Ok, for the full story see the e-mails below. I am larger than the average KR pilot and when I built my KR I took this into consideration. I added two inches in fuselage length forward of the main spar thus moving the firewall forward. This resulted in a CG range measured from the datum (forward tip of spinner) of 62 to 70 inches. My CG is not in the aft range nor is it it anywhere close to it. With full tanks my CG is at 64.2 inches and at empty tanks it only moves forward to 63.2 inches. I have no header tank. If I fly a 150lb passenger with full tanks the CG is at 66 and empty it is at 65.4. The only time I have hit the tail was when I approached landing at a very steep angle and at a very slow speed. My tail tie down ring sticks down about 2 inches. My wing incidence is set at the specs for the AS504x airfoil. I never hit my tail anymore.
Mark Jones (N886MJ) Stevens Point, WI E-mail: flyk...@charter.net Web: www.flykr2s.com ----- Original Message ----- From: "Larry&Sallie Flesner" <fles...@frontier.com> To: "KRnet" <kr...@mylist.net> Sent: Thursday, April 07, 2011 3:51 PM Subject: KR> Tri gear tail first on runway > >I have a tri-gear plans-built KR-2 with standard Diehl gear. Stub wing is >set at 3.5 degrees AOA in level attitude. With the tail skid pushed down 5 >inches off the level concrete, my inclinometer shows an AOA of 14 degrees. >With the tail skid on the concrete the AOA goes to 17.5 degrees. My >conclusion: I would stall the wing before the tail skid touches the runway. >Not accounted for is the low wing ground effect, static load on the gear >and >use of flaps on the above data versus actual flight performance. I suppose >it would be possible to momentarily touch the skid to the runway by over >controlling with PIO. Another possibility is planting the tail on the >runway with max aft cg and full elevator deflection. >Sid Wood +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Mark Jones was the individual that posted saying he has had his tail touch on landing. His KR is a 2S so the longer fuselage would be closer to the ground in the same attitude. He is also flying the "new" foil and I have no idea what the "critical AOA" is on it. If he followed Langford's suggestion, he may have set his wing at less than 3.5 degrees, maybe closer to 2.0 degrees. I'm guessing his tail tie down ring is 1.5 inches in diameter. Also, if he hasn't lost weight since the last Gathering, his CG is a bit aft. :-) (sorry Mark, couldn't pass that one up. I'll owe you a beer at the next Gathering ) Larry Flesner _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html
