> There is still something going on with the wing design of the JW and my
> flying wing. The wing planform and not so much the airfoil changes how the
> wing performs. I use the same airfoil on both my DS Raptor (straight leading
> edge) and my Combat Raptor (swept back wing) and the CG, control throws and
> flight performance is much different. The DS Raptor has a CG that is at 13%
> of chord rather than 28%. The DS Raptor needs less than half the control
> throws that the Combat Raptor needs. Finally the DS Raptor corners like it
> is on rails. The Combat Raptor will not fly if it is set up like the DS
> Raptor so the planform has an affect.
> What I am trying to figure out is why. If I can figure out the Lift Roll
> program I will set up both wings and see what the difference is.
Are you accounting for the zero-lift angle changes from
the surface deflection? The Zagi's inversely-tapered
elevons will produce more loss of lift outboard.
Also, there will be a pitch rate effect on the
lift distribution. On a swept wing, different spanwise
locations see a different freestream angle if there's
a substantial pitch rate present. This in effect modifies
the effective twist angle distribution, or the effective
zero-lift angle distribution, whichever way you want to
look at it.
In practice, this pitch rate effect cancels some of the
up-elevon trim power near the tips of a swept wing, so
more up-elevon is required to get the same effect. That's
probably what you're seeing in flight. I'm not sure if
Liftroll takes this pitch rate effect into account.
Up-elevon significantly reduces the CLmax of the section,
so the larger deflections required by the swept wing may
induce partial stall, or at least a large profile drag rise.
- Mark
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