matt417

hey guys, Irecently put together the Great Planes Extra 300SP ARF. I put an OS 46FX in for power. The instructions stated when using a glow engine to mount the rudder servo in the tail of the airplane. I mounted the battery right underneath the reciever as stated in the manual. Basically I built the plane just how the manual told me to. Iput the plane on the CG machine and it was extrememly tail heavy. Just wondering if anyone else has run into this problem. Idouble and triple checked the measurments from the lead edge. it says 3 3/4 from the leading edge. I double checked everything and still the plane is largely tail heavy. Just wondering if anyone else has run into this problem. Not sure if I'm doing something wrong or not. any help would be greatly appreciated as I am going to maiden her tomorrow..thanks!

dignlivn

Which way did you balance, upright or inverted ?
Fuel tank empty? OS 55 might help add nose weight
also (jmo)

Bob

matt417

I balanced it inverted, with the tank empty...ended up moving the battery up and mounting it above the fuel tank..and added a little weight up front...first landing was dead stick, and it floated in..gonna move the rudder servo up from the tail and remove some weight and should be good....fun plane to fly for sure!

fly24-7

As a suggestion, before I finalize mounting locations for batteries, switches, servos and such, I'll temporarily mount them in the desired locations and do a preliminary balance check. This will at least let you know your options before permanently mounting anything. Unless you use the exact equipment recommendations from the manufacturer, you can't go off of their mounting recommendations 100%. Even small differences in servo weight can mean a lot with balance because of the tail moment. Many airplanes have about a 4-5:1 nose to tail ratio. For every ounce of weight that's added to the tail, you'd have to add 4-5 ounces to the nose to offset. So, you have to be very mindful of servo weight for tail mounted servos.