LS3A Wing Profile Data

The LS-3 measured higher in L/D than the 3a according to Dick Johnson's
tests. I actually have a letter from Wolf Lemke that was with papers that
came with my LS-3a assuring owners that there is no difference in
performace from follow-up factory tests of the 3a after Dick's flight
tests??

I also noticed the following quote on wikipedia for the LS-3:
"In spite of its weight the LS3 is a nimble climber. It is also less
sensitive to rain or dirt than other types with the same profile."

I'm not sure who posted this to the Wiki or if this applies only to the 3
or 3a? Was there any change in profile for the 3a?

Matt
LS3-a "RX"

At 15:44 22 October 2008, Frank Whiteley wrote:
On Oct 21, 9:26=A0pm, "Bill Daniels" wrote:
You know, I've been flying FX 67-150 and -170 airfoils for years.
=A0I've
smashed thousands of bugs, flown through many rain showers and even
collected substantial ice on occasion yet I've not seen any unusual
performance degradation when analyzing flights with SeeYou nor did I
feel
any in flight. =A0In fact, those glides with crappy wings often show a
height/distance ratio well above the published L/D. =A0I know Bob
Faris
g=
ets
great results with his LS-3a in the same conditions. =A0I wonder if
these
airfoils are getting a bad rap.

Bob Faris flies an LS-3, which is rather different than an LS-3a in
the flap/aileron vs flaperon and wing weight areas. Read something in
the past year that suggested that the FX67/170 and 150 did not degrade
on long spans where the thickness was 15%, but can't find it at the
moment.

Frank Whiteley

The LS-3 measured higher in L/D than the 3a according to Dick Johnson's
tests. I actually have a letter from Wolf Lemke that was with papers that
came with my LS-3a assuring owners that there is no difference in
performace from follow-up factory tests of the 3a after Dick's flight
tests??

I also noticed the following quote on wikipedia for the LS-3:
"In spite of its weight the LS3 is a nimble climber. It is also less
sensitive to rain or dirt than other types with the same profile."

I'm not sure who posted this to the Wiki or if this applies only to the 3
or 3a? Was there any change in profile for the 3a?

Matt
LS3-a "RX"

At 15:44 22 October 2008, Frank Whiteley wrote:
On Oct 21, 9:26=A0pm, "Bill Daniels" wrote:
You know, I've been flying FX 67-150 and -170 airfoils for years.
=A0I've
smashed thousands of bugs, flown through many rain showers and even
collected substantial ice on occasion yet I've not seen any unusual
performance degradation when analyzing flights with SeeYou nor did I
feel
any in flight. =A0In fact, those glides with crappy wings often show a
height/distance ratio well above the published L/D. =A0I know Bob
Faris
g=
ets
great results with his LS-3a in the same conditions. =A0I wonder if
these
airfoils are getting a bad rap.

Bob Faris flies an LS-3, which is rather different than an LS-3a in
the flap/aileron vs flaperon and wing weight areas. Read something in
the past year that suggested that the FX67/170 and 150 did not degrade
on long spans where the thickness was 15%, but can't find it at the
moment.

Frank Whiteley

The LS-3 measured higher in L/D than the 3a according to Dick Johnson's
tests. I actually have a letter from Wolf Lemke that was with papers that
came with my LS-3a assuring owners that there is no difference in
performace from follow-up factory tests of the 3a after Dick's flight
tests??

I also noticed the following quote on wikipedia for the LS-3:
"In spite of its weight the LS3 is a nimble climber. It is also less
sensitive to rain or dirt than other types with the same profile."

I'm not sure who posted this to the Wiki or if this applies only to the 3
or 3a? Was there any change in profile for the 3a?

Matt
LS3-a "RX"

At 15:44 22 October 2008, Frank Whiteley wrote:
On Oct 21, 9:26=A0pm, "Bill Daniels" wrote:
You know, I've been flying FX 67-150 and -170 airfoils for years.
=A0I've
smashed thousands of bugs, flown through many rain showers and even
collected substantial ice on occasion yet I've not seen any unusual
performance degradation when analyzing flights with SeeYou nor did I
feel
any in flight. =A0In fact, those glides with crappy wings often show a
height/distance ratio well above the published L/D. =A0I know Bob
Faris
g=
ets
great results with his LS-3a in the same conditions. =A0I wonder if
these
airfoils are getting a bad rap.

Bob Faris flies an LS-3, which is rather different than an LS-3a in
the flap/aileron vs flaperon and wing weight areas. Read something in
the past year that suggested that the FX67/170 and 150 did not degrade
on long spans where the thickness was 15%, but can't find it at the
moment.

Frank Whiteley

The LS-3 measured higher in L/D than the 3a according to Dick Johnson's
tests. I actually have a letter from Wolf Lemke that was with papers that
came with my LS-3a assuring owners that there is no difference in
performace from follow-up factory tests of the 3a after Dick's flight
tests??

I also noticed the following quote on wikipedia for the LS-3:
"In spite of its weight the LS3 is a nimble climber. It is also less
sensitive to rain or dirt than other types with the same profile."

I'm not sure who posted this to the Wiki or if this applies only to the 3
or 3a? Was there any change in profile for the 3a?

Matt
LS3-a "RX"

At 15:44 22 October 2008, Frank Whiteley wrote:
On Oct 21, 9:26=A0pm, "Bill Daniels" wrote:
You know, I've been flying FX 67-150 and -170 airfoils for years.
=A0I've
smashed thousands of bugs, flown through many rain showers and even
collected substantial ice on occasion yet I've not seen any unusual
performance degradation when analyzing flights with SeeYou nor did I
feel
any in flight. =A0In fact, those glides with crappy wings often show a
height/distance ratio well above the published L/D. =A0I know Bob
Faris
g=
ets
great results with his LS-3a in the same conditions. =A0I wonder if
these
airfoils are getting a bad rap.

Bob Faris flies an LS-3, which is rather different than an LS-3a in
the flap/aileron vs flaperon and wing weight areas. Read something in
the past year that suggested that the FX67/170 and 150 did not degrade
on long spans where the thickness was 15%, but can't find it at the
moment.

Frank Whiteley

I echo UH's cautionary remarks. My observations based on owning and
campaigning an LS-3 (not LS-3a) for 13 years, including profiling the
wings, plus speaking with another owner who profiled his wings:

1. The original LS-3, when new, was fully equal to the ASW 20 in both
climb and cruise. As time went on, many (most?) LS-3s seemed to
degrade in cruise. They always climbed well. I found that the lost
cruise performance could be regained by sanding/smoothing the waves
out of the wings. A polished finish isn't necessary. I know guys who
used 600 grit all the way down to 220 grit, although the latter was
tough to live with as it collected fingerprints and dirt. THe matte
finish was an attempt to have water droplets (rain) spread rather than
bead up because this airfoil was notable for being sensitive to rain.
That said, the last time I worked on mine, I waxed it up and flew it
through rain several times in a contest and it seemed to go fine. One
PIK driver told me the secret to that glider (same airfoil, panicky in
the rain) was to fly it with more flap than spec'd when there was rain
and that's what I did.

2. Eventually you can't smooth the wing enough by sanding. The problem
is curing over the spar caps. The airfoil develops flat spots so
severe that you'll sand into the fiberglass trying to make them go
away. Not unique to the LS-3 but a particular problem. Building these
flat spots back up to the approximate contour restores the cruise
completely and makes the airplane equal to the ASW 20 (including B),
the Ventus 1, and the LS-6. It's a lot of work. Don't let anyone just
remove the gel coat and spray the wing, sand, polish, and expect it to
work right. On this specific model, the underlying structure is not
correct. Unless you correct the flat spots cause by shrinkage over the
spar caps, it will climb great but it won't cruise as well as these
other gliders.

3. THe LS-3a (split flap/aileron, bigger tail, some with 17m tips) was
reputed to have a thicker wing on some gliders because of mold
distortion at the factory. That story was the reason for the factory's
letter assuring everyone that the wing profiles of the 3 and 3a were
the same. Some 3a's were great gliders, others were far inferior in
cruise. I suspect all could be corrected by working on the profile. As
UH suggests, read the Dick Johnson series on his PIK 20. It's very
similar work. The coordinates are public domain and you don't need the
factory's help. The "different sets" of coordinates relate to two sets
of revised numbers that corrected small errors in the original
published coordinates. All were in Soaring magazine (and elsewhere,
I'm sure), though the last set was in a letter to the mag, IIRC).

4. The leading edge of the LS-3 wing from the factory was not as sharp
as it should have been, especially in the outer section. The owner I
spoke with corrected this, too. I don't know how much effect this had
and I didn't do it. If you're profiling the whole wing, this will show
up, obviously (esp. in JJ's first 4 inches, although not if you use
the existing airfoil as the mold). If you're going after bang for the
buck, you could probably focus on the wing over the spar caps if the
rest of the gel coat is OK.

5. I found a small but noticeable improvement from installing
turbulator tape on the lower surface. I don't recall how far back; we
did it by trial and error flying against George Moffat's Ventus. I
also played with various flap settings and discovered that the full 10
degrees isn't usually necessary although it's easier to thermal that
way. 5 or 7 degrees works better most of the time.

6. I don't know if anyone ever put winglets on a 3 but I suspect they
would improve the glider as much as they do other gliders, in
particular with the way the flaperon extends all the way out to the
tip.

These gliders were essentially abandoned by most serious pilots
decades ago (Manfred Franke here in the US is one notable exception).
But when properly prepared, they still offer great performance, are
very strong, and handle nicely. There are several at our airport that
perform well even though the finish is less than perfect.

Chip Bearden
ASW 24 "JB"
USA