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#1
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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 |
#2
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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
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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
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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
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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
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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
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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
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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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