Designing and cutting sections for the bilge keels.

Most builders use NACA sections for keels.
Not me.
Bescause NACA sections are made for airplanes and the NACA sections have infinite aspect ratio far from my bilge keels that have a cord of 1.5 meter and a lenght of 0.25 meter that is an aspect ratio of 0.167.
The inducet resistance, the creation of tip vortecis is very different.
Also the Reynolds number is different.
Also my keels have an important function not considered by airplanes. That is to let the product rest on its tip at low water.
I used parabolic sides.
Many twin keeled boats angle the keels toe in that way they hope to make less lee way. But there is two keels on a twin keeled boat. The othe one will create more drag.
Also most cruisers spend much time sailing down wind now toe in is just more drag. I am not using toe in.
The builders of twin keeled boats also design with the lee keel vertical when heeled. The lee keel will not lose so much projected area that way but the windward keel will lose much. Angling the keels makes the boat lose projected keel area in total. That is a function of the cosine of the angel and the cosine function is not linear.
For more see Yrvind.com
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