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Old Dec 05, 2004, 04:23 PM
Striving to Rip the Bring
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No, it pushes bottom and top flow out. THere is no spanwise flow at the center, and it just goes out from there. This does NOT give a beneficial effect; in fact quite the opposite. It make the wing stall early and at the tips.

The tip vortex in the sense you spek is not signifigant on any real wing. All wings have the vortex fromshear effects between the downwash and outside air, but the vortex caused by spanwise flow does not occur on some planforms like an elliptical or pointed wing.

--Alex
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Old Dec 05, 2004, 08:51 PM
Ninja of the Nasty
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Joined Jan 2004
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Quote:
Originally Posted by AustinTatious
Ive flown a sonic ( King of the Hill's) and it was awesome!



They seem to turn much tighter and also have way more yaw stability. They fly more like a real airplane than a wing. Plus they never tip stall and start spinning!
just saw this.... yes the JW and sonic are the same foil/thickness.... and the sonic (old name aurora) was bowmans first real DS built plane a few years back.... from what ive talked to pat about it, from what ive been told

wings dont like to stay knifedge'd they have a tendancy to correct themselfs and flatten out... also when you take a wing (any wing ive flown at least) when you put a lot of elevator in and you go to POP the top turn it kinda washes out and spins... like turning on ice...

those are what ive heard and felt in all wings ive DS'ed... and the planks ive owned (jw, moth, m60, electron) i have never felt that wash out or felt them fighting to stay knife edged....

those are just my takes....

JOe
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Old Dec 05, 2004, 10:11 PM
Feeling FrSky
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United States, CA, Santa Barbara
Joined Feb 2003
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Hehe, I know why!

Because most of the swept wings on the market are designed for combat, not for DSing, and the planks are mainly designed for speed (and DSing) and not combat!

I'm a genius!

Steve
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Old Dec 05, 2004, 10:15 PM
Ninja of the Nasty
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haha...... and the award goes to surfimp steve...

LOL

great answer... you should be on jepordy

JOe
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Old Dec 21, 2004, 12:05 PM
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It seems to me there is a need for a swept wing that uses a spanwise difference in airfoil shape instead of twist to make a bell shaped lift distribution..something with CF 1/4 chord and rear spars to remain stiff in fast flight. EPP to give the airfoil shape, covered in mylar. The hope is to create a wing that will need neither twist nor control deflection (reflex) to maintain level flight.

been floating in my head for a while...I need to get back into crunching numbers...
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Old Dec 21, 2004, 07:42 PM
Striving to Rip the Bring
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Quote:
Originally Posted by grindel
It seems to me there is a need for a swept wing that uses a spanwise difference in airfoil shape instead of twist to make a bell shaped lift distribution..something with CF 1/4 chord and rear spars to remain stiff in fast flight. EPP to give the airfoil shape, covered in mylar. The hope is to create a wing that will need neither twist nor control deflection (reflex) to maintain level flight.

been floating in my head for a while...I need to get back into crunching numbers...
The twist generally isn't used for the lift distribution, though. It is used to counteract the downwards pitching coeffecient of the non-plank airfoils.

--Alex
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Old Dec 22, 2004, 12:15 PM
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With correct design (I.E. change your sweep to give the correct moment arm for the downforce),it can be used for both. You can get a bell shaped lift distribution (if your not familiar, it is similar to the eliptical lift distribution in that it is optimised for drag but has the added benefit of being suitable for trimming swept flying wings) while in trimmed flight.

In essence I am talking about the same thing you are...

ok...so anyway, reasons for the twist asside; what about changing the airfoil along the span instead of spanwise twisting? It might yield a stronger structure (at least a structure less sensitive to torsional loads) and less frontal area (reducing drag)
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Old Dec 22, 2004, 12:56 PM
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Modern airfoils nave their aerodynamic center at 25% (generally). That means they will twist around the 1/4 chord (25%). If the 1/4 chord is straight (i.e. plank wing), the wing is best able to resist this twisting force. This could be really important with EPP that doesn't have much natural strength.

A swept wing is easier to balance. No need for a nose hanging off the end (like JW's etc) to get the balance right.


Ken
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