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EAA Young Eagles - Ask the Expert

Question :
Does an airfoil generate more lift in water since water is more dense than air?
 
Answer :
A very perceptive question. Since water is approximately 1,000 times more dense than air, moving the same airfoil through water does generate more lift.
It also generates more drag, which is why foils used for lifting in water (such as a hydrofoil boat) use thinner "waterfoils" to generate the lift needed. The "wings" are also quite a bit smaller than an airplane's, since the water is so much denser.

Here are a few Web sites I found that can explain the use of foils to make a boat go faster:
http://www.foils.org/index.html
http://lancet.mit.edu/decavitator/Basics.html
http://www.lesliefield.com/other_history/alexander_graham_bell_and_the_hydrofoils.htm

Best Regards,

H.G. Frautschy
Editor, Vintage Airplane magazine
Executive Director, EAA's Vintage Aircraft Association

Check out our Web site at www.vintageaircraft.org.

It's never too early to start thinking about your visit to The World's Greatest Aviation Celebration, EAA AirVenture 2006. See highlights of EAA AirVenture 2005 and learn more about the annual EAA convention at www.airventure.org.

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