Blended wing drones - how do they even steer without obvious control surfaces?

I built a twin 70mm EDF delta a couple seasons back and the throttle sync thing was exactly as annoying as you'd expect. Even after calibrating both ESCs together they'd spool at slightly diffrent rates, so the plane whould wander left on launch until I fed in trim. What finally worked was putting both motors on one channel trough a mixer in my radio instead of a plain Y-harness, so any trim I added corrected both at once. Still not perfect, but good enough that I stopped noticing it after a few flights. On a turbine version I imagine the lag between spool-up and thrust makes it even worse, wich is probably why the real ones don't bother with redundancy on an airframe that only flies once. On the control surfaces, my take is they're there, just small and blended into the trailing edge where photos don't show them. My own wings always needed big elevons and a heap of expo to feel sane, and I put that down to the air acting thicker at our size. A full size wing gets way more bite out of a small surface, plus a computer smoothing things out behind the scenes.

I'd love to see that trickle down to foamies, but honestly my cheap wing with honest big surfaces taught me more than any smoothed-out design would have.

On the surface question, my money is on blended trailing edge control surfaces plus flight computers doing alot of the work. I say that because I tried the opposite experiment on my 48 inch foam wing. I built one version with big full span elevons and one with narrow strip surfaces tucked close to the root, roughly a third of the chord area, and flew them back to back. The small surface version flew okay until the air got bumpy, then it was all over the place. My cheap gyro in the tail helped but it could not fully make up for the lost authority. So yes, I think the full size stuff leans on computers to get away with less surface, but at our scale the air is just thicker relative to the wing and you pay for it. On twins, I ran twin pusher props on a scale project a few years back and it was misery. Two ESCs, two throttles, constant tweaking. I ended up going single motor with a bigger prop and never looked back. For a one way airframe I agree the second motor is dead weight. If one quits you are probably done anyway, so why carry the spare. The only reason I woud do twins again is for the look at a scale fly in, and even then I would put both on one mixer channel like the poster above described, because a plain Y harness was exactly what burned me the first time.

That mixer trick for the twin motors checks out, I did basically the same thing on a twin pusher and it made the throttle wander go away. My extra bit was putting a little rudder into the throttle mix so any leftover mismatch actually yaws the plane instead of just drifting. Made hand launches way less scary. On the surfaces side I agree with the blended trailing edge theory too. Mine had small hidden elevons that looked tiny in photos but worked fine once I bumped up the throws.

I don't buy the blended surface theory as the whole answer. I stuck a cheap stabilizer box on my old plank wing and it let me shrink the elevons way down, but the surfaces were still there and still visible. What changed was the receiver correcting tiny wobbles dozens of times a second, not the air getting friendlier. I'd bet these full size wedges have pretty ordinary moving surfaces that just sit flush til the computer throws them around hard. Also nobody in this thread has mentioned differential thrust much, and for a twin turbine airframe that seems like half the story to me.

Update: tried the narrow strip elevons on my spare foam wing, small surfaces with a stabilizer box doing the corrections like the plank guy described. It flies calmer than I figured but I still need a touch more throw for landing flare, so there's a floor to how small you can go. Also started playing with a rudder into throttle mix on the twin pusher, makes launch wander way less obvious. Still curious about spool rate, did anyone get that fixed in software alone?