fluid to explain the actions of a foil in a compressible gas. Redo this film, it’s misleading.

• Bob Noonan

I enjoyed the program except for a distortion of the history of sailing. In the program it was suggested that old time sailing vessels were always square rigged and that sailing into the wind (tacking) is a modern innovation. Fore-and-aft rigging and the ability to sail into the wind are very old innovations in human history. Arabs used fore and aft rigging (lateen sails) on their dhows. Fore and aft rigging were common on smaller boats in European history as seen in old paintinngs. There are the three, four, five and six masted schooners that were common workhorses in coastal maritime trade in the late 19th and early 20th century.; The intensive scientific research is new, but the rig is not.

• Paul Townsend

I run a learn-to-sail program and I hope none of our sutdents see this video. While some of it is correct, there is some highly misleading and just plain wrong material.

0) It misrepresents the history of sailing – boats have been sailing upwind using lift for thousands of years.

1) Blowing over a piece of paper does not demonstrate Bernoulli’s principle. This is a common misconception that is clearly refuted by peer-reviewed schollarly papers in Physics. (e.g. See Babinsky’s “How do Wings Work?” http://iopscience.iop.org/0031-9120/38/6/001/pdf/pe3_6_001.pdf ) Granted, this old-wives tale is often repeated in elementary school demonstrations, but it’s folklore and incorrect science. You shouldn’t be spreading it.

2) The program tries to explain lift using Bernoulli’s principle. While there’s nothing wrong with Bernoulli’s principle, it doesn’t do a very good job of explaining why sailboat sails and airplane wings develop lift. Bernoulli’s principle is one very small piece of a large mathematical theory that explains lift. Unfortunately, most attempts to explain lift using Bernoulli’s principle without the overall mathematical context (i.e. vector calculus, partial differential equations, boundary conditions, the Navier-Stokes equation, etc.) are either so confusing that few readers can follow them, or they are just out and out wrong. Often both. I’d say this program is both. Watching this program will do more to confuse novice sailors that to enlighten them.

3) at 7:30 one of the engineers interviewed says “…separated flow. That would be stall in the case of an aircraft. It would be a luffing sail on a boat.” This is exactly backwards – a luffing sail results from undertrimming the sail while separated flow (stall) comes form over trimming. I’m sure the engineer just misspoke, but had the editors had a clue about the material they were producing this would have been editod or corrrected. As is, it’s bad information.

4) The overall takeaway one gets from the program is that the physics of sailing is too complicated for most people to understand. That is not true. Granted, no one will get much out of this presentation because its very confused and convoluted, but there are simple, straightforward ways of explaining what makes a sailboat go.

In sum, this presentation has so many problems that I would discourage anyone from viewing it. The best thing you could do for science education would be to take it down.

• GP

The did say they only scratched the surface of sailing physics….

## Author

### Jenny Oh

Jenny is a long-time contributor to Bay Area Bites, KQED's popular food blog. She formerly worked as an Interactive Producer for the Science & Environment unit. Jenny graduated with honors from New York University’s Tisch School of the Arts Film and Television program and has worked for WNET/PBS, The Learning Channel, Sundance Channel, HBO and the University of California.

## Author

### Joan Johnson

Joan Johnson is an TV Associate Producer for QUEST. Joan got her start making science television back in 1998 when she joined the team at Sea Studios in Monterey, working as a researcher and production coordinator on National Geographic Television projects for 4 years. Following that she pursued a career in features and network television down in Los Angeles, working on seven full length feature films, three television shows and several pilots. Joan graduated in 1993 from U.C. Santa Cruz with honors in Biology, and spent several years working as a marine biologist, naturalist and SCUBA guide. Originally from San Francisco, Joan is thrilled to be home and working on QUEST, fulfilling a long-term goal of combining her interests in science and entertainment.

## Author

### Josh Rosen

Josh Rosen was the TV Series Producer for QUEST from 2007-2009. He is a senior writer and producer specializing in documentary series and factual programming. Over the last decade he's produced a wide range of non-fiction hours, covering everything from Antarctic expeditions to Civil War history. With a background in feature film, Josh spent four years working with legendary German filmmaker Werner Herzog on multiple documentaries, including the Emmy-nominated "Little Dieter Needs to Fly," "Wings of Hope," and "Klaus Kinski: My Best Fiend." His more recent projects are currently airing on the Discovery Channel, the National Geographic Channel, the History Channel, and worldwide through Granada Media and RDF Television.