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New project : Fokker III Eindecker

Hai-Lee

Old and Bold RC PILOT
#5
a year ago or so I did my own wing warping E1. The tail was simple enough using Pull-Pull control lines and the wing also used a pull-pull setup on a large loop through both wings.

The guy wires were braided fishing line to reduce the stretching over time.

Whilst I managed to get it airborne I classed the effort as a failure due to the very short nose and the need to add significant weight to get it to balance properly. The extra weight made it very sluggish in the air and difficult to control as the speed fell away on landing.

The aileron servo needed to have significant torque as I did not remove the paper from the wing at all As for the warping itself the inboard section of the wing must NOT be connected to the fuselage from the approximate balance point and the moving of the inboard section of the wing is in excess of the tip movement.

If the build is light enough a half inch of movement is plenty for the warping and the wings can have dihedral for the first flights using the fixed guy wires and later reduced to no dihedral after a few proving flights. The most difficult part is the attachment of the guy wires to the wing, (I embedded toothpicks into the wing with the guy wires attached). Fine adjustment of the guy wire lengths and the tension therein can be difficult and it caused me much drama initially.

The real design trick is to keep the tail and the tail boom extremely light or you will need a huge amount of lead to get it into the air. Extending the fuselage forward a small amount can help a lot in balancing.

Watching with interest!

Have fun!
 

Maxx

Active member
#6
a year ago or so I did my own wing warping E1. The tail was simple enough using Pull-Pull control lines and the wing also used a pull-pull setup on a large loop through both wings.

The guy wires were braided fishing line to reduce the stretching over time.

Whilst I managed to get it airborne I classed the effort as a failure due to the very short nose and the need to add significant weight to get it to balance properly. The extra weight made it very sluggish in the air and difficult to control as the speed fell away on landing.

The aileron servo needed to have significant torque as I did not remove the paper from the wing at all As for the warping itself the inboard section of the wing must NOT be connected to the fuselage from the approximate balance point and the moving of the inboard section of the wing is in excess of the tip movement.

If the build is light enough a half inch of movement is plenty for the warping and the wings can have dihedral for the first flights using the fixed guy wires and later reduced to no dihedral after a few proving flights. The most difficult part is the attachment of the guy wires to the wing, (I embedded toothpicks into the wing with the guy wires attached). Fine adjustment of the guy wire lengths and the tension therein can be difficult and it caused me much drama initially.

The real design trick is to keep the tail and the tail boom extremely light or you will need a huge amount of lead to get it into the air. Extending the fuselage forward a small amount can help a lot in balancing.

Watching with interest!

Have fun!
Thank you for taking the time to share your experience . Very much appreciated !
 

quorneng

Well-known member
#7
There is of course a good reason why wing warping was dropped in favour of ailerons other than for structural reasons.;)

If you think about it warping creates 'wash in' on the wing that is trying to create additional lift so any stall is almost bound to start at the tip first which exactly what you don't want particularly on a slow flying plane with a thin section under cambered wing. :eek:
I suspect some form if differential warping (more twist on the 'down' wing than on the 'up') would be beneficial but not so easy to arrange.
 

Maxx

Active member
#8
I started the warping wings prototype for my Fokker EIII .
Bamboo , plastic straws
002.JPG

007.JPG
008.JPG
013.JPG

Those fly fishing wire coils are VERY useful . I glue the two pieces ( each pieces are natched ) with just a bit of CA . When it's dry , I wire everything in all directions , ty a knot and cover it al with CA . This is very solid .
Will update soon .
 

Maxx

Active member
#9
a year ago or so I did my own wing warping E1. The tail was simple enough using Pull-Pull control lines and the wing also used a pull-pull setup on a large loop through both wings.

The guy wires were braided fishing line to reduce the stretching over time.

Whilst I managed to get it airborne I classed the effort as a failure due to the very short nose and the need to add significant weight to get it to balance properly. The extra weight made it very sluggish in the air and difficult to control as the speed fell away on landing.

The aileron servo needed to have significant torque as I did not remove the paper from the wing at all As for the warping itself the inboard section of the wing must NOT be connected to the fuselage from the approximate balance point and the moving of the inboard section of the wing is in excess of the tip movement.

If the build is light enough a half inch of movement is plenty for the warping and the wings can have dihedral for the first flights using the fixed guy wires and later reduced to no dihedral after a few proving flights. The most difficult part is the attachment of the guy wires to the wing, (I embedded toothpicks into the wing with the guy wires attached). Fine adjustment of the guy wire lengths and the tension therein can be difficult and it caused me much drama initially.

The real design trick is to keep the tail and the tail boom extremely light or you will need a huge amount of lead to get it into the air. Extending the fuselage forward a small amount can help a lot in balancing.

Watching with interest!

Have fun!
Thank you for sharing your experience , I took notes .
 

Maxx

Active member
#10
I ran some tests of the warping system and it kinda work ... the problem is the bamboo stick ( even if it's a giant skewer ) is too twisty .
So to make the wing warp just enough , the two little sticks linked to the servos have to travel way too much . So I will need a carbon rod or tube or an arrow shaft . Something that will not twist . Although it didn't work , it still was a good test and I think it will work with a bit adjustments . Feel free to make suggestions about that system or comment , I like it . Just remember no cable action ... :)

005.JPG
002.JPG
 
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BATTLEAXE

Well-known member
#11
There is of course a good reason why wing warping was dropped in favour of ailerons other than for structural reasons.;)

If you think about it warping creates 'wash in' on the wing that is trying to create additional lift so any stall is almost bound to start at the tip first which exactly what you don't want particularly on a slow flying plane with a thin section under cambered wing. :eek:
I suspect some form if differential warping (more twist on the 'down' wing than on the 'up') would be beneficial but not so easy to arrange.
Or you could reverse the warp by having the wing root move the most and have the tips solid, may take some designing and experimenting but it could be done.
 

Maxx

Active member
#12
Or you could reverse the warp by having the wing root move the most and have the tips solid, may take some designing and experimenting but it could be done.
It would eliminate the need of a non-twisty rod since it's so close to the servos . I think it would work , but kinda funny on the scale side .
 

BATTLEAXE

Well-known member
#13
It would eliminate the need of a non-twisty rod since it's so close to the servos . I think it would work , but kinda funny on the scale side .
The physics of aerodynamics dictates that is probably the way they should have done it in the past. It has advantages in two ways. The inner span of the wing needs more throw because there is less leverage, and the tips will stall last due to 0 angle of attack. If you had a solid spar running all the way to the tips supporting free rotating ribs to the root in my head it would work. It would also be a easier to fly I am guessing
 

quorneng

Well-known member
#14
Particularly with a rigged biplane wing warping can be easy to achieve just by the stick moving a pair of wires but this picture of the Wright wing does show the aerodynamic issue that results particularly as most flight took place not much above the stall speed.
WRIGHTWARP1910.jpg

Amy significant warp and the tip was bound to stall first!
 

Hai-Lee

Old and Bold RC PILOT
#15
It is very important that the wing LE on a warping wing does NOT move up and down under roll control. With TE warping the forces on the roll control input are progressively increasing with roll input whereas a moving LE will produce an additive roll input and eventually the aerodynamic forces will want to maintain full warp angle or rip the wings off of the craft.

Before powered flight controls the way they reduced control stick forces was with balanced control surfaces and the portion of the control surface LE that was moved was very small as the forces generated by the balancing portion of the control surface were far greater, (for unit area), than the portion of the control surface TE that was moved.

Effectively you need to make the front portion of the wing very rigid and only warp the wing TE. Wing warping designs generally have fixed guy wires to stabilize the LE and a set of guy wires on the wing TE that were able to be moved under control stick input.

Without locking the wing LE geometry a gust of wing will cause serious roll issues and even the stripping of the aileron servo/s.

Just a thought!

have fun!
 

Maxx

Active member
#16
It is very important that the wing LE on a warping wing does NOT move up and down under roll control. With TE warping the forces on the roll control input are progressively increasing with roll input whereas a moving LE will produce an additive roll input and eventually the aerodynamic forces will want to maintain full warp angle or rip the wings off of the craft.

Before powered flight controls the way they reduced control stick forces was with balanced control surfaces and the portion of the control surface LE that was moved was very small as the forces generated by the balancing portion of the control surface were far greater, (for unit area), than the portion of the control surface TE that was moved.

Effectively you need to make the front portion of the wing very rigid and only warp the wing TE. Wing warping designs generally have fixed guy wires to stabilize the LE and a set of guy wires on the wing TE that were able to be moved under control stick input.

Without locking the wing LE geometry a gust of wing will cause serious roll issues and even the stripping of the aileron servo/s.

Just a thought!

have fun!
O.K. I get it now ! Thank you , that makes a lot of sense .