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what am I doing wrong?

zev

lumpy member
#1
soooooo, two days ago I finished up my nutball, and I did the idiotic thing of flying it before I checked COG. It flew about 4 feet and then flipped over backwards, smashing the firewall, gouging the prop and bending the control rods. anyway, is turns out the COG was about 7.5 inches back, not the 5 inches back that it should be. I thought it was a bit odd, because I put all the electronics in the exact same place as flite test does. so when I was rebuilding it later that day, I just put all the electronics a little further forward. still tail heavy. more forward. still behind the 5 inch mark.

I kept doing that until all the electronics were as forward as they could be, and it was still about 3/4 of an inch behind where it should be. what am I doing wrong?

COG.jpg

as you can see, I cant move anything more forward.
electronics.jpg
 

zev

lumpy member
#3
well, I know that would work but I am trying to understand why.

EDIT: 500mah 2s.
 
Last edited:

IamNabil

Senior Member
#4
If I had to guess, I would say light battery and motor. The other option is that you have too much stuff sticking out the back. Did you add larger elevators or otherwise deviate from the plans?
 

earthsciteach

Moderator
Moderator
#6
Don't waste your time wondering why. Add weight so the cg is where it is supposed to be and go fly the thing.
Never trust plans to be reality. There will always be some adjustments to be made.
 

pgerts

Old age member
Mentor
#7
Dont add any weight - just fly!.
Those models are not critical regarding COG. As long as you have "some speed" you wont notice anything.
The plane is not a great glider anyway.......
When you cut the motor for landing, the plane will stop and fall down flat instead of darting down with the nose.
If you are trying to make a turn at slow speed - you will se something interesting ;-)
 

zev

lumpy member
#8
thanks or the recommendations Earth and Pgerts, but well, those are some very different opinions. hehe… should I start a poll?
 

jhitesma

Some guy in the desert
Mentor
#9
On my nutball built from the FT plans I had to move my landing gear way far forward and use a 3s all the way forward to get the weight far enough forward to fly well. With a 2s I strap a couple of AA batteries to the top for extra weight and it's ok but I find it much easier to fly on the 3s.
 

romeo26

Junior Member
#10
finished building mine 2 days ago. Take off at 75% then it would go into a stall. with my dumb thumbs i try to pull the elevator stick back and loop out of it, didnt work at all. ended up nosediving about 4 times. gave up.

Tried it again. this time instead of giving back elevator, i would go to full throttle and go foreword on the elevator stick. It works great for me. still trying to get used to flying the nutball. Graduated from a champ(well not really, its just really beat up right now.)
 
#11
Not sure why you're landing gear is all the way back there. Should be forward. Motor too small? Is that the 24 gram motor? Battery too small? 500 2 or 3 cell.

Anyways, the original video shows some pretty beefy gear on the very front of the pod.
CG and that BB on the front of the shotgun are there for a purpose. Don't just hold it in the general direction and think that's good enough, put it on target.Your landing gear can't weigh much more then an ounce but it's 3-4 inches behind where it's supposed to be. If you don't know what you're doing a CG that far aft of intended is un-usable. Even if you know what you're doing I'm not sure that's a usable CG

So, you say your electronics are per plans. Do you count your power group in electronics? It's just a puzzle for us how yours is so butt heavy. In any case, get the balance where it's supposed to be. For those that say it isn't a big deal, just as Aaliyah how critical CG is.
 

zev

lumpy member
#12
landing gear is further back because it was too short and the prop hit the ground if it was forward. yup its the 24g. its the 500 2s, I have a bigger battery in the mail thou (1000mah 3s).
 
#13
Yup, that'll be a bit bigger.

Take the gear off then, that far back will make it tip over all the time anyways. Get some more music wire and bend one up right. I know the frustrations of getting a planned ship to balance. I built a CL Akromaster from kit, used the motor it was designed around, tank etc. Thing needed and ounce and a quarter under the horizontal to balance. This was a 15 size plane that I think would be heavy with a COX .049 in the nose. HOW did the original balance. Of course the answer was wood selection and construction techniques but the fix was just the same. Dead weight on the tail. Now not only is it heavier making it perform worse BUT the weight is all the way out at the end, giving it a barbell effect AND any abrupt stops with the weight way back there will end with the tail snapping off. Very frustrating.

Just get it balanced right and it will fly right.
 
#15
Hi all, I'm having the same problem as romeo26. My nutball takes off but loops right over or stalls and then noses into the ground. I have my COG set a little bit nose heavy at 5 inches back. I will say this, the nutball can take some hard hits!
Prior to this I've been flying a Champ and I can land and take off pretty well. I don't have very much experience so there is a possibility that my crashing problem is poor piloting.
Below is a pic of my nutball balanced on two pieces of wire which are on the COG Xs.
nb-cog.JPG
 

pgerts

Old age member
Mentor
#16
The Champ is a very good plane and it will fly and land by it self.
There is normally a big step up to fly planes like the nutball and other flat foam planes.
There is "no aerodynamics" and the planes will fly with help of the motor and controls quite different from the Champ.
The CoG is much up to the pilots desire. If the plane is nose heavy it will dive when loosing speed. If the CoG is in the back and you cut the motor it will more or less fall like a leaf and control will be critical (tip stall) unless you have some speed.
I preffer the plane (flat foam "delta" types) to be more tail heavy myself.
 

zev

lumpy member
#17
I think that why mine was tail heavy was because I used elmer's foamboard, not adam's. the elmer's stuff is wayyyy heavier.
 
#18
Thank you for getting back to me. I'll keep practicing. I'm amazed at how hard the Nutball can hit the ground and only sustain moderate damage. Just a little hot glue, some packing tape, maybe a new rubber band for the prop saver and it's ready to auger in again!