At 07:30 AM 5/2/06, you wrote: >Hello all, > >Is anyone out there in KR land considering (or now building) a KR2 >that would meet the qualifications for LSA certification? I made a >search of the archives but there didn't seem to be a lot there as >far as LSA and KRs go.
<originally posted 3/10/06> After today's spate of LSA discussion, I put together a quick spreadsheet to calculate various performance parameters based on the discussion and formulae on this page: http://zenithair.com/kit-data/ht-86-8.html The straight Excel version is at: http://home.mebtel.net/~rbutterfield/KR/Stall_speed_&_performance_calculator.xls If you (or your isp) have problems with spreadsheets, the same file compressed with WinZip is at: http://home.mebtel.net/~rbutterfield/KR/sspc.zip I have entered CLmax from the stated sources for the two wings under discussion, but you can change that for other wings if desired. Constructive criticism welcome. And remember, it's worth what you paid for it (or maybe less ;-) ) I have NOT personally confirmed ANY of the data or formula in the spreadsheet, so use it at your own risk. <end old post> Top speed can be easily artificially limited by placarding a reduced max continuous rpm. Stall speed is the hard part. LSA requires the maximum stall speed to occur at gross, without the use of "lift enhancing devices", ie flaps. Wing area and weight play a big part, but Cl even more so. Good hard data seems a bit hard to come by, especially at the lower Reynolds numbers a KR flies at near stall. An interesting page of airfoil information is here: http://www.oriontechnologies.net/Documents/Airfoil.htm I personally have settled (for now, anyway) on a KR1 with 72 sf of 23015 tapered to 23012. With an estimated Cl of 1.6, that gives me a stall of 50.4 at a gross of 750. The spars and attachment of the KR2 are the same section, just longer, so it should be well within limitations without re-engineering. For a KR2S and the new airfoil, the numbers get so far out of hand that the spars and attach fittings would need to be completely re-engineered. At a gross of 980, with Cl of 1.28, you need 111 sf to get a stall of 52. Regards, RonB "expert riders use expert judgement to avoid using expert skills" Phill Ross
