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Flying wing scratch build help

#1
Hello guys,

I put this flying wing just this morning, and this will be my first wing, besides a failed FT-delta.

I got it up in the air, but i noticed that it's having a hard time gaining altitude.

I know i'm using a bigger motor than needed, so I lowered the end points on it to not give it so much power. could that be the problem?
I'm also only using a 1.25 inch control surface, Should i make it bigger?

It also has a want to kinda wobble up and down kinda like it's giving me a nod going up and down but of disapproval.

Any help would be much appreciated 999373_314519738683808_367119419_n.jpg
 

earthsciteach

Moderator
Moderator
#2
Go ahead and open up the throttle endpoints. Its always good to have the power if you need it.

The control surface size should be adequate. Do you have enough travel on them?

The "nod" may be due to the KF airfoil. Being flat, the wing can tend to snap through horizontal similar to you sticking your had out of a moving car and twisting your wrist. My first wing had a KF and it behaved the same way. Try dialing in some reflex to see if that helps.
 
#7
the reflex kinda helped, but i'm still having trouble making the plane recover.. eg. I was a good 4-5 stories high (idk how many feet that is) and i decided to try a flip. It took a forever to gain altittude, and even longer to recover once i was nose diving into the ground.

Should i have used kf-2 instead of kf-4?

Am i too nose heavy?

or just too heavy in general? (i'm using a 2200 battery)
 
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xuzme720

Dedicated foam bender
Mentor
#8
It might be nose heavy. Do the controls feel sluggish in pitch? A good quick check (If you feel comfortable doing it) on planes has been to roll inverted and see how much back pressure it takes to fly level. It being a wing may make a difference to this technique.
 
#10
heh, where i put my finger? I don't have a proper way of doing it, so I've been going mostly by feel.

but I've been measuring it about 4-5 inches from the tip of the nose of the plane
 
#12
well i got it flying good, other than the plane wanting to snap... Thank you everybody for you guy's help and input. Gonna try to build another one with a kf-2 airfoil, or maybe even a kf-3..

anyone got a plan of a 30 inch wing?
 
#13
nunieboy
Hmmm!
You say you are using KF4 airfoil.
How close is yours to the one in this diagram.
Is your leading edge really square as in your picture?

Your poor climb rate sounds like too little thrust or too much drag or both!
A simple test is to hold it pointing vertically up and at full power does it feel like it is virtually supporting its weight on the prop?
A good 'wing' should have a thrust almost equal to its weight.
With a good thrust to weight ratio it should climb well even if the CofG is a bit forward.
If the thrust is no more than half its weight flight will become pretty marginal.

I hope this helps
 
#14
hey quorneng.

I destroyed that wing.. sadly lol
but the thrust is plenty. i'm using the suppo 2208 motor with a 8'' prop
I just built another 30 inch
and this time i slowly kept pushing the cg back
and finally it's flying almost like how i want it to.
i changed to a kf2 also, and the sweep on the wing is a lot steeper.

now to make it 60 inch and fly fpv once my gear comes in =D
 

xuzme720

Dedicated foam bender
Mentor
#15
hey quorneng.

I destroyed that wing.. sadly lol
but the thrust is plenty. i'm using the suppo 2208 motor with a 8'' prop
I just built another 30 inch
and this time i slowly kept pushing the cg back
and finally it's flying almost like how i want it to.
i changed to a kf2 also, and the sweep on the wing is a lot steeper.

now to make it 60 inch and fly fpv once my gear comes in =D
Oh no! what happened? or did the airframe get scrapped to part out the 30"?
 
#16
I just crashed hard.
plane wouldn't let me pull itself up so it crashed. motor dislodged itself and ate away at the frame. good thing my electronics where all safe and it cost me $1 to build.. $1.50 for glue and labor =P
second one is flying tons better
 

xuzme720

Dedicated foam bender
Mentor
#17
I just crashed hard.
plane wouldn't let me pull itself up so it crashed. motor dislodged itself and ate away at the frame. good thing my electronics where all safe and it cost me $1 to build.. $1.50 for glue and labor =P
second one is flying tons better
Good to hear Ver. 2 is flying better. Instant re-modification is how most of my airframes get retired also.
 
#18
I thought about building a Delta wing and probably will after my glider project. I would suggest to try using the FT wing design they used in the FT3D and just cut at the proper angle you want and glue them together. Their airfoil design was simple enough to modify for me to use a whole 30" foam board. I think it will give a huge advantage in lift. Just my noob opinion.