What's the common thinking about making the main spar one piece? +++++++++++++++++++
I share your discomfort here John, plus a few others. I accept that the KR spar is stronger than a brick outhouse and there have been no reported failures etc. etc. It still worries me. As ever, I express my views in the hopes that the more informed among us will step in and put me straight. It is not so much the strength of the WAF's that concerns me, it is drilling all those holes in the spar (cap). Even the landing gear mounts require holes drilled in the upper and lower spar cap at the very point of highest load (almost). I cannot bring myself to do this - my intention is to add a wider pillar between the caps where the undercarriage mounts, add a 2mm 4130 "back-plate" behind the spar - then drill the mounting holes through the pillar - not the spar caps. This way the legs are sort of clamped to the spar without any holes in the load bearing caps - maybe even one size up on the ply web between the legs (and the necessary precautions against stress risers). I may compromise by having holes in the top cap (no plans for any inverted flight any time soon). The above approach is probably not acceptable for the WAF's, so this is my chosen way to deal with this particular concern and a few other short-comings at the same time. I plan to build a bent, laminated spar with the dihedral starting at the fuselage (as suggested by Mark L on his web site). Riley Collins has already done this and it worked out great. The next trick is to relocate the WAF's outboard to about half span. I.e. the centre section spar is "bent" up just as it passes through the fuselage side - and continues further out. = the load on the WAF's is now substantially reduced (shorter moment) so using the same (or similar) WAF design and material will substantially improve the margin. = doing away with the crank wing may look nicer to some of us - I personally like the way a KR looks anyway. = Fuel tanks (centre section) will drain better. = Flaps of better proportions. Take care Steve J
