NACA 12. from what i've learned on the subject. this is a good basic profile. i used www.flyingfoam.com Bob there was a very nice and the price was right. maybe check with hobie as to what there foil is so they match the wells. i had Bob cut the cores. this is for a dagger board. as for rudders a naca 12 s/b close. maybe something slightly thicker/shorter chord. let the pro's chime in but i belive naca 12 is what is used on the inter 20 daggers. the rudders are a much more complex foil