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  • August 22, 2017, 10:11:52 PM

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Author Topic: Control Surface Deflection .  (Read 326 times)

Offline Matt Spencer

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Control Surface Deflection .
« on: July 28, 2017, 07:37:30 PM »
Throwing the Pigeon amougst the Cats ,  S?P

Asssuming you secure the leadouts ( say with a wire thru the eyes and hang it or use a hand there )

WHAT FORCE is required to displace control surface alignment . ( DONT GET TOO CARRIED AWAY HERE - YOULL WRECK SOMETHING , OR AT LEAST MISALIGHN THINGS, till you realign them )

Ones averge 3/32" horn .40 size sucker , it seems if you displace one elevator , say . the rest of the control surfaces join in the dance .

The Proviso would be , looking at the 70 Oz dunger Spitfire , That Flew Well in wind up to 20 Knots , where its two hands and
twanging a line in some square bottoms . . . .
This Had say 1/2 in ( ea Way ) deflection , spinging straight back , at the elevator ( 4 in. chord ) t.e.
with a non tempered 3/32 ' K ' wire dual wire horn , rear . BUT with elevator Ear Aerodynamic Balancers .
So Control loads where even , up to say 18 Kts breeze , doin the schedule . ( had a few other tricks too insside of it  :-X)

The Long bowed 3/32 flap wire alowed a degree of spring , say 1" to 1 1/2 " , if you got really carried away . ( 1 in elastic , 1 1/2 plastic
TECHNICALLY - Plastic is where it starts deformation .Say 1 1/2 Across Both side to side, just both flaps , elastic . 3 / 32 untempered wire .
( the wire Aryldited Along the surface at the hinge line , so only BETWEEN surfaces is it a torsion bar , rather than the full length of the wire ) .
Thus I guess where looking at ' What Is The ELASTIC deformation ( where it stays alighned ) technically It'd be degrees & Tourque ,
if in a Lab.

To visualise this tripe , consider the free length of the Wire as a TORSION BAR , like a MOPAR or D-Type Jag Fr. Spring . :(






AND , what is the Limit where it starts Missalignment ( Tourque applied ) where it give deformation of alignment , Starts to go ' plastic ' ,
Missaligns Control Surfaces .


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If We Look at the AIR LOADS ( Aerodynamic loads , Flying ) at say 18 Knots Air / Wind ,

Do these on occasion exceed the ' alined force ; of the surfaces- and control lines .

5 1/2 in NewZealand is when it starts getting your attention . If theres ' any wind ' , coastal - theres whitecaps .
When theyre steady and continuous , with pressure waves rolling through , flattening the sea
( The Regular Flying Site was near the Yacht Clubs , Boat Ramps etc ), a two Ft. ( + ) chop ,
one starts to pay undivded attention to ones flying .



We dont recomend flying in a Force 10 , but having done so in the early seventies with a Ton Plus Combat Wing ,
aquired an appreciation of control ridgidity .

« Last Edit: July 30, 2017, 07:45:37 PM by Matt Spencer »


Online Brett Buck

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Re: Control Surface Deflection .
« Reply #1 on: August 16, 2017, 09:28:54 AM »
Point 1 has been extensively discussed, and it why we use 1/8" flap horns. Note that the same problem happens with the wood part of the flap, leading to extensive measures like Howard's carbon tube LE.   I have even designed (but not built) a system that drives the flap from 3 different places along its length to keep it from flexing as much and remove the torsion bar associated with the conventional flap horn.

Point 2 is a restatement of the discussion surrounding the Netzeband wall. Howard also has a solution or improvement for that, his servo tab system.

    In every case I have seen, the lack of control authority means you hit the Netzeband wall before you are going to get to the plastic region of the flap horn, and if you *do* get there, your airplane is going to last about a week, because the fatigue will cause the horn to break

    Brett


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