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*Unofficial* FT Simple Cub


Old and Bold RC PILOT
I do frequent RC Groups and whilst I appreciate the effort in altering the design by changing the tail incidence angle it is something that is difficult to accomplish for many readers post build, especially when either building a FT supplied kit or following FT provided plans!

Rather than directing people to another website for answers it is normally better to provide a simple solution in words that they can follow or understand to give them an easily obtained, and somewhat immediate result or improvement.

Most of the newbies here are unable to plot a datum line and so measuring and altering them to improve a design is not what they are seeking. Most just want to fly the design they have just built. Centre of gravity is about as technical as it gets. Understanding centre of mass, the effects of varying thrust lines, and other aerodynamic concepts are best spoken of in general, rather than the scientific, terms where possible.

Keeping the information simple and easy to implement is the big difference between forums and whilst technical solutions and scientific explanations may be requested, or required, sometimes generally all that is required is an easily implemented solution by someone whose tools box contains a glue gun only, besides not all builds are equal.

Keep it light and helpful!

Have fun!


Old and Bold RC PILOT
It took me a while to learn to simplify the answers!

My early days even saw me involved in some heated exchanges but I took the experience and changed my approach. Even so I sometimes find my answers getting far too technical and that I need to back off a little.

FT planes are just short lived wonders and I do appreciate the highly engineered generational models as found of RC groups. Heck I actually do restorations in what little spare time I have!

Keeping the thought processes technical and the answers simple is not always easy to achieve. Often I just let others reply if I cannot get my post simple enough! (Even when I do post some answers are not understood).

Keeping the balance is not easy!

Keep posting and as always Have Fun!


Well-known member
I did increase the wing incidence angle slightly.
Angles for the wing incidence, horizontal stabilizer and motor up or down thrust are based on a longitudinal datum line.
The way this Cub is designed, that datum line is parallel to the top of the fuselage.
Setting the horizontal stabilizer to -1.5 degrees, creates a new datum line using the horizontal stabilizer. Using a 180 degree line, passing through the stabilizer thickness creates a new the horizontal datum line. The angles then become +1.5 degrees of incidence for the wing, like raising the front of the wing some, 0 degrees for the horizontal stabilizer and -1.5 degrees of down thrust.

Be sure to check out the full details in the RC Groups link that I previously posted.

Thanks for the info. There is a lot of good ideas in your other post!

I was wondering, if the motor was shimmed at the top for down thrust, could you just trim up slightly and this would increase the angle of incidence? I know that deflecting a control surface will cause some drag but would it accomplish the same thing?

My cub has pontoons but I have never taken off/landed in water. Just snow. Anything to slow it down a bit would be nice.

I'm glad you found them useful.

The angle on the fuselage doublers was adjusted so that when installed it provided 3 degrees of down thrust relative to the FT datum line using the top of the fuselage. Without getting technical, the actual down thrust, relative to the new horizontal stabilizer position is now -1.5 degrees. The firewall is resized to set flat on the angle of the doubler and extend to the bottom of the top hatch I added. The firewall is actually 90 degrees to the fuselage doublers.

All of my modifications were 'built-in', which would be a problem for someone with an already built version, as Hai-Lee noted.

I'm not sure how to slow it down as designed. A low pitch, 8" diameter slow fly prop can slow down the pitch speed, but because of the relatively high wing loading for its size, it needs to fly a bit faster than a plane designed as a slow flyer or even a park flyer.

Now, I'm uncertain if I should say this or not, but here goes;
If you use all of the same components as the FT Simple Cub and increase the size (yes, most folks can't do that), it will have a much lower relative wing loading, as the amount of 'added' foam, to make it larger, contributes very little to the final ready to fly (RTF) weight. That is why you may read here that when some enlarges a FT design it seems to fly better. The power system is way more than adequate, in my opinion, and could easily fly a Cub, based on this design, at 1.31 times the original, giving it about a 50" plan form span and over 500 sq.in. of wing area.

Simplified; build it bigger, use the same components, it will fly 'better' and also appear to be slower.
I hate using the word better, but can't think of a better (I know) way to describe it.
Finally my turn to give back. I really appreciate what FliteTest is doing for the RC community. I'll be adding my 3D printed mods to thingiverse anyone is interested. I would love to get some feedback.

https://www.thingiverse.com/thing:2999491 (landing gear, vortex generators, and wheel collars).

The landing gear was inspired by https://www.thingiverse.com/thing:2940224 which didn't work out so well for me. I'm hoping to give it a try Sunday if the weather permits.

IMG_3133.JPG IMG_3132.JPG

I am totally new to the hobby and just started the build and ran into an issue with the motor. I have the new 2213 and it doesn't have the removable adapter Josh demonstrates in the build video, nor does it come with wood screws. When I put one of the hex bolts in through the back of the firewall (which seems to be what's being demonstrated in the insert that came with the Cub) the motor's shaft appears off-center in the big hole in the middle. What am I missing here?

Sorry if this has been addressed elsewhere, I tried to search

EDIT: okay, I discovered the motor's mount is wider than it is tall. The wires seem to have a long way to go to the opening for them now though...

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Well-known member
So I'm just about to begin a build of three Cubs for my friends and I to fly this weekend and I plan on trying a few mods to the builds (I've built... 5 cubs now I think.) anyway, my question for all of you is I want to try for a three channel setup with bank and yank (I believe that's what ailerons and elevator is called, correct?) Has anyone flow the cub with this configuration?


Slow, low and dirty.
So I'm just about to begin a build of three Cubs for my friends and I to fly this weekend and I plan on trying a few mods to the builds (I've built... 5 cubs now I think.) anyway, my question for all of you is I want to try for a three channel setup with bank and yank (I believe that's what ailerons and elevator is called, correct?) Has anyone flow the cub with this configuration?
Fly like that most of the time. Except at very slow speed or with full throttle at low speeds the ailerons work great.
Can't wait to hear how the aileron, elevator with no rudder versions fly.
When I used the 4-ch wing, with the same dihedral as the 3-ch wing, it suffered from adverse yaw pretty badly.
Can I ask what was the problem with them, I JUST printed out several last week for this next build. :(
My landing gear wire didn't fit into the grove very well so I had make the hole in the fuselage wider then the original design because it wouldn't squish as flat as it should have and the print is wider then the original. I was having problems keeping it all together. Eventually the wire pushed it's way up into the fuselage. Probably just issues with my printer settings since I'm new to 3D printing.


Well-known member
If you have a vise you can try what I did.
I used 5 min epoxy and clamped that sucker in there until the glue cured (I waited a good hour or more.)
This is just posed for a picture, I had the mount further down when I actually glued them.
They seem really solid now!

I've tweaked the design of the cub a little from the example I saw in the legacy, beefing up the fuselage where the gear attach (if it works out, I'll share)
I make my landing gear tab out of 1/8" thick and 1/16" thick plywood. It is holding up pretty good so far.
One photo shows the parts and the other when it is assembled. The 'extra' 1/8" plywood on the axles helps hold them in alignment while the epoxy dries.



Rogue Pilot
So I'm just about to begin a build of three Cubs for my friends and I to fly this weekend and I plan on trying a few mods to the builds (I've built... 5 cubs now I think.) anyway, my question for all of you is I want to try for a three channel setup with bank and yank (I believe that's what ailerons and elevator is called, correct?) Has anyone flow the cub with this configuration?
i fly the Simple Cub as a 3 channel bank and yank aircraft with no issues at all. I have no dihedral in the wing, it was built flat. It flies more like a warbird/fighter than a Cub ;)
I would expect that to be true for sure.
The problem, if you want to call it that, is when using the 3-channel dihedral with ailerons. When Sig changed their original 3-channel Kadet to ailerons, they also tried using the same dihedral as the original Sig Kadet 3-channel trainer. It also suffered adverse yaw problems until they recommended removing most of the dihedral.


Old and Bold RC PILOT
The adverse yaw can be minimised if you ensure that you use a lot of differential on the ailerons. If you build the wing flat you will find that the cub has rather strong pendulum stability anyway and so the dihedral as shown in the plans is almost a stability overkill. If you build and fly it as you would a scale aircraft then it performs remarkably but it was never a truly aerobatic model or design.

On my example I fitted a flat wing and even then needed to increase the wing incidence angle to make it more conducive to stable and somewhat aerobatic performance.

What worked for me!

Have fun!
The point that I've been trying to make is that if the Simple Cub is built using the 3-ch wing, with adequate dihedral for stable 3-ch flight, and then adding ailerons by cutting them out, as noted in the build video, the beginner is most likely going to have an adverse yaw problem. They won't even know about adverse yaw and some may even believe they might be having radio failure, as the plane did not "turn" as they expected it to.

They won't know about aileron differential or how to set it up mechanically by moving the control horn back away from the hinge line or in the transmitter when using independent aileron control inputs for the servos. Nor will they know about mixing in the rudder movement with the ailerons.

For no time and low time pilots, I'd recommend building two wings if they want to start with the 3-ch version with the recommended dihedral and then "upgrade" to a 4-ch, purpose built wing, with no or low dihedral.

Just sharing my thoughts,