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XLFR5 Reverse Engeneering Verhees Delta

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berridos

Well-Known Member
Joined
Oct 10, 2009
Messages
1,164
Location
madrid
Hi everybody

I am having a hard time understanding the verhees delta in xflr5.
Basic parameters of the original: CoG between 1270 and 1390 cm
Cruise speed 220kmh = 62 ms
Nowhere is stated the reflex used in cruise, but on the main plans, i measured on an uncommented picture, an up reflex of 1,5º
After doing hundreds of trial and errors i tried to put some system into the exercise.
I launched three packs:
The first pack shows the plane on type 2 analysis with the elvon at 3º reflex and varying the cog from 1050 up to 1550cm, beeing the white one the lowest with the most forward Cog.
The second repeat the same exercise but with 2º reflex.
The last picture repeats the exercise with 0 reflex. (this pic is the only useful i guess and its the last one)
The airfoil at the root is a 63020A, thinning to 63011A at the tip.
Anheadral is 7 or 7,5º, washout 1,5º.

Appearently this plane doesnt need reflex, as the fin is pitching up more than enough so my previous research was superflous. Is my interpretation right?
The model is incomplete by a short stubb fin that protrudes below starting at the thickest airfoil section and that hosts the rear landing gear.
We do i only get all the curves on the CM vs AOA graph?

Is the nose attitude really 4,5º uop in cruise flight in the 0 reflex version?

In the 0 reflex version i always have pitching moment. Shouldnt i have steady flight with neutral pitch?
For a plane to be stable, the cm curve has to be downward sloping?
When the cm curve is horizontal, is that the neutral point?
I have a spanwise lift distribution. Does this graph have any value without the local cl max as a comparison in order to evalue the quality of the bell shaped distribution?
How does the lift distribution look like according your experience.?

I have tried reflexed elvons from 5º up to -1º degree down, but xlfr5 will always stop calculating at an AoA of 3º because the lift turns 0. Shouldnt the up reflex allow lift below 3º in steady flight?
I have a thousand more questions but hope some of these will be commented on. Thx
reflex 3.png


reflex 2.png
iso.jpgside view.pnglift distrib.jpgtopview.jpg

0 reflex.jpg
 
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