Now I am torn between following the manual or using something less than 3.5 degrees to yield a more "normal" in-flight nose up/down attitude. Then I ask myself, "If I use less than 3.5 degrees at the fuselage, what happens to the normal wing tip washout of +.5 degrees...does it become negative? stay the same or what?"
+++++++++++++++++++++++++++++ Bernard You have received several replies to this question, most of them address elements of the topic but I am not sure that you have heard enough help you make a firm decision. If this is old hat ignore, but just in case. As you know, washout means setting the wing tips at a lesser incidence angle (than the inboard side). The purpose for this reduced incidence at the tip is to ensure that the wing tips stall last (relative to the rest of the wing). This reduces the likelihood of "tip stalls" (wing dropping) and makes the airplane less likely to spin when stalled. Loads more could be said about this, but that is the gist of washout. Because it is the improved stalling characteristics at the wing tip that we want - some airplanes have little (or no) angular washout as such - instead they have a different wing (airfoil) section at the tip that stalls at a higher angle (and thus delays the outboard stall). It is also true that there are aircraft with zero washout of any nature. How much washout? Any amount of washout will contribute to the above advantage, but as we add washout (reduce incidence over some of the wing) we also reduce the amount of lift the wing is creating. As such, washout is good - but only to a point. I would suggest that somewhere between 1.5 and 2.5 degrees of reduced incidence at the tips would NORMALLY be about right. But normally the washout (wing twist) would start where the wing "starts" - right by the fuselage. Because the KR has a centre section, the washout only starts where the outer wing panel starts, so we need to get in a bit more twist over a shorter distance. The angular amount should thus be a bit more - so maybe 2.0 to 3.0 degrees for a KR. The optimum amount is effected by so many things (wing section, wing span, wing loading, speed range, mission requirement, etc.), but I believe that anything in this zone will do the job. To refine your decision, have a close look at web sites like Langford and Reid - they discuss their reasons for what they have decided on - these are informed opinions. Above we talk about the angular relationship of the wing tip to the wing root. Your other question is about incidence - the relationship between the whole wing (washout and all) to the fuselage. Kenny made it 3.5 degrees (root) and hundreds of KR's are happily flying about like that. The little bird looks a bit like an Apache helicopter on a beat-up, but the nose-down "sit" is a part of the KR character. So, for openers, the plans way works just fine. It is however also true that 3.5 degrees is not very efficient for the KR as it has evolved, particularly for the airplanes that are aspiring to 140mph and more. It does not sound like you are using the new wing section so it is less significant for your KR, but 1.5 to 2 degrees less than the plans call for may be a good idea. Ask 10 guys and you will get 11 different answers. The 12th answer is (RAF 48) 2 degrees at the root with 2 degrees washout (0 at the tip). Take care Steve J
