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FT Cub Owners/builders thread- off topic allowed!

BATTLEAXE

Well-known member
#42
Ok so here it is, I have an idea for how I would like to emulate the Kitfox....
Kitfox paint scheme.jpg

This 3 view is what I am basing the wing and tail feather profiles from...
Kitfox Design.JPG

What I am looking for is the same kind of plane that you would see in a Competition STOL bush plane. I am not going for an exact replica of the stock Kitfox but more of a custom look like someone used a Kitfox profile to build a cage frame and laid just enough skin on it to cover it, kinda like a NASCAR.
20191219_220424.jpg

If you look at what I got and say that's not a Kitfox, you will be right, it's not, but it will have recognizable Kitfox characteristics. This picture is obviously the fuse, based on FT Cub plans at 130% I wanted to slim things down some and make it seem like only the essentials are well, essential. And it kind of takes out the cartoony look FT is well known for in these style of planes. Away with the rounded nose and belly, same with the undercut tail section both on top and below. Here is where things get interesting which any Kitfox fan will agree is Kitfox...
20191220_204857.jpg

This is the wing cut out, it will not have the usual Cub rounded wing tips or even the under camber. The LE will be continuous from root to tip as with the bottom panel of the wing. The TE as you can see has been cut out from the top panel where the aileron sits to accommodate a separated stepped down aileron. I am not sure of what the technical term is for this style of aileron, but if my theory serves me correct it will be served the cleaner faster airflow from under the wing on the majority for better authority and control. Tell me please if the theory is wrong but it works on the full scale plane and I cant see why it wouldn't work here. In the wing cut out i left the TE C fold on the bottom panel but i am also thinking of eliminating that to have just two layers of FB total thickness instead of three layers, for a smoother transition of air to the aileron and more respective drag on the top of the wing, hence more lift for the money.

Thoughts?!
 
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BATTLEAXE

Well-known member
#43
Got the wing on the Kitfox folded up
20191222_123333.jpg

It is 50" wing span and has a thickness of 1.25" at the spar, wing chord is 10.5" at the chord.
20191222_123401.jpg
The cut out TE is where the ailerons will go, but stepped down on stand off hinges, (still working that one out in the R&D department). I did eliminate the C fold on the TE of the bottom plate to match the profile of the LE thickness. The wing tips are made from 4 layers of poster board laminated together, trimmed to fit, then glued on and sanded to smooth out the edges
20191222_123526.jpg

You can see how I angled them at 30 degrees, used a crude but effective technique of cutting this angle on the table saw I got from @L Edge I think. It worked really well actually and I will be doing this again. The wing tip droops start at the LE and taper down to hang about 2" off the bottom at the TE.

I think I will use the same laminated poster board to fab up some VG's and the aileron hinges too. It works out to be as strong as polystyrene or even medium grade 1/16 ply.
 

L Edge

Well-known member
#44
Got the wing on the Kitfox folded up
View attachment 151818
It is 50" wing span and has a thickness of 1.25" at the spar, wing chord is 10.5" at the chord.
View attachment 151819 The cut out TE is where the ailerons will go, but stepped down on stand off hinges, (still working that one out in the R&D department). I did eliminate the C fold on the TE of the bottom plate to match the profile of the LE thickness. The wing tips are made from 4 layers of poster board laminated together, trimmed to fit, then glued on and sanded to smooth out the edges
View attachment 151820
You can see how I angled them at 30 degrees, used a crude but effective technique of cutting this angle on the table saw I got from @L Edge I think. It worked really well actually and I will be doing this again. The wing tip droops start at the LE and taper down to hang about 2" off the bottom at the TE.

I think I will use the same laminated poster board to fab up some VG's and the aileron hinges too. It works out to be as strong as polystyrene or even medium grade 1/16 ply.
On a F-22, designed it with fences as well as end plates to see what happens, ended up very little changes with an increase of rocking. Not worth it.

 

L Edge

Well-known member
#46
We will see how it does with the high wing. @Grifflyer did a Shrubby with lower tip fences and he said he got more authority out of the ailerons. The 22 is a different monster.
Just wanted you to know what I explored with on a F-22.

Actually, proper designed flaps are the best STOL for high wings. Have one, even have taken off going backwards. Fun plane for flying it in a dome.


 

BATTLEAXE

Well-known member
#47
Just wanted you to know what I explored with on a F-22.

Actually, proper designed flaps are the best STOL for high wings. Have one, even have taken off going backwards. Fun plane for flying it in a dome.


Very true. I am gonna call Spektrum and see if there is a way to program flapperons into the DXe, I haven't found a way yet but there might be something there I don't know about.
 
#50
Ok, so now some pictures on how to repair your cub/other fb plane if you have crashed it.

Just about anything can be repaired, this cub has already had the tail replaced but I recently had an 'interaction' with a power line and it brought me down onto concrete from about 265ft and the result wasn't pretty lol.

It's work in progress and I'll post more pics as the repairs are finished but here is the damage and the repairs so far.

View attachment 142163 View attachment 142162

.
Hey that looks like my cub. Stalled it over the pavement from about 30 feet and didn't react appropriately. Lost a motor and batter in the crash.
 

L Edge

Well-known member
#52
I do have dual ailerons and there is differential on there, but if there is an update for flaperons I will read my manual and find it, thx
Have you watched the video Alaskan contests for STOL airplanes. Real cool to see(brakes on) add some power, bring the tail up, release brakes and as they advance wih speed, drop flaps, pull back and there is your STOL takeoff.
Can we do it? We have no brakes, so most just sit tail on ground, add brute power,flaps down, an it gets airborn with flaps down.

I set mine up so when there is a wind, I add enough power to get the tail off and then advance the throttle to trigger the flaps down. In the better radios, there is 3 zones that when you in the 3rd zone, it triggers the device(mine is the flaps) just like a switch except advancing it does it automatically. So all it takes is for me to advance the throttle slower until I hit enough speed to have the flaps drop and go full throttle.

When you buy an advance radio, think about the DX9.

Here are some leading edge fences I played with and unless you want to spend countless hours trying to maximize a higher angle, not woth it.
IMG_0345.JPG
 

BATTLEAXE

Well-known member
#53
I do watch the Alaskan STOL comps and the High Sierra stuff as well. Cool stuff. That's what kind of inspired this build. Watching Trent Palmer vids is where I got the idea for the Kitfox thing. I did want to try the Draco but it is a airframe with a lot of compound curves to it and I wouldn't do it justice trying to do that one. Maybe some other time.

I have VG's on the FT-3D, first plane I have tried them on. Mind you it is a very reactive plane with a wide speed envelope and it stalls with so much control so it's hard to say if they help so far if they make a difference. I was thinking of using them on this build but made out of poster board, all across the LE
20191210_013616.jpg
 
#54
I do watch the Alaskan STOL comps and the High Sierra stuff as well. Cool stuff. That's what kind of inspired this build. Watching Trent Palmer vids is where I got the idea for the Kitfox thing. I did want to try the Draco but it is a airframe with a lot of compound curves to it and I wouldn't do it justice trying to do that one. Maybe some other time.

I have VG's on the FT-3D, first plane I have tried them on. Mind you it is a very reactive plane with a wide speed envelope and it stalls with so much control so it's hard to say if they help so far if they make a difference. I was thinking of using them on this build but made out of poster board, all across the LE
View attachment 152055
If you put VG's all along the wing make the ones that are in front of the ailerons bigger, so that if the center of the wing stalls the ailerons will still have authority.
 

Hai-Lee

Old and Bold RC PILOT
#56
Just a little caution is required with the dimensions of VGs. As the Vortex is generated and centred around the upper edge of the VG it is possible if they are too tall that the generated vortex can actually cause lift to be lost at high angles of attack, at landing speeds. Instead of controlling the boundary flow if they are too tall they can actually destroy it.

In addition you need to consider the angle of incidence of the VG elements as they should be no more that 15 degrees with respect to the airflow and with an equal distribution of those pointing to the right and left. On swept wings remember that the VG elements should be angled with respect to the airflow and not angled with respect to the wing LE.

Have fun!
 

BATTLEAXE

Well-known member
#58
No, only put them on the front, but make the ones that are in front of the ailerons bigger than the others, make sense?
Yea ok so what if it's a full wing ailerons, wouldn't they be all the same size?

I mean I get what you are saying, and it's a valuable tip, I had a different picture in my head of what you had in mind.

What if the ailerons are installed 3/4" below the wing? Where do the VG's go then, under the wing to be effective on the ailerons?
 

BATTLEAXE

Well-known member
#59
Got a little tinkery work done on the Kitfox thing. Got the nose covered, tail-feathers on, elevator hooked up to the servo, power pod built, motor and prop dry fitted and mocked up some landing gear
20191224_182322.jpg

Got the 11x7x3 on with the bullet nose spinner/nut, need a 3 blade spinner some day. The skewers for the wing hold downs and for the landing gear as well. The power pod is widened to 2 1/4" to accommodate the 130% fuse, and I even used doublers in the entire front end, plus a third layer in the bottom under the power pod, like I did on the Sportster...
20191224_182348.jpg

The landing gear struts are recycled over from the second set I made for the FT-3D just for the ski's. They fit well here, maybe a bit small, but then again the wheels are tiny 2.5". The next size up for wheels I have are 3.25" and rubber not foam. I might just make the Bushwhacker wheels work
20191224_182418.jpg

The direct front view really shows how narrow still the fuse is to the wing. Aesthetically it looks goofy, but it might be a tiny advantage to lift with more wing exposed. This is a view down even with the bottom panel of the wing, 3/4" below that is where the ailerons will be hinged at.
20191224_182436.jpg 20191224_182505.jpg
I still have to hook up the rudder to the servo and figure out the electronics positioning based on balance. Then its off to the minwax department. I will probably maiden it sans paint. I used leftover black FB on the fuse and it worked out well. Even though i did buy some paint for this project I might not use it. I might just leave it raw like this. The black once sanded as you can tell in the corners leaves a contrast between the paper color and the FB core. I like it actually, and then the orange nose pan... I dig it
 
#60
Yea ok so what if it's a full wing ailerons, wouldn't they be all the same size?

I mean I get what you are saying, and it's a valuable tip, I had a different picture in my head of what you had in mind.

What if the ailerons are installed 3/4" below the wing? Where do the VG's go then, under the wing to be effective on the ailerons?
The VG's would still go on top, their purpose is to stop airflow separation when the wing goes into high angles of attack.