Help! Deflection of control surfaces not even on both sides of the elevator in FT Flyer

Karthik1130

New member
Hello all, have built FT Flyer. The deflection of elevator control surface is not even in both directions.I have used 1mm pushrod, selected the closest hole to servo arm, placed the elevator control horn hole directly above its hinge line.
But still the deflection is found to be uneven, like high in the upside and low in the down side.
Please help.
 

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Foamforce

Well-known member
It doesn’t explain why the deflection is different on both sides, but your hinge was cut upside down. It should have been cut in the bottom instead of in the top. Effectively that just means that you’re in a hole further from the actual hinge, and are geared lower than expected, giving you less total throw. That’s not a big deal though, because you can just move the linkage out further on the servo arm.

I don’t see anything obviously wrong that would cause much difference in deflection. The only thing I can spot is that because the push rod is coming down at a slight angle instead of being parallel with the elevator, and because the control arm hole is exactly above the hinge (correctly), it ought to give slightly more down throw tab up throw. It won’t be a big difference though.

Just increase the throws by moving the servo linkage out until you have at least enough throw to match or slightly exceed the throw gauge on both sides. The use end points in the radio to reduce both sides to match the gauge.
 

AIRFORGE

Make It Fly!
Moderator
Hello all, have built FT Flyer. The deflection of elevator control surface is not even in both directions.I have used 1mm pushrod, selected the closest hole to servo arm, placed the elevator control horn hole directly above its hinge line.
But still the deflection is found to be uneven, like high in the upside and low in the down side.
Please help.
Yes, the bevel cut on the same side as the control horn will create a slight limit of upward elevator movement in this case. (Horizontal stab appears to be upside down) It's best to have the control horn on the paper side of the hinge, like you have done on the rudder. Also, check for excess glue all across the hinge point and uneven or not enough of a bevel cut.
 

Karthik1130

New member
Yes, the bevel cut on the same side as the control horn will create a slight limit of upward elevator movement in this case. (Horizontal stab appears to be upside down) It's best to have the control horn on the paper side of the hinge, like you have done on the rudder. Also, check for excess glue all across the hinge point and uneven or not enough of a bevel cut.
It doesn’t explain why the deflection is different on both sides, but your hinge was cut upside down. It should have been cut in the bottom instead of in the top. Effectively that just means that you’re in a hole further from the actual hinge, and are geared lower than expected, giving you less total throw. That’s not a big deal though, because you can just move the linkage out further on the servo arm.

I don’t see anything obviously wrong that would cause much difference in deflection. The only thing I can spot is that because the push rod is coming down at a slight angle instead of being parallel with the elevator, and because the control arm hole is exactly above the hinge (correctly), it ought to give slightly more down throw tab up throw. It won’t be a big difference though.

Just increase the throws by moving the servo linkage out until you have at least enough throw to match or slightly exceed the throw gauge on both sides. The use end points in the radio to reduce

It doesn’t explain why the deflection is different on both sides, but your hinge was cut upside down. It should have been cut in the bottom instead of in the top. Effectively that just means that you’re in a hole further from the actual hinge, and are geared lower than expected, giving you less total throw. That’s not a big deal though, because you can just move the linkage out further on the servo arm.

I don’t see anything obviously wrong that would cause much difference in deflection. The only thing I can spot is that because the push rod is coming down at a slight angle instead of being parallel with the elevator, and because the control arm hole is exactly above the hinge (correctly), it ought to give slightly more down throw tab up throw. It won’t be a big difference though.

Just increase the throws by moving the servo linkage out until you have at least enough throw to match or slightly exceed the throw gauge on both sides. The use end points in the radio to reduce both sides to match the gauge.
Thanks for pointing out the mistake, yes the control horn should be placed on the flat side and not on the bevel side.
The control horn location will remain the same right, as the hinge line location will still remain the same when the horizontal stabilizer is placed inverted.
 

Foamforce

Well-known member
Thanks for pointing out the mistake, yes the control horn should be placed on the flat side and not on the bevel side.
The control horn location will remain the same right, as the hinge line location will still remain the same when the horizontal stabilizer is placed inverted.

It‘s in the same place front to back, but it’s too high. The distance between the pivot point of the hinge and the hole where the control rod connects determines the amount of throw. Since you pivot point is on the opposite side, it’s the same as if you put the hole an additional 3/16” higher on the control arm, meaning that you have less throw than you would otherwise.
 

LitterBug

Techno Nut
Moderator
Are you getting deflection/bending of your push rod when it pushes? When it pulls, it will always be in a straight line. I had a similar problem with my FT Cub with the rear control surfaces. I ended up using tubing to keep the pushrod in line. Using a larger diameter wire would have worked too, but in my case would have been harder to implement.
 

Karthik1130

New member
Are you getting deflection/bending of your push rod when it pushes? When it pulls, it will always be in a straight line. I had a similar problem with my FT Cub with the rear control surfaces. I ended up using tubing to keep the pushrod in line. Using a larger diameter wire would have worked too, but in my case would have been harder to implement.

It‘s in the same place front to back, but it’s too high. The distance between the pivot point of the hinge and the hole where the control rod connects determines the amount of throw. Since you pivot point is on the opposite side, it’s the same as if you put the hole an additional 3/16” higher on the control arm, meaning that you have less throw than you would otherwise.
I am unable to understand.If possible could you share any image for understanding.
 

Karthik1130

New member
Are you getting deflection/bending of your push rod when it pushes? When it pulls, it will always be in a straight line. I had a similar problem with my FT Cub with the rear control surfaces. I ended up using tubing to keep the pushrod in line. Using a larger diameter wire would have worked too, but in my case would have been harder to implement.
Yes, I am getting a lot of deflection in the pushrod when the control surface move up and down, even after using ziptie. I ziptie at at many points along the pushrod to restrict it's bending but, the servo locks and makes a cranking sound.
I am using 1mm pushrod. Does tubing solve the problem? could you share any tutorial on tubing of pushrod.
 

Karthik1130

New member
Today made maiden flight of FT Flyer. It was windy with 13km/h wind.In the first handlaunching it nosedived and bamboo skewers got uprooted from wing and the wing got broken at front end.
I used packaging tape to secure the front end of powerpod to wing and handlaunched second time. Due to wind it couldn't fly straight, and again was about to nosedive.I immediately increased the throttle to 2/3 and took a turn and took it to high altitude and circled 2 times and suddenly the wing got broken and FT Flyer crashed towards ground.

I would like to know what is the recommended wind speed, and throttle to fly this as a beginner?
 

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Foamforce

Well-known member
Here’s a really poor illustration of what having the hinge on the other side does. The position of the pushrod connection relative to the pivot point determines the size of the arc. The hinge pivot on the bottom makes the arc bigger. The bigger the arc, the less movement in the control surface.
 

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Foamforce

Well-known member
Today made maiden flight of FT Flyer. It was windy with 13km/h wind.In the first handlaunching it nosedived and bamboo skewers got uprooted from wing and the wing got broken at front end.
I used packaging tape to secure the front end of powerpod to wing and handlaunched second time. Due to wind it couldn't fly straight, and again was about to nosedive.I immediately increased the throttle to 2/3 and took a turn and took it to high altitude and circled 2 times and suddenly the wing got broken and FT Flyer crashed towards ground.

I would like to know what is the recommended wind speed, and also the throttle to fly this as a beginner?

Hey, actually that’s not too bad for a first attempt! Congrats! Seriously, I didn’t get mine airborne for that long the first time I attempted to fly.

For beginning, you want <5 mph winds. It can be hard to be patient enough for a day like that, but it makes a huge difference.

For throttle, 2/3 to full is pretty good. You need to give it a good hard toss, a little upward. Just make sure it’s straight throw, like a dart, not like a football. 🙂
 

Karthik1130

New member
Here’s a really poor illustration of what having the hinge on the other side does. The position of the pushrod connection relative to the pivot point determines the size of the arc. The hinge pivot on the bottom makes the arc bigger. The bigger the arc, the less movement in the control surface.
Thanks a lot, it is really helpful.Now I am again rebuilding a new FT Flyer.
 

Karthik1130

New member
Hey, actually that’s not too bad for a first attempt! Congrats! Seriously, I didn’t get mine airborne for that long the first time I attempted to fly.

For beginning, you want <5 mph winds. It can be hard to be patient enough for a day like that, but it makes a huge difference.

For throttle, 2/3 to full is pretty good. You need to give it a good hard toss, a little upward. Just make sure it’s straight throw, like a dart, not like a football. 🙂
Thanks a lot for the information! Yeah here that wind speed happens from 6-10am most of the days.
I am handlaunching because , there is no landing gear.I couldn't bend 2mm pushrod by nose-plier. It's very hard.
So currently I am handlaunching.If you have any ideas on how to make diy landing gear it would be really helpful.
 

Karthik1130

New member
Lot of bending and twisting happening in the elevator control surface pushrod. when ziplock tied, the servo chatters during movement and still the elevator is not equally moving on either side.
 

AIRFORGE

Make It Fly!
Moderator
Lot of bending and twisting happening in the elevator control surface pushrod. when ziplock tied, the servo chatters during movement and still the elevator is not equally moving on either side.

With your transmitter, move the elevator up as far as it will go. Note/measure it. Then, remove the push rod and see how far the elevator moves upward. Are they the same?

Try removing or mashing a small bit of foam directly in front of the control horn where it touches the horizontal stabilizer. It should increase the elevator up deflection.

If your transmitter has end point adjustments, try adjusting them for the deflection you need.

Can you make and post a vid of the deflection from left, right, above, beneath, behind? I think it would help us see what's happening better.
 

Karthik1130

New member
Completed the built of FT Flyer, and I could use Bamboo skewer with z-bend at one end of pushrod and other end connected to bamboo skewer by ziptie and hotglued, and another pushrod connecting the other end of bamboo skewer and servo arm for the rudder.
For the elevator, used the first hole in the servo arm and found no bending in pushrod and there was even deflection in the elevator.

I don't know, why sometimes there is abrupt bending of pushrod in all directions and uneven deflection in elevator and rudder.But this time it was ok.

Took for a first flight at wind of 11km/h and it was success.No immediate nosedive crash after handlaunching. This time it was turning always to the right, and didn't responded to left turn.Then somehow I landed safely and found that motor was not screwed properly and tilted towards right.I rescrewed and then it was responding to left and right input.

I tried high- alpha flight by shifting the CG slightly back.
I took it to some high altitude to gain some time to react to the plane and took a big 180° circle left to right and was almost hovering for a few seconds and suddenly right wing got broken in the wing root in mid-air and plane crashed to ground.

I don't know why it has happened. I have posted the images here for your guidance on what could be the reason.
 

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Karthik1130

New member
I tried today,and it crashed the moment, after it was handlaunched.The plane not at all went straight, instead it immediately turned left, spiralled and crashed into ground. I couldn't able to recover as it was just a split second.
I checked all the things in parts in plane before flight, and everything was straight,centered.

I don't know what is the issue, it didn't happen like this last time.
 
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Foamforce

Well-known member
Regarding the wing breaking, that might be due to the foam used? I see the foam you used doesn’t have paper on it. The stuff that these planes were designed with has paper which gives it a lot of strength (at the expense of more weight). If you don’t have access to the same foam, you could reinforce your wing with a carbon fiber strip spar, or even a wooden dowel.

Regarding it turning hard left, it likely needs a lot of trim due to a warped wing. Look very closely at the wings from the back and see if you can spot any twist. Even a small amount of twist, like 2mm, is like having ailerons turning you in that direction. Remove whatever twist you can and then glide test.

Find some tall grass that you can launch your plane over. Put the battery in it like you were going to fly, plug it in so that the servos are centered, and then give it a good launch over the grass. If it doesn’t glide straight, either adjust the wings further, or enter trim on your transmitter. If it pitches up or down, adjust the COG by moving the battery. Do that until it glides mostly straight and level. Then you’ll be ready to fly it.

Good luck!
 

Karthik1130

New member
Regarding the wing breaking, that might be due to the foam used? I see the foam you used doesn’t have paper on it. The stuff that these planes were designed with has paper which gives it a lot of strength (at the expense of more weight). If you don’t have access to the same foam, you could reinforce your wing with a carbon fiber strip spar, or even a wooden dowel.

Regarding it turning hard left, it likely needs a lot of trim due to a warped wing. Look very closely at the wings from the back and see if you can spot any twist. Even a small amount of twist, like 2mm, is like having ailerons turning you in that direction. Remove whatever twist you can and then glide test.

Find some tall grass that you can launch your plane over. Put the battery in it like you were going to fly, plug it in so that the servos are centered, and then give it a good launch over the grass. If it doesn’t glide straight, either adjust the wings further, or enter trim on your transmitter. If it pitches up or down, adjust the COG by moving the battery. Do that until it glides mostly straight and level. Then you’ll be ready to fly it.

Good luck!
Thanks a lot for the information.This time I did do the reinforcement with the picture attached below before the crash happened.

I have also attached the front view of the plane showing the wing geometry, with respect to fuselage. When I measured the dihedral it was not equal on both sides. There was 1.5cm difference,as one wing is low and the other was high at the wing tip from the ground.

But how to remove the warpage from the foam wing and make it flat?
 

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Foamforce

Well-known member
I wouldn’t worry about the dihedral being a little off. That wouldn’t affect flight too much. In your first picture though, it looks like the wing on the right is twisted down toward the front. That would cause the left wing to drop and turn left. Don’t take my word for it though, it could just be the photograph.