I have noticed that the form blocks from Sonex have been chipping away. They are partical board and not MDF. So after building about 6 ribs, I went back and compared one to the full size drawing in the plans, and yep they are off. The curve over the top of the rib is flatter than the drawing. That area of the form appear to be flat as well. So I made my own form block out of MDF and have remade the 6, plus 4 more and they ae all correct. Plus the MDF form block holds up better (no chipping)
I suggest you not buy th eSonex form blocks, rather mahe your own.
