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Extra 260

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Old 11-03-2006, 08:09 AM
  #1
isaacslaw
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Default Extra 260

Hi Guys!

I am doing my first-ever scratch build. I have decided to do an Extra 260 set up for my YS110. I was thinking the wingspan should be around 66-69 inches or so and am trying to hit 8 1/2-9 pounds all up. I am doing this in order to learn about airfoils and construction techniques. I am getting some help with autocad, but as far as appropriate airfoils I still need some info. Does anyone know where to find a good definitive source for airfoils? I am hoping to design a good slow speed 3-d capable plane that will also do allright with pattern.

Also, it appears to me that the wings are perfectly perpendicular to the fuse on the leading edge -- can anyone confirm this? or is there a slight taper?
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Old 11-03-2006, 08:24 AM
  #2
jowily
 
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Default RE: Extra 260

there is a slight taper I have an airwild extra 260 the only plane I know if that has a perpendicular front leading edge is the EDGE
I may be wrong but this is my experience.
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Old 11-03-2006, 11:56 AM
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mmattockx
 
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Default RE: Extra 260


Quote:
ORIGINAL: isaacslaw

Hi Guys!

I am doing my first-ever scratch build. I have decided to do an Extra 260 set up for my YS110. I was thinking the wingspan should be around 66-69 inches or so and am trying to hit 8 1/2-9 pounds all up. I am doing this in order to learn about airfoils and construction techniques. I am getting some help with autocad, but as far as appropriate airfoils I still need some info. Does anyone know where to find a good definitive source for airfoils? I am hoping to design a good slow speed 3-d capable plane that will also do allright with pattern.

Also, it appears to me that the wings are perfectly perpendicular to the fuse on the leading edge -- can anyone confirm this? or is there a slight taper?
For airfoils, the NACA 00XX series are decent for all-around use. I would thicken the trailing edge up a bunch, though. A thick TE gives better control response, softens the twitchiness around center (like expo) and is more resistant to hangar rash. Easier to build, as well.

For more pattern oriented use, the NACA 63 and 64 series are good performers. It should be noted that Dick Hanson has told me he simply draws his own airfoil with a curve at the front, with the high point at about 30% and a straight taper back to a thick TE. His experience (vast experience, that is) has shown the airfoil is not very critical for model use and that wing loading and power loading along with straight, light construction are far more important. I have drawn up a couple of planes using Dick's approach, by drawing an ellipse (in AutoCAD) that has the high point and thickness I want, then a tangent line from the ellipse straight back to the TE. It looks reasonable, but none have flown yet. I did build a couple of small 15 powered models years ago with a similar home brewed airfoil (before I ever spoke to Dick H about it) and they flew fine.

The 260 has a LE taper. The way I would do it is to have my high point line run perpendicular to the fuse center line, and let the wing taper form the LE and TE tapers. No dihedral, either, the centerline of the tip airfoil should be dead level with the centerline of the root airfoil. Also, for pattern flying start with a 12% root and taper to a 10% tip airfoil.


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