My recollection, from an aerodynamics class long ago, is that the tendency
of a wing to stall first at the tip and progress inward is not a function
of sweep. The sweep just makes it LETHAL.

Assuming that the wing has no twist, also known as wash-out, and that the
wing is well constructed and finished; then:
1 A straight (Hershey Bar) wing will stall from the root outward.
2 An elliptical wing will stall all at once.
3 A radically tapered (2:1) wing will stall from the tip inward.
4 A moderately tapered wing will approximate an elliptical wing.

The earlier comment regarding the canard vortex on the Vari-Eze is an
excellent note of caution, as it will tend to simulate reverse wash-out
of the main wing. Therefore, it the main wing was ever allowed to stall,
it could be expected to do so in the manner of a wing with a much more
radical taper ...

BTW, radically swept tapered wings have the reputation of being impossible
to recover from a stall -- if you allow it to occur!

Peter

Paul Lee wrote:

I know about what should be about CG and main wing should
not be allowed to stall, etc. etc. But my question is about
possible further improvement.

I mistyped the last sentence question.
"..has anyone investigated placing a few vortilons near
outer wing part to compensate for the early tip stall tendency?.."

Should have been
..has anyone investigated placing a few vortex generator tabs near
outer wing part to compensate for the early tip stall tendency?

I am talking about the popular small VG tabs on top of the wings.
And if a few could be placed near the last 1 or two feet of the outboard
wing part to improve wing stall. The usual vortilon tabs used on swept
wings are not really on the extreme part of wing outboard but rather almost
mid wing.

Inboard (imagine wing sweep)
---------------------------------------------------------------

/ \ / \ - extra VG's
---------------------------------------------------------------
| | | - current vortilons

David Lednicer wrote in message ...
I have the copy of the CAFE test of Cozy Mk IV canard where it states
that swept wings tend to start stalling at the tip rather than the root.
This moves the center of lift forward and is a bigger problem for aft
CG.

By the very nature of a canard configuration, if the aft wing stalls,
the tip will stall first, as it it in the upwash caused by the tip
vortex coming off the canard. The inboard part of the aft wing is in
downwash from the canard. With that said, the aft wing of a canard
aircraft should NEVER be allowed to stall. If it does, the neutral
point will shift forward and the aircraft will become longitudinally
unstable. The idea is for the canard to stall first. This makes the
airplane more stable and causes the nose to pitch down.

While canard planes swept wings typically already have those
"vortilon" tabs, has anyone investigated placing a few vortilons near
outer wing part to compensate for the early tip stall tendency?

The vortilons are always placed on the outer part of the aft wing of a
canard configured aircraft, to keep the outer aft wing from stalling.
There is no sense on placing them on the inboard wing, unless the
aircraft is really screwed up.

On early VariEzes, it was found that the outboard portion of the aft
wing, of poorly built aircraft, would stall. Rutan retrofitted a cuff
on the outboard aft wing, to prevent this stalling.