How do airplane designers determine flap deflection angles for flap chords of various % wing chords? E.g. flap chord of 30%, 40% or 50% of wing chord.
I understand most flaps' chords are about 25% of the wing chord, but I understand Rutan's Grizzly had a flap chord of 55% of wing chord.
I assume you could use theory to figure this out, but that doesn't mean it works like that in the real world.
Is this information readily available in graph or chart form?
I thought I saw a link in a post on StackExchange re this from Peter Kaempf, but I can't find it.