On Monday, April 16, 2018 at 6:48:25 PM UTC-5, wrote:
Steve,
Page 57 of the 1997 SSA Sailplane Directory says; "The 16.5 meter Diamond built by FFA was the first all glass fiber production sailplane, not using balsa or other wood sandwich between the fiberglass layers". Have you seen a core inside the 16.5 wing? The 15 meter wings were built by Glasflugel and did use balsa cores.
JJ

Hi, JJ. Yes, I have seen the foam core inside the Diamant wings on several 16.5 meter variants. Also have the repair manual. Section 4 page 6 shows a cross section of the wing skin. Agree that the wings on serial 1-10 were built by Glasflugel and are balsa core. But, the 16.5 and 18 meter are foam core. The key in the statement you quoted is "...balsa or other wood sandwiched between the fiberglass layers." PVC foam isn't wood. So, the Diamant became the first "all plastic" sailplane. It used another "plastic" as its core.

Cool history collected here on the Diamants.

http://www.b2streamlines.com/FFADiamant/index.html

Steve Leonard