Full-span flaperons as airbrakes?

I don't know of any sailplane design that uses full span single surface
flaperons.


I know I'm getting in late on this but the original LS-3 had one full-
span control surface per wing panel. It was fairly flexible (said
anyone who ever removed one from the wing for maintenance) and
apparently required a fair amount of lead to mass balance (IIRC, 40
lbs. was mentioned, probably split between left and right). The result
was that the wings were not only quite heavy (175 lbs.each) but the
balance was biased towards the trailing edge, making it more awkward
to handle during rigging. Maximum flap settings were -7 to +10
degrees, probably to prevent the one-piece surface from distorting or
even splitting/buckling at the trailing edge at higher wing
deflections. The wing itself was very stiff (probably another reason
for its weight since this was pre-carbon fibre) so the deflection in
turbulence was low (read: it was a rough ride on the ridge). It sounds
a little odd but the glider was a joy to fly and both climbed and ran
very well when new. Alas, LS-3s experienced shrinkage over the spar
caps over time, which hurt the cruise performance though they still
climbed well. Some owners (including me) sanded and/or added gel coat/
filler to restore the original profile and the glider was transformed,
making it equal to the ASW 20, Ventus, and LS-6 of its day. It's still
a great, wonderfully strong airplane with a lot of performance that
gives its owners a great deal (for one with a good finish).

Not to be confused with the LS-3a or LS-3 17, both of which had more
conventional flap/aileron control surfaces and lighter wing panels.

Chip Bearden
ASW 24 "JB"
USA

On Mar 19, 2:58*pm, Chip Bearden wrote:
I don't know of any sailplane design that uses full span single surface
flaperons.

I know I'm getting in late on this but the original LS-3 had one full-
span control surface per wing panel. It was fairly flexible (said
anyone who ever removed one from the wing for maintenance) and
apparently required a fair amount of lead to mass balance (IIRC, 40
lbs. was mentioned, probably split between left and right). The result
was that the wings were not only quite heavy (175 lbs.each) but the
balance was biased towards the trailing edge, making it more awkward
to handle during rigging. Maximum flap settings were -7 to +10
degrees, probably to prevent the one-piece surface from distorting or
even splitting/buckling at the trailing edge at higher wing
deflections. The wing itself was very stiff (probably another reason
for its weight since this was pre-carbon fibre) so the deflection in
turbulence was low (read: it was a rough ride on the ridge). It sounds
a little odd but the glider was a joy to fly and both climbed and ran
very well when new. Alas, LS-3s experienced shrinkage over the spar
caps over time, which hurt the cruise performance though they still
climbed well. Some owners (including me) sanded and/or added gel coat/
filler to restore the original profile and the glider was transformed,
making it equal to the ASW 20, Ventus, and LS-6 of its day. It's still
a great, wonderfully strong airplane with a lot of performance that
gives its owners a great deal (for one with a good finish).

Not to be confused with the LS-3a or LS-3 17, both of which had more
conventional flap/aileron control surfaces and lighter wing panels.

Chip Bearden
ASW 24 "JB"
USA

And due to the lead in the wings, the German speakers in this group
will understand why the "LS-Drei" was referred to as the LS-Blei"...


Ray Lovinggood
Carrboro, North Carolina, USA

I've heard the LS-Blei joke many times, and laughed ruefully.
Interestingly, however, while the wings ARE heavy (my entire ASW 24
wing weighs as much as the root end of my LS-3 wing!), they're
comparable to those of the ASW 20B, a much more highly thought of
glider with almost identical performance (when the LS-3 wings are
profiled properly, that is).

Pursuant to the original poster's question, I should have added that
the LS-3 has large, very effective conventional dive brakes and does
not rely on the flaps for glide path control. Also, while the ailerons
are light and very effective when the flaperons are set at 0 to 10+
degrees, the stick is very stiff with the flaperons at -7 degrees (at
least in my old glider). I didn't have much ridge time in my LS-3 but
I recall on more than one occasion yanking the flaps down when
encountering a strong rolling motion so that I could apply countering
aileron. This also had the effect of lifting me off the ridge at the
same time. It was a nice combination but I would have prefered just
being able to roll a little easier. Pilots with more ridge time might
disagree this was necessary but the ailerons were still very stiff. I
presume this was from the geometry of the mixer since much of it was
apparent even on the ground. I hope I'm not making the LS-3 out to be
unpleasant in any way. It was a great glider that I flew happily for
many years.

Chip Bearden
ASW 24 "JB"
USA

On Mar 20, 4:27*pm, Chip Bearden wrote:
I've heard the LS-Blei joke many times, and laughed ruefully.
Interestingly, however, while the wings ARE heavy (my entire ASW 24
wing weighs as much as the root end of my LS-3 wing!), they're
comparable to those of the ASW 20B, a much more highly thought of
glider with almost identical performance (when the LS-3 wings are
profiled properly, that is).

FWIW, 20B wings are 155 lbs ea.

Go find your old -3 and let's go race. It'll be tough luck for you if
there's any rain on course, won't it grin.

-Evan Ludeman / T8