Micro RC CG issues

Sly Fox

Active member
Hey everyone, I have a micro RC 2 channel foam plane that came RTF (KFPlan KF606 - Wanted something small to mess around with in my backyard). From what I can tell the CG is off and it is very tail heavy. On full power it climes steeply until it stalls and then drops. If I try to use half power, then it will not climb. I tried to add some weight to the nose but then it didn't have enough power to climb at all, it just does a slower decent.

The wing is a convex/concave design so it gets a lot of lift. Trying to see where it currently balances, it is halfway back maybe a little more of the wing. There really isn't any way to move the battery any farther forward as the wire to connect isn't long enough.

Where should the point be that I am using to determine the correct CG for this? Also is it possible that the motors may be reversed? The right motor turns counterclockwise, the left turns clockwise.
 

JasonK

Participation Award Recipient
that looks like it is setup to climb on high power and sink on low power, that is the only way to get it working with only 2 channels. Should it climb to a stall - no. but given how cheap it is, I wouldn't be surprised if the amount of quality control that went into the design could be lacking.
 

mrjdstewart

Legendary member
yup. don't give so much throttle in the climb, if you do give, it a slight bank. it will help with the stall. the plane is already on it's side and you will see it stop climbing before the stall. if it does stall, you are already positioned to recover. win/win.

good luck,

me :cool:
 

Sly Fox

Active member
But how do I find the correct location to check the CG? Yes it is designed to climb with more power and decend on lower power, but can't seem to find that right mix to just get it to fly level.
 

JasonK

Participation Award Recipient
the right 'mix' is the correct amount of throttle, not moving the CG around.
 

mrjdstewart

Legendary member
like mentioned above, throttle is your control but with that said...

for CG take measurement of the wing cord (center section from leading edge to trailing edge of the wing), and do some math and figure out what 25% of that measurement would be. that is a good place to start for CG. adjust as needed based upon flight characteristics.

once set you can always do simple glider tosses and see how plane reacts. hard nose down = nose heavy, nose up, then stall = tail heavy.

good luck,

me :cool:
 

Merv

Site Moderator
Staff member
Regardless of the scale of the plane, CG should be 25% to 30% of the wing area. On a straight, rectangular wing, this easily calculated. It’s 25% of the wing cord. If the wing is tapered or swept the calculation becomes more complicated.
 

Sly Fox

Active member
like mentioned above, throttle is your control but with that said...

for CG take measurement of the wing cord (center section from leading edge to trailing edge of the wing), and do some math and figure out what 25% of that measurement would be. that is a good place to start for CG. adjust as needed based upon flight characteristics.

once set you can always do simple glider tosses and see how plane reacts. hard nose down = nose heavy, nose up, then stall = tail heavy.

good luck,

me :cool:

Ok the Wing is 2.5 inches wide (rectangular except for slight rounded front corner). so 25% would be 5/8" inch back from the leading edge. At that location, with the battery inserted, it is still way tail heavy. it balances at approximately the 50% (1 1/4" back from leading edge). looks like 1 penny near the nose brings the CG back to the 25% mark. Will try it out later and see what happens.
 

mrjdstewart

Legendary member
ok, you deff tail heavy.

can you cut a new place for the battery that is closer to the nose? this way you use the weight you have to help with CG rather than adding more weight. may not be pretty, but it would help.

good luck,

me :cool:
 

Sly Fox

Active member
ok, you deff tail heavy.

can you cut a new place for the battery that is closer to the nose? this way you use the weight you have to help with CG rather than adding more weight. may not be pretty, but it would help.

good luck,

me :cool:
I could but then the battery lead would not reach the esc