>Shouldn't the flap and ailerons move the same amount >to keep drag to a minimum where the flap and aileron meet?
No. This would create an even bigger discontinuity at the center between the two flaps. Repost from a previous message some time ago: >I'd like to more about your thoughts >on aileron to flap mixing. A small >percentage of mix, one to one, >somewhere between? Why is good too. Deflected ailerons deform the load distribution away from the ideal near-elliptical shape, and hence increase induced drag. Partially slaving the flaps to the ailerons can alleviate this load distribution deformation, and thus mitigate the ailerons' CDi penalty. The question is what's the optimum amount of ail-> flap mixing. The lowest-drag aileron system is wing-warping as used by the Wright Brothers -- the wing is linearly twisted from tip to tip. When such a twisted wing reaches its steady roll rate, the load distribution returns to its optimum level-flight shape, and the drag penalty is zero. With a finite number of hinged control surfaces such a linear twist cannot be achieved. But it can be approximated as close as possible if each surface's deflection is made proportional to its distance from the aircraft's centerline, measured at the surface midpoint. If the four control surfaces have equal span, we then have: surface mid_span_loc. deflection ------- ------------- ---------- L.aile -3/4 -100% L.flap -1/4 -33% R.flap +1/4 +33% R.aile +3/4 +100% So for this wing the flap motion should be 33% of the aileron motion. Using AVL I've verified that this mixing ratio produces very nearly the smallest induced drag penalty. If the flap span differs from the aileron span, the table above can be adjusted accordingly. Longer flaps will have larger travel and vice versa. BTW, this "distance-proportial deflection rule" strongly argues against stopping the ailerons short of the tip. The resulting unhinged tip portion should in fact have the largest deflection. The "distance-proportial deflection rule" can be fudged if there is a tip stall problem in a sustained turn, where some opposite aileron must be held. By increasing flap travel over its "optimum" amount, the flaps can carry a greater share of the roll power, which reduces the required downward deflection of the inside aileron, and thus delays tip stall. So if your TD glider has insufficient tip stall margin, I suggest increasing the flap mixing and you should see some improvement. The extreme case would be 100% flap mixing, which mimics full-span flaperons. Flaperons give excellent tip stall resistance, as is obvious to anyone who flies a DLG with a good 2-servo wing. A 4-servo TD wing with decent planform should not need to go to this extreme, especially if it has some washout like the Aegea wing. RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
