Mike,
Thanks for the great history lesson.

Great information all around in this thread.

-Tom (The high school kid who helped you rig the ASW-15 when you flew it in Tucson '74-'75)

On Sunday, January 31, 2016 at 8:30:10 PM UTC-8, Michael Opitz wrote:
My father (P. Rudolf Opitz) was a German flying wing test pilot
specialist during the 1930's and 1940's. He got to fly a lot of what
was out there at the time. The Hortens had the same high aspect
ratio swept back wings, and they also had the same annoying and
dangerous pecking longitudinal stability issues that the SB 13
had. When Dad heard that They were building the SB 13, he
wondered if they had solved the pecking problem. When we didn't
hear much more after the initial flight tests, Dad rightfully
concluded that they had not solved the old Horten nemesis. Dad
always said that the Hortens designed beautiful looking aircraft, but
they were a real handful to fly. The pecking essentially limited them
to slow speeds only. Dad could not comprehend how the Hortens
thought they were going to go fast, when they couldn't sort out the
handling even at slow speeds. Dad did campaign a Ho IV in the
USA for the 1952 contest season. He finished 7th at the US
Nationals in Grand Prairie, TX, and won a couple of regionals. Like
the SB 13, take-off's were an issue. Dad solved the problem by
using a 300' (~92 meter) long tow rope, and a 300 Hp Stearman
tow plane (as compared to the regular 220 Hp). See this YouTube
clip at the 1:21 point for film of a take-off:
https://www.youtube.com/watch?v=0M84AKSyGZk
Notice, it is normal, and he is able to go right into a high tow
position. The pecking became uncontrollable at speeds above 85
mph, so Dad limited himself to a top speed of 85 mph. That, along
with the high powered tow plane and 300' rope allowed him to
safely campaign the glider for a full contest season. Afterwards, he
was also able to check out Dr. Raspet's pilot (Falvy) at Missisippi
State University for follow-on performance flight testing.

Before he passed away in 2010, Dad saw there was a beautiful Ho
IV restoration/(new build?) going on in Germany. The builders
never contacted us for advice, but he wanted them to know that if
they were thinking of flying it, they should use a powerful tow
plane, a 300' rope, and not to dare go faster than 85 mph... I have
never heard if they tried to fly that Ho IV after its completion or
not... It would be a shame if they broke it after all of that hard
work..

Mike Opitz - USA