On Wednesday, September 14, 2016 at 8:24:00 AM UTC-4, Bruce Hoult wrote:
On Wednesday, September 14, 2016 at 3:04:30 PM UTC+3, Roy B. wrote:
In this month's Gliding International article on the Ventus 3, Aldo Cernezzi writes, "According to Berd Weber, I flew with a relatively forward CoG, which may have an impact on roll speed". This got me to thinking of my own anecdotal experiences with very forward CGs having a negative impact on roll rate, and I think that a forward CG does degrade the roll rate. But I can't figure out why that happens. Can anybody explain it in simple terms?
ROY

I don't know, but I've found that in some gliders lacking in roll rate (in particular the original Janus) it seemed to help to unload the wings. e.g.. pull up a bit, then push forward to reduced G and roll at the same time.

This also ties in conveniently with reducing from cruise speed to thermaling speed :-)

Bruce: I understand that. Unloading the wings reduces the roll moment of inertia (think of why a tightrope walker uses a heavy long bar instead of a short light one) and also impacts the wing torque problem that happens when (on a long span glider) the wing twists against the aileron deflection. But I can't understand why forward CG impacts roll rate at all - yet I am sure that it does. ROY