On this page, skin thickness refers to 'T' as shown below.
- Maximum thickness of a foil is equal to the maximum thickness of the core plus twice the thickness of the skin.
- The chord length of the foil is equal to the chord length of the core plus the thickness of the skin plus the taper of the skin beyond the core (designated by '?' below).
Giving you an idea of some of the forces at work (and how strong your foils have to be)
- Center of Gravity of seated crew is 6" inside gunwales
- C of G of hiking crew is 25% of crew's height outside of gunwales
- C of G of trapezing crew is 50% of crew's height outside of gunwales.
Why should you care about righting moment? This is one factor in
determining the maximum lift your centerboard needs to generate, and how stiff
and strong it should be.
You may wish to multiply the result by a weighting factor > 1 to account for
crew dynamics and pumping.
Sample Coefficients of Lift
These are to be used only as general guidelines - coefficient of lift varies
according to aspect ratio (and other planform factors) and Reynolds number, to
name just some of the variables.
||NACA0012 at angle of attack of 15 degrees (max before it stalls)
||NACA0012 at angle of attack of 3 degrees (typical leeway angle upwind)
||NACA0009 at angle of attack of 10 degrees (max before it stalls)
||NACA0009 at angle of attack of 3 degrees
For maximum lift generated by your centerboard, think in terms of hullspeed
upwind (if you're planing, you're probably also retracting the
centerboard). For maximum lift generated by your rudder, think in
terms of hgh steering angles at maximum speed downwind.
Multiply the lift generated by your centerboard by one half of its submerged
length, and determine if that exceeds the righting moment that your crew
I'll break my rule about not including links here - check out Martin
online foil analysis.