Bob, without getting out my trig tables or calculator... I did not use the bottom of the lower spars as a reference of any kind in my KR2S. The preferred method ( for me) was to establish the zero chord line through the rib templates ( all of them) and drill small 1/4" tooling holes , 12 inches apart. The ribs are then slid over the spars ( as per Mark Langford's continuous plot rib method ( temporary humps over the spars , sanded off later). Then put a straight piece of L shaped, aluminum extrusion (sitting on 1/4 dowels or bolts through these holes) and sit a digital protractor ( SMART LEVEL ,without the level frame) on this . The ribs can now be positioned to give EXACTLY whatever incidence you choose versus the fuselage thrust line as zero, ( using firewall 90deg. ( first choice) or top longerons). This method works well right side up or upside down ( when glassing the bottom of the wing). I used 3 degrees incidence at the root and 0.5 degrees at the tip rib, for a total of 2.5 degrees washout.
My plane flew hands off from the first flight using this method and stalls clean with no wing drop. Hope this is clear , if not please E mail me off line and I can send you some photos . Regards Chris Gardiner KR2S C-GKRZ ----- Original Message ----- From: "robert tallini" <robertjtall...@earthlink.net> To: <kr...@mylist.net> Sent: Friday, January 02, 2004 3:48 PM Subject: KR>Angle of incidence > Hi gang, here I go again, > I am going to risk the possibility of another personal attack on my building know-how by asking for help in a problem I have with the KR plans. > In checking the plans, Drawing #2 for the KR2, [this sheet is included , as you know ] in plans for the KR2S I checked the angle of incidence by running a line from the bottom of the two spars and extending it till it intersected with the extended chord line of the rib. Measuring 48" from the intersection the distance between the thrust line, and the angle of incidence of the wing could be determined in inches. > As most of you agree, the plus 3.5 degrees incidence is excessive. had intended to reduce this regardless of the airfoil I used. However, I wanted to see how much I would have to shim the lower longeron at Stations G & H. > To my surprise my measurements indicate the angle of incidence, if you follow the plans exactly, give a 7 degree angle, not 3.5. I arrived at this conclusion by multiplying the 48" chord by pi. Finding the circumference, I divided by 360 to get the inch equivilent to a degree. Multiplying this by 3.5 I would get the angular difference between the chord line of the rib and the thrust line of the fuselage in inches. > Let me digress for a moment, I KNOW that ALL of you are perfectly familiar with finding the relationship between degrees and inches. I just felt that letting all of YOU know that I do, too. It might finesse aspersions re. my I.Q. > I believe, with all the KR's that have been, or are being built, someone checked this out. The only mention in the manual or the plans is to use the top longerons as reference. But the attach points on the lower longerons are parallel at Stations E and H at 20" to the top longerons. > Could it be possible that a "strictly plans built" KR2 or 2S could be flying with a 7 degree angle of inc. > My question is, as Bill O'Reilly would say, where have I gone wrong Is my geometry that bad, should I abandon all hope of building a KR2S and as has been suggested, start learning to be a GOOD pastry chef? > Happy New Year to everyone, Bob Tallini > > _______________________________________________ > see KRnet list details at http://www.krnet.org/instructions.html
