Speculation about the KR-1 empty weight.... Disclaimer: I don?t yet have my KR-2S plan (but it is on order) so I can only speculate, not calculate. Having said that, there are other lighter single seat wood planes of similar configuration to the KR-1 that tells me that although a 310lbs KR-1 is very hard therefore unlikely to make, it is NOT impossible. My logic is based on the following:
A dozen SD-1 Minisport flies in Germany on the 120kg category and since the Germans are much more sticklers about specifications than we are here in the US, I have to assume that they measured at least one under 120 kg (264.5lbs). The engine on the SD-1 that is equivalent of a 36hp VW is the Verner JVC 360 (35HP, 32kg = 70.5lbs). If we deduct the engine weight from the 264.5lbs empty weight of the SD-1, we get the airframe only weight as 194lbs. A basic 1835cc 60HP VW is 135lbs per Hummel Engines website. If we hang this engine onto a 194lbs airframe, the empty weight of the resulting airplane would be roughly 330lbs. Not exactly 310lbs, but also not 450lbs. However, the SD-1 is not the lightest one, the Colomban MC-30 Luciole empty weight is only 214lbs (with roughly the same engine weight as the SD-1), so if one could hang a 135LBS VW engine on that airframe, the plane would weigh roughly 280lbs. Now I understand that this is all theoretical and to put a larger engine on an airframe would need changes to the SD-1 or MC-30 airframe, but I just wanted to point out that in theory one could add 30lbs carbon strength to the MC-30 airframe before it become 310lbs. Or the other alternative is to add a 36hp ? (half) VW to a light KR-1 saving 65lbs relative to the full VW and end up an SD-1 (KR-1 alike) airframe 194lbs plus a ? VW engine 81lbs with a total empty weight of 271lbs. Anyway, I mention again, my intention with this email was only to point out possibilities, because if one believes that a 310lbs KR-1 is not possible, that no one will ever try it. However if one tries it, one may end up with a 330lbs plane and that is still very light by any KR standard. I hope you forgive me to voice my opinion without even a plan. (Steve J?) Thanks, James
