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*Unofficial* FT X-29

SP0NZ

FT CAD Gremlin
Staff member
Admin
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#1
FT X-29
Designer: Andres Lu

FT X-29 Forums.png

Release Date: September 18, 2017

Description:
The X-29 was developed by Grumman in the 1980s as an experimental aircraft to test new design technologies such as using forward-swept wings, full-flying canards and carbon fiber composite materials.

We have simplified some aspects of the plane to allow it to be constructed out of foam board and common materials while still retaining the sharp looks of the design. The aircraft’s unique flying characteristics such as its gentle stall have also been retained, but the inherent instability of the full-scale aircraft has been improved in our foam version.

Its relatively short, air foiled wing and long fuselage keeps the plane tracking straight in fast passes and allows it to slide into sharp turns while still having the locked-in feel. The speed and agility as well as its slightly more complex build means that it is a good fit for intermediate pilots and builders.

The FT X-29 can be flown with the Power Pack C motor in a pusher configuration, or it can be powered by a 64-70mm EDF, expanding the jet portion of the Flite Test speed build kit fleet.

- Andres Lu



Specifications:

  • WEIGHT WITHOUT BATTERY: 1.65 lb (.75 kg)
  • CENTER OF GRAVITY: 22.75 in (577.85 mm) from the nose
  • CONTROL SURFACE THROWS: 30 ̊ deflection - Expo 30%
  • LENGTH: 45.5 in (1155.7 mm)
  • WINGSPAN: 27.5 in (698.5 mm)
  • RECOMMENDED MOTOR: Park 400, 1100 kv minimum or 64-70 mm EDF w/appropriate ESC
  • RECOMMENDED PROP: 9 x 4.5 CW on 4s
  • RECOMMENDED ESC: 30 amp minimum
  • RECOMMENDED BATTERY: 2200 mAh 4s - 4200 mAh 4s
  • RECOMMENDED SERVOS: (2) 9 g servos

FT X-29 Forums 02b.png

Store Links
:
Speed Build Kit
Power Pack C

Article: FT X-29

Videos:

Preview Video: $30 DIY JET | VLOG0087

Release Video: DIY NASA Jet | FT X-29

Build Video: DIY Jet | FT X-29 BUILD

Build Article:

Plans: All-In-One | Full-Size | Tiled A-Size | Tiled B-Size

Simulator Files:
 
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SP0NZ

FT CAD Gremlin
Staff member
Admin
Moderator
Mentor
#2
Congrats Andres on getting your design released on the Flite Test store as a speed build kit. I can't wait to build one!
 
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FoamyDM

Building Fool-Flying Noob
#3
I'm so excited to build this. I have an EDF standing by! looking forward to the write up and plans to get working on.
 

Mid7night

Jetman
Mentor
#4
Way to go Andres! Can't wait to see the build video and check out this bird!

EDIT: Release video is up! Congrats Andres!
 
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X-29

New member
#6
X-29 High Alpha

Great Job Andres!! I was the engineer responsible for the design, development and test of the Grumman X-29. I appreciate the effort that you put into getting the model to fly well. The actual aircraft was 35% unstable. That means that the center of gravity was about 40 percent of the wing chord FURTHER AFT than on your model. Don't try that at home!! Three flight control computers moved the canards 40 times a second to stabilize the aircraft.

You may not know this, but the forward swept wing will NOT tip stall. That's why in the limbo video you could fly it under control at high angle of attack. In fact if you had enough pitch control to trim it, you could easily fly it at 45 degrees angle of attack. I think you'll find it difficult (probably impossible) to spin in part because the wing tip is so hard to stall.

Good luck in school!
 

SP0NZ

FT CAD Gremlin
Staff member
Admin
Moderator
Mentor
#7
Great Job Andres!! I was the engineer responsible for the design, development and test of the Grumman X-29. I appreciate the effort that you put into getting the model to fly well. The actual aircraft was 35% unstable. That means that the center of gravity was about 40 percent of the wing chord FURTHER AFT than on your model. Don't try that at home!! Three flight control computers moved the canards 40 times a second to stabilize the aircraft.

You may not know this, but the forward swept wing will NOT tip stall. That's why in the limbo video you could fly it under control at high angle of attack. In fact if you had enough pitch control to trim it, you could easily fly it at 45 degrees angle of attack. I think you'll find it difficult (probably impossible) to spin in part because the wing tip is so hard to stall.

Good luck in school!
I think you just won the "Best First Post Ever" award! :cool:
 

AkimboGlueGuns

Biplane Guy
Mentor
#9
Great Job Andres!! I was the engineer responsible for the design, development and test of the Grumman X-29. I appreciate the effort that you put into getting the model to fly well. The actual aircraft was 35% unstable. That means that the center of gravity was about 40 percent of the wing chord FURTHER AFT than on your model. Don't try that at home!! Three flight control computers moved the canards 40 times a second to stabilize the aircraft.

You may not know this, but the forward swept wing will NOT tip stall. That's why in the limbo video you could fly it under control at high angle of attack. In fact if you had enough pitch control to trim it, you could easily fly it at 45 degrees angle of attack. I think you'll find it difficult (probably impossible) to spin in part because the wing tip is so hard to stall.

Good luck in school!
Welcome to the insanity ;p

Seriously though, please do stick around on the forums, I'm sure the amount of work put into something like the X-29 would translate into some pretty mean experimental models!
 

earthsciteach

Moderator
Moderator
#11
WELL DONE, ANDRES!!! Awesome episode! I have a ton of respect for you, sir. Keep up the good work, kick butt in school, go to college and get that degree, then conquer the world, buddy.
 

TexMechsRobot

Posted a thousand or more times
#12
I'm pretty sure this is the EDF Unit FT is looking at currently. That may or may not change by the time the are ready to release to Power Pack. But, I believe this unit will certainly get the job done.

https://www.motionrc.com/products/freewing-70mm-12-blade-edf-4s-power-system-w-2849-2850kv
Awesome. Thanks! I'll probably just wait for the speed build kit and EDF pack and buy one. I like spending my money at Flite Test rather than somewhere else if I can help it.
 

Mid7night

Jetman
Mentor
#13
Great Job Andres!! I was the engineer responsible for the design, development and test of the Grumman X-29. I appreciate the effort that you put into getting the model to fly well. The actual aircraft was 35% unstable. That means that the center of gravity was about 40 percent of the wing chord FURTHER AFT than on your model. Don't try that at home!! Three flight control computers moved the canards 40 times a second to stabilize the aircraft.

You may not know this, but the forward swept wing will NOT tip stall. That's why in the limbo video you could fly it under control at high angle of attack. In fact if you had enough pitch control to trim it, you could easily fly it at 45 degrees angle of attack. I think you'll find it difficult (probably impossible) to spin in part because the wing tip is so hard to stall.

Good luck in school!


I think you just won the "Best First Post Ever" award! :cool:
I can't "+1" this enough!!! :applause::cool:
 

earthsciteach

Moderator
Moderator
#14
Awesome. Thanks! I'll probably just wait for the speed build kit and EDF pack and buy one. I like spending my money at Flite Test rather than somewhere else if I can help it.
I hear you one that one, TexMechsRobot. However, MotionRC is a solid outfit worthy of patronage. And, it sounds like they are partnering with FT, which is really cool.

Just to throw this out there in general... I've built A LOT of FT designs by taping the plans together, cutting templates and cutting foam. Its part of the gig as a Beta Builder. That part becomes very tedious pretty quickly. The speed build kits are of great value. Think about the time saved for the meager cost of a pre-cut kit. The SBKs are a win-win. Save your valuable time and support FT. But, if your wallet does not allow that, there is nothing wrong with going the full DIY approach. We live in a wonderful era for RC Aviation!
 

TexMechsRobot

Posted a thousand or more times
#15
I hear you one that one, TexMechsRobot. However, MotionRC is a solid outfit worthy of patronage. And, it sounds like they are partnering with FT, which is really cool.

Just to throw this out there in general... I've built A LOT of FT designs by taping the plans together, cutting templates and cutting foam. Its part of the gig as a Beta Builder. That part becomes very tedious pretty quickly. The speed build kits are of great value. Think about the time saved for the meager cost of a pre-cut kit. The SBKs are a win-win. Save your valuable time and support FT. But, if your wallet does not allow that, there is nothing wrong with going the full DIY approach. We live in a wonderful era for RC Aviation!
You're right on the nose. I plan build stuff at home sometimes when my hobby budget is stretched thin but also buy some stuff when I have a little extra. It's great to have both options!

I haven't purchased from MotionRC yet. I've got my eye on a few of their ducted RTF's though. The Freewing A-10 is gorgeous....
 
#16
X-29 Pitch Authority Impovements

If you watch the video of the model flying, it rolls like crazy but the pitch rate leaves something to be desired. Josh makes a comment about it. There are a couple of ways to address this. The actual aircraft uses the canard, flaps, and a control surface (stake flap) located at the rear of the strakes that run on either side of the fuselage for pitch control. On the model, the easiest mod is to create a moveable strake flap and connect it to the existing flap mechanism. It acts just like an elevator. A better solution is to split the wing flap so the the outer half can be connected to a servo and used as an aileron. Then the inboard flap (and strake flap) would only be used as pitch control. This approach requires two more servos and servo cable extensions, but it allows the pitch and roll channels to be controlled separately. That will allow lower max roll rates and faster pitch rates with appropriate gains and expos for each channel.

Before somebody asks, I wouldn't suggest moving the canards with servos. Because of where the CG is located, the canard may stall if it is deflected leading edge up, and if it stalls, the nose of the model will drop even though a nose up command is being given. That is a VERY bad event and can lead to a crash.

None of the above is meant to diminish what Andres has accomplished. I really appreciate what Andres has done. I just have the unfair advantage of 1,000 hours of wind tunnel testing.
 
#17
Great Job Andres!! I was the engineer responsible for the design, development and test of the Grumman X-29. I appreciate the effort that you put into getting the model to fly well. The actual aircraft was 35% unstable. That means that the center of gravity was about 40 percent of the wing chord FURTHER AFT than on your model. Don't try that at home!! Three flight control computers moved the canards 40 times a second to stabilize the aircraft.

You may not know this, but the forward swept wing will NOT tip stall. That's why in the limbo video you could fly it under control at high angle of attack. In fact if you had enough pitch control to trim it, you could easily fly it at 45 degrees angle of attack. I think you'll find it difficult (probably impossible) to spin in part because the wing tip is so hard to stall.

Good luck in school!
If you watch the video of the model flying, it rolls like crazy but the pitch rate leaves something to be desired. Josh makes a comment about it. There are a couple of ways to address this. The actual aircraft uses the canard, flaps, and a control surface (stake flap) located at the rear of the strakes that run on either side of the fuselage for pitch control. On the model, the easiest mod is to create a moveable strake flap and connect it to the existing flap mechanism. It acts just like an elevator. A better solution is to split the wing flap so the the outer half can be connected to a servo and used as an aileron. Then the inboard flap (and strake flap) would only be used as pitch control. This approach requires two more servos and servo cable extensions, but it allows the pitch and roll channels to be controlled separately. That will allow lower max roll rates and faster pitch rates with appropriate gains and expos for each channel.

Before somebody asks, I wouldn't suggest moving the canards with servos. Because of where the CG is located, the canard may stall if it is deflected leading edge up, and if it stalls, the nose of the model will drop even though a nose up command is being given. That is a VERY bad event and can lead to a crash.

None of the above is meant to diminish what Andres has accomplished. I really appreciate what Andres has done. I just have the unfair advantage of 1,000 hours of wind tunnel testing.
Wow, thank you for sharing your knowledge, this is awesome! First of all, thanks for your contributions to the design/development of the X-29 because without it, this plane would never exist in a foamboard format.

The fact that the CG on the full scale was so far aft blows my mind, I remember crashing the first version about 4 or 5 times before I finally got the CG close enough to stay in the air, and it really surprised me that the CG was so much farther forward than where I had expected it to be. Those computers must've really been doing their job well to keep the full scale aircraft in the air!

The thought of making the canards and strake flaps controllable did cross my mind, but I didn't want to make the plane more complicated than it already was haha. Also you have a good point about the canards, the CG sits on them so they wouldn't work like they should; also not having a flight controller to help, they would be really easy to over-control. It would be awesome to see someone try it though, especially the movable strake flap idea and split aileron/elevator.

Again I really appreciate your input, ideas, and the quirks of the full scale design that you shared! I aspire to be an aeronautical engineer in the future and can only hope to have the opportunity to work on such a unique plane that you have! Thanks for the inspiration, and like several others have said, awesome first posts on the forums. :D
 
#18
X-29 Canard Effectiveness

Wow, thank you for sharing your knowledge, this is awesome! First of all, thanks for your contributions to the design/development of the X-29 because without it, this plane would never exist in a foamboard format.

The fact that the CG on the full scale was so far aft blows my mind, I remember crashing the first version about 4 or 5 times before I finally got the CG close enough to stay in the air, and it really surprised me that the CG was so much farther forward than where I had expected it to be. Those computers must've really been doing their job well to keep the full scale aircraft in the air!

The thought of making the canards and strake flaps controllable did cross my mind, but I didn't want to make the plane more complicated than it already was haha. Also you have a good point about the canards, the CG sits on them so they wouldn't work like they should; also not having a flight controller to help, they would be really easy to over-control. It would be awesome to see someone try it though, especially the movable strake flap idea and split aileron/elevator.

Again I really appreciate your input, ideas, and the quirks of the full scale design that you shared! I aspire to be an aeronautical engineer in the future and can only hope to have the opportunity to work on such a unique plane that you have! Thanks for the inspiration, and like several others have said, awesome first posts on the forums. :D
Here is the cherry on the top of the X-29 design. The fact that your CG is close to the trailing edge of the canard does not mean that the canard is ineffective. How can that be? You would think that the pitching moment from the canard would be equal to the lift of the canard multiplied by the distance from the 1/4 chord of the canard to the CG. Since that distance is short, the pitching moment must be small, right? I thought so too, but I was wrong. Here's why:

The canard and wing are aerodynamically coupled. So, when the canard lifts it deflects the air flowing toward the wing down. That downwash strikes the wing and reduces the lift on the inboard end of the wing. So we have an nose up moment generated by the canard lift and a corresponding nose up pitching moment from the loss of lift on the wing. If you play with the math a little bit you'll find out that because of this coupling the pitch effectiveness of the canard is independent of where the CG is. If you look at the wind tunnel data, the net lift change of the aircraft from moving the canard is almost zero because almost all the canard load results in an equal and opposite load on the wing.

We ran a computer program when we were initially designing the X-29 and the program predicted this coupling. But it didn't feel right. So we had Nick Ziroli build an RC model using an F-16 fuselage with new forward swept wings and canards. The model took of, pitched up 180 degrees and rolled 180 degrees on takeoff and never got 10 feet above the runway. We then moved the CG forward to the trailing edge of the canard and it flew. We learned to trust the computer analysis and finally figured out how the aerodynamic coupling worked.

The X-29 may have been the most sophisticated aerodynamic design ever flown. I'll bet you'll never look at the model the same way again.

On a personal note, work hard in school and you'll make a fine aerospace engineer. You've got a love for aviation and a willingness to persevere until you succeed. Those two traits will take you a long way in life.
 
#20
X-29 Photo

Here's a NASA photo during the third flight taken from the chase T-38 inverted above the X-29. The black marks on the X-29's right wing are from wires for a flight deflection measuring system that measured how the wing bent and twisted in flight. The X-29 had graphite epoxy composite wing covers which were designed to make the wing twist leading edge down when it bent. This prevented the wing from being torn off the fuselage at high speeds which is called divergence. Divergence is the reason that we haven't built many aircraft with forward swept wings before the X-29.

If you look closely you can see the strake flap at the rear of the strakes. The strakes were fuel tanks that were emptied using pressurized air from the engine. The shadows you see on the strakes are from the cover bulging out slightly because of the pressurization.

The wing flaps were split into inboard, mid, and outboard segments. The mid and outboard segments were driven by an actuator that hung below the wing. The inboard segment was driven by an actuator in the wing just like the model. Each flap segment on the aircraft was split into two pieces, a forward and aft segment. When the actuator rotated the forward segment one degree relative to the wing, a linkage caused the aft segment to rotate an additional one degree relative to the first segment. This allowed the wing to change shape (camber) in flight and the flight control computers kept the shape optimized based on the altitude, speed, and g's. So the X-29 could automatically drop it's flaps to fly slow, raise them to cruise, or partially lower them to improve it's turning ability in a dog fight. One smart Grumman cat!
 

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