Sid, Assuming you are using 8-16 (some say 14 max) from the front edge of the wing, my KR2S has a 11.5 cg at same condition, pilot and half fuel. You are a little farther aft, but not out of bounds by any means. I know sounds silly, but can you just add a temp weight forward of the main spar? Obviously the further forward the less weight it would need to be, but if you have a spreadsheet set up you could figure it out.
Rob Schmitt -----Original Message----- From: KRnet [mailto:krnet-bounces at list.krnet.org] On Behalf Of smwood via KRnet Sent: Saturday, July 5, 2014 5:20 PM To: krnet at list.krnet.org Subject: Re: KR> KR Forum-gear placement A retractable pogo stick on the tail does not seem to practical for my KR-2 at this time. This morning with just myself onboard and half fuel, the cg is at 12.6 inches. I tried raising the nose on a fast taxi down the runway. With an estimated steady ground speed of 25 knots, I can easily raise the nose wheel off the pavement with back stick about two inches. I estimate the speed because the ASI does not register until 40 knots. I think I have the cg about correct for flight, but the cg is only 3.4 inches ahead of the main wheels. Hence the tendency to dump on the tail. If I used longer gear legs, that would move the main wheels further aft. But then there would be spring or stiffness issues, along with level stance on the ground. If I angled the gear legs further aft, then the bottom of the leg would need rework to get the toe in correct; that would also need extra length on the legs with spring and stance considerations. Mr. Pazmany shows lots of math to design the gear geometry to properly comply with Part 23. I am trying to avoid re-designing my KR-2. I want a practical machine I can fly now without another year or two down time. So, not dropping bombs yet, anyone have any other suggestions? Sid Wood Tri-gear KR-2 N6242 Mechanicsville, MD, USA -------------------------------------------------------- > > At 01:11 PM 7/4/2014, you wrote: >>For tri-gear I am very much aware that the main wheels are not set far >>enough to the rear to consistently keep the tail from dumping when >>trying to mount or dismount. > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++++++++++++++++++++++++++++ > > It's their placement when loaded for flight that is of primary > concern. Put them too far to the rear and it will be more difficult > to rotate of takeoff. One lightweight aircraft that we all know won't > even set with the nose wheel on the ground without the pilot on board. > If loading and unloading is a problem a retractable tail stand might > be in order. The B-24 puts out a pogo stick when parked. > > Larry Flesner > _______________________________________________ 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
