Dag,

Once again with respect you are stating the obvious and it does not relate directly to my point.

Let me try again: Almost all modern designs have a surfeit of potential longitudinal stability. That is you can balance them over a wide range and still have some. What they don't have is a surfeit of directional or yaw stability (which is also CG dependent) and so when choosing a CG position it is often compromised by the need to retain some yaw stability. What is needed is a redistribution of vertical area i.e. bigger fins. This is something that designers seem to have cottoned on to if you look at Chip Hyde's new bipe and I'm sure Bryan Hebert will have it sussed with his new Allure.

Here's a case in point. My new Hybird bipe when balanced at the designer's recommendation goes to the canopy in knifedge. Up lines are perfectly straight in yaw and pitch and down lines are straight with a smidgen of low throttle/down elevator mix. All my trimming experience tells me it is nose heavy so I start to move the CG back. When I get to 30mm behind the designer's position it starts to straighten the knifedge and it needs to go back further. BUT it has started to wander directionally on pushes and doesn't feel as nice to fly generally. So as a temporary fix I have moved the CG forward to the design point and put in a very small rudder/elevator mix. The real cure is an increase in yaw stability which will require some strakes or other devices on the tail. Unless somebody knows different............

Malcolm