maxvadas wrote: ↑
December 14th, 2019, 6:38 am
On both of my flaps, the trailing, middle edges of the foam are about an inch lower than the trailing middle edges of the balsa wings, I don’t really know how to explain the deflection of my rudder, but I’ll try. The very bottom of the balsa leading edge is 4 mm from the carbon, and the bottom of the trailing edge of the foam is 6 mm from the carbon rod. I don’t have any incidence shims, and the CG is pretty much exactly where the foam meets the balsa at the middle of the wings.
Good job with additional detail. Please remind me of the wing chord dimension (width of the wing). Is it 3” so that the balsa forward portion of the wing is 1.5” width and the flaps 1.5” width also?
Flap deflection of about an inch sounds like a lot. Typical for a 3” chord wing would be 3/16” to 5/16”. We measure this deflection with a ruler using a reference point that is parallel to the forward portion of the wing, like the fuselage top or bottom edge (depending upon design).
A lighter glider will always transition better than a heavier glider. If it possible to build another copy of the glider using lighter wood (possibly with carbon reinforcement, if necessary) or, sand the wing thinner (see my instructions for building the 2014 flapper in Hip Pocket Aero/Science Olympiad topic) etc. the closer your glider is to 3.0 grams (as long as each component is adequately stiff) the better it will transition.
Possible solutions to transition issues would be:
1. Add 1/100” shim (small shim cut from a playing card or card stock business card would work) between the leading edge of the wing mount and the fuselage and then tape the wing mount back in place. Test with low power, moderate inclination, and 20 or 30 degrees of bank after a change like this and gradually find the new optimal bank and inclination angles in successive flights as you increase power.
2. Steeper launch angle. This is risky as you might get a hard stall and nose down dive.
3. Build lighter.