*Unofficial* FT Simple Cub

[Chiparooo]

Hi All,

I'm new to flying and Flight Test. I bought the Simple Cub speed build and "B" power pack as my first plane. I decided to save my speed build parts and trace them on Hobby Lobby foam which I now see is noticeably heavier than the FT foam. It's very nice to work with, but is almost twice as heavy. I thought foam board was foam board...

My concern is whether the "B" power pack will get this in the air for a beginner. Any thoughts or suggestions for a starter combo (motor, prop, ESC, and battery) if you think the "B" pack will be too under powered. Thanks!

 

[rockyboy]

Welcome to the forums Chiparooo!

Where are you located at? If you do have a Dollar Tree nearby, it would be much better for a first plane to go buy three sheets of that and not have to worry about the weight penalty. If you are overseas or otherwise can't get the classic Adams foamboard, yes - it's usually possible to build these designs with heavier weight foam board, but there are a couple things to deal with.

a) Because the other foam boards are usually heavier, having too much tailweight and problems getting the plane to balance right is common. If you need to use these materials, try everything you can to make the tail lighter, including extra lightning holes in the back of the fuselage, very little glue, moving servo mounting points forward, etc.

b) Because it's generally going to be heavier, and sometimes even needing extra dead weight in the nose to balance out, the stall speed is going to be higher than the original design. Basically, it's going to have to fly faster to generate enough lift to stay in the air. This can be challenging, especially for a new pilot who is trying to learn the sticks when every time you slow down the plane stalls and falls out of the sky. There are sometimes options to help increase the lift generated by the wings through design changes - i.e. undercambered airfoils, flaps, etc. but again these are not recommended for a first plane if you have another option. Usually the stock motor and prop will still work on these designs, they just won't be quite as sporty. For the Simple Cub in particular I'd recommend using a 3s1000 battery to keep your power up, while conserving weight.

Hopefully some others who have tried this design with the heavier material will be able to chime in with their experiences to.

Good luck, and keep asking questions!

 

[Filbert650]

Questions on Flight characteristics

I have a few batteries though my Cub now and have survived some scares.

I am flying it three channel right now as it has been a while since I have flown. Decades, actually. I have found that I need to roll my Cub out of a bank, that is, if in a left turn, I need to apply right rudder to straighten it out. It will not straighten out by itself when I release the stick. I am used to flying gliders (and a UMX Radian) with polyhedral so they would level themselves easily and the Cub doesn't have a lot of dihedral. So I assume that this is normal to have to straighten it out. True?

The plane has a tendency to fall out of tight banked turns, apparently stalling out, particularly on right hand turns. Now that I know that I have to roll the plane out of turns, this tendency to make a dive is lessened but still surprises and scares the crap out of me.

Is this normal for the cub and planes with flatter wings? If I moved to four channel with ailerons and mixed in rudder with the radio will things settle down for me while I get more comfortable?

Finally, I am running the recommended B Power pod with a 3s 1000 mAh battery. The voltage still reads over 10 volts after 15-18 minutes of flying. What kind of flying time are people seeing? Is part of my problem not staying on the throttle and letting the plane stall out, particularly in turns?

Thanks for any and all suggestions.

Phil

 

[KB9KHM]

Finally, I am running the recommended B Power pod with a 3s 1000 mAh battery. The voltage still reads over 10 volts after 15-18 minutes of flying. What kind of flying time are people seeing? Is part of my problem not staying on the throttle and letting the plane stall out, particularly in turns?

Thanks for any and all suggestions.

Phil

I am also running Power Pack B with a 1000 mah batttery. I get about a 10 minute flight before my Taranis tells my my voltage has dropped below 10.8 volts and it's time to land. When I put my battery on my charger after a flight like this, it puts almost exactly 1000 mah back into the pack. If you are running your battery down to 10 volts, you run a real risk of damaging it.

 

[manykarz]

I'm excited to get off the ground

Hey everyone,

I just finished building the base Simple Cub yesterday. I started with the speed build kit, and it was relatively easy, despite a few mishaps that were entirely my fault. For starters, I cut one of the wing halves right down the leading edge... A little tape and a lot of hot glue fixed that right up. After I finished, I realized the horizontal part of the tail is a little out of whack. It's maybe 4 degrees out of straight. I have yet to fly it, so I'm not sure if this will have any affect on handling.


The basic kit as received.


Power Pack C. I went with this for a little added power, as I'm planning for the added weight of the floats after I get the hang of flight.


Building the fuselage.


Fuselage complete!


I took a trip to visit the cat at the local hobby shop and to pick up a battery charger, wheels, and the correct sized props. Power Pack C comes with 10 inch props. I ended up going with 8x4.3, trying to match the recommended 8x4.5 slow fly.


The finished product out in the yard.

A few questions:

1. What kind of primer/paint do you recommend to achieve the best Cub yellow on this foam board?
2. Has anyone built retractable landing gear for the floats? I've designed something I think will work well. I plan to give it a shot and then report back.
3. Do you expect the slightly off-angle horizontal stabilizer to create any issues?

Thanks!

 

[JUSS10]

[*]Do you expect the slightly off-angle horizontal stabilizer to create any issues?
[/LIST]

Thanks!

I have found that these planes are very forgiving to things being a little off here and there. That may affect the flight characteristics but if its only a little off, it'll fly fine. I've flown quite a few planes that things were off after crashes and what not and they still flew.

Take your time to trim it out on a dead calm night and you should be ok.

Justin

 

[manykarz]

Awesome! Thanks Justin; that's good to hear. I'll see how it handles and go from there.

I set it up as a 3-channel for now, but I went ahead and put the servos in the wings and suspect I'll cut the ailerons and add the 4th channel very soon.

-Aidan

 

[JUSS10]

I ran my as a 3ch for one night then added the ailerons. It flies so easy as a 4ch and its much easier to trim out with the ailerons than trying to trim any sort of roll issues with just the elevator/rudder.

 

[ccdman]

Newbie Experience, modifications for crash and wear protection.

I have been (trying to) learn flying for the last two weeks with the Simple Cub.
Being a newbie, most of my time is being spent in crash repair because because it seems the light cub gets tossed around the sky in roll and yaw with the slightest of gusts.

This is how most of my flying sessions go:
Take off (hand toss or lift off from grass) is quite easy, it gains altitude quickly, but for good visibility of this small plane I have to keep it fairly close and low (100'). This gets a bit frantic, and I have never been able to adjust the trim to the point where I can have a few moments of steady tracking.

Fortunately the plane is surprisingly rugged and though I have crashed it on 75% of the flights, I have it back up in the air the next day after minor repairs. From that point of view this is the ideal trainer.

The exception to this is the easily bent CF2822 motor shafts ( I am on the 4th. one!), though I have cut them short to make the prop adapters seat firmly against the bell housing. I even tried modifying the power pod, both ways - a stronger one with coroplast, and a weaker one using standard DTFB. I wish there was a pusher version!

One suggestion I would make to new fliers and builders would be to brace the chopstick power pod retaining holes with small gift card squares (Hot glued to the foam board surface after peeling of the paper in area where you apply the glue). I have also done the same with the wing rubber band hold downs.

I am planning to add aileron controls to see if that would solve the problem. Any suggestions?
Oh, I forgot to add that I shimmed the motor mount slightly to provide 2 degrees of right thrust to minimize the torque roll.

 

[mikeporterinmd]

ccdman, what prop are you using?

Mike

 

[ccdman]

ccdman, what prop are you using?

Mike

Mike,
It's a 9X4 Taipan-Australia prop, something I had since 15 years ago during my last foray into the hobby. I bench tested it, and it provided a static thrust of 23.5 oz. at about 11A with a GForce 30C 1300mAh 3S 11.1V LiPO.

Admittedly this prop is very rigid which probably contributes generously to the shaft bending. I am switching to an orange GWS 9X4.7 with a prop saver / rubber band arrangement. I have not had an opportunity to try it yet, but a quick hand held full power test indicates that it wants to climb out. The A.U.W. (with Aileron servos just added today) is 20.5 oz.

 

[baronbernie]

Yellow Paint

The full scale J3 Cub is one of my all time favorite planes ( besides the Cessna 150 and 172). Can anyone tell me the color (yellow) of the paint used on the one plane, and the manufacturer of the paint. I know that the paint used on the full scale plane is Cub Yellow.

 

[rockyboy]

If the interwebs are to be believed, this paint: "Testors enamel spray paint #1214 (High gloss yellow)" will match the Ultracote covering "J3 Cub Yellow"

For full scale paint info, there's some history over here: http://www.pipercubforum.com/yellow.htm

 

[baronbernie]

Many thanx.

 

[kdobson83]

So, I have had nothing but issue after issue with my cub. I'm not new to scratch building as this is my 9-10 ft model but I just can't get it in the air for long. First was issues with my rudder gimbal messing me up, crash and repair 3-4 times before I figured out the problem. And now that that's solved, it fly's like it's drunk. It has elevator, almost too much, had to tone it down with the rates and expo, but now, it feels like it won't turn. It'll bank, but when I pull back on the elevator to turn (yank) lol it won't turn. Not to mention I feel like it's on the edge of chaos the whole time. I don't think it's trim issues as everything looks straight and nice, plus it's not pulling, it just doesn't respond to stick movements like you'd think it would. I added a wheel to the tail for taxiing and what not, could my CG being tail heavy keep it from "yanking"/turning?I check cg and with a 1200 3s pushed all the way forward it is just slightly tail heavy. Should I add nose weight or use my 2200s? I ask first because I don't know how many more crashes it can withstand before I get the enevitabl life ending crash. Lol

 

[Paden501]

Kdobson,

Try a 2200. I've been using a 2200 mounted under the power pod and pushed back just far enough that it doesn't stick out the bottom of the opening. That should balance the plane so that it is just very slightly nose heavy. Set up like this with an 8x5 grmfan prop and it flys very smooth and predictable. It also gives me about 12-13 minutes flight time (i have my transmitter yell at me at ~10v and then I bring it in a minute or two later).

I did dial in some rates and expo on all the control surfaces also. I'll have to check how much later tonight.

See if that solves your problem.

 

[ccdman]

Kdobson,

Try a 2200. I've been using a 2200 mounted under the power pod and pushed back just far enough that it doesn't stick out the bottom of the opening. That should balance the plane so that it is just very slightly nose heavy. Set up like this with an 8x5 grmfan prop and it flys very smooth and predictable. It also gives me about 12-13 minutes flight time (i have my transmitter yell at me at ~10v and then I bring it in a minute or two later).

I did dial in some rates and expo on all the control surfaces also. I'll have to check how much later tonight.

See if that solves your problem.

Is that a 2S or a 3S ? My own saga continues -- I dropped down to a 2S 1300mAH, and 1045 GemFan, Was OK as long as there was no wind, but the lightest gusts stopped the plane almost dead in it's tracks. Perhaps I too should sling a 2200 beneath the power pod, though now I would have to hand toss and belly land, as the landing gear will interfere with the battery. I am beginning to wonder if this plane would be easier to control with the heavier Power Pack C especially when the weather is not absolutely calm.

 

[Hai-Lee]

So, I have had nothing but issue after issue with my cub. I'm not new to scratch building as this is my 9-10 ft model but I just can't get it in the air for long. First was issues with my rudder gimbal messing me up, crash and repair 3-4 times before I figured out the problem. And now that that's solved, it fly's like it's drunk. It has elevator, almost too much, had to tone it down with the rates and expo, but now, it feels like it won't turn. It'll bank, but when I pull back on the elevator to turn (yank) lol it won't turn. Not to mention I feel like it's on the edge of chaos the whole time. I don't think it's trim issues as everything looks straight and nice, plus it's not pulling, it just doesn't respond to stick movements like you'd think it would. I added a wheel to the tail for taxiing and what not, could my CG being tail heavy keep it from "yanking"/turning?I check cg and with a 1200 3s pushed all the way forward it is just slightly tail heavy. Should I add nose weight or use my 2200s? I ask first because I don't know how many more crashes it can withstand before I get the enevitabl life ending crash. Lol

For you lack of elevator response I would first check the wing/tail incidence angles and then make it balances around the recommended CG point regardless of the method. Readjust the elevator throws back to original values. When balanced and the incidences are correct the elevator trim position, (trimmed for level flight), should align the elevator with the Horizontal Stabiliser.

Also check if the "Yank" effectiveness is effected by throttle setting because severe downthrust angles can offset elevator effectiveness at high power settings.

Just a few things to check!

Have fun!

 

[Paden501]

Is that a 2S or a 3S ? My own saga continues -- I dropped down to a 2S 1300mAH, and 1045 GemFan, Was OK as long as there was no wind, but the lightest gusts stopped the plane almost dead in it's tracks. Perhaps I too should sling a 2200 beneath the power pod, though now I would have to hand toss and belly land, as the landing gear will interfere with the battery. I am beginning to wonder if this plane would be easier to control with the heavier Power Pack C especially when the weather is not absolutely calm.

I've been using a 2200mah 3s Battery. Link is here:
https://hobbyking.com/en_us/turnigy-2200mah-3s-30c-lipo-pack.html


I suspect that a 2s battery with the A motor setup isn't giving you enough power and/or you're going to pull a ton of amps to get that power (especially with that big of a prop), and that's why the slightest headwind has you flying in place.

I run a C pack with 2200mah 3s battery and a Gemfan 8x4.5 prop, and I have flown through a 10mph+ headwind (not fast, but I didn't have to firewall the motor to keep the plane moving against the wind either). taking off in that much wind is another story.. and I've had an ugly crash trying to do it.

To kdobson83:

I echo Hai-Lee's suggestion about incidence angles. What is the angle the top surface of your horizontal stabilizer (just ahead of the elevator control surface) relative to the wing? The two should be about parallel. If your stabilizer is biased up or down relative to he wing, it acts just like having up/down elevator applied all the time, and that could explain some amount of your problems.

take a picture of the plane if you have a chance. Post it here and we may be able to visually see what's going on.

Hope this helps.

Matt P

 

[Hai-Lee]

For those new to the idea of checking the wing incidences the Simple Cub is a good plane to start on.

Firstly ensure that the wing sits flat on the fuselage in its designed location as there have been numerous issues with the wing sitting as designed. If the wing fits as designed then the following is a simple way to check that the incidences are equal.

Find, Beg, borrow, or steal a level, (I use a 6 inch spirit level which cost me $2 AUD).

Put the level on the wing saddle, (Mounting platform), and chock up the tail until the level shows that it is level. When leveled the level is removed and placed upon the horizontal tail. The tail should also show that it is level. If it the readings are not the same you will need to place a little Thin packing on the wing saddle and repeat the measurements until the readings are the same. If and when equal refit the wing and you are ready to go flying.

On other aircraft where a flat and easy to access wing saddle is not available a wing profile gauge will be required to be made from FB or similar to use to determine the wing incidence angle but the gauge itself and its proper usage would require a separate post elsewhere.

I hope this helps!

Have fun!