On Saturday, July 4, 2015 at 11:38:55 AM UTC-4, Jonathan St. Cloud wrote:
The mixer is actually very different and Schleicher spent much time on this. So is the lay up schedule for the spar, and an extra layer of carbon on the wing. Wing root airfoil is different and the outboard sections of airfoil have been changed. The empty weight of a 29 compared to a 27 both at 15 meters is about 80 pounds.

Interesting to read this. When the '29 came out I heard there was a new outboard airfoil and wanted to modify my '27 with it. I pulled templates off a friend's '29 and lo and behold there was no perceptible difference. Certainly the winglet changed but we had done that in 2000. The winglet is very similar to what we did for the '27 back then with thicker, more conservative airfoil.
Obviously the structure changes when you go to 18M.
UH