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Help! Simple Cub Balance problem

#1
I've built a Simple Cub (kit) and have all the electronics installed. Using the Power Pack B setup. Using velcro type fasteners for holding the battery in place. Battery is 3S 3000mAh lipo. I've attempted flight 3 times with no success. I've had it balanced with just a touch of nose heavy as per the build video. My launches have been by hand vs ROG. Each time it has gone up into a stall as if it were extremely tail heavy, then nose over left. Not much damage, except the last time I broke the prop. Still have 2 more from the power pack set. I've been launching with about 75% of throttle. Not sure if I've built something wrong or what. Thinking all of my flying is going to have to be ARF's, which makes me sad. Suggestions/recommendations? Going to go fly my Apprentice S tomorrow just to fly something.
 

The Hangar

Well-known member
#2
First of all, your battery is a bit big. I use 1000 mah and 1500 mah 3 cells in my cub. Double check your elevator goes up when you pull the stick back and goes down when you push the stick up. Then be sure it is trimmed neutral. Then maybe if that doesn’t work shift the cg a little bit foreward.
 
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buzzbomb

I know nothing!
#3
Your chosen battery pack probably weighs twice the one recommended. Even though you've got the plane balanced, the added weight is going to adversely affect the flight performance. The motor and wings can only generate so much lift, and you've added a lot of weight. I suspect that when you want to go up, it tries, and when you want to go down it plummets. In between it probably doesn't fly well at all.

I suspect it would be like flying a tub with wings. You can give it a lot of power and be really, really smooth and it'll struggle along. That's pretty much it, though. My suggestion would be to purchase the recommended battery size before you fly again. Then take her out and enjoy the flight! :)
 

Jackson T

Well-known member
#4
Not sure if I've built something wrong or what. Thinking all of my flying is going to have to be ARF's, which makes me sad. Suggestions/recommendations? Going to go fly my Apprentice S tomorrow just to fly something.
My first FT plane (Mini Speedster) was smashed into pieces due to the elevator being reversed by mistake. I didn't even get any flight time out of it, it was just straight into the ground. Luckily I learnt my lesson, and my next plane was successful. I don't have any advice, except for don't give up! There is so much more to the hobby when you can build stuff yourself.
 

Hai-Lee

Old and Bold RC PILOT
#5
As others have stated the battery is a little large and heavy. When heavy the simple cub does not like to fly in a fuselage level as the wing incidence angle does not allow for a lot of excess lift in standard form.

Many simple cub users find that increasing the wing incidence slightly is necessary for the cub to fly properly when overweight! You can increase the wing incidence by fitting a paddle pop stick under the wing LE where it rests on the fuselage.

In addition you could bring the CG slightly further forward and if you think it might help add a little down thrust, (with a little right as well). That should calm it down totally. If not the only remaining thing you can do is use a SF prop which can help reduce the turning tendencies on take off!

Have fun!
 
#6
Thanks guys. Been using those batteries for a couple of years in my old Apprentice. Didn't think there would be any problem. Was thinking, how big of a difference could there be? (Maybe D to triple A? LOL) Thanks a lot. I will pay closer attention to the specifics beyond the 3S part. Lol!
 
#7
Your chosen battery pack probably weighs twice the one recommended. Even though you've got the plane balanced, the added weight is going to adversely affect the flight performance. The motor and wings can only generate so much lift, and you've added a lot of weight. I suspect that when you want to go up, it tries, and when you want to go down it plummets. In between it probably doesn't fly well at all.

I suspect it would be like flying a tub with wings. You can give it a lot of power and be really, really smooth and it'll struggle along. That's pretty much it, though. My suggestion would be to purchase the recommended battery size before you fly again. Then take her out and enjoy the flight! :)
LOL! I've built the Flite Test Brick! LOL! I'll delegate those batteries to the Apprentice and go get some others for my Power Pack B. LOL! NEVER crossed my mind. Thanks!