Hi Sid It is not that the centre of lift for the RAF48 wing has been inaccurately mapped. That would have been well calculated by the wing designers (not Stu Robinson) and has little or nothing to do with the aircraft it is put on. Rather the issue is that the CoG envelope for the KR2 was set too broadly and perhaps somewhat arbitrarily at 8" to 16".
We know that flight in the rear 2" or so has whiskers on it and in fact in Australia in the early days the authorities downright banned it. However, this does not mean that the forward limit at 8" is also incorrect. I think reducing it to 6" may be ill advised without proper analysis and you may find difficulty in raising the nose at low airspeeds such as in the flare. As I have explained previously you cannot simply equate Centre of Lift with Centre of Gravity because the balance is the outcome of four vectors, the other two being thrust and drag. Further, the CoL varies with Angle of Attack and at the stall moves backwards lending support to a nose down tendency that aids in recovery. If the CoL is actually 2" further forward as you claim then this design aspect would be compromised. I suspect the problem with your aircraft is not the CoL but the fact that it was tail heavy and too far back in the envelope as you have correctly addressed. It is not necessarily to do with an inaccurate mapping of the CoL. Please do not blame the designer for what is essentially a construction error. There are many KR2s flying without a problem and have been for years. Cheers John John Martindale 29 Jane Circuit Toormina NSW 2452 Australia ph:61 2 6658 4767 m:0403 432179 email:john_martindale at bigpond.com web site: -----Original Message----- From: KRnet [mailto:krnet-bounces at list.krnet.org] On Behalf Of Sid Wood via KRnet Sent: Wednesday, 19 August 2015 5:54 AM To: krnet at list.krnet.org Cc: Sid Wood Subject: Re: KR> weight and balance The KR-2 Plans have a serious error regarding Weight & Balance. The designer, Stu Robinson, chose the RAF48 Center of Lift 2 inches to far forward......snip ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2015.0.6125 / Virus Database: 4401/10469 - Release Date: 08/19/15
