Flying Wing Control Surfaces

[Tailwind]

When playing KSP 1.0.4 I had come up with a pretty good airplane to do the aerial survey contracts.  It was a flying wing design with a fuselage.  It had radial intakes near the Mk 1 cockpit up front a Wheezly in back for normal thrust.  The fuselage had one liquid fuel tank and a rocket fuel tank to feed a pair of Thuds at the rear of the fuselage for the zoom climbs.  The wings were swept with strakes and a single fin and rudder on the fuselage.  It was rather remeniscent of a LongEZ without the canard.  (I hadn't unlocked the canard yet.)  The airplane flew very well, with stall speed under 30 m/s.

Now in 1.0.5, still fairly early in a career campaign I'm trying to build a similar airplane.  The problem is the control surfaces, (elevons and discrete elevators) deflect in the opposite direction needed.  I don't remember from 1.0.4 if there was a setting to reverse the throw on the controls, or if it just recognized that there was no canard.  Has this function been removed from the game in 1.0.5?  Is there a way I can reverse the control throws manually?

 

Gerry

[Val]

I believe, control surfaces automatically determine their deflection direction depending on whether their hinge axis crosses the centerline infront or behind CoM.

Though I'm not 100 % on that. But it's definitely dependent on CoM.

[Claw]

Val is right. What you might be running into is when using a swept wing...If the connection point of the swept wing happens to be in front of the CoM, but the control surface is behind the CoM, the control surface will not deflect the correct direction (appears inverted). The fix is to move the swept wing further back.

[Tailwind]

Thanks for the thoughts Val and Claw.  I'll play with it some more and report what I find.

Gerry

[cephalo]

Another issue regarding the deflection angle of elevons is that wings seem to have a pre-determined leading edge. So if you have a delta wing on backwards, and then put elevons on what is now the rear, the pitch controls will work correctly but the roll controls will be reversed for some reason. Seems like a bug.

This bothers me a bit, because it's useful sometimes to have a reverse angle on the trailing edge when you have a flight profile with a high angle of attack, such as re-entry. It keeps things a bit more stable in that situation. Ah, maybe the game doesn't model things to that detail and it's just in my head. It sure looks cool though.

EDIT: It should keep the drag closer to the CoM in that situation, so your plane doesn't want to pitch toward prograde as much.

Edited December 10, 2015 by cephalo

[Tailwind]

Val, I think you've hit the nail on the head.  I played with the wing mounting position, as I moved them back when the hinge line projected back to the centerline of the fuselage behind the CG, then they started to work correctly.  I tried a few other things as well. I moved the wings forward again, and adjusted the sweep with the rotate tool.  With the wing tips ridiculously in front of the CG, but the hinge line still behind, the controls still work "correctly".

Anyway, my solution was to start with a 'structural wing B' with the long side (not the hypotenuse) at the fuselage, then added the swept wing outboard.  I moved the wing inboard with the offset tool, clipping well into the B wing.  At this point I still wasn't happy with the location of the center of lift position so I added a 'C' section of wing with the long end forward, to extend the strake.  I set up all of my conventional aircraft with the CL ball within the back half of the CG ball.  Tanks are centered at or slightly behind the CG so as they drain the CG moves marginally forward.

Anyway, got it working now, thanks for the thoughts everyone.

Gerry