Spars construction with high density inserts at ends for pivots. I used "1034" filleting compound to make the HD inserts but very heavy foam would have been easier. Note: One 4' x 8' 13 mm thick composite panel weighs 18 lbs! Lighter than a 1/4" in. plywood (24 lbs).
Tracing spar on sandwich panel using template:
Cutting parts:
Vacuum bagging 2 thicknesses of sandwich panel for a total of 26mm:
Cutting cavity for High density inserts:
Molds for HD inserts:
HD inserts ready for light sanding: