Thin laminar flow sections for centerboard

[tspeer]

Originally Posted by Karsten

...For example if you find out that you can make the centreboard 10% smaller because you have a lightwight crew or you are out of the low drag bucket anyway you save about 10% of friction drag. If you decrease the chord length and keep the span the same you also increase your aspect ratio which in turn will reduce your inducted drag.
..

Not quite. If the span is the same, the induced drag will be the same. Induced drag does not depend on aspect ratio. The confusion comes because the induced drag coefficient depends on aspect ratio. But when you calculate the dimensional drag (in N or lb), aspect ratio disappears and is replaced by the square of the span. It turns out aspect ratio really should be regarded as the nondimensional form of span-squared instead of focusing on slenderness.

But you're spot on with reducing the profile drag by reducing the wetted area.

[BOATMIK]

I don't know ...

Looking at the original criteria we have a foil that is strongly limited in span.

To my mind getting enough lift may be a problem.

Think rough water and lots of drag from not being able to reduce the sailplan.

Is there much weed in the area? If there is, a less critical foil section may come out on top.

I would be going with the thickest foil possible and would not be overlooking the NACA00xx sections either.

The general rule is design for the lift - THEN look for means of reducing the drag.

Or am I missing something that is too subtle for me to grasp.

Best wishes to all

Michael Storer