RE: Spark F3A, from Krill Models - SPAIN TEAM
I have had a circuitous path to trimming the airplane to my satisfaction because (I believe) the recommended CG is incorrect (way too forward)IMO the drawing showing the CG position relative to the wing tube has the CG and wing tube mislabled (reversed). Once I recognized that and corrected it, I have been able assess the design....
The Spark has no negative aerodynamic tendenciesit has minimal to no pitch or roll with rudder; it does not pull/push in verticals. This is at a near zero-zero-zero wing-stab-thrust setupI may have about 0.25 degrees down thrust at this point. With rudder it tends to carve as opposed to skid around turns. It looks much more like a bipe in the rolling loop stuff in terms of yaw authority. This kind of yaw authority takes a bit of getting used to. The yaw authority is the product of the large fuse side area and careful design of side area distribution. Despite the side area, it responds well in a cross wind—its bias is towards over crabbing, which I find very desirable. All that fuse side area makes for easy rolling. Snaps are easy and reliable with this airplane, particularly stopping the snap. I believe this is due to the staggered wing plan form, which serves to make the airplane easier to stall (the opposite of what is done on full scale to prevent stall). This is one of the main reasons I bought the plane—easier and more reliable snaps.
Regards,
Andre Bouchard