Hi Ya Jeff I reckon it's bit more complex than just moving the wing. As a weight alone, moving the wing back away from the CoG increases weight on the tail for sure. To this extent Mike was correct in his comments on 10th May about moving the wing forward to offset the tail heaviness.
However, the centre of lift is also moved backward which could act aerodynamically to counteract this which I think is what Sid was getting at. The extent to which these two interact and are then influenced by the other two vectors of thrust and drag is what ultimately determines whether the nose or the tail hits the ground first and whether the elevator has the authority to control it before it happens. Sid has added 49 lbs at about say 24" in front which suggests he has about say 20 in the tail at about 60". It may well be those elevator weights are a significant part of the problem. It all seems academic now. Sid will either fly or he won't. 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 Jeff Scott via KRnet Sent: Tuesday, 12 May 2015 12:35 PM To: krnet at list.krnet.org Cc: Jeff Scott Subject: Re: KR> Ballast weight installation Hi John, You are correct in that the fuselage was extended to address elevator sensitivity and the firewall moved forward to move the engine forward to make the plane easier to balance. Sid just stated it a different way by saying the wing was moved back by 2". Either statement is correct. I don't think the CG envelope changed at all between the 2 and 2S as far as CG range relative to the wing cord. I don't know why Sid's plane is so terribly tail heavy, but adding a ton of weight to it isn't the way I would go about fixing it. As someone pointed out, he has balance weights on the elevator. Those are really unnecessary on the KRs. I'd lose those in a heartbeat. When I rebuilt the tail on mine to a much larger elevator and stab, I designed it to accommodate a set of balance weights, but when it came down to it, I couldn't convince myself to add 4# of lead to the tail. Sid seems determined to fly his plane as equipped. That seems fool hardy to me and others have implied the same on the net. Hopefully he won't hurt himself in it. Best regards, -Jeff > > Hi Jeff > > I thought the -2S had the rear fuselage extended to reduce elevator > sensitivity and had the firewall moved forward to compensate by altering the > engine mount position. I can well understand then why you correctly needed > to add weight up front in various ways without building the firewall > extension. I wasn't aware that RR changed the CoG envelopes as well to > reflect any changes to wing position. > > I sincerely hope Sid has a successful flight but I don't understand his > reluctance to get his conclusions verified by a professional given the > stakes. To me it's a no brainer given the magnitude of the weights > apparently needed. > > Regards 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 Jeff Scott > via KRnet > Sent: Tuesday, 12 May 2015 4:03 AM > To: krnet at list.krnet.org > Cc: Jeff Scott > Subject: Re: KR> Ballast weight installation > > Sid brings up a good point here, especially for builders that are early on > in their projects......snip > > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 2015.0.5863 / Virus Database: 4342/9752 - Release Date: 05/11/15 > > > _______________________________________________ > Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. > To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org > please see other KRnet info at http://www.krnet.org/info.html > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options > _______________________________________________ Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org please see other KRnet info at http://www.krnet.org/info.html see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2015.0.5863 / Virus Database: 4342/9753 - Release Date: 05/12/15 ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2015.0.5863 / Virus Database: 4342/9753 - Release Date: 05/12/15
