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LS3A performance



 
 
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  #1  
Old June 18th 07, 04:21 AM posted to rec.aviation.soaring
Rob Dunning
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Default LS3A performance

I'm looking for info about the performance of ls3A.
I've seen the Dick Johnson report which basically
said the wing was 1/4' thicker at the wing root than
the LS3's, which lowered performance but was inconclusive
because he has only tested one plane. Perhaps some
real polar information? I've heard the A climbs better
but runs worse than the ls3 -- is this true?

Thanks - Rob



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  #2  
Old June 19th 07, 03:25 AM posted to rec.aviation.soaring
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Posts: n/a
Default LS3A performance

I have owned a LS3A and have flown both the 3 and 3A. I found no difference
in performance when the wing loading was the same. The 3A will have a
lighter wing loading with out water than the 3, therefore, has better climb
performance. The 3 wings are heavier due to the extra lead required for the
mass balance on the control surface.

"Rob Dunning" wrote in message
...
I'm looking for info about the performance of ls3A.
I've seen the Dick Johnson report which basically
said the wing was 1/4' thicker at the wing root than
the LS3's, which lowered performance but was inconclusive
because he has only tested one plane. Perhaps some
real polar information? I've heard the A climbs better
but runs worse than the ls3 -- is this true?

Thanks - Rob





  #3  
Old June 19th 07, 02:57 PM posted to rec.aviation.soaring
Chip Bearden
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Posts: 69
Default LS3A performance

I owned an LS-3 for 13 years. In my experience, all LS-3 versions
climbed equally well but many (not all) A models didn't run as well.
The lower weight of the 3A should have had some impact on climb but I
never saw it. The most likely cause of the cruise discrepancy is wing
profile, for two potential reasons. First, as you note, is that the A
model airfoils may have been thicker than they should have been (per
Dick Johnson and some correspondence in Soaring mag. from the factory
that followed Dick's test). Second, at least for the 3, is shrinkage
over the spar caps that caused a flat spot to develop after a few
years with significant impact on cruise performance. I contoured my
wings twice and profiled them over the spar caps once (to build up
this flat spot) and my glider was equal to the ASW 20s, Ventus, and
LS-6. A few other pilots who did similar things had the same
experience (e.g., Jim Cox in TX, IIRC). Unmodified LS-3As fell away
pretty fast at higher speeds, but so did unmodified 3s.

The above covers why a 3 might perform better than a 3A. Another
factor that relates only to how a 3 or 3A might perform against other
types is that the leading edge of the wing was said to be too blunt,
especially on the outer wing. The aforementioned Jim Cox profiled his
entire wing and built up the leading edge to the correct profile and
saw a dramatic improvement. But as far as I know, both models of LS-3
had this characteristic.

Personally, I'd probably take an LS-3 over an LS-3A even though the
wing is heavier--the 3 has fully automatic controls whereas the 3A
requires some control connections--but I suspect that either glider
would perform very well with the proper wing profile. They're still
very nice, very strong gliders. It's not well known that when the LS-3
and ASW 20 first appeared here in the US around 1977, the '3 was the
hot ship to have.

Chip Bearden
ASW 24 "JB"
New Jersey, USA

  #4  
Old July 3rd 07, 02:18 AM posted to rec.aviation.soaring
Eric Greenwell
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Posts: 1,096
Default LS3A performance

Chip Bearden wrote:


Personally, I'd probably take an LS-3 over an LS-3A even though the
wing is heavier--the 3 has fully automatic controls whereas the 3A
requires some control connections--but I suspect that either glider
would perform very well with the proper wing profile. They're still
very nice, very strong gliders. It's not well known that when the LS-3
and ASW 20 first appeared here in the US around 1977, the '3 was the
hot ship to have.


Even though George Moffat won the 15 M nationals at Ephrata in 1976,
using an ASW 20?

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org
  #5  
Old July 3rd 07, 04:29 AM posted to rec.aviation.soaring
Chip Bearden
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Posts: 69
Default LS3A performance

On Jul 2, 9:18 pm, Eric Greenwell wrote:
Chip Bearden wrote:

It's not well known that when the LS-3
and ASW 20 first appeared here in the US around 1977, the '3 was the
hot ship to have.


Even though George Moffat won the 15 M nationals at Ephrata in 1976,
using an ASW 20?


Yeah, there are always exceptions.

Actually, I think George's win was in 1978. The year I'm thinking of
was, IIRC, 1977, in Hobbs? Rudy Mozer had one of the few (maybe the
only) '20 in the USA at the time. One day before the start, the flap/
aileron mixer broke loose in the fuselage. Skillfully and miraculously
Rudy pulled the dive brakes and put the nose down, which gave him some
fantastic dihedral and with whatever control he retained kept the
whole thing fairly level. By ruddering it around he was able to land
on a long runway there. He thought he'd forgotten to hook something up
that morning so, as the story goes, he didn't even bother to climb out
of the cockpit. He just told one of his kids to open up the hatch and
hook up the controls. With the puzzled response that the control
connections looked just fine, the situation got more complicated and
his contest was over.

So in 1977, the LS-3 was going great (Dick Johnson tested the '20 and
the '3 to be essentially equal), the '20 was dogged by a few doubts
about the flexible wings, and it was uncertain which way the wind
would blow. At least one former national champion we spoke with said
that if he had to pick between the two, he'd take the LS-3 because of
the more robust structure, the outstanding build quality, and the
price advantage (it was the cheapest of the new 15M ships at that
time).

A few years later, the story had changed and most hot pilots were
moving into the '20. Not long after that, the shrinkage over the spar
caps on the LS-3 wing began to affect cruise performance (except for
the handful of airplanes, like mine, that were corrected). It's
interesting how two airplanes with identical performance when new had
such dramatically different lives.

Chip Bearden
ASW 24 "JB"
USA

  #6  
Old July 3rd 07, 10:54 PM posted to rec.aviation.soaring
Eric Greenwell
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Posts: 1,096
Default LS3A performance

Chip Bearden wrote:
On Jul 2, 9:18 pm, Eric Greenwell wrote:
Chip Bearden wrote:

It's not well known that when the LS-3
and ASW 20 first appeared here in the US around 1977, the '3 was the
hot ship to have.

Even though George Moffat won the 15 M nationals at Ephrata in 1976,
using an ASW 20?


Yeah, there are always exceptions.

Actually, I think George's win was in 1978.


You are right, as a search of Soaring magazine archives
(http://soaringweb.org/Soaring_Index) reveals. Dang, I can't remember
stuff that's only 30 years ago?


--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org
  #7  
Old July 4th 07, 12:22 AM posted to rec.aviation.soaring
Andreas Maurer[_1_]
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Posts: 91
Default LS3A performance

On Mon, 02 Jul 2007 20:29:48 -0700, Chip Bearden
wrote:

It's
interesting how two airplanes with identical performance when new had
such dramatically different lives.


Looks like the early LS-3s were flown in a climate with very little
rain....

Didn't the dramatic performance loss of the LS-3 in rain show up
immediately?


Bye
Andreas
  #8  
Old July 7th 07, 03:38 PM posted to rec.aviation.soaring
Chip Bearden
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Posts: 69
Default LS3A performance

On Jul 3, 7:22 pm, Andreas Maurer wrote:
On Mon, 02 Jul 2007 20:29:48 -0700, Chip Bearden
wrote:

It's
interesting how two airplanes with identical performance when new had
such dramatically different lives.


Looks like the early LS-3s were flown in a climate with very little
rain....

Didn't the dramatic performance loss of the LS-3 in rain show up
immediately?

Bye
Andreas


Well, sort of. I got rained on many times when flying an annual
regional contest in Cordele, Georgia and noticed it. I can't say it
was the "falling out of the sky" feeling that PIK-20 owners complained
about, but performance suffered. In retrospect, it didn't seem any
worse than the few other gliders I've flown in rain (Libelle 201 and
ASW 24) even though I understand that airfoil does suffer more than
the newer airfoils from roughness.

I thought the LS-was somewhat less sensitive to rain after I contoured
the wings the first time and left them at 400 grit finish and I knew
other LS-3 drivers who did the same thing for the same reason. But
just before I sold it, I sanded it one last time and brought the
finish back up to a gloss. I might even have waxed it (not sure).
During my last contest with these polished wings, I flew into a
rainstorm flying the ridge in Pennsylvania. The sink rate did increase
but not as much as that of the DG-400 right behind me whose highly
experienced pilot complained he was forced to turn back to get out of
the rain and then use the engine to stay aloft. I eventually turned
back also but had no trouble staying aloft and waiting out the rain.
This was not exactly a scientific test but my impression was that
having polished wings hadn't really hurt and that the performance
degradation was significant but not unusual.

I concluded that the LS-3 probably wasn't much worse, if any, than the
other ships of its time when new. It's possible that it was more
sensitive after the flat spot over the spar cap developed due to
curing of the composite structure, making most other LS-3s more
vulnerable. Based on feedback from one PIK pilot, I also tended to use
more positive flap than normal when the wing was wet, which seemed to
help.

It's also possible that the LS-3's reputation developed more rapidly
in Europe due to the greater degree of bugs that can be deposited on
the wings. Bugs aren't generally a problem here in the U.S., even in
south Georgia in the summer (at altitude, that is; they're definitely
a serious problem on the ground!).

Chip Bearden
ASW 24 "JB"
USA

 




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