Brief Description: Weight and balance measurements
Placed six 1-quart oil containers on top of the engine above the oil sump. Installed the upper cowl, and removed everything from the airplane that isn’t to be included in the basic empty weight. Lifted the tail to the level position and placed a saw horse under the tail spring.
Hung plumb bobs from the leading edge of each wing at the third rivet line outboard from the fuselage and from the center of the tail wheel. Marked points 10 inches forward from the wing plumb bobs (to clear the tires on the main LG) and used a laser level to connect the two points. Measured back from the laser line to the tail wheel plumb line. The distance is 191.25 inches which is 181.25 inches aft of the wing leading edge which is 70 inches aft of the datum so the tailwheel arm is 251.25.
Measured the distance from the wing plumb bobs to the centerline of the main LG wheels. The distance is 1.24 so the arm of the main gear is 68.76 which matches the arm listed on the sample W&B in the RV-8 construction manual.
Next, with the help of some fellow RV builders at the airport I lowered the tail back to the ground, placed ramps and scales in front of the main wheels and rolled the aircraft up the ramps and onto the two scales. We then lifted the tail up and set the tail wheel down on a third scale which was supported by a shop stool with a few 2x4s on top and some shims under the tail wheel to level the aircraft longitudinally.
Once all three wheels were supported by the scales, we recorded the weight values shown on each. The values are as follows: Right main gear = 507.1 lbs, Left main gear = 530.6 lbs , tailwheel = 64 lbs for a total weight of 1101.7 pounds. Doing the math using the arms measured earlier, the cg is at 79.36 inches
