*Unofficial* FT Simple Cub

[Gazoo]

A landing gear mod for the Cub. I used marker flag wire for the landing gear and it is kind of bendy. To compensate, I put some rubber band "bungees" on. The center is a wire bent in a U shape and pushed into the bottom of the gear foam and glued in place.


Edit: I forgot to mention that the bands are just looped around the wire at the wheel and under the foam. If one breaks, they are not glued in and easily replaced.

 

[XDmToter]

You could conceivably use Corrosion X HD on the motor, Battery & Servos :
https://www.amazon.com/Corrosion-X-...qid=1500419760&sr=8-1&keywords=corrosion+x+hd

For the ESC, I would coat with conformal coating:
https://www.amazon.com/MG-Chemicals...=1500419898&sr=8-1&keywords=conformal+coating

then place inside heats hrink and pack up the two open sides with epoxy.

I tried it on RC boats and it works great.

Yes, Flite Test has done a video:
https://www.youtube.com/watch?v=s4z8QMgTEA4

Good luck!

I'm my experience, CorrosionX is very bad for motor bearings. It creeps so well that it will force the high viscosity grease out of the bearings causing the bearings to overheat. Brushless motors actually run fine underwater. If you are running them in salt water, just rinse it thoroughly with clean water when you're done.

I wouldn't recommend CX for servos either for the same reason. I just paint the seams in the plastic case with some clear fingernail polish to seal the case, and put a dab of petroleum jelly on the servo gear.

CorrosionX does work well on ESCs and Receivers though, as they don't have any moving parts.

 

[Michael9865]

A landing gear mod for the Cub. I used marker flag wire for the landing gear and it is kind of bendy. To compensate, I put some rubber band "bungees" on. The center is a wire bent in a U shape and pushed into the bottom of the gear foam and glued in place.
View attachment 90978

Edit: I forgot to mention that the bands are just looped around the wire at the wheel and under the foam. If one breaks, they are not glued in and easily replaced.

Nice mod. Thanks for sharing.

 

[ccdman]

Waterproofing

Thanks, XDmToter.
I am glad you pointed this out. I stand corrected - I have often wondered about the the bearing grease leaching out. And clear nail polish is a good substitute for Conformal coating, I wonder if it's the same thing, certainly smells like it, and dissolves easily in acetone.

My initial attempts at waterproofing ESC's did not work well until I removed the existing heat shrink, carefully painted the entire circuit board with conformal coating on both sides taking care to fill all gaps, then putting in a new heat shrink (needed to hold heat sink against the FET's, then filling the opening at either end with epoxy. For good measure I cut a rectangular window on the heat shrink on the flat heat sink side, sealed the edges with hot glue and added a small heat sink (arctic silver thermal epoxy). So far it works well though I did not perform an immersion test.

 

[kdobson83]

Ok, so I'm seeing other people having similar issues that I have. I'm not a new to the scratch building scene as I've built 8 or 9 so far with the cub being my newest. I went to maiden and as soon as the wheels leave the ground it tilts up pretty hard and hard to the left. Needless to say after a few of those and trying to compensate with right rudder it needed repair. Tried a week later and hand tossed this time, keep in mind it is 4 channel. I got it in the air and it felt ok, but only after about 5 minutes of bad trim issues I stalled it and death spiraled it into a lawn dart. Now, to attest to the builds strength, it survived with minor damage. Had to repair a wing tip, landing gear and skewer holes. I decided my super cheap $10 motor/ESC was part of the issue and replaced with Flitetest's B pack but before I attempt again, what would be a decent fix for the violent up and left it does when taking off from the ground? More nose weight and more rudder? I'll be using a 1200 3s on the B Pack.

 

[daxian]

not had the weather to re test mine yet ...did not have the climb with mine ,just the left turn ,which i am hoping was down to the rudder being offset ..i had a 1300 mah 3s to get the cg right .
try a bit more weight in the nose see if it helps with the climb ????also check the powerpod is sitting correct in the fuselage (no up in the thrust line).

 

[Hai-Lee]

I decided my super cheap $10 motor/ESC was part of the issue and replaced with Flitetest's B pack but before I attempt again, what would be a decent fix for the violent up and left it does when taking off from the ground? More nose weight and more rudder? I'll be using a 1200 3s on the B Pack.

I would recommend a few different things.

1. As it is a high/shoulder wing design I would shim the motor mount to give a little down thrust and some side thrust, (Right for CCW motor installation).

2. Revise my take off procedure by allowing for a faster ground run before lifting off and open throttle more gradually and not slam the throttle to Max and lift off as soon as possible.

3. Rework the aileron setup to ensure that I have differential to balance YAW from aileron usage.

4. revise prop selection and fit a SF to see if roll on take off disappears. If no SF look for blade profile for more general usage and not a prop for high speed usage.

The items listed above are on the assumption that you have built a plane that is not warped or otherwise distorted badly.

Just what I do for my own designs/prototypes!

Have fun!

 

[ccdman]

I would recommend a few different things.

1. As it is a high/shoulder wing design I would shim the motor mount to give a little down thrust and some side thrust, (Right for CCW motor installation).

2. Revise my take off procedure by allowing for a faster ground run before lifting off and open throttle more gradually and not slam the throttle to Max and lift off as soon as possible.

3. Rework the aileron setup to ensure that I have differential to balance YAW from aileron usage.

4. revise prop selection and fit a SF to see if roll on take off disappears. If no SF look for blade profile for more general usage and not a prop for high speed usage.

The items listed above are on the assumption that you have built a plane that is not warped or otherwise distorted badly.

Just what I do for my own designs/prototypes!

Have fun!

Hai-Lee, Thanks for the insightful tips.

Looking at at Suggestion #1., Would it also help if I slung the battery below the power pod ? That should lower the vertical C.G. a bit.
And Suggestion #4., what is "SF"
Should I try switching to a larger diameter, lower pitch prop?

Interestingly enough, I did not really have great difficulty controlling the take off on the three occasions I flew it, but it was a handful once it was up in the sky. Being a rank amateur, that made it difficult for me to decide whether that was due to my flying inexperience, or something inherent in the flight characteristics.

 

[kd8mst]

WAS a great plane!

This was a great little plane for me, flew very nice, I wasn't a fan of the landing gear design but I designed some 3D printed parts to strengthen it up available on thingiverse (Landing gear mount) (weight distribution) I even added a bomb drop to the bottom of the fuse instead on the wings, (great for a parachute guy!) but tonight I thought, hmmm wonder if I can fold that wing, I flew as high as I could still see it (8:30pm) and nosed it down straight to the ground! I did this a couple times with no luck of folding wing or even breaking the rubber bands, on the third try I found that I didn't have enough elevator to come out of it! This was the result! It actually held up better than I thought, if it were earlier in the day I would have gotten out the hot glue gun and repaired on site but decided I had had my fun with it and it was time to try a new model so I salvaged my electronics and trashed it haha. Shout out to FT for making some great planes and those free plans are amazing! I'm in the process of building a MPCNC (Mostly Printed CNC) so I can cut out my foam a little easier! Cant wait to buy my next speed build kit in the meantime!

 

[Hai-Lee]

Hai-Lee, Thanks for the insightful tips.

Looking at at Suggestion #1., Would it also help if I slung the battery below the power pod ? That should lower the vertical C.G. a bit.
And Suggestion #4., what is "SF"
Should I try switching to a larger diameter, lower pitch prop?

Interestingly enough, I did not really have great difficulty controlling the take off on the three occasions I flew it, but it was a handful once it was up in the sky. Being a rank amateur, that made it difficult for me to decide whether that was due to my flying inexperience, or something inherent in the flight characteristics.

Lowering the battery further would add to the pendulum stability but no other change.

Sorry SF means Slow FLy it is a range of props that have broad blades and the twist or variation in pitch from root to tip is lesser than a standard or speed prop. In other words less twist.

As for it being a handful once airborne I would suggest reducing the control throws, Checking to make sure that the control linkages do not have too much play, and the pushrods do not flex or bend under load.

Also consider making sure the Ailerons have differential and increasing the amount of Expo that you have programmed.

Finally if still a little twitchy I would move the CG a little further forward. As the wing is constructed by folding a flat sheet the bends can vary as can the sloping surfaces angles so the CG can be a little different if the wing profile is different to the original design.

Hope this helps!

Have fun!

 

[SP0NZ]

Mine is still a work in progress. Just needs electronics now. Picked up the Cub lightning decals at Flite Fest last week.

 

[SlingShot]

Mine is still a work in progress. Just needs electronics now. Picked up the Cub lightning decals at Flite Fest last week.

Nice. What sort of finish is that?

 

[Maxstudio]

I'm my experience, CorrosionX is very bad for motor bearings. It creeps so well that it will force the high viscosity grease out of the bearings causing the bearings to overheat. Brushless motors actually run fine underwater. If you are running them in salt water, just rinse it thoroughly with clean water when you're done.

I wouldn't recommend CX for servos either for the same reason. I just paint the seams in the plastic case with some clear fingernail polish to seal the case, and put a dab of petroleum jelly on the servo gear.

CorrosionX does work well on ESCs and Receivers though, as they don't have any moving parts.

Mine did not run well underwater! fried it like bacon only a lot faster, LOL!

 

[Maxstudio]

I'm gonna try some thrust angle on mine to try and avoid the left pitch.....and i went to wheels, gonna stay off the water for awhile, lol
I went with 4" dia wheels

 

[kdobson83]

I'm gonna try some thrust angle on mine to try and avoid the left pitch.....and i went to wheels, gonna stay off the water for awhile, lol
I went with 4" dia wheels
View attachment 91152 View attachment 91153

How do you make those decals? They just printed and tape covered?

 

[ccdman]

I shimmed the motor mount with 1 mm thick washers to bias it to the right. Visually that seemed excessive but in spite of gusting winds I tried it, just had to! It did seem to make a big difference, though the wind was catching the dihedral sideways quite a bit , so I am not sure if the problem was fixed or over corrected. . Although I had noticed some weakening near the firewall after my previous crashes, I pressed on and the result was that the landing gear got loose and dropped out of the sky, necessitating an emergency landing attempt which resulted in a somersault or two I am rebuilding the power pod in coroplast, and reducing the shim thickness to 0.75 mm.
I've got to say this is a tough little plane.

 

[Del-Dredd]

Just maidened mine today. It does fly really nice. I did have the same issue as you did though.

I thought by putting a spacer under the trailing edge that it would help but it didn't. I noticed that it was pitchy. Sometimes it would want to climb at a specific throttle and sometimes descend. My Storch did the same thing until I fixed the issue on that wing.

View attachment 90823

I'm thinking of a nylon nut and bolt to hold it in place. A hole through the spacer at the back of the wing (the offending area).

This might be the lowest weight fix I can think of. Unless someone else has a good idea (pictures please). I'll post a nut and bolt fix if I come up with one.

I think the main reason the wing is lifting there is that the rear skewer / dowel rod is far to close to the wing trailing edge.

I have flown a lot of planes with wings held on by bands from old gassers to electric, all of them have at least half an inch from trailing edge to the dowel.

Too close and the band does not hold the wing down securely and in this case is actually putting a squeezing force on the wing chord, the single thickness there does not help.

The band should come off the trailing edge in a shallow angle, not like here less than 90 degrees.

 

[Gazoo]

I think the main reason the wing is lifting there is that the rear skewer / dowel rod is far to close to the wing trailing edge.

I have flown a lot of planes with wings held on by bands from old gassers to electric, all of them have at least half an inch from trailing edge to the dowel.

Too close and the band does not hold the wing down securely and in this case is actually putting a squeezing force on the wing chord, the single thickness there does not help.

The band should come off the trailing edge in a shallow angle, not like here less than 90 degrees.

I agree. But, there would need to be some mechanism to keep the wing from re-positioning. Otherwise the CG would be all over the place.

I did not post a pic of my fix but for this one, I just glued some tongue depressors longitudinally where the rubber bands cross to keep the foam from bending in that location.

I suspect that my next iteration will have a bunch of mods. I really like this design and the way that it flies. The frame is quite strong as well.

 

[Maxstudio]

How do you make those decals? They just printed and tape covered?

I posted about that on the thread "show off your paint job!" Page 5 i think. They're printed, then spray glued on and coated with two coats of water base polyurethane. Better explanation on the paint thread, but ezzy peezy.

 

[SP0NZ]

Nice. What sort of finish is that?

It's just Krylon rattle can. Sun Yellow if I remember correctly.