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Spoilers on Flying wings? - 11/9/2012 1:15 AM   
shaunrbell



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Status: offline 		I'm putting a X8 FPV aircraft together and was wondering if spoilers would help get the craft on the ground using less airstrip.  I know it's an electric pusher, but I figured nobody knows more about spoilers than glider pilots.  I realize that when the spoilers are deploded, it will more than likely pitch the aircraft nose up being a flying wing.  But would mixing down elevator correct the pitch and allow the craft to slow down even further.  Just thinkin' lol....  Not really, I've got a pair of Hobby King electric spoiler units and my router waiting in the shop : )  Just thought I'd see what you guys thought before I start cutting.

 

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RE: Spoilers on Flying wings? - 11/9/2012 1:32 AM   
da Rock



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Status: offline 		Look at the location of the spoilers in relationship to the elevons. If it's up to you where the spoilers are going to be, you probably don't want them to blank the elevons. If you've got separate elevators and ailerons, you'll have to muddle over where to put them.

Automatic trim should always work to some degree so long as the elevator is still effective.

The location chordwise of the spoilers might effect which way the plane pitches when those spoilers are deployed. Do you know what airfoil is used by that model?

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RE: Spoilers on Flying wings? - 11/9/2012 2:55 AM   
vintagesailplnr


 

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Status: offline 		Hi:

I have one of the original WINDLORDS, scratch built from plans. BTW a fantastic 100" TD ship and FUN!
The WINDLORD is now offered as a kit from Ray Hays's website.
The barndoor spoilers are located on the bottom of the wing. If you are flying in the ground effect - deploying the spoilers will cause pop-up 5 or 6 feet.
I'd used the WINDLORD's design as a VERY good example of where to place the spoilers.
Looping the WINDLORD is a very tight 15ft circle. It can be banked over vertically in a thermal. I looped it once (on approach) to bleed off speed for a landing, ONCE!!!!
GOOD LUCK
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RE: Spoilers on Flying wings? - 11/9/2012 2:55 AM   
shaunrbell



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Status: offline 		Thanks for the quick response!  As you can see from the photo (the black wing), the elevons could be completely clear of the spoilers as long as the spoilers are mounted inboard on the wings.  As for the airfoil, I have no idea what it.  But as shown in the photo there's a good amound of reflex on the top.  None on the bottom though.   

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RE: Spoilers on Flying wings? - 11/9/2012 9:10 PM   
shaunrbell



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Status: offline 		Here's the same picture with the spoilers (added in photoshop lol) located inboard on the wings.  Do you think with some down elevoron mixed with the spoilers would work?  Kinda like backwards crow.   

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RE: Spoilers on Flying wings? - 11/9/2012 11:20 PM   
da Rock



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Status: offline 		It might work. It might work great. But I would not try it first thing.

Reflex airfoils with ailerons can lose their reflex when the ailerons are deflected downward. Wings with any type airfoil wind up with wash-in when both ailerons are deflected downward. Wash-in is the opposite of wash-out. Wash-out is what is used to cure tip stall. Wash-in increases the possibility of tip stall. It might be best to approach that backwards crow idea after trying some other things first.

In fact, you might discover the spoilers work better than you imagined they would. They also might cause problems. It'd be good to sort the plane with spoilers out first, and then throw some other stuff at it. It's already in unknown territory.

Man, it would be kewl to live close enough to be around when that thing is maidened.

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RE: Spoilers on Flying wings? - 11/10/2012 12:13 AM   
shaunrbell



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Status: offline 		Guess I could always put a second set on the botton.  Of course that would call for some landing gear lol! 

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RE: Spoilers on Flying wings? - 11/10/2012 2:20 PM   
webdragon


 

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Status: offline 		how about using a drogue chute instead?

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RE: Spoilers on Flying wings? - 11/26/2012 2:47 AM   
OzMo



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Status: offline 		Have you considered spoilers out on the tip fins? Drag is drag after all, verticle won't matter. They could be set up to both swing in or out and be mechanized like a spring loaded pull only rudder.

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RE: Spoilers on Flying wings? - 12/5/2012 10:30 AM   
guille2006



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Status: offline 		Shawn; word of aeroengineer: DON'T PLACE THE SPOILERS THERE; YOU SURELY WILL CRASH THE PLANE.
Spoiler there cancels the lift of the center part of the wing; wich is in front of the CoG. With so, the center of pressure (CoP) for lift will be way long behind the CoG and the effect is a build up of stability and most probably, control surfaces will be not enough... the lack of lift will do the rest.
This type of wings (relfex airfoils + small twist), normally uses split elev/ailerons to increase wing twist contemporaneusly with a drag increase; keeping always the CoP in the same place relatively to the CoG.
Note that F-wings are very sensitive to changes on pressure distribution as most of commands are executed by small changes on wings moments intead of a lift force on a tail (on conventional planes).
A small foam model can be built in 1/2 hour and will allow you to make all the necessary findings for a spoiler placement.
Hope it helps...
G.

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RE: Spoilers on Flying wings? - 12/5/2012 1:41 PM   
aeajr



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G.

I don't understand how spoilers combined with up elevator would not balance.  Naturally you have to play with the mix. 

Another thought is flaps.  If you were to extend the moveable area of the wing by adding flaps you could enact a crow mix that lowers flaps and raises the elevons in a crow like fashion.    I would think you could significantly slow the wing and with the right balance of mix perhaps not create too much  instability. 

It would require some trial and error and, of course, you would need mixing capability in your radio.

 




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RE: Spoilers on Flying wings? - 12/5/2012 1:44 PM   
guille2006



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quote:

ORIGINAL: aeajr

Would the wing handle flaps?  If you were to extend the moveable area of the wing by adding flaps...



No; flaps alters severely the moments balances of a wing. The only option is to increase twist; which increases also drag and Lift too...



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RE: Spoilers on Flying wings? - 12/5/2012 1:49 PM   
aeajr



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Status: offline 		Well, if you are in an experimenting mood, I would  add the spoilers.  Do your testing WAY HIGH.  If they don't work out, just don't use them. 


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RE: Spoilers on Flying wings? - 12/5/2012 1:53 PM   
guille2006



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Status: offline 		...If so, let us know the results... I'm curious anyway.

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RE: Spoilers on Flying wings? - 12/5/2012 2:05 PM   
ARUP


 

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Status: offline 		The Horten III had spoilers on top of wing. They were very small... ~8% of span and were located behind the c.g. The Horten IV and VI used air brakes top and bottom of wing which were of ~20% span. Try the spoilers but don't make them as large as you have in photo. Move them as foward to the c.g. as possible, too. If they are too far back they will induce an 'up' type of trim. It doesn't take much to reduce lift for a flying wing because a large percentage of the wing is for 'stabilizer' effect. It's a short coupled stab... that's why c.g. for flying wings is so critical. Hope that makes sense. I don't have experience with flying wings but have talked with folks who have. A scale flying wing is in the 'cue' for building very soon so I have been getting lots of practical data together.

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RE: Spoilers on Flying wings? - 12/5/2012 2:16 PM   
aeajr



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Status: offline 		My suggestion is that you cut and remove the foam for the spoiler very carefully.   Retain it for the top of the spoiler so that the spoiler conforms to the shape of the wing.  This way, during flight, it has minimal impact on the shape of the wing.  And, if you decide you will not be using them, again, minimal disruption to the shape of the wing.

On most of the glider wings the spoiler is right behind the spar. 




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