Originally Posted by g_munu
Well, the prototype's got wing trouble. I took a chance by mounting the wing "upside down" with the larger KF step on top. The resulting configuration requires a ton of up trim to fly right and has a nasty tip stall. Oh well, I'll probably revisit this design again soon.
One large step on top would not be "upside down". That is simply a KFm2
type airfoil and should be a decent choice for prototyping this sort of wing. i would not give up so easy. Just move the CG back a touch at a time.
Did you test glide the model before truing to take to the sky? I always give my prototypes short test glides (neutral trim) to see how they go. I toss them from the bedroom door onto the bed (soft landing) and see if they come down nose first, tail first, or land flat on their belly. 5 - 10 tosses like that will give you a reasonable idea as to where your CG is, and get you ball parked enough to head out to the field. About the only thing I would of done differently this the wing is given it a KFm4
airfoil as it is a symmetrical type and usually works a bit better with flying wings than the type 2. I personally like using the KF airfoils for prototyping as they are very fast and cheap to build while allowing one to test new designs for flight worthiness.