Hey guys, probably a simple question, but I'd like some input nonetheless.

When making built up flaps, is it better to do a zig-zag warren truss style arrangement or a set of chordwise ribs?

I would have thought a warren truss would be better for torsion, no?

I have seen blue sheet foam used in built up flaps with good success and kinda negates any further need for internal bracing.

Just a thought here.

You mean xps foam, yeah? I have a pile of it in my workshop....

I only know it by the name "Depron."

But have seen Oz fliers use it with balsa laminations and it turns out extremely flat and very stiff when finished.

Hey guys, probably a simple question, but I'd like some input nonetheless.

When making built up flaps, is it better to do a zig-zag warren truss style arrangement or a set of chordwise ribs?

I would have thought a warren truss would be better for torsion, no?

Flaps aren't thick enough to have a lot of air in them.  I've found that ribs and glue can easily equal the weight of any wood saved.  Physics says that flat flaps(no taper) with square trailing edge are stiffest.  Especially if covered with light carbon fiber.  Do a scientifical esperiment and build a test piece first and measure how stiff it is compared to plain balsa or built up.

Phil C