[Rick Masters]

1964


STALLING AND TUMBLING OF A RADIO-CONTROLLED PARAWING AIRPLANE MODEL
by Charles E. Libby and Joseph L, Johnson, Jr.
Langley Research Center
Langley Station, Hampton, Va.
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. C. JULY 1964
http://www.australian-hang-gliding-history.com/pass-word-only/reports/TN%20D-2291.pdf

"After whip stalls, the model was found to have extremely violent dynamic
longitudinal instability in the form of a nose-down, end-over-end tumbling
motion. This tumbling motion appeared to be caused by the low position of the
center of gravity relative to the wing and by the reversal in parawing fabric
when the model pitched down to negative angles of attack."

[Frank Colver]

YUP!

FC

[Rick Masters]

This tumbling motion appeared to be caused by the low position of the
center of gravity relative to the wing...

I know how to fix that.
We'll just suspend the pilot by a strap!    
It's amazing how far we've come without addressing this problem!


I remember in 1980, I think, Eric Raymond fastened lines from his harness to the lower control frame of his incredible Sunseed to protect him in the event of negative loading during successive loop attempts.
The idea didn't catch on.