Wingspam

My nice new plane is becoming a pain in the back side....

I have a Cmp Katana 120 size, powered by a Saito 180.
After the first round of completed assembly it was time to test the CG, and much to my suprise it would need 23 ounces of weight to balance. So I decided to move a few things around.

On the second round of building I moved the rudder, and elevator(2) servos up close to the wing tube. I used the kevlar pull pull system for the rudder and the Sullivan Gold n Rod for the elevator. I have the battery secured to the motor box (Hydramax 2000), and moved the motor forward 1/2 an inch. Now I still need 14.5 oz to make my recommended Cg of 130mm.

Do you guys see anything I missed to offset the Cg?

What would be the best way to secure 14.5 oz of lead to the plane? and should I put it on the bottom side of the motor box?
and last question for the moment, where do I find a chunk of lead this size? the stick on weights at the LHS are crap IMO....

Thanks again




If I make it look easy then you are watching the wrong plane.

alan0899

G'day Mate,
I have 1 question for you, are you measuring the balance point from the right place, mine balanced perfectly with an OS 160FX, & all servos in their suggested position.
Be aware, you must measure 150mm out from the fuselage, then back 130mm, to find the right point.
If I were you I would start at about 120mm back from the leading edge to begin with.
I have had 2 Katana's & neither of them required any lead in the nose with a 160FX.
And I believe the Saito would be about the same weight.

Wingspam

Alan

I double checked my Cg marks and they are 150mm from the fuselage and 130 mm from the leading edge and still needs the lead to balance...

Ed Smith

If the airplane needs nearly a pound in the nose to balance it, it is the airplane that is crap, ot the weights in the hobby store.

Ed S

bbbair

WOW! A pound and a half out of balance reduced to a pound ... good effort on your part, but [] that style of AC has been around for a while.

Most of the bugs have been worked out long ago.

If you have checked everything out and cannot find a solution - I would suggest that you take the plane to a local AC Guru and ask for a 2nd opinion. Embarassing as it may be it is less embarassing than loosing a plane on it's maiden. [&o]

I recently picked up a half finished plane from a fellow - it looked good but I went through the instructions carefully and found that he had installed the servo trays backwards. No real problems but all of the control rods were the wrong length and the balance was off ... the maiden would have been ... interesting. [:'(]

As they say; "The Devil is in the Details."

telejojo

It took 2 1/2 pounds of lead to balance my H9 27% Cap with a DL 50 in it........................

Robotech

My Feedback: (9)

I had the same model with a Saito 150 ( which I think is about the same weight as the 180 ) and it took 15 Oz. of weight up front to balace it. What I did was made a aluminum foil mold of the bottom of the engine/engine mount then melted some lead weights and poured them into the mold and strapped the then molded weight to the bottom of the engine.

Probably would have been better to just put a larger/heavier engine on it instead. Maybe even a gasser.

skrplyr23

This isnt a Creek Hoobies Katana is it ?

Jetdesign

My Feedback: (8)

If you need weight in the front of the plane, you can try moving your engine forward. Helps a lot.

Wingspam

skrplyr23
It was a Cmp Katana...

MasterAlex

Hey Wingspam, how bout adding some additional functional weight? Maybe an additional battery for onboard glow? Probably not the additional 14.5 oz you need but begins to lesson the "dead weight" of just lead. I always hate adding non-functional weight ... sometimes you have to do it, but I try and make it an absolute last resort.

-MA

Blade 65

Wingspam, I also bought a CMP Katana using a RCGF 26 cc gas engine. I almost crashed my plane on its maiden flight. The plane was very tail heavy. I didn't realize that I needed 32 ounces of weight at the nose with the CG at 120 mm from the leading edge of the wing. Any suggestions for my setup. I kept the elevator servos and rudder servos in the tail. Thanks.

sugarfox

My Feedback: (1)

wingspam, stop by wherever you buy tires and ask for some of their used wheel weights taken off wheels when they balance your tires. Melt the lead as suggested by the guys above and screw it to the bottom of the engine box. Don't just glue it as eventually it will fall off and you will have a disaster. Something just doesn't seem right here as over a pound of lead is a bunch, Good Luck sugarfox

Blade 65

Sugarfox, I moved the engine forward an inch and also placed my 2300 A123 batteries aft of the CG which made a difference. I only require 16 ounces of lead. I will certainly take your advised by bolting the lead down under my firewall box. Thanks for your recommendations. The weight of my plane should be around 13 lb.

sensei

If they all come out this tail heavy then the manufacturer is hanging you out to dry, that is just wrong on so many levels. If I were faced with this problem on a smaller airframe like this one; I would move the wing aft before I would ever add that much weight; it would be some work, but I would do anyway.


Bob