Trailing Edge Angle on a Delta

[NX-687]

I tried a few different LE sweeps on my delta and I can see what that does now in relation to rudder commands

My question is does the angle of the aileron hinge line on a delta type have any effect on the effective dihedral of the wing

In other words if I move my aileron hinge line at the wing tip towards the wing centre will that give the wing effective anhedral

[NX-687]

On the Slofly Forum and he said if you heavily angle the hinge line in that way ,it will cure adverse yaw with rud commands , I guess that means either upright or inverted , with this design,, as he is a true 3D flyer

I cant see it myself unless I test it on a model

[JetPlaneFlyer]

I think you are getting your yaw/roll couple mixed up with adverse yaw...

I cant see any reason that an angled elevon hinge would have any influence at all on rudder initiated yaw/roll couple (which is what you have been complaining about previously).
Adverse yaw is a different thing .. It's is when the model yaws to (say) the left when given an aileron roll command to the right. This could possibly be helped a little by having the elevons wider toward the tips as wider control surfaces may be less prone to adverse yaw than narrow ones.

Steve

[nmasters]

...wider control surfaces may be less prone to adverse yaw than narrow ones.
Not exactly. Tapered elevons reduce adverse yaw because they approach the minimum drag, half lemniscate, shape. Even if you could reduce the drag of the control surfaces to 0 you would still have adverse yaw because it's not the drag of the control surfaces that creates the yawing moment, it's the aft tilt of the resultant vector (http://www.rcgroups.com/forums/showthread.php?p=5887550&highlight=adverse+yaw#post5887550) i.e. induced drag of the wing NOT the control surface.

--Norm

[JetPlaneFlyer]

Norm,
Yes, you cant get away from the fact that the reality of induced drag means for given planform more lift = more drag... However having a wide aileron deflected at a relatively small angle produces a 'better aerodynamic shape' with better l/d ratio than a narrow aileron deflected at a large angle... so wide ailerons 'may' be slightly better.

Steve

PS... would 'approach to a half lemniscate' or otherwise caused by a tapered elevon not also depend on the planform and twist of the wing? If the wing was designed to already have such lift distribution then having tapered elevons (wider at tip as I think has been suggested) could cause the wing to deviate further from it? Couldn’t it?

[NX-687]

Im talking about a flat plate delta wing foamy at high AOA , high motor thrust , massive aileron deflections, no forward speed , with massive inboard counterbalanced ailerons and we want exactly symmetrical performance whether upright or inverted, , nmasters ,,,does that diagram still apply , I think they mentioned it was for 5/
10 degrees deflection , my plane is sort of an out of the ball park type flyer

High deflections, low speed mixed with prop thrust of a very large dia prop

For myself I dont see my model having a yaw problem , with a straight aileron hinge line ,
I will build one with a lot of angle and just fly it to find out


thanks for the comments


Its helpful in some ways , in others I dont get it

[JetPlaneFlyer]

At some pont you will have to accept that deltas and any highly swept wing have certain flying charecteristics that are inherent in the layout, dihedral effect yaw/roll couple is one of them. You can do things to modify these charecteristics (like adding anhedral) but these modifications also have their own side effects (like making the issue worse when inverted).

Bottom line is that if you want the model to perform like a contest aerobatic ship then it's probably going to have to look pretty much like one.

The only way to remove the yaw/roll couple (or at least remove most of it) is to take out any sweep and or dihedral/anhedral and . Of course if you remove the leading edge sweep you wont have a delta anymore because a delta by definition is 'an object shaped like a triangle'.

[MCarlton]

nmasters ,,,does that diagram still apply , I think they mentioned it was for 5/
10 degrees deflection , my plane is sort of an out of the ball park type flyer


I would have thought so, because it doesn't matter what sort of model it is, you still have the same parameters of induced drag etc which you affect by control surface deflection.

I don't know if it would work, but if you extend the rudder height so that 50% of the area is BELOW the wing, you might get a better and truer rudder response at high AOA, as the wing will not be blanketing the rudder as could be the case otherwise.

I know thats not the answer to your question, it just occurred to me.

I don't think that changing the hinge line angle will make a difference to roll/yaw couple, at least, I can't see how it can. Tapering the elevons MAY, but that would be the same effect with a right angle hinge line and tapering the elevons from the TE.

I think the real answer is that if you want anhedral effect, then add anhedral.

[Brandano]

I think that the angle on the hinge line of elevons might well affect the yaw coupling the same way the hinge angle on the rudder affects pitch coupling. You have to consider how much side area of the elevon is visible on the side projection of the plane, and at what angle this is when compared to the airflow.