Foil design

[Dr X]

In studying foils on boats for my a-level coursework I have struggeled to find enough detailed reasoning for how a foil
works. I understand both the coanda and bernouli effects, from what I understand the bernouli effect has no influence on
lift from a symetrical foil as both sides of the foil are of equal length. For the coanda effect the foil can't be directly
in line with the flow of water and must have a certain angle of attack, is this the case in boats or not?

Any help or any links to related sites would be much appreciated.

Many thanks.

Alec.

[sorenfdk]

Google for Airfoil Primer by Dreese.

[GDelerm]

Hi Dr X,

You can find something interesting here :

http://www.aa.washington.edu/faculty/eberhardt/lift.htm

--
Gérard

[markdrela]

Another very good reference is http://www.av8n.com/how/ by Denker. See Chaper 3.
He convincingly dispels the most durable myths about lift -- longer distance on top, Bernoulli versus Newton, etc etc.

[Karsten]

On symmetrical foils the vortex? method works quite well. The idea is to overlay a vortex and the parallel flow of water. The vortex looks like the thing you get if you pull the plug out of a full bathtub. The rotation makes the stream faster on one side and slower on the other. This generates the lift. To calculate the strength of the vortex you put the centre at 1/4 of the chord length. Then you make sure that no water flows through the foil at 3/4 of the chord. Once you know the strength of the vortex you can calculate the lift.