Flying wing?
04-19-2013, 08:38 AM
#1
Senior Member
Thread Starter
My Feedback: (9)
Join Date: Nov 2008
Location: White,
GA
Posts: 1,958
Likes: 0
Received 0 Likes
on
0 Posts
Flying wing?
I have a trainer wing that I have no use for in the 50-60 inch range, do you think it's possible to make it into a flying wing?
04-19-2013, 10:56 AM
#2
Join Date: Oct 2002
Location: Chilliwack, BC, CANADA
Posts: 12,425
Likes: 0
Received 22 Likes
on
19 Posts
RE: Flying wing?
Unless it has a symetrical wing or is nearly symetrical I'd say no.
I'm assuming that it's a straight constant chord sort of wing with strip ailerons and the usual flat bottom generic "shoe sole" shaped leading edge and upper shape. So what you're asking about is a plank style flying wing.
For a plank wing to be stable it has to have a positive pitching moment airfoil. And the usual flat bottom trainer wing airfoil is strongly negative pitching.
The way to get around this is to add some upward "reflex" to the strip ailerons. But on a typical trainer the ailerons are not wide enough. And besides, the fixed forward portion of the wing is typically so strongly negative pitching that you would need to double the width of the ailerons and even then use a LOT of up trim. By that time the airfoil is so inefficient that it's like flying with spoilers deployed all the time.
On the other hand if this wing has a symetrical or "semi symetrical" airfoil with zero or very little camber it does not require much reflex to change the airfoil's pitching effect from negative to positive.
So in a way the answer is "it depends".
I'm assuming that it's a straight constant chord sort of wing with strip ailerons and the usual flat bottom generic "shoe sole" shaped leading edge and upper shape. So what you're asking about is a plank style flying wing.
For a plank wing to be stable it has to have a positive pitching moment airfoil. And the usual flat bottom trainer wing airfoil is strongly negative pitching.
The way to get around this is to add some upward "reflex" to the strip ailerons. But on a typical trainer the ailerons are not wide enough. And besides, the fixed forward portion of the wing is typically so strongly negative pitching that you would need to double the width of the ailerons and even then use a LOT of up trim. By that time the airfoil is so inefficient that it's like flying with spoilers deployed all the time.
On the other hand if this wing has a symetrical or "semi symetrical" airfoil with zero or very little camber it does not require much reflex to change the airfoil's pitching effect from negative to positive.
So in a way the answer is "it depends".
04-19-2013, 11:38 AM
#3
Senior Member
Thread Starter
My Feedback: (9)
Join Date: Nov 2008
Location: White,
GA
Posts: 1,958
Likes: 0
Received 0 Likes
on
0 Posts
RE: Flying wing?
It has a semi-symetrical foil, I think it's an avistar wing but I'm not sure. To be honest I'm not sure what the chord of a wing is, Im fairly new to planes.
04-20-2013, 11:56 PM
#4
Join Date: Oct 2002
Location: Chilliwack, BC, CANADA
Posts: 12,425
Likes: 0
Received 22 Likes
on
19 Posts
RE: Flying wing?
The "chord" is the term for the width of the wing from the leading edge of the main panel to the trailing edge of the ailerons.
I looked up some pictures of the Avistar wing and it looks promising for conversion. You will require a stub fuselage as you will need a place to put the radio gear and engine or motor. You also require a vertical tail. It won't fly in a stable manner without one. So all in all the easiest way is to build a short stubby fuselage for all this.
Because there is no horizontal tail you cannot balance the flying wing version at the same point as with the original model. Instead you will want to get the balance point to be about 18% of the "chord" length back from the leading edge.
The strip ailerons look to be wide enough that with the ailerons can be angled upwards enough to get the amount of airfoil reflex you require to make the airfoil positively stable in pitch. You will need to program the channels with a mix between the elevator and aileron functions. This way you can use the two servos with one on each side to act as "elevons" so they go up and down together for elevator and travel opposite each other for roll control.
I looked up some pictures of the Avistar wing and it looks promising for conversion. You will require a stub fuselage as you will need a place to put the radio gear and engine or motor. You also require a vertical tail. It won't fly in a stable manner without one. So all in all the easiest way is to build a short stubby fuselage for all this.
Because there is no horizontal tail you cannot balance the flying wing version at the same point as with the original model. Instead you will want to get the balance point to be about 18% of the "chord" length back from the leading edge.
The strip ailerons look to be wide enough that with the ailerons can be angled upwards enough to get the amount of airfoil reflex you require to make the airfoil positively stable in pitch. You will need to program the channels with a mix between the elevator and aileron functions. This way you can use the two servos with one on each side to act as "elevons" so they go up and down together for elevator and travel opposite each other for roll control.
04-21-2013, 04:27 AM
#5
Senior Member
RE: Flying wing?
Sounds like a good experiment to me! Uncover the wing. Remove the dihedral. Remove the ailerons. Build a jig so that it can be used to sand 'reflex' into each rib (i.e.- the top and bottom of each rib will be altered in profile). Build new ail-evators. Add a fin(s). Finish and fly. Good luck. Please post your reports, here!
