At 03:23 AM 5/12/2015, you wrote: >I reckon it's bit more complex than just moving the wing. As a weight >alone, moving the wing back away from the CoG increases weight on the tail >for sure. To this extent Mike was correct in his comments on 10th May about >moving the wing forward to offset the tail heaviness. > >However, the centre of lift is also moved backward which could act >aerodynamically to counteract this which I think is what Sid was getting at. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
This issue of W&B is being made much more complicated than necessary. Kids figure it out every day on the play ground on the tedder toter. The fat kid moves in toward the pivot point or the skinny kid moves away from the pivot point to achieve balance. In our case we want to achieve balance slightly ahead of the Center of Lift for stability in the air and then position our landing gear to achieve balance on the ground. In the case of a tail dragger we place the gear to give us tail weight and a nose wheel configuration we want nose weight on the ground. Moving the wing back would in fact move weight to the tail but we also move the C of L to the rear, thus adding mass forward to the C of L, decrease mass aft of the C of L, and making the airplane more nose heavy in the air. Gear placement would have to be considered with such a change. In our case, with the airplane built, we don't move the wing but we move other items to get our center of mass slightly forward of the C of L, engine, battery, etc. In case of a gross error in the design or building, balance may not be achievable without radical changes. In our case we know that moving the engine mass a few inches forward of the C of L is usually enough to correct the problem. That was with the standard KR with a VW engine. As builders make changes , lengthen fuselage, heavier engines, fuel tank changes, balanced elevators, etc., they must take in to account this balancing act. The further you get in to the project and realize an error, the harder it is to correct. So, if the fat kid is setting on the tail, move the skinny kid further out on the nose, or make the fat kid lose weight, or make the skinny kid gain weight, the options are numerous. It's as simple as that. :-) Just remember, it's the C of L we need to work around, that being basically the C.G. spec's given in the plans. Larry Flesner
