Weights and Balances

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When I first got my KR2 the initial weights and balances showed the aircraft to be tail heavy, I added a ballistic chute to the fire wall to bring it into the C of G range.

Next I replaced the engine, my process was to remove everything from the fire wall forward, replace the undercarriage (which was planned to be done at the same time). Next I did a weights and balances on the aircraft. Then I did a weights and balances on the engine, prop, cowling and everything that was relative to the engine. The engine's weights and balances was done with a datum of the engine mounting position. I then calculated the engine mount length using the engine's and the aircraft's weights and balances. I then did a weights and balances on the completed project using bath room scales. I calibrated my bathroom scales by getting 5 x 20 litre drums filled with water to weigh exactly 20kg each on certified scales and then putting them on the scales and recording the variation in the scales (which was more than 15% at 100kg on one set of scales). It all looked OK so I went flying. After 8 hours I then flew my KR2 to Mareeba airport and had a weights and balances done on certified scales.

NOTE: When doing the weights and balances on the aircraft without the engine everything else must be in the aircraft, all instruments, radio, GPS, EPIRB, seats, wings on and preferably painted. In my case I was building a new instrument panel and just sat all the instruments on the floor directly under where they would mount, everything else was finished. Same goes for the engine, you need to take into account everything, engine, prop, oil cooler, oil, scat hosing, bolts for engine and prop, etc.(See "Weights and Balance Excel Document 2" for details")

The end result was an empty weight of 252kg (12kg saving from the Hirth engine and 25kg saving on a VW), Full of fuel and me in the aircraft puts the C of G 2.29mm (0.09in) in front of the forward C of G range, this is not a problem at I normally fly with a water pack weighing 2kg in the luggage compartment. The other option is to leave 3.5 Litres of fuel out (about 15 minutes of fuel). Also, my bathroom scales were pretty close after calibration:-).

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